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Electric Stunt => Gettin all AMP'ed up! => Topic started by: bob branch on October 03, 2009, 04:52:30 PM
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I have started a Brodak T-Rex electric arc. I thought, if I can figure out how to download the pictures that I'd share the experience here.
My power system will be as follows: Axi 2826/12 motor. Castle Creations ice 50 esc. Will Hubin 6a timer. Turnigy lightmax 3000 mah lipo. I am setting it up to test two flavors, 4S and 5S. My electric development has been primarily with Rick Sawicki and Frank Carlisle. I bought franks Original 3S axi 2826/10 smoothie from him that Rick helped him set up. This was a clone of what Rick was flying about 4 or 5 years ago. Flying and developing with Rick and Frank genesis went to 4S 4000 mah packs then to Axi 2826/12 motor. Then to Will Hubin timers and 3000 mah 4S power. Props have progressed from woods to APC-E and now APC-E pushers. Frank is not currently flying electric but takes part in a lot of Rick's and my test and tuning sessions. Rick and I have alot of experience with the power system thru the castle creations phoenix 45 but I have switched to the ICE 50 for the data charting feature. I'll probably be changing this esc out with a phoenix 45 as well since I start flying an electric strega on Wen and while I'll start with a pheonix 45 there it will get the ice 50 on occasion as well. We fly the axi 2826/12 planes on 63 ft eye to eye lines usually in the 83 to 8500 rpm ballpark to get 5.3 sec laps with the APC 12X6's. Power has always been outstanding and the /12 motor draws less than 2000 mah per pattern. We have also tested the motor on a 650 sq in 62 ounce plane on the same power and prop system and it flies the plane with authority so motor size is not an issue and we have 3 years of very accurate test data with the system (this year with Will's excellent timers) so we have a plug and play setup that we do not worry about.
Initial weigh in shows the airplane with all components in the bones is 33 oz. The arf covers out in 3.6 oz of ultracote and that is what I will be covering with. The motor with mounts, prop, connectors etc is 9.8 oz with the esc and timer included. Battery options are 11.1 oz for the 4S pack and 13.5 oz for the 5S pack. So all up weight is expected to be 57.5 4S and 59.9 oz 5s. Obviously the 5S will require a different prop combination.
bob branch
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Well, here goes nothing with the pictures. I hope its easier than our AMA district VII forum. This is a pic of me with the fuse. Frank wanted me in it to show the size of the fuselage. If you get the feeling there is a lot of room up front you are quite right. This is the first electic CL plane (exluding RC conversion) including the strega that I feel I have enough room for whatever I want to do and have multiple options of where to put stuff.
bob branch
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Keep us informed!
I am not sure if you know how to download the photos or not. In case you don't, all you need to do is to click the "Additional Options" just below the text entry window. Then you will see an "Attach" button that allows you to choose a file. The file size restriction is less onerous than over on SSW, but it probably is a good idea to do a little compression to save Sparky some storage space!
ok you replied when I was typing and clearly know how to download!
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Fit and finish on the fuse is excellent, btw. This is a whole new level of control line arf constuction. The wood is exceptional. Glue lines are ample. Finally a wood cowl instead of fiberglass. Thank you Paul & John! Now I can finally have a nice film finish on the cowl and not have to paint at all!
This pic shows the front end from the bottom with the cowling off an just after motor mounting. You can see the large fuel tank area. Also note the area that winds up being left behind the motor mount bulkhead. This is a seperate non installed part that you position where ever yo want for your installation. Glow fliers will mount to it as well with RC type mounts. It is absolutely ideal for electric and will adapt to what ever power system you want to use.
The motor mount system I have used I learned from Rick Sawicki. The motor mount bulkhead is located and any motor offset you desire located. A ply strip, in this case 1/8 inch ply is glued to the fuse side in front of the bulkhead location with the bulkhead not in the plane. This is done on both sides. This retains the motor from moving forward. Another similar strip is glued to the fuse side behind the bulkhead. This prevents any rearward motoion. Since most of our stunters have a rail somewhere that is parallel to the thrust line its easy to do this with no incidences. Finally the motor mount bulkhead is slid into place and it is retained simply by two small screws, in this case #2 allen heads that essentially only keep the motor mount from falling out of the airplane. Its simple, light, easy to do, and works. I know doublers are an issue with electrics, to use or not. I use the doubler to act as a stop for these retaining screw heads. It winds up looking leaner than a washer. Thanks Rick, this was my most unfavorite part of electric installations til you showed me this method! I have enlarged the center cutout of the mounting bulkhead to allow more airflow thru the fuse. May not be needed but I am going to be mounting my esc on the front surface of the next rearward bulkhead and want a good air supply going by it.
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This shows the front end installation a little further down the road. The ice 50 has been installed onto the bulkhead with velcro. Shown is the Turnigy lightmax 5S 3000 mah pack. The fuse is so wide it could be mounted on the outboard side and decrease the amount of tip weight needed. I would do that but since I am going to be moving back and forth from 4S to 5S packs I would wind up with a lateral trim issue so I will mount the batteries on the center line for now. Later when I have settled on the pack I want (and I'm betting it will be the 4S but we will see, that is one of the experiments I am doing on this bird... I always try to do two or three experiments on each new plane to learn more from actual flight testing rather than theory what does what, what works for me and what does not, but always with a distinct hypothesis and planned method of testing each). The timer will be mounted on the inboard fuselage wall in the battery compartment. I use Will's remote start and remote fine tune pot on my timers since I fly with heli hi mode rather than fixed RPM mode. It allows me to adjust the rpm at the circle without a computer, I just dial in the rpm I want. If I want to test a change, I just dial it in and return if I don't get what I want. Same with prop changes. In my hands that's simpler than doing it thru the esc. Your milage may vary. In this thread I'll just be including what has been working for Rick and myself. Btw, Rick usually does not use the remote fine rpm pot, but the one on the board. I just like to be able to change the rpm with the plan on its wheels and running. Once I have what I want I leave it and don't change it. Stays the same every flight just like fixed rpm mode.
I have a problem retaining little screws in my life. Grass seems to eat them and gravity doesn't pull down in my part of the world (maybe because I live on an island) it seems to pull sideways. All little screws seem to have a habit of jumping sideways out of their holes and into the grass. Also I don't like the idea of pulling 4 screws every time I change the battery. Sometimes I use the quater turn latch I learned from Bob McDonald, but I am a little leary of one of those flailing around with all the wires in the front end of an electric fuse. My solution for the T-Rex is magnets. I have place 4 one half inch rare earth magnets (available cheap at Jo Ann Fabrics). Two are in the nose block, and two on the sides of the fuse. I had hoped to get by with only one in the aft section but the cowl didn't sit flat when I did so I had to add the 4th for esthetics. NOT for retention. Good thing the nose is wide open. It takes a small explosion or strong karate chop to open the cowl with half ounce magnets. But the flip side is the cowl will not come off in flight. I retained the mounts for the screws that were in the kit and mounted on the cowl itself as they provide lateral and for and aft limitation for the cowl. This is the ideal situation with magnets. Don't ask them to do both lateral guidance and retention. Lots of cowls and canopies littering the woods and fields around our RC sites from doing this.
bob
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This is the cowl showing the magnets and their mounts in the cowl. Notice also the glue lines on the stringers. Oh, no blocks on this kit, its all stringer and sheeting and the sheeting is nicely blended, not corners but nicely rounded and blended. Kinda looks like how you might build one yourself doesn't it? The installation of the magnets I learned form my RC building partner Jerry LeLacheur. The mount plates are 1/8 ply. I use a brad point 1/2 inch drill to drill a shallow recess about 1/2 the thickness of the magnet, ie about 1/16 inch deep into the ply. The magnet is sanded to roughen the flat surface and edges that will get glued and it is then glued to the ply with epoxy or thick CA. If using thick CA I wet the bonding surface of the magnet with CA kicker and place the glue in the recess in the ply plate. That causes it to kick and set completely on the inside. One plate is then mounted, I mounted in this case the fuselage plates first. Always check before you glue the magnets by the way that they are facing each other in attraction and not repulsion... they are polorized and only join on one surface. Only each pair has to match. To mount the opposing magnet place a piece of wax paper between the magnets and join them. Apply glue to the ply mount to be mounted (in my case the cowl ones, did one at a time, and join them then seating the cowl. I did it this way cause I had access inside the cowl from the front intake and I had cut out the air duct channel in the bulkhead just in front of the wing. If you look at the first pic of the front fuse area you will see that in the kit this has already been mostly cut through. This allows for the pipe tunnel if you are going that route in glow or for our air exhaust in electric.
I should point out that the magnets wind up being a little proud of the mount plate. That is what you want. On the nose block to orient the opposing magnets, I installed the fuse ones first. Then I painted some black dope on them and seated the cowl down on them. This left a nice black mark on the cowl nose block exactly where the cowl magnets should be placed. I then cut the receiving hole for the magnet deep enough so the magnet would not hold up the cowl fuse joint, put the wax paper between the magnets, and filled the recess with epoxy and set it all together. After the epoxy kicked I separated the parts and trimmed the excess epoxy.
bob
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Here is a look at the wing. I have assembled it and failed to take pics during assembly. The wing is very similar to the current strega wing. There are two spar boxes in the wing, one in front, one in back which receive lightweight joining spars. These perfectly align the wing halves. They are epoxied in place and the center ribs are epoxied together as well. The manual doesn't mention it that I could find but in that I found a strip of fiberglass tape in the kit and no where else it could be used that I could think of I attached it over the wing joint with thin CA (rather than have the weight of epoxy). Any new arf is going to have some issues on the first go around. This is commonplace in RC and control line. And while this is a much higher step in CL arf/arc construction than anything we have seen before, there are one or two wrinkles to be ironed out. First the pushrods are too small for the pushrod end fittings. I believe I encountered this on my last strega (my fourth btw and first one to get electric power, ... two with Saito .72, one with PA .51 on a pipe (best performer by a very long ways so far). In that I keep carbon fiber pushrod tube on hand that fits the 4-40 end fittings this is no biggie for me. Just made new ones. I missed it in the manual but the tubes are not the correct length in the kit and must be trimmed to the right length. I know it sounds like a no brainer but the RC kits I build alot of that have carbon pushrods all have them precut to the correct length these days. My bad!
A second issue I encountered you can see in the pic. The exit slot for the pushrod is on the wrong wing panel. It needs to be on the inside panel, not the outside. Again, no biggie, just cut a new one. Also, the flap pushrod must be installed before assembling the wing halves. I did this but did not realize that the slot was on the wrong side til I tried to assemble the wing together (with the glue on it of course... good thing I used 30 minute epoxy). The wing will not go together with the pushrod going out the slot on the outboard wing. The alignment spars will not allow it. So I had to remove the pushrod and assemble the wing halves real fast so I didn't get the glue kicking and then later cut a second flap exit slot in the outboard wing. Since I could not get to the bellcrank hole for the pushrod (its a large belcrank, all Tom Morris like control system... ball links, suspended bellcrank... nice job Brad, nice bellcrank reinforcement system too. Be proud of it!) I had to cut a longer slot and again an access in the bottom of the wing to get to the nut to mount the pushrod. Again, no biggie. I may do primarily arf's these days but I spent a lot of years building and it drives me crazy when RC fliers grip about a little mod like this. Be nice in a perfect world if everything was perfect, but first go around it rarely is.
Flaps are built up and covered. Look adequately stiff especially since they are not full span.
Well that is as far as I am for tonight. I'll post further as the process goes along.
Btw, I will apologize now. I am a terrible speller, a terrible typist, and make no apologies for odd grammer. You get how i talk. Besides you all know Midwesterners have an accent don't you? <=
bob branch
Harsens Island, Michigan.
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Great start Bob! that AXI loooks lost in there, heck you go room for TWO packs!
Harsens Island, that's almost a yoooper isn't it???
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Dennis
Those Uppers got nothing on us Islanders. Canada is only north and east of them. Here Canada is north, south, east, and west of us! Neat piece of geography!
So what are you saying? 10S?
bob
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On to cooling issues. There is a very big hole in the nose of this airplane. Air can get in but if it can't get out we are no where. And a small hole ain't gonna do it. We need about twice the area of the hole up front for air exhaust. My solution is going to involve 3 exhaust ports. One on each side of the aft section of the lower cowling, and one in the belly pan. There is an opening in the aft bulkhead of the battery compartment as i already pointed out but its only about 1/3 the size of the intake opening so air flow thru that alone will not pull adequate exhaust flow out. My solution was to cut two openings in the lower cowl one on each side of the centerline stringer and extending up to the first lateral stringer on each side of the cowl. Each is by itself almost the size of the area of the nose intake opening. Add to that the bulkhead exhaust thru an opening in the belly pan larger than the bulkhead opening (just to make sure I get draw) and we have more than twice the intake opening in exhaust opening.
I was concerned though about loosing structural integrity of the cowl when I did this, especially with the strength of the magnets holding the cowl down. Sure enough the first time I removed the cowl it started to crack down the center stringer at the openings. So I placed a vertical keel between the aft and mid bulkhead of the cowl. To reinforce it and help direct air flow so I get exhaust flow thru both the bottom cowl openings and the belly pan opening I placed a divider above the keel that is glued to the keel and the two lateral stringers in the cowl. The structural integrity was recovered and I think airflow will be improved, especially out the belly pan opening. Additionally it resolves the visual impact of a hole completely thru the fuselage from one side to the other. In 100% scale aircraft one of the major issues we encounter is cooling air flow for the air cooled aircraft motors. Full plenum boxes are the norm to direct airflow around and thru the cylinders. Directing the flow the way you want it to go along with adequate exhaust opening are the keys. Many a homebuilt 100% scale aircraft goes thru a long arduous teething process getting this worked out. A little duct work can go a long ways.
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Finally a wood cowl instead of fiberglass. Thank you Paul & John! Now I can finally have a nice film finish on the cowl and not have to paint at all!
Heh heh... that would be "thank you Brad". HAHAHAHA!!
The proto #1 had a fiberglass cowl and I hated it. So I specifically asked them to make it out of wood. So they did. I like it much better. they did a wonderful job in fact. It fits like a glove, is lighter, and looks much better cosmetically... and you can cover it will film.
The magnet idea on the idea is one that I missed. I will look at putting it on the next run. I have seen the magnets on many of the other RC ARF cowls and they work great.
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(its a large belcrank, all Tom Morris like control system... ball links, suspended bellcrank... nice job Brad, nice bellcrank reinforcement system too. Be proud of it!)
I am... it is one of the major accomplishments of the design.
I wanted a way to join the wing and still make a fully suspended fuselage supported bellcrank system THAT THE USER INSTALLS THE MOUNTS.
Read that last part again. I wanted the builder to glue in in his OWN bellcrank. So, no more bitching when one pulls out. If it pulls out is your own dang fault. The system that I designed not only makes the bellcrank attach the to fuselage sides, it help join the wing itself.
I have all the pictures I sent to the manufacturer. I had to make 3D models!!!
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Brad
Yea, where did I get "Paul" in that post for cryin out loud! :o Was too late last night when I posted it. I should have stopped earlier.
bob branch
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Bob, you are doing a great job. I am forever your humble servant. <=
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Brad
Just hope everyone will be patient with me as I usually only get to build on weekends.
When I get there I'll cover how to do a quality film covering job. With practice (well, ok, its taken me 7 years with guidance from a very good RC coverer, but who ever learned to do a quality paint result in one airlane?) you can get to the point where you can do a contest level film covering job with curves and shapes. There are some tricks though and when I get there I'll cover some of the things I have learned. Here's a picture of my electric Strega as an example. Everything is film including the lettering.
bob branch
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I used the small 1/8" magnets on a Vector and they were not up to the task. Yours look like the 1/2" size? Gotta be great. NICE job on the airflow management too. Neither the AXI nore the batteries stand much of a chance at heating up.
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Dennis
Yes they are 1/2 inch magnets and are very up to the job.
bob branch
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What is the weight of the magnets you are using for the cowl ?
What is the total cost of the electric power system you are installing in the T-Rex ?
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Allan
Magnets are 0.1 oz each, 1/2 inch diameter
Motor: Dualsky XM4260CA..........................$99.99 (dualsky america)
esc: CAstle Creations pheonix 45...................74.99 (Todd's Models)
timer: Hubin 6a w/ 2 remote leads..................30.00 (Will Hubin)
battery: Turnigy lightmax 5S 3000 mah........... 37.79 (hobby city) (I have 3 of each of the batteries with CL stunters. seems all I need)
apc 13X6.5E pusher prop............................... 7.50 (Tower Hobbies)
charger: Turnigy accucell 6 balancing............. 34.99 ( Hobby City)
That's the whole deal. Dennis Adamissin is flying his with less expensive and smaller motor and it is working fine. I would use a Turnigy but I wanted to try this size motor to see what it is about. Its larger and more expensive than needed, but several of the experiments I am conducting on this model relate to larger motors in heavy airplanes and how they act in comparison to smaller motors on governor mode. Dennis and I will be comparing data very closely on this. I have an ice 50 esc that I will take some data with as well for comparison and may go to that esc in the end. But this is where I am now.
bob branch
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Allan
Excuse me I gave you the data on the strega electric in the previous post. Sorry.
The T-rex system is as follows:
motor axi 2826/12 $109.99 (Lobby Hobby)
axi radial mount 17.00 (lobby hobby)
ice 50 esc 80.99 (Todd's Models)
turnigy lightmax 4S 3000mah battery 31.55 (Hobby City) (Again I have 3 of these)
turnigy accucell 6 balancing charger 34.99 (hobby city)
APC 12X6E pusher prop 3.39 (apc)
Also as an alternative one of turnigy motors of similar kv and weight class would provide motor for under $40.
As you can probably see from following the forum there are lots of ways to skin the cat. I look to keep my battery costs manageable after starting in electric with at the time very expensive polyquest batteries none of the 4 of which laster 20 flights in the cl environmnet. My turnigeys have been going multiple years with no issues. Good news is when the plolyquests were not longer adequate for cl they still made great sport flying cells for my electric rc airplanes. Also until I recently purchased teh turnigy chager I have been using cellpro's 4C charger, also a very nice unit but limited to 4 cell packs.
bob
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That's it? :o
How long will that rig run (pattern time).
Is there such a thing as a remote shutoff?
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Brad
I can fly the entire pattern with a 5min 32 sec run that starts the prop when I reach the handle (32 sec delay after hitting the start button... so I use no energy while I saunter to the handle). This gives me 6 to 10 laps after the pattern before engine stops ... the timer does this.
but that is not the good news! The good news is you don't need to fly an entire pattern. I set the timer for its minimum run during all trim flights. About 2 minutes. That way I can do the trim flight. Evaluate the changes on several maneuvers, land, make any additional changes, and fly another trim flight without changing or charging batteries. I can easily get two flights from the 3000 mah packs. Used to easily get 3 from the 37-4000 mah packs but prefer now not to carry the weight. Could easily get two trim flights from a 2600 mah class pack as well. Its amazing how much more trimming you can do in a day not having to fly entire pattern for each flight. You really can get a plane dialed in alot faster electric than glow because of this.
bob branch
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The T-rex system is as follows:
motor axi 2826/12 $109.99 (Lobby Hobby)
axi radial mount 17.00 (lobby hobby)
ice 50 esc 80.99 (Todd's Models)
turnigy lightmax 4S 3000mah battery 31.55 (Hobby City) (Again I have 3 of these)
turnigy accucell 6 balancing charger 34.99 (hobby city)
APC 12X6E pusher prop 3.39 (apc)
No timer ??
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Alan sorry, the timer is the Hubin 6a with 2 remote leads, start button and fine tune rpm pot.
The T-rex system is as follows:
motor axi 2826/12 $109.99 (Lobby Hobby)
axi radial mount 17.00 (lobby hobby)
ice 50 esc 80.99 (Todd's Models)
turnigy lightmax 4S 3000mah battery 31.55 (Hobby City) (Again I have 3 of these)
turnigy accucell 6 balancing charger 34.99 (hobby city)
APC 12X6E pusher prop 3.39 (apc)
hubin 6a timer w/ 2 leads 30.00 (Will Hubin)
bob branch
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Bob laments his typing lapses, and looks like you caught him in the act. The Hubin timer is listeed in one of his equipment posts but not the other, he WILL be using it tho!
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Dennis
I hate it when someone beats me to a pun. Good job! Everyone else: I apologize
In these photos I am showing the install of the Will Hubin 6a timer. This version of the timer has the following features: Adjustable flight time from 2 to 6.5 minutes. Adjustable start delay from 0 to 32 seconds. switch to set either governor mode or fixed rpm mode. Two speed adjustment pots. Gross adjustment pot on the board for setting governor high or low and ballpark rpm setting, and fine tune pot on a remote for fine rpm adjustment with about a 1500 rpm range. Provision for retracts. Ability to select multiple rpm settings for flight. I fly in governor mode vs fixed rpm mode so the mode switch on the board is in that position and I set the final rpm with the fine tune pot. Also the second remote is a start button. The first pic shows the setup from the outside of the plane. The red button is the start button. The stem is the fine tune pot. To those of you who fly glow power, think of it as my needle valve. I use it the same way you use yours to adjust rpm. I adjust it to create the rpm that gives me the lap times I want. If its windy and I'm going too fast, I slow it down. If it is dead calm and I need a bit more power I dial it up a bit. But once I set it it does not need to be adjusted again unless I want to change rpm. It will always fly to exactly the same setting throughout the flight. The two 4-40 allen bolts are the mounting bolts for the timer.
The second pic shows the inside of the plane. The start button is the rear most remote, the fine tune pot the closest to the timer board itself. The orange wires are the communication wires from the timer to the speed controller. The blue square devices on the timer board are the adjustment pots and the black switch on the red section is the selector for governor or fixed rpm mode. The 3 bottom connector wires on the board not used are for a retract servo if used. The velcro will be discussed in the next sequence of pics.
bob
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There are probably as many battery attachment methods as their are electric fliers... probably more. We each have probably tried a bunch. This one is one i have used often in both rc and cl and works well in my hands. It allows me to move the battery forward and aft for cg adjustment, and it allows me to change to different size batteries but use the same mount system with no modifications. In my RC planes I can vary from 2300 3 cell to 4000 mah 5 cell without changing anything, and have in the same plane. But again, its just what works in my hands. Your milage may vary. (Its the first place I try to peak when I see someone else's cl electric.)
First pic the velcro loop material is epoxied to the what would be the tank upper floor if this were a glow model. This is ply in the T-rex and in Strega as well. I think most battery mounts I have seen are ply these days. I also use two #2 X 1/2 inch allen head screws with washer heads (though the washer heads do not show well in this pic) that I get from R&L fasteners. btw, they have excellent fittings at exceptional prices. Good folks.
The second pic shows the battery. I epoxy velcro hooks to the top and bottom surface of the battery. Notice that I have the battery so that it will mount not lowest profile to the mount surface, but highest. This lets the cg of the battery be lower and helps bring the lateral CG closer to that of the glo motor. Just decreases another trim issue that a few have noted with electric since our power systems usually have more localized vertical cg than glow installations.
The third pic shows the battery installed. It is at the rearmost position in the compartment. I have about 3/4 of forward movement without modifying the bulkead at the front of the compartment. If I need to of course I can open that up and move further forward if I need to. The velcro hooks on the side of the battery you do not see (ie against the tank floor) locates the battery from moving for and aft and laterally. The Hooks on the bottom of the battery, the surface you see, retains the pack. Gives good stable battery location with out any more weight than required, even in 3D rc with 4000 mah 4 cell pack and extremely violent 3D snaps.
That's all for tonight. Winds in the 45 to 50 mph range here in the Detroit area prevented my electric strega having its first flights today. Maybe Friday, but we have wind in the forecast then too. We'll see. Sounds like a few of the glow T-Rex arf's are ready to fly. Looking forward to reports.
bob
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Hi Bob:
Many thanks for your most informative build documentary. This is very helpful to E-neophytes like me and I have adopted several of your ideas into the China Clipper E-project. It is so much better to have a road map than have to find the way by yourself. I really look forward to the "covering with film" segment when you get to that point.
What holds the motor mount plate in place? It appears to simply slide into the slot between the bracing ply pieces.
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Mike
The motor mount does indeed slide into place as you envision. There are two #2 allen head wood screws (from R&L Fastenings), one on each side of the fuse going thru the fuse side and into the motor mount plywood. Their only load is to keep the motor mount from falling out the bottom of the plane. That is all that is needed. Because there is a plywood doubler on the inside of the fuse, I did not use the version of the screws with a built in washer (allen head servo screws). I used the version without the built in washer and when I placed it the first time (use a 1/16 inch pilot hole) I just drew the screw head into the balsa fuse exterior until it bottomed out on the plywood. Deal done and the head comes out flush with the fuse side.
I'm glad you have found some things on the thread you can use. Whenever you can get a look inside anyone's planes you can to see the methods they use. Nothing original in any of my work. I'm just copying what I have seen others do and where I can remember the original source I'll certainly give them the credit they deserve. Where I can't remember, just know its copied from someone.
bob branch
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Bob,
I noticed that the picture of the T-rex wing shows far less ribs than the prototype pictures I saw from Bradleys thread. The gaps between the libs look major to mee. Any issues with torsional stiffness of the wing ? How about covering sagging between the ribs ?
Keep up the good work; we are all taking a lot from this thread.
Han Slaats
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Hi Mike, Hi Bob,
Mike, in response to your question 3 up. This is from Rick Sawicki, we chatted earlier in the "45 year old model" thread.
I can offer a little more about the motor mount system and offer an additional use of it. I developed the motor mount system about 4-5 years ago back when electric stunt was in its infancy. At that time we did not have the wealth of data and data sharing that is now so readily on the web today. The system was initially developed to allow a "quick change" of motors in an airplane. Different motors could be pre mounted..including any spacers, washer offsets etc onto their own firewalls. All of which were made to fit in the same location on the plane and anchored by, in my case 4 screws through the body sides (all the planes had plywood doublers added) and in Bobs case 2 screws, same method. This proved invaluable about 4 years ago on an electric Viking OTS when I had 3 different motors all individually mounted on their own firewalls and were taken to the flying field for an all day session (weather was perfect). By the end of the day all 3 motors were tried several times each and one was selected as being superior to the others in this specific airplane. Being able to change a motor is less than 5 minutes sure helped. I have been using it in all my planes since then and so has Bob. I think it is a great, easy to install, and easy to change motor mounting system.
Mike,...you mentioned you were looking forward to Bobs "covering with film segemt"...believe me it will be well worth the read. He truly has done some fantastic work in film covering.
Hi Bob,
You are doing a great write-up with a lot of important detail that I'm sure will help many others in their incorporation of electric power into either a T-Rex or also be very useful in adapting electric power into other planes. I am really looking forward to your sharing with the electric community your methods of film covering since I have seen all of them first hand and can atest to their beauty.
Rick Sawicki
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Hi Bob and Rick and anyone else involved:
I do want to try several motors in the China Clipper so this approach to motor mounting is very useful. I plan to use the TGY 42-50 as the primary motor but have that AXI 28-26 on loan and want to pick up a Scorpion 30-26 (probably) to compare. Like Goldilocks, I want to see which of the three is "just right." Incidentally my TGY seems to be put together well, no visible problems. Has 5mm shaft and Japanese bearings. I will say the "notchiness" as you rotate the can is much more pronounced on the AXI than the TGY but don't know if this has any operational implications. The Adamisins (IIRC) are using this TGY with great success, and it sure is a bargain.
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Bob, I'm enjoying every post of your T-rex electric build, finally understand the motor mount system you're using and that Rick developed. Being able to slide the firewall in and out for quick motor swaps is pure genius! Things like this make this forum a great place!
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Han
I do not see any torsional rigidity issue at this point. In 3D RC this kind of spacing is pretty much the norm and no problem with film covering, even crapcote which none of us use here (I hope). From quality films like monocote and ultracote certainly no issues at all. I'm not sure about silkspan and polyspan. I have not done silkspan since I was a kid. Polyspan doesn't seem to pose any issues from my experience but maybe someone with more than the 3 or 4 planes I have done in it could confirm that. I am sure someone else will do an arc and paint it. I just don't paint any more and will not accept the weight. (note: not accept the weight is slang for "I've wet sanded for the last time in this life!".... just more in stunt slang. Bless you all who do it so light and so well!).
Bill
I know Rick doesn't want me to say this and no one on this forum wants me to but since there are some glow fliers reading it I thought I would interject, this mount will also work for glow motors easily if you want to trade in and out.... or IF you have the courage to compare your glow powered version tit for tat with an electric powered version. Just slide the motor and tank out, slide the electric system in! Don't look now, but we are going to beat alot of the glo powered planes weights that have already been posted with some electric power sytems in this bird!
bob branch
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This may sound like a silly question,
but do you think that your multiple cowl magnets might interfere with the operation of the ESC or Timer?
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This may sound like a silly question,
but do you think that your multiple cowl magnets might interfere with the operation of the ESC or Timer?
Not a silly question, but no it won't matter. The ESC could careless since a static magnetic field wouldn't affect it in the least. And any effect on the motor also would be slight---maybe a small eddy current in the iron shell. I use them in all my setups.
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Before I leave the cowl and engine compartment for other components I'm going to jump ahead a tad to a step of the film covering that I will go into later in more detail. But this comes under the area of a minor detail, but one that can make a nice difference in presentation of the finished project and a huge decrease in frustration level. The basic color scheme of this aircraft is going to be similar to the strega pictured above. Black primary color, white secondary and trim in yellow and orange. Maybe a little something else, I have to wait to see how it lays out. But the entire lower half of the fuse is going to be black. Some places are just aweful (read nearly impossible) to cover well. So why kill yourself? Most notably in this plane the area where the cowl joint is at in the nose block that the magnets are mounted in and the air exhausts and ducting. If you notice when I did the air exhaust I added a keel between the two openings to visually eliminate the hole thru the fuselage that would have been visible both on the ground and in the air. Then I added a duct above it to increase stiffening and direct air thru the belly pan as well as out the exhaust ducts. Covering all that intricate small surface would be nuts. (sorry my humble perspective there). Its inside the fuse. Its not part of the outside surface. It doesn't have to be high gloss, or even smooth. Its all in shadows. It just needs to not be seen. In this case it needs to be black. The area were the magnets face on the cowl nose block will be similar, you could look into that area and not see black and its going to be a tough area to cover and the bottom of the nose bowl opening the same. Solution? The traditionalists are going to love this..... dope.
Notice I did not do the entire insides of the plane. You can. But I have found I often need to do additional grinding and glueing later on. Paint just inhibits the bonds. Remember, battery packs will change (as we will find later, already have), timers and esc's may get changed out, indeed motors and mounts may get redesigned and changed. Not having paint in there leaves this a much easier deal. Glow folks obviouisly have to seal some how. Your choice with your favorite. And I know there has been some discussion about protection from glow fuel at circles getting blown into electrics. Again, your choice. But all I want is to get rid of non black visuals on the model when its done. On the inside all I did was the areas that might show. The battery will cover the rest of the opening area of the exhausts when viewed from the bottom looking up so no reason to black there.
Also, I do not want a smooth nor a sealed surface. When I go to cover, I want the surface as porous as possible. I want grain and as we will see later, I'm even going to make the surface so porous you aren't gonna believe it. I'll warn you now, you will think I have lost it when we get there. Suffice it to say now that smooth, non-porous surfaces trap air and make bubbles that are difficult to make go away. I want to avoid having film finish on painted or sealed surfaces whenever possible.
bob branch
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Now onto the wing for a bit. I'll have to defer to someone who got the wing together correctly. I just missed how to do it right and as no one esle has mentioned it this was obviously an area of brain lock on my part. The flap pushrod exit is indeed on the right side of the wing as it is in the kit. I still no idea how the wing goes together when the pushrod is in, but since others have done it it obviously does. Sorry for the confusion to everyone following this and my apologies to Brad for not being able to figure it out. At any rate, as we all have to do from time to time, I had to improvise to get myself thru it. I had cut an additional opening on the inboard wing section. Didn't want to leave that open and wanted to strengthen the area so I added a bit of sheet balsa on top of the wing. Its going to be in the fuse, so not seen. Just me an one or two of you will know and I know none of you will tell.
I am not using a standard flap horn. I have an adversion to tweaking wires in flaps to get wings to fly level, and I'm not good at it. Many of you are masters at it. I marvel. Frank Carlisle is just scarey good at it. I used to use separately hinged and adjusted tip trim tabs like beyond the flaps on this plane. But Bob McDonald showed me a fitting he makes that I have used for a number of years now. The horn is in two sections with the actual horn arm on one side and a quadrant with a slot on the other half. A locknut is soldered to the side of the horn arm opposite what we see in the pics and there is a slot in the quadrant so that the two sides of the horn can rotate free of each other and be locked by tightening down the bolt. There is also an index of one side of the horn into the other so that there is no flex between the two halves and they stay centered. Sorry, I'm not CAD literate to do a nice cad representation like Brad and some of the rest of you, but I show it here just to show what it looks like and the extent of the travel available. A small hole is placed in the fuse side opposite the head of the bolt for the allen wrench to pass thru to loosen and tighten as needed. Of course once you are trimmed you are done. .... unless you change something, in which case you can reset it any time. No torquing on the horn wires or the flaps themselves. The flaps do not have to be made so strong and heavy where the wire passes because they do not have to be able to handle the loads of tweaking the flap wires. For me its just easier. You milage may differ of course.
The first pic shows the horn locked with the tow sides even. The second shows the range of adjustment available.
bob branch
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Bob, how about another picture of the flap horn from the opposite side..please?
Thanks.
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Christ
Here ya go.
bob
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You may recall I also made the flap pushrod too long. So tonight I am redoing it. Now that I had the flap horn glued in and connected so I could get the right length. One of the things this let me do was some deconstruction analysis of my end fitting joint to the carbon tube. I have used carbon tubes exclusively since returning to cl and had used them a lot in rc previously. I was really surprised when I read reports of failures by some folks. I spoke with Curt Nixon about it at the time and we compared methods of joining and found we were both doing it the same. I learned this method in bonding sailboat masts and carbon fiber canoe paddles. Its used in other places and I'm sure by many of you, but being able to deconstruct this end fitting shows why the key step works so well.
In assembling the end fitting its important to make it so that it cannot rotate. There is no anti-rotation built into the end fittings other than the bond of the J.B. Weld to the tube. This is normally very good, but there is a way to get extra security to enhance anti-rotation properties and to give a better bond in the process. The key is to provide relief to the J.B Weld inside the tube and to provide exits for the epoxy that key it further to the tube. I do it by drilling several 1/16th inch holes thru the tube at 90 degrees to each other in the area the end fitting will be. When the end fitting is slid into place it the J.B. Weld will flow out these holes, seal them, and create antirotation for the fitting. Also one of the holes must be beyond the end fitting at at least one end of the tube. Otherwise the epoxy will form a seal, compress the air inside, and partially push the end fitting out during the time it takes the material to set... ie a number of hours. When you go to place the J.B. Weld into the tube after it is mixed, angle the tube at about 60 degrees to the mixing pad and scrape the tube into the mixture tube opening first. This will force the material up the tube. You will be able to confirm it cause it will flow out the holes! When it has come out the last hole that the end fitting will pass it is filled. Dab some on the end fitting and slide it to place. Wipe off the excess and then apply heat shrink to the end of the tube and the end fitting. This helps hold the end fitting in place and strengthens the tube against splitting, its weakest direction. Then do the other end. The J.B. Weld fills the hole and restores sturctural integrity to the area the hole was drilled in.
In this pic I have cut off the end of the tube with the end fitting in it. I then used side cutters to crush the tube and pealed it away on one side. You can see the JB Weld clearly around all areas of the end fitting and in the indentations in the end fitting. I removed the J.B. Weld that was beyond the end fitting into the tube, about 1/4 inch of it. Sorry, would have been better had it been there for you to see but I was trying to capture one of the relief holes. If you look very closely at the pic at the tip of the arrow you will see one of the relief-anti-rotation holes with the lighter gray J.B. Weld filling it. As you can see, like the rest of the fitting, its an intimate fit. Hope this helps clarify this type of pushrod and end fitting some. They really do work well and you can do them yourself. Just be sure to give the J.B.Weld a full 24 hours before disturbing it.
bob branch
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Hmmmmmmmmmmmmm. Now this is disappointing. I went back down to my shop to see what was to do next. Set all the hinges in place to prefit everything.... it did. All of it. Well, I had to increase the depth of an elevator hinge pocket. That was it. There are no cowl holes to cut. The cooling openings are all done. I joined the shortened elevator pushrod end fitting. Now I am at major disappointment. BRAD!!!!!!!!! What have you done to me? The rest of it is perfect! You have left me with no choice but to do my most unfavorite part of the whole thing! I have to start sanding! EUCH! HB~> HB~> HB~>
Its really that well done! So tomorrow I will start the sanding. I'll start at about 150 grit and take it out to 320 and do any filling I need to. Some of the dents will come right out with a few drops of water and the heat iron to swell the wood back up to contour. One or two I may have to add a little filler but not much. After the sanding is done at 320 is when I will return cause one of the most important steps in covering follows before final sanding. It the one that will abhore you.
See ya when the dust settles.
bob branch
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Oh Yea! I found one more thing to do before I had to start sanding! Here I am constructing the belly pan air exhaust. I did the same thing as with the cowl. Cut the openings, built a keel, and topped it with a floor. In addition as you will see in one pic I closed off the lightening hole at the back the duct area. There is a mid bulkhead in the belly pan that has an opening to i imagine ease pipe installations. Least that's what I would use it for. Anyway, I want the air directed out this opening and so do not want air going aft in the fuse past it. Lastly of course, I got out the dope and turned the area black for the same reasons as before.
EUCH! Now to sanding! HB~> HB~> HB~>
bob branch
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Guess it would have helped in the last post if I had added the pictures. Sorry, senior moment.
bob branch
n~
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You might think that is alot of exhaust opening but its not. Each pair of exhausts is 3.5 inches long and the area of each pair is the equivalent of the area of the intake in the nose. Its a big hole up there! So twice the exhaust area as intake area will give good airflow.
bob branch
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I'm including this next step just cause I learned it this last year. I know many of you know about it but no one told me before and since I hate to sand it saves a lot of sanding and filling and sanding. Its the way to get rid of dents and scratches and such without sanding. The pics are of the top of the horizontal stab. But if you want to know the magnitude of what the method can do, if you have a T-Rex you will probably have already found the dent in the wing tip caused by the packing of it next to the bellcrank nut. I have seen it mentioned by several people so I am sure someone else has seen it. Unfortunately, even I did not think the method would remove it, but it did. If you have the arf and need to get it fixed, it might be worth opening the wing tip covering to do so.
To do this you place a few drops of water on the divot, dent, whatever. Then you apply a hot monocote iron to it. I use 300 degrees on mine so we are not talking low temps but pretty high. You do not want to rub the iron over the surface, but lay it on the surface of the wood and let it steam the defect. You should hear a good hiss and see steam rise if you are hot enough. The iron should be to temp and you should apply it right after applying the water. You are going to steam the wood. If you are on a curved surface, roll the iron over the defect so the iron is able to provide the limit of contour for the raising of the wood. The wood will swell and come right up to the contour of the iron. If you move the iron or run the iron over it you will probably not transfer enough heaat right where you want it and you will probably mar the very soft wood at this point. (No fear, just steam the area you dented.
The pics were taken with a macro lense from about 6 inches away. The two pics were taken about 30 seconds apart.
bob branch
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I won't say my next thought, but you can probably guess.
HB~> HB~> HB~>
bob
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hmmm, that doesn't sound good! :P
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I won't say my next thought, but you can probably guess.
HB~> HB~> HB~>
bob
Nothing left to do but sand.... ;D
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You might think that is alot of exhaust opening but its not. Each pair of exhausts is 3.5 inches long and the area of each pair is the equivalent of the area of the intake in the nose. Its a big hole up there! So twice the exhaust area as intake area will give good airflow.
bob branch
Bob:
Seeing how old Rex was designed for one of those Infernal Combusting engines, the air intake actually may be larger and in the wrong place for your needs - Have you considered baffling? Maybe closing off all but a circle around the AXI, so that all the air tat comes in MUST pass by the motor? That would certainly re-balance you areas too - exits would be comfortably large...
Looking most excellent - now get back to your sanding. HB~> %^ na#
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cough.... cough....
180 grit.
bob
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Well, not all is well in mudville. Or should I say Windville? You guys from Texas would be right at home this week on my island! Can't get a fly day in for nothing.
Well, the conversion from T-Rex to E-Rex has hit a snag I hope Brad can forgive me for. I have had one thought on this canopy style that I also see on so many airplane from Europe. Personal preference only, but I think its ugly. No offense intended Brad. Your milage may differ. And Brad and some folks locally have been concerned at the weight it looks like this bird is going to come out at as being too light. So I thought I'd remove a little weight and add a little weight. Bout 3/4 ounce net weight gain.
Hope Brad will still talk to me. At least it will be a little heavier.
bob branch
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240 grit
cough.... cough HB~> HB~> HB~>
bob branch
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320 grit!!!!!!!! YEA!!!!!!!!!!!!!!!!!!!!!!!! #^ #^ #^
Unfortunately, now its gonna get real ugly. So sit down. Put the coffee out of reach (not a good thing to spew coffee all over the monitor), and take a deep breath before going any further.
bob
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When you are covering in film you can sand less than you would with paint (thank God!). How far you go is up to you and up to the wood you are using. Remember you are sanding bear wood, its soft! But some is harder than others and will not sand as nicely or as easily. I often stop about 240 grit but you will see grain under the film in sheeted areas that are broad and flat like a flap. In an open bay area, not so much an issue. I ifnd 320 is a nice place to stop and you get a pretty good surface. Ultracote which I use is thinner (and lighter) than monocote and will show up a little more surface texture than monocote. It pretty much comes down to knowing your surface. Actually, as we will see I have decided to go to 400 grit on this plane just to see if I can tell a visual difference between 320 and 400 once its covered... but we don't go there yet.
The next step is to use that horrific looking tool you see in the Tower catalog, the Topflite Woodpecker. It is more viscous than the pictures even look. Each point is scalpel sharp and they are about 1/4 inch long. The device is rolled over the entire wood surface (I don't do cap strips cause they are too fragile). It is not used real lightly either. The idea is to poke holes. You do not have to push down much to do it. Just a little pressure and it will go right thru 1/16 sheeting. The problem with all film coverings is that they release gas when heated. This offgassing is more pronounced with monocote than ultracote and less so with the modern version of monocote than it was with the original. The holes let the gas escape thru the balsa. When the holes can't go completely thru the holes let gas get into the wood, off the surface. My goal is to not have to stick the film with a pin to release gasses. Sometimes I succeed, sometimes I still need to here and there. But with ultracote and using the woodpecker there is very little bubble popping to do.
The first pic shows the device, the second pic a view of the horizontal stab after it has been woodpeckered. Interestingly, very little wood is raised above the surface by the device. Ono my Strega electric I did not sand after the woodpeckering and had no issues at all. On this plane I am going to woodpecker the entire plane and then sand with 400 grit, again to see if I can detect any difference in the two procedures. One thing that will be important will be to clean the surface after that last sanding. If I fill the holes up with sawdust, they do no good. So the entire surface will be blown off with compressed air. A tac rag will not do it cause it cannot reach in the holes. I will tac rag before I cover, last step before applying the film.
bob branch
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The Woodpecker holes will not show thru the film. I probably should have said that earlier. One place where they would is with a transparent film. I have not done that with a woodpecker yet to see how it presents. If you are going to use transparents, try it on a piece of scrap and see if its objectionable or not. This is one place where our light stunt wood is a benefit cause if you do not woodpecker more gas can escape into the less dense wood than with heavier wood like we see in RC.
You may have discerned a place where there will be more difficulty than others and that is the fuselage. The issue doesn't develope so much from our top and bottom blocks as they are usually soft and thin. But the sides where we have the doublers are the most difficult area to get gas to escap. You will often have to reheat and pin prick this area.
I should also mention that time of year has a huge determinate on your covering job. More importantly the humidity. In the winter in parts of the country where we have to use heat the wood will loose moisture content and shrink... a lot! This will produce wrinkles in your covering jobs. Its what causes planes coming from the far east to arrive with bubbles and blisters that have to be shrunk down. Many manufacutring faciilities are now carefully climate controlled to minimize this. If you cover in summer with high humidity be prepared to see ugliness in winter when the humidity drops.
I often wait til late winter when the humidity is lowest and the planes present with alot of wrinkles and reshrink a that time. Again, another good reason to not over heat and overshrink your plane's covering films and another good reason to use a film that has alot of shrink degrees in it. I have on a number of occasions run out of shrink on ARF's that have been overheated to come out of the box in America with no wrinkles. I actually feel better when I see some because then I know I have some room to work with. When you cover your own, you are in control.
As a side note here, there are some irons that actually have the temperature of the settings in degrees on them. Both the full size and trim iron by 21st Century Products are such irons. Unfortunately, I cannot recommend their films at all. These are much safer to use cause you know where you are at. I always calibrate a new iron with a temp guage when its new. Trim irons are pretty difficult to measure. Maybe an infrared thermometer would work with them. Also an iron with actual temp can be used to give you an idea of how much heat you are using in your hot air gun technique. There is no good way to measure this accurately. It all depends on how close you are with it, if you are using a defuser nozel (please do), and how fast you are moving the gun over the surface. But You can compare the shrink you get with an iron at a given temp and then use the gun to just shrink an adjacent area to about that amount and have some idea where you are at. Over time you can get pretty good at this.
Well, off to woodpecker the entire airplane. After that I will sand it with 400 and then blow it off. Then the dust has to settle. The heat in the shop will go off, and I will not go near the shop for a good while. If you wouldn't shoot paint in the place cause of dust, don't expect to cover in it and not get dust showing up in the finish.
bob branch
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Ok, today I'll start the covering with Ultracote. I'll show some of the things I have learned in covering over the years and empahsize that I am still learning. But you can with practice do a covering job that will let you gather reasonable appearance points at contests in a lot less time and with a lot less weight than a paint job. Please don't think I'm trying to put down paint jobs. I love them. Used to do them. But I do not have the patience to do it any more nor the desire. I don't fly at the NATS and am not now or ever interested in having a plane sit in the front row there. Just not my thing. But I do want a plane that I can be proud of and that looks really nice. What I will share are the things that work in my hands. Are there other ways and materials? Absolutely! I'll also be showing the Windex method of applying film later on in the thread as I get to the trim colors.
For starters I'll just go over the materials I'll be using. Two are not shown in the pic below. The first is a sheet of glass. There is nothing else to cut trim on that will get you a fine clean line. Formica can til you get the first cut on it and then when you rn a blade over it sometime in the future you wind up with a glitch. Glass is the only thing I have found. Wood of any kind has grain and will deflect a blade and give a non straight cut. The second not shown (cause I forgot to put it in the pic HB~>) is a tac rag. Not the one you have been using for the last 3 years or even the last model. A brand new, unused tac rag. If it had dust on it it will shed dust to the model. You can make them yourselves or buy them, but use a new tac rag on each each model and go over every surface before you do it. You do not have the option of wet sanding off dust or burying it in clear. Its going to show so get it off now. You can't do it later. Also on the same line, be careful not to seperate the backing of the film until just before you are going to place it on the model for attachment. It will pick up dust and it will show. This is the most frustrating part of film covering. You want to know how good the arf builders are? Everyone is always putting them down. Just look at the covering jobs and the lack of imperfections under the surface. It will humble you.
Blades: You need more than you can imagine. I ue straight edges and scaple blades. I don't use curved blades but have, its just harder to get consistant cuts cause you never know where on the blade you are actually cutting. Buy them buy the bunch, buy them cheap cause no mater what you use and how much you pay they are going to get pitched so often you will not believe it. If you feel the slightest drag on a cut, if you have to repeat a cut to get it, if you feel any vibration in the blade during a cut, its time to change the blade. When you are cutting on glass, guess which is harder, a thin steel edge or glass? I just cannot stress enough how important a fresh sharp blade is to your end result. Lastly in blades, you need a disposal container. In medicine we learned to use sharps boxes. Since we are not dealing with body fluids here (if we are its your own, so no worry about cross contamination...sharp remember?) we do not need a puncture proof plastic container. But you should use something thick enough that the garbage man isn't going to get hurt from I use the thickest cardboard box I have with a slit that only lets the blades go in. When its filled I tape it shut with a few layers of duct tape and pitch it.
Irons: You need at least two. A full size one and a trim iron. I will sometimes use a third one with a sock on it. Socks where out very fast, commercial or home made. I think a cotton sock home made one gives a better surface but it requires a higher temp setting to get the temp you want to the film. If you use a sock you must check the temp on the surface of the sock with a monocote thermometer, the temp settings on teh irons are not accurate enough. As I said I like the 21st Century irons because they have actual temp settings on them, but any brand is fine as long as you ck the setting temp and know what temps you are using.
A heat gun is used by most but must be used judicously. Use it heavy handed and you will melt holes and crate warps, and make messes. Used right and it is a huge time saver and lets you arrive at a much higher quality finish.
Lastly you need some kind of a soft surface to rub the film to the surface. I use a monocote glove most of the time, that is what is in the pic, but I also usually have a terry cloth washcloth available as well. Sometimes something thinner works better.
Also notice the irons are not on the worktop surface, but on holders. This keeps them from bleeding heat to the work top and increases their life. Also do not neglect the towel to work on. No mater how clean you have the surface, there will be stuff on it that can cause a divot in soft (and even hard) blasa. Foam under it is even better. But don't do this on your glass surface. You are going to need access to it as you work.
bob branch
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No step has helped me more to get a really nice finish than when I finally gave up trying to cover an entire surface with one piece of film and started doing the tips and curved surfaces with separate pieces. First I am going to do the show the inside tip of the elevator. I have cut a narrow piece of film that will give me about 1/8 to 1/4 inch of coverage past the edge of the end after being wrapped around the tip. This doesn't have to be precise. Iron it to the very end first, if its a curved surface like the outboard tip, iron it along the center line of the wing first. The iron temp should be the adhering temp for the film. Its on the directions. If a range is given use the middle to upper end of the range but stay away from the shrinking temp at this point. You just want to adhere it.
Where you have a corner, cut a relief slit on teh excess that will overlap the top and bottom surface as I have for the hinge line bevel. When you have a round surface to go around like at the back of the elevator's inboard end, cut slits top and bottom to allow the film to not bunch up or crinkle onto itself when you iron down the surfaces.
bob branch
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The sequence of the next step is variable depending on if you are doing a glow powered model or an electric. With electrics it does not matter. With glow power it does. The concern is fuel getting under the seams of the film. Think of the direction of the exhaust oils coming from the motor and passing over the plane. You do not want the oil to be blown into a seam. You want it to pass over the seam. Thus IF YOU ARE DOING A GLOW POWERED PLANE: :o Cover from back to front and bottom to top! This places each succeeding seam on top of the one behind it. Oil passing over the plane will flow from top to bottom due to gravity. Cover the bottom first, then the sides, then the top so the seams are not open to oil going over them. Its just like shingles on your house. I am doing an electric here so it makes no difference. All my excess electrons are scavenged before they reach any seams LL~. The photos show me sealing down seams from front to back of the elevator... fine for electric but not for glow. For glow this sequence would be done back to front so each seam overlapped the one behind it. Nuff said. Just think of the shingles on the house and you will usually be ok. Before someone mentions it yes, wind flow could conceivably blow a seam open. So nothing wrong with always following the glo protocol. But these seams are going to be covered with an overlapping piece so I'm not concerned at all.
In the photos I sealed down in the following order: the hinge line bevel, the straight section of the tip, the round section of the tip one segment at a time. The segment cuts are about 1/4 inch apart in this curved section. If its not close enough and you see a wrinkle is going to form just make another slit. Iron motion is from the tip rolling over onto the upper or lower surface as the case may be . The rolling movement from the previously adhered tip to the surface prevents bubble entrapment.
Once the entire surface is ironed down flip it over and do the other side. This has all been done at attachment temp, 225 degrees in my case with Ultracote. If you look at the 3rd pic you will see that after the overlaping was done there are some ridges and wrinkles we would like to see go away. Now I change to an iron at shrinking temp. I have my trim iron set at 300 degrees and went over these now letting the heat shrink the film and eliminate the wrinkles. It also flattens the overlaps. Once the top and bottom sheets of film are applied they will disappear.
bob branch
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Next I'll cover each hinge pocket. These are done separately and I use just one piece of film for each. I am going to overlap the top and bottom, the sides of the pocket, and the bevel beyond the pocket. I'm not concerned about the little gaps we will see form after making slits at the corners becaue the top and bottom sheets of film will overlap and cover them. This work is all done with a trim iron and at adhesion temperature.
First I apply the film along the back of the pocket. Then I adhere to the sides of the pocket. This is followed by cutting a slit above and below at the corner of the pocket so the film can be folded back onto the adjacent surfaces without a crease or bubble.
Lastly, I cut the hinge slit and then take the end of the trim iron and seal that down inside the slit. This essentially just makes an opening that the glue that will hold the hinge in place can pass through into the slot in the wood rather than having the film scrape it off as I insert the hinge. I'm not concerned about esthetics here cause the hinge is going to hide it all.
Well, I'm now off to spend the afternoon covering tips and hinge pockets. When I get to the wing tips I will return. They will be done the same way essentially, with the end being covered first. But I will be using the heat gun rather than slits there because with the big surfaces I do not want slits to show up at the big rounded tips of this plane at all.
bob branch
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To prepare the elevator to receive the top and bottom sheets of film I next go around and with a blade trim the overhanging film to an even amount of overlap. This is more important in light colors or transparent than dark colors. Oddly enough dark colors don't show what is under as dramatically as in paint. But an even appearance just makes the end result look neater.
Before applying the covering I take the tac cloth to the surface again. Been handling this a long time now. Left the shop a few times. Needs to be done. Also I went over my workboard and got any excess pieces of covering off so they don't get trapped under the covering.
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There is one precaution you should take to keep one particular type of glitch from your finish with films. There is a crease you can get in them that is the dickens to get out. Oddly enough it comes from taking the backing off the film! To prevent this hard crease from happening, never peal the film from the backing paper. Always peal the backing paper from the film. And if possible peal it perpendicular to the direction it came off the roll from. This prevents a crease from forming in the film. I always set the film shinny side down on the board, then peal the paper backing (or clear backing if you are using monocote. (Note its hard to separate monocote from the backing. To get it started use blue masking tape. Apply a few inches to the film on one side and directly opposite it to the plastic backing on the other side with the tape extending past the edge of the films. Pull the tapes apart and the backing will stick to the tape and the monocote will stick to the tape and they will come apart). Oh, ignore the already covered elevator in this pic. I forgot this pic until I had already covered one side. We'll get there though.
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Now we are going to get limited by my working alone and I am going to have a little trouble showing what I do so I will explain it and show pics of the end of the steps.
1. Always cover the bottom first. You want the last overlap on the bottom so it does not show, thus the top should be covered last so the seam is on the bottom. No, you do not want seams along an edge! They will separate.
2. This step I do differently than the videos on covering show. Just works better for me. Your milage may vary. I apply one straight edge first. I tack it in the middle then stick it down along a center line from the first tack continuously all the way to an end. I then come back to the center tack and stick it down all the way to the other end. Most videos show tac points a few inches or half a span apart. This causes additional creases for me that are tough to get out. On the elevator the leading edge along the hinge bevel is my longest straight line so that is the edge I do first. I have cut the film to overlap at least an inch in all directions from the surface to be covered and I do not want to try to create a straight edge with the end of the covering along the edge. I want it to overlap the edge. In this case the tip of the bevel is an inch inside the edge of the film? Clear as mud?
3. I next go to the longest edge opposite the first one I laid down. In this case the trailing edge. I start in the middle here and pull it tight over the trailing edge and down towards the opposite side and tack it in the middle. Then I work towards an end, inboard or outboard and seal down that edge continuously to the end. I am always pulling the film tight. When I am doing this I try to get as much surface tacked as possible. On the bevel I sealed the entire bevel surface. Here on the trailing edge I am rolling the iron (adhesion settings please) over the edge as I go so I get the entire rounded trailing edge sealed down. Once I get to an end I go back to the middle and seal down to the other end.
4. All of this I have done with the full size iron at the adhesion setting. New we change gears and go to a shrink setting. Ultracote shrinks from about 275 to 350 degrees. I'm at 300 degrees on my trim iron. I am using the trim iron on the elevator tips cause they are so small. When I get to the main wing tip you can use either the full size iron or the heat gun for this step. I use the gun but my building partner and teacher Jerry Lelacher uses an iron. Just whichever works better in your hand. The idea is to pull tightly over the curved surface (and its a compound curve here) and apply the heat just about where the film contacts the surface. You start from pulling in line with the surface and then deflecting over it. As heat is applied the film will stretch and adhere at the same time. On the elevator tip I used the iron like a pencil and just apply the heat to the tanget area of the film touching the wood. I move the iron slowly letting the film adapt to the curve all the while pulling firmly around the curve. I'll usually go from one end to the other then back and over the curve a little further til I have gone just past half way around the curve. Then I will cut off the excess and seal the edge to the wood. Try not to have the edge on the center line. Continue past it so it does not show.
5. The photos may shock you. This is as tight as I have the surface. Its about as tight as I could get it due to the flex. There are some wrinkles left, right? Yup! Big ones too. It is one of the nice things about ultracote as you will see. It shrinks A LOT!
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Trim the edges beyond the center line all the way around and then apply the film to the other side. DO NOT SHRINK IT YET!!! Just as with silkspan or any other covering if you shrink one side at a time you will create a warp. When both sides are covered then shrink a portion of one side then go to the other side and shrink a portion of that side then go back to the first side and shrink a little further along and repeat til you get to a tip. This way you minimize warps, just like with doping silkspan.
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OK, how bout some ugliness? This is what happens if you get film too hot too soon. I had my large iron on a high temp rather than adhesion temp when I went to adhere down the inboard tip here and the iron slipped and hit the film. Disaster, got to start over, right? Not if you are using ultracote. Monocote and this would be a problem you would probably not recover from without stripping. Stay tuned.....
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My tool of choice for shrinking is the heat gun. You can also use an iron. If you use a bare iron you will scratch the film. Ugliness. So you use a sock of some type over the iron. Now we have a problem getting accurate temperatures. When the film is hot it needs to be pressed down onto the wood to get it to adhere ... or else delaminations and bubbles. But when you use the iron to do this it dents the wood very easily. The lighter the wood (ie us) the easier it dents. More ugliness. The alternative is the heat gun to create the heat to shrink and activate the adhesive and a soft cloth of some type to press it onto the wood without denting it. A soft washcloth folded over several times works well as does the monocote soft glove I'm showing here. For me its a little easier to control but either works well. The trick comes I hate to say from just practice and experience S?P but I'll try to share what I see and I think I have some photos that should make it somewhat clear.
First the gun must have a heat defuser on it. That is the fan shapped thing at the exhaust end. Otherwise the heat will come out too concentrated and you will have very high local temps and melt the film.
The temperature of the gun is controlled on its intake end by opening or closing the vents. I usually close mine about half way which is about as far as they close, but again I have had some experience. If its going to slow for you then close the vents til you get a good result. The other way you control heat is by how close you apply the exhaust end of the gun to the film. Closer to the surface is hotter, further away is colder. And THIS is the biggest and quickest control you have. It the one to learn to use as your primary control as you work.
You are going to apply the heat in small areas, about the width of the defuser so about 2 or 3 inches at a time moving across the span or from leading edge to trailing edge. Use a brushing stroke and start with the gun 4 inches or so off the surface. Nothing much will happen there but just use a brushing back and forth motion and slowly move closer to the surface until you just see it start to shrink. Don't go any closer and brush back and forth til the film shrinks and the wrinkles in that area are gone. I stopped and took a picture of that point so you can see what you are looking for.
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You can see by looking at the pic there is no wood showing in the shrunken area of film. It is shrunk, it is not attached to the wood. You would not stop here, I did to take the picture. The film at this point is hot and you immediately rub it down using the soft cloth or soft glove to adhere the film to the wood. If you do not do this step the film will look smooth, but it will not be adding anything to the strength of the model. A model will be immensly stronger with film applied and adhered down. Additionally if you do not adhere it down it risks being pulled off by air pressure. Just rub the film back and forth onto the wood for a few strokes. You will see the wood when it had adhered. Notice also in the picture how localized the heat is. It has only shrunken the area under the defuser's flow. I will usually do two passes then flip to the other side and shrink and adhere the directly opposite surface before moving on. This prevents warps because you are shrinking the two sides together. Check as you go to be sure everything is staying straight.
If you have a residual wrinkle like at the inboard leading edge corner above after you have rubbed it down, just apply some more heat in that area and rub it down. It will go away.
Oh I neglected to mention when you trim all the edges be sure to trim them so the overlap is on the bottom of the center lines so they do not show on the top and they do not show on the center where reflections most often occur.
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Anybody catch it? ???
That last picture is the same area of extreme ugliness that I showed in post # 64 three posts back where the hot iron got onto the film too early #^. Add that to the amount of shrink you have seen and you can start to get a picture of why so many rc builders prefer ultracote and why the top premium arf's all come covered with it. The amount of shrink I have shown is about 300 degrees. There is still over 50 degrees or roughly one half of the shrink capability remaining in the material. If I get some blisters in the sun I can accomodate them. I usually go over all my planes in late winter, usually around the end of February here in Michigan when our humidities are the lowest of the year and the wood has shrunken to its driest and shrink out any blisters or bubbles that have formed. When the wood swells from humidity in the spring I rarely see any form in the sun. Some still will, but that is part of the compromise you have with films of any type. Some do it more (monocote) some do it less (ultracote).
So now I am on to covering the rest of the plane. It will all be in black to start. When I get to the fuselage I will return and go thru the sequence I use to cover it and the same with the wing. I'll be back and post pics when I get there. Yea, I do wish I could fly it tomarrow as i could if it was an arf. But I have the E-Strega and my rc electrics that I'll fly tomarrow. The wind is supposed to drop... finally!!!!!!!
bob branch
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GREAT THREAD! In hindsight this part of the build ought to be in the Finishing forum - there is as much great info here as in any of the painting posts.
Bet you are happy to be past the sanding stage! :X
That Ultracote has an amazing amount of shrink available. I have not (yet) tried Ultracote but it will definitiely be on the list for the NEXT round of projects. ...
Don't know what your weather is like on the Island but here in mid-MI it's been good weather for buidling and covering.... :P
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GREAT THREAD! In hindsight this part of the build ought to be in the Finishing forum - there is as much great info here as in any of the painting posts.
Bet you are happy to be past the sanding stage! :X
That Ultracote has an amazing amount of shrink available. I have not (yet) tried Ultracote but it will definitiely be on the list for the NEXT round of projects. ...
Don't know what your weather is like on the Island but here in mid-MI it's been good weather for buidling and covering.... :P
Yeah, I agree. Great thread.
My building season has already begun on my next electric ship.
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Thanks Christ and Dennis. Yea I thought about it being in the finishing area but I thought the continuity deserved to have in in electric.
Actually, the temp is mid 50's this morning, winds under 5, I'm going flying! Got an e-smoothie to retrim and a strega to see about a cut down prop with.
bob
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On to the fuselage. One thing you will find if you do much covering is there will be days when one method works better than another in your hands. And there will be times when you will try one method and are not happy with the result doing something one way and will want to redo it in another. Just take the heat gun, add some heat and lift off what you don't like and redo it. Don't pull it up without heating though or you will tear wood and leave adhesive behind and then have a mess to deal with.
I'm going to move on to covering the cowl and belly pan vents to demonstrate this. Some of these photos you will notice will be a tad out of sequence but when I got an out of focus picture or found a better one later to illustrate a point I used pics out of sequence. First I'm going to show a fairly common method you would use on a vent or cowl with a round opening to cover the round. I did not like the result I got in this case and tried 2 other ways unitil on the third I got what I wanted. Maybe cost me an hour in total time start to finish and once I found the method that worked best on my contours it was fast to finish up the other 4 vent openings the same way. Think of how much time it takes to lay dope down silkspan in the same location.
First I tried to cover the section all in one piece and then cut the openings out and use cores or slits around the curves to get the shape covered. I did not like the results as you will see, but its a way that often works, just not for me here on this day. Since I'm going to go into the covering of the belly pan in detail a little further along I'll just start with it covered with a single piece of film and then show the cutout and the slits made in the covering. I then used the trim iron to iron these down. Notice I had wood showing thru. Not what I wanted. I did go back and apply dope and it hid it and it would be acceptable, but I wanted something better for this model. As always though, its your inidividual decision how far you are going to go on a finish, film, dope, or whatever finish you use. I'm just trying to show some different methods here. This method often works well with a smaller radius like on a cylinder head opening in a cowl ... the small radius corners. The gores wind up overlapping on the inside and no space shows between them... you'll see this on the section on covering the belly pan when I get there.
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After looking at the result with the black dope to cover the slits I decided to try applying a thin tape of film on edge along the inside of the vent opening, and then ironing it down over the curved lip to cover the slits. Method number one was quick and dirty. Method # 2 was try to fix quick and dirty. I wound up with creases and wrinkles I could not make go away. So heat gun out and do it the way I should have in the first place.
Most often when you have an edge the best result will come when you use seperate pieces of film to cover the edge first then apply the overlying section of film. Much as I did on the hinge pockets previously. So here I am laying down 4 separate sections of film cut in rectangular shapes along the edges of the opening and overlapping the opening by about 1/4 inch. The pic shows where the various pieces will go.
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Then I make a single cut at the beginning of the radius (blue arrow in pic #2) so that there will not be a crease where the radius begins.
As an aside I found in the pics of this sequence excellent examples of how to tell if you blade is sharp enough. In the first pic the line points to a very sharp line cut. The blade is sharp enough. In the second picture the line without the arrow indicates a ragged cut. The blade is too dull. Stop immediately and replace the blade. These are the best pics I have ever gotten to show this so that is why I interjected them here.
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No I am going to use the iron in a different way. I will be using the trim iron and since I am doing a curve I will match the contour of the iron to the curve. I'm using the trim iron here and have outlined the curve of the iron since the contrast was poor. Also I am not going to just adhere the film here but I want to shrink it around the curve as well. I am going to turn the heat up to about 350 degrees here. Yes, going to max shrink to do this. I apply the iron and at angle to the curve that is sanded on the opening of the vent (i.e. the opening is rounded in cross section, not just a sqare cut opening) and roll it from the center to the sides of the curve in a slow sweeping motion letting the heat do the work. The film adapts to the curve and adheres to the wood. Lastly a pass down the straight section on normal adhesion temp and this is the result in the second picture. I'll go back over any irregularities with high heat until they disappear and the vent is done.
bob branch
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Now to cover the rest of the belly pan with the vent edges done I use a single piece of ultracote and adhere it first just along the center line of the bottom of the belly pan about 1/4 inch wide. I just want to secure it from moving and gain something to pull against (pic 1.. shows the middle where I ironed it down. Next (pic 2) I went to the middle of the edge and pulled the film down tightly to the edge of the pan and adhere it along that edge, but on the outside of the pan, not trying to go around the edge.
The third pic shows how the edge is secured around the curved cutout of the airfoil of the wing. Slits are cut perpendicular to the edge and the film folded over with the iron and ironed down to the edge.
The fourth pic shows the same thing done on the ends but this time on a convex rather than concave contour. These are all ironed down well with the long excess still attached. Lastly I pull out the heat gun (or you can use a socked iron at about 275 to 300 degrees) to shrink the film down and then when it still hot immediately rub it down with your covering glove or soft towel to adhere it to the wood. Finally the excess is cut off AFTER all the shrinking is done. Its a good idea to go over the wrapped around edge with the heat gun on adhesion temp again before cutting. I usually use a blade and leave about 1/16 inch wrapped over the edge to help hold it, especially against any reshrinking I might do in the future.
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In this sequence I will show the covering of the nose ring of the open front cowl. Again I am at liberty and using it here since I am doing an electric and have no fuel entry issue. Were this a glow powered plane I would have covered the bottom of the cowl first THEN applied the nose ring area so any fuel passage going aft would be over and not into a seam.
For the cowl nose I first applied the outside then the inside. First I adhered the back edge of the section of film that would do the piece in one section of film. (pic 1)
The Starting at the center line (pic 2) I pulled straight down over the lip applying heat with the heat gun going towards the nose, all the time pulling down and around into the opening of nose so the material is stretched around the lip of the cowl at the same time it is shrinking around the outside.
Finally (pic 3) I move lateral to the first area and repeat til I get all the way around the cowl. You can probably see this is the same way you do the compound curve of a wing tip. I then trimmed the excess and applied a strip on the inside of the nose opening about an inch wide to present a smooth appearance inside the nose opening. But I'm not interested in going all the way to the back of the nose block. Just my choice. I've blacked it out and its not visible in the end. If it turns out to present otherwise, I'll come back and add to the area with another piece. This inside piece is then trimmed and sealed to the outside piece with just a small amount of overlap.
Well, that's all for now.
bob branch y1
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Oh, just in case anyone thinks I would be so cruel as to allow my pilot to suffer a broken neck on a hard corner.... LL~
bob
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The fuselage is covered in sections. Sequence wise I find it looks neatest if done as you would for a glow model: bottom first, then sides, then top. If its a glow plane this prevents oil from being drawn by gravity into the seams. You want to apply one section, sealing the edges first, all the way around. I usually go along one long edge, heat that down, then do the opposite edge Pulling as tightly as I can across the film so the wrinkles are minimized. However, I will not get them all out and am not trying to. The heat will do that. If you do not seal and edge down and then apply heat that edge will curve into a convex contour and the film on the very edge will roll up. You will not hide it. Pull it off and recover it.
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To cover an access opening like an elevator control horn hatch, or the hatch over the tail gear wire, place the hatch part on before you cover the plane. Don't glue it, just set it on and cover over it. When you are all done with that section then cut along the seam cutting closest to the hatch itself so you will have a tad of film to roll over the fuse surface edge of the hatch. If you do not come out with enough you will have to cut a thin strip and apply it to keep the wood from showing thru the seam.
This often winds up requiring you to remove the film from the hatch itself and recovering it. The real purpose of covering with the hatch on was to keep the film on the surrounding sheeting at normal contours. Otherwise it will dip into the opening and you may not have the contour you want. It can work both ways. On the T-Rex I did the cover then remove hatch and recover the hatch method. Why? So I could show you what it looks like if you remove film without using heat!
The first pic shows the two elevator hatches. The top one I have left covered after cutting it free from the covered fuse side. You can see it is a nice smooth surface. (btw, the close up pics are all with a macro lense so its pretty magnified, my eye cannot see the level of detail in many of these pics). The bottom hatch has had the covering removed without applying heat to soften the film adhesive and then recovered. You can see the difference. When you pull film off without heating you will see wood fibers have been torn off the wood and adhere to the adhesive side of the film. The bottom one lets you see just how much damage is done. Not to worry, you just have to remove the film (with heat of course) sand it, then recover. That's what I'll be doing but this was such a nice place to show it that I thought I would (also small and easy to fix).
The next pic shows the opening with the film rolled around the edges of the fuse side. I usually do not put any on the underlying surface unless after I get it all assembled I see wood through the seam, then I will lay a small band of covering over the landing surface of the underlying hatch support if there is any. The film should also just wrap around the hatch itself when you cover it. Oh, always label the parts on the inside. Once in a while you may do a really good job of cutting the parts out and preping them the same and not be able to tell which is which. I'm not that good a builder so it doesn't often mater, but in the world of laser cut parts you can never be too cautious.
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Finally the fuselage is covered. Once the edges have been sealed down, just shrink the material with heat and rubbing it down as before. Start in the middle of a section and work towards the ends.
The next step will be to do the trim. I do not iron trim on initially. I place it by the windex method. The only material you can reliably do this with is monocote. It can go over any other film. But it must be monocote. Only their adhesive works. It does not work with ultracote as the trim. And you can do this with adhesive trim sheets as well as film. Cut your trim piece... use templates... but you already know that. Tack cloth the surface before the next step! Spray the surface the trim is going to be applied to with windex... liberally. The windex somehow activates the adhesive and allows it to bond to the underlying film without heat. Do not use a fine mist of windex, get it wet! You will be able to position the trim piece on the windex covered surface for quite a while. When you are satisfied, squeege the excess windex from under the trim with a credit card moving towards the edges. In some places, usually over a rib or other quick contour change it will seem to not want to stick. Have patience and just keep squeegeeing ... in a few minutes it will stick. But pretty much everywhere it will stick right away. Be sure all the bubbles are removed. They will all come out. That is part of the beauty of this method. Finally wipe off the excess windex, then let it dry... for 24 hours! Don't rush it.
Once it is dry you take a bottle of monocote solvent. READ THE DIRECTIONS! You will apply it along all the trim edges with a cotton swab and it will flow under the edge permanently sealing it down. Once you it has set there a bit and before it evaporates off rub the excess off with a soft towl or cotton gauze. You will notice it polishes off leaving the films with a nice soft patina with a high shine. If you leave it on it til it evaporates it is the devil to get off. I'd recommending using monocote solvent to get it off if you do this. Its easy to work with though and the trims will not lift up so do not worry about it.
Now the debatable point. I have done it both ways and had both work fine. Do you heat the trim down or not. Most people do not. I do not if everything stays looking the way I want. But I have seen times when I start to see some seperation or I think more often it is from the monocote never having been shrunk at all it starts to react differently to humidity changes from the underlying film that has been shrunk. I have taken recently to waiting another day or two after the solvent has dried and then using a socked covering iron set on low heat, about 225 to 250 degrees... remember the ultracote has already been shrink to that temp or higher) and adhereing the monocote with some heat. If I am seeing wrinkles in the monocote trim I'll up the heat til they go away but just a bit at a time. Its really just a mater of understanding the films and responding to what they do.
In these pics I have applied a checkerboard trim strip to my T-Rex fuselage after it has been completely covered.
Next I'll cover the wings.
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WOW You changed up! I was expecting black & white just like the Strega - that checkerboard stripe is HOT! This is a great build thread - and I'm predicting this will be the BEST looking T-Rex out there.
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Dennis
Thank you for the compliment. I think the design Brad came out with on the arf is stunning. But I want to be able to get appearance points so I have to do something different. Besides, no way I would put myself in the class with the folks that cover arf's. They are after all professionals and it shows if you try to duplicate their work. I've learned no to. Still, there are different ways to see things. The wings will have some of the Strega's themes, but I am trying to use the checkerboard theme there as well. We'll see if it works or not. If not, one of the nice things with film is you just heat and peel and change what you want. No huge amounts of sanding go by the boards. No weight gain either. It does require more maintenance than a paint finish of course because you have to keep it up. But like everything there are tradeoffs. I trade off time for a result I know I am going to be satisfied with. Sometimes I'm satisfied with a paint finish, sometimes I'm not. But as in painting, you don't get a perfect job the first time. It takes time and patience. I think lots of times people think you just go ironing on film and get a good job and then they are disappointed with the results. The nose ring on this thing took me 6 attempts to get satisfied with. But I knew it was going to be tough when I saw it. Anyone who covers one and then looks at the arf will gain a lot of respect for the workers skill level.
bob branch
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Make that 7 attempts on the nose and I've already stripped the front fuse checkerboards twice looking for something that I like. May be getting close. Will share it when I get there.
bob branch
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Another nice feature of film covering is that if you decide your design just does not work on the plane you can easily change it after you have seen it in full scale. I had drawn the design I had on teh nose but it just did not look good on the plane when I covered it. The checkerboard arms just looked bulky and did not seem to work with the the shape of the nose of the plane. So off it came in search of a better look.
This is what I settled on. I blunted the checkerboard at the nose to match the contour of the nose. Then I used 3M metalic silver auto pin stripping tape in metallic silver to outline the checkerboard with a black line between them and a red to create an outline stripe over and under the nose and run the length of the fuse outside the silver. Three very nice features to this material. It takes a very tight bend without a wrinkle or lift off and it allows repositioning easily when it comes off the roll. 24 hours later it really stays stuck! Third, its cheap and easily available online at auto paint suppliers and local paint sopes as well. Add to that a huge range of sizes, colors, finishes, and combinations of stripes.
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This thing just keeps looking better. I thought I liked the original stripe but I agree this one looks better. This is turning out to be... the T-REX of the T-Rexes.
Keep it going, gotta see this one in the air soon!
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This thread is insanely good... y1
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Brad
Some might put the emphasis on insane. But then, we are all among friends right? Regardless of paint or film, we all have to be a bit..... well, anyway.
Its time to start the wing. As with the elevators, anywhere you can dovewr an edge so you do not have to rely on using teh top or bottom sheet of film to cover a surface do it. I'll start with the wing tip cause that is where you should start any wing. The T-Rex has a wing tip that has 2 for and aft ribs and a very thick and blunt rounded tip. Think of making a solid wing block and then instead of hollowing it out, just cut it out instead. The big blunt end should be covered separately from the wing itself. Resist the temptation to do it all in one piece. I know. You won't. I didn't for years. And I felt I was getting pretty good at it, but this is one of the things that really helps the total end result. I thought this big blunt tip would be easier to cover than a thinner one, but it turned out it was quite a challenge.
In the first pic I have tacked on the setion of film that will cover the blunt portion of the tip. But I am not going to try to do the entire tip with it. I decided that after tacking it on and seeing what was going to happen to the contours of the film. So I went back and first covered teh trailing edge and the aft 30 % of the wing tip. These in separate pieces. Then In the second pic we see that done and the end piece again tacked onto the wing tip just along the very outside edge of the tip... along the wing center line.
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Opps! sorry, didn't get pic #1 uploaded. ~^ Try again, but now of course out of order.
bob
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To start forming the film over the wing tip you pull the film over the area to be shaped to and apply the heat on the film where you want it to stretch. You can use your fingers to hold the film, but while they would match the color of the plane nicely, I noted that white pants and color matching outfits to your plane seems to have become passe in stunt, so I opted to use a hemostat instead. Since I attached the film along the cord line of the wing tip I am pulling the film up and then towards the wing as the first pic shows. The second pic shows the heat gun and the angle I apply it to the film (see why the hemos work better?... oh, be careful, the tips of those things get really hot. HB~>) Pic 3 shows the covering adapted to the wing tip and it was then trimmed and you see the final surface in the last pic. The sheet of film that will actually cover the wing itself will just be attached to this tip covering for about 1/4 inch and then trimmed off. The wingtip remains nice and smooth. It is after all where all of you look anyway, right?
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Now we can almost start to cover the wing but there is one more surface to precover, the edge against the fuselage to wing joint. You can just adhere the film down to the sheeting here. But you will find it is very difficult to get good adhesion. When you go to shrink the film it will pull away some and leave a non straight edge. Oh, that is one of the little things you have to learn to account for. No mater how well you think you have film ironed down, if you put enough heat to it to shrink the film, the seam will move. That can really be a bummer if your seam opens up or your line of demarcation of colors bends. Lest you think RC guys can't build, go to the Toledo show or a similar level show and look at the planes being judged. 1/8 and 1/16th inch overlaps of edges with no lifting and no migrating of the edges. God bless them.... fact may be God actually building the things for all I know, as for me, I ain't that good yet. So I plan it and arrange to cover it. I am placing a strip of film about 3/4 inch wide on the wing center sheeting where the covering sheet will attach. Its the same color as the wing sheeting. I can get it down smoothly without any shrinking to speak of and be sure I have a good attach to the sheeting. The wing cover sheet of film will not have to be perfectly aligned with the fuse which of course tapers so will not be straight with anything on the wing anyway, but I have enough edges to worry about, I can eliminate one with this simple step and its invisable when you are done.
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I am going to cover the bottom of the wing first, then the top. I am not going to shrink the covering until both sides are covered, except for the wing tips which will just help me avoid a mess of the top and bottom film sheets attaching to each other as we will see and spoil those nice wing tips I worked so hard to cover and Brad and the folks at Brodak worked so hard to create. Nice shaping job guys. Rather ye than me!
I attached the film fist at the leading edge inboard corner and the trailing edge tip where the trailing edge notches for the flap. That's the widest point and secures the film so it will not move. Next was that edge over the fuselage strip. Then I went down the leading edge, the top of the wingtip covering I had already done, then notched the film at the flap notch and bent the film down to cover the trailing edge. Yes, I know it is already covered. Are you a glow flier? That's two layers of adhesive to keep out the oil. Guess what? Its gonna get a third... as will most of the leading edge!
Then I trimmed the excess. You of course noted without me saying that I tack clothed the plane just before applying the film to each section? Of course you did! Murphy's law of film covering. The one spec of dust under the film it WILL be on a sheeted surface on the top of the wing. Sorry, its the law. On the bottom sheet of film I trimmed it along the center line of the leading edge. Next the top sheet of film is applied and I overlap the bottom sheet about half an inch. This way the seam is not visible from above, and the seam is protected from oil intrusion. The leading edge where the greatest amount of oil could blow in is covered with now two layers of film and two adhesive layers. The slipsteam air is blowing oil over and away from the seam, not into it. Overlap the leading edge by a small amount to your peril. But then you can gripe about an oil soaked film covered plane!
Notice on the pics where the film has not been shrunk yet the fingerprints, and splotches of dust, dirt, and who knows what else? Where does all that stuff come from? Not to worry. It'll get solved after its all shrunk.
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Once both sides are covered its time to start shrinking the film. Again, do a section of one side then flip it over and do the opposing section of the other side to avoid warps. I started at the wing tips. I do not shrink the open bay first, I do the leading edge first then the trailing edge, then the open bay. As i shrink (I use the heat gun remember) I immediately rub the area down onto the wood with my lambswool mit or you can use a soft cloth... don't let there even be a fragment of film adhering to the cloth or it will leave a mark! Because the ribs are so far apart on the T-rex I only did one bay at a time. I work to the center sheeting and do it last. Remember the inboard film is already attached to the underlying film.
I wish I could get a picture of it but I could not make a pic of the shrinkage and pull of the film edge show up well. It will look like a bit of a foggy edge where the adhesive is still attached to the underlying film. Usually its about 1/16 in or less and you will only see it on film. This will attract dirt forever if you do no get it off. The way to do it is the same way you get off all those fingerprints and crud before moving on to trim... Monocote solvent. Sorry, I know of no other product that works. It really cleans things up and gives you very nice clean edges that will not attract dirt. You must treat it kind of like way but without the time for it to dry and haze off. I put it on with a gauze and immediately take a soft paper towel and start buffing it in a circular motion just like I'd remove hazed over wax off a car. It will haze over while you are buffing and then leave a nice soft shine on the film and be totally free of steaks and oil and crud of any type. You will never get the surface as clean with soap and water. Can't use it for general cleaning as will become evident further on in the thread but its wonderful here.
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I am going to create a white leading edge band with curved edges on the ends. It will become the base for further trim. First I cut out the pattern. The top and bottom will be all done in one piece. To center the piece on the leading edge of the wing I fold it in half and crease the end edge so I have a center line. This will be more clear when I place it. pic 1
As an aside, and cause no one showed me, I had to find it buried on RCU somewhere, I'll demonstrate how to separate monocote from its clear plastic backing. Ultracote has a white paper backing and it separates readily. Not so monocote. I have fought with the cut edges with a scalpel and all maner of things til I found this. Apply a piece of blue mask tape (fresh) to the film side and the backing side, exactly opposite each other but do not let them touch (pic 2). Pull the two pieces of tape apart (pic 3) and the backing comes right off the film. ... you're welcome.
Pic 4 shows the white trim centered on the leading edge center line and I have lightly tacked it to the center line of the leading edge with heat along its entire length. The two creases at each end provide my reference.
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The trim film is then rolled back and the wing surface sprayed with Windex. ... Liberally. Squeegee the liquid out with a credit card and keep doing it til it all lies flat and stays down. Repeat on the other side and let it sit still for 24 hours to dry.
to be continued. H^^
bob branch
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Somehow I knew the Windex bottle was coming out again ;D
I can see using WIndex on narrow pieces like stripes, bu can you truly get a piece that large to lay flat? Seems that if there was the slightest 3D curvature or discontinuity in the shape that you would have to shrink to fit. Instead are you literally appeal to pull/stretch the piece into place while it is cold & windexed?
I use Windex under things like stars & bars insignias if the surface is something like the droop betwen the wing ribs it is near impossible to rub it down enough to get it to lay down,
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Dennis
You mean like this? This is the lettering on the E-Strega wing. It goes over the ribs. It was put down with the windex method as well without heat. You just keep rubbing with the credit card and it will eventually lay down when you have all the windex squeegeed out. You may think its not going to happen but with patience it will. Sometimes might take 5 or ten minutes of rubbing on one spot.
bob
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Dennis, sorry the ribs did not show on the previous pic. Having seen the plane you know that its all film covered and not sheeted as it looks in the pic. At this point the windex had just dried and it had not been cleaned yet... had to wait the 24 hours and that is why the flat nonreflective surface.
Finally coming back to the theme on the fuselage I wound up with this as the wing final scheme. The lettering will I think be metallic silver again cut from monocote and applied with the windex method. I plan on a similar theme on the horizontal stab. The rudder scheme I have yet to work out.
bob branch
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Wing and fuse together.
bob branch
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Bob,
I was wondering if you work for Ralston-Purina? LL~
Plane looks nice---really!
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Alan
Do you think Brad might take offense if I called it "Dog Food" ?
LL~
bob
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It's funny, but only after I posted my comment did that thought cross my mind! >:D
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I am including this pic so that those of you who are finishing a wing tip to a cord centerline can see how it is done. It is certainly another way to do it. I still recommend finishing the end separately first as I have done. The key is to pull the film down over the wing tip. You want to adhere the film to the entire wing all the way around and do the tip area last. I decided to do this tip this way so you could see it and the leadout guide kinda makes it easier anyway, depending on the shape.
I have grabbed the film with the hemo and start in the middle, work to the trailing edge, then came back to the middle and worked to the leading edge. You need to pull down very tight to stretch the film as it shrinks. I know it sounds like a contradiction in terms, but its really what is happening and when you do it you can see it quite clearly. If you want to practice do the edge of your workbench. The heat is applied inboard of the edge over the area you want to shrink. Do just small areas at a time. If you start to get too much wrinkling on the attached surface you are grabbing too far apart. On the leading edge area you may grab it every 1/4 inch, pull, heat and pull over and around the surface. When you get it to this state in the pic you notice its all smooth to the cord center line. Now its ready to be trimmed off. But do not cut into the wood! Rather, peel the film up just a bit so the smooth area about 1/16 in is pulled loose. Cut it with the blade vertically slicing just into the film and air in a curved arch that matches the shape of the tip. Your blade MUST BE SHARP! Always do this cut and a leading edge slice with a brand new blade or pay the price of a very visable seam. Once it trimmed take your iron on high temp, about 300 degrees for monocote or ultracote is fine, and move the iron down over the seam from attached surface to unattached surface. Because it has already been shrunk to the shape it will lay right down with no wrinkle and be nearly invisible. Wipe it clean with monocote solvent and you should be happy.
Next I'll cover the tail surfaces. I'll go all the way around the horizontal stab with edge trim, including the leading edge. This will again give 3 layers to protect the edge against oil or those slimey stray electrons I'm always wipping off my electrics....(just to bug my glow flying friends!). When I have the trim on I'll come back with photos of that and then show how to cover the vertical stab. The key there? Edge trim piece all the way around of course! But you knew that already.
bob branch
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Sometimes the eye will not be happy with something no mater what you think in the first place. Checkerboards are very busy to the eye. It can take some but as it turns out if you have too much it gets lost, it cannot find a focal point. I bounced my cover scheme around with a few folks and busy was not just my feeling but some others as well. After I had covered the white on the inboard wing I could see it very clearly. So again, nice thing about film is if you don't like it you can remove it. I removed the checkerboard from the wing. Now I had developed a focal point and it was not the checkerboard. The checkerboard now is a feature rather than the focus. Try to imagine the feeling you would have if this was in paint and you decided that!! Please don't get the idea I want to degrade those who work so well in paint. I think it is a whole nother skill set. But I find even when I paint, I have to see it to tell if I like it. Drawing or cad'ing it just will not do it for my eye. A limitation I guess. So see what you think. Obviously all the taping is not done yet on the horizontal stabs. Oh, and yes, I did not align the white edges with the fuse or airflow on purpose. Reason is I'm not that good yet. This is only the second plane I have done with this wing treatment and it kept me from doing a competitive plane in film for a good while. When I finally figured out I could do the white in one piece with the crease that opened the door. But I wanted to do a second one to see if there were any hidden bears I did not find the first time out (of course there were!). Next time I'll try doing the alignment, but it complicates things a lot.
bob branch
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Do you have an airbrush?
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Brad
I do but I hate the think. Why?
bob
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Fuse with Rudder and landing gear doors. Tomorrow I should be able to start assembly then clean up the details. First flight will be Monday at a practice session with Rick Sawicki, Frank Carlisle, and Arch Adamisin. Oh, we'll get to be the first to fly 2 electric stregas at the same time that day as well. Maybe we'll attach steamers and try square corner combat!
bob branch
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Head rest installed.
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Brad
I do but I hate the think. Why?
bob
Lightly spray the canopy with your favorite color. It will smoke it.
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Brad
Ahhhhhhhhh. I do that routinely on my rc planes. Just as an aside, candy apple red is really interesting! But I have a pilot here and he has to see where he is.... oh, no wrong, his head is turned and he's looking at the spectators (judges and pretty girls in particular...) In truth though I reglued the canopy on a few days ago and the pilot is now glued in so that is all pretty well fixed now. :'(
bob
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Bob,
Thanks for putting this build out there. I've decided to go for an E-T-Rex myself and have barely started it. Like yours, mine is also an ARC. I am just curious as to where you bought your pilot and Do they have others? I will not do a build thread on it as there are enough of them out here already and I will be pretty much mirroring yours anyway. I will post pictures of the finished product and ask questions when I need help.
Thanks,
William
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Bob,
Very informative thread! Thanks.
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William
The pilot is one of the Slimline Extreme Pilot series. They make a number of shall we say, "interesting" pilots. http://www.slimlineproducts.com/online_shop/xtreme_pilots.htm is their web site. I noticed that Tower has two more listed this morning that are not posted on the web site yet.
Glad to hear you are doing another electric one. I think there will be a lot of them in the future. Please send me a pic or post it here when you are done. I'd love to see it.
Christ
Thanks. I enjoyed talking with you at the Signal Seekers Contest in August. Your profile is one sweet flying bird.
btw, anyone noted what a sacraligous lot we electric fliers seem to be? Look at all the film covered airplanes! And they are looking pretty darn good! Even film covered I-beams! Talk about killing theories! Carrying around 7 to 12 ounces less weight in the finish is going to make electrics that much more difficult to compete against and a lot of us are getting pretty decent at it. Going to be tough when some of us get really good at it!
btw #2. Has anyone used gorilla glue for hinges as the T-Rex manual suggests? Results?
bob
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Thanks Bob,
I'll post a few finished pictures when done and only a build picture if I happen to make a significant change from something that you did.(I don't see that happening). I'll also email you some. If I get the importunity to make another DTW trip in the spring hopefully I will get to meet you and see yours fly. Thanks for the link.They have some very interesting looking pilots for sure.
William
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The remainder was just doing what you have already seen and repeating it.
One item I'll mention was the wing saddle area. When I was fitting my wing to the saddle and was testing stuff I noticed a fair amount of flex in the bottom sheeting of my center section. I was a little uncomfortable with this so I placed some 1/8 inch cross grain across the center section to about 2 inches behind the leading edge and 2 inches in front of the trailing edge. Basically the same thing done on the top of the wing. This eliminated the flex. I know the fuse is going to handle the loads, but with the belly pan being so large and a seperate piece I thought some other measures would make me feel more comfortable. I gluing the wing on I used the thin CA method to position it but then did a small fillet to fill in any areas of imperfect fit. Its as small as I could make it. I used the 30 minute epoxy and stuctural microfiber filler material by WEST System that I discussed earlier in the thread. I also used this mixture to glue the belly pan to the ply bulkheads at the front and rear of the wing compartment so it is now a solid structural member with the rest of the fuselage. When it was set I then used one of the wonders of covering in black film. .... black Brodak dope... to paint the fillet rather than try to cover the area. If you can cover a fillet, fabulous. Come here and show me how. You're a better man than I am.... and I'll admit it up front.
So the wing got joined to the fuse and came out nicely. I was so concerned with getting it to fit properly (as I always am cause I'm not good at this step in building) once I got it fitted I immediately glued it in. Then I got the fillet on so it would harden while I ate dinner. Unfortunately, while eating dinner and watching U of M get pummeled in football I realized I forgot to install the elevator pushrod. Well, I did not want you to think I'm some 'God's gift to building'. I'm willing to admit when I screw up and the bigger the screw up the more willing I am to admit it. So I cut a hatch (through the already covered fuse) behind the headrest area to gain access and installed the thing. Then reglued in the hatch and recovered it in film. As Charlie Brown would say..... "sigh"..... as we would say here HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~> HB~>
Finally it all got put together. I did use the gorilla glue method for hinging rather than epoxy just cause I hate digging out epoxy. I really like pacer hinge glue but was out and the last batch I got at the hobby shop was hard in the bottle. Apparently its so seldom sold you need to get it directly from Pacer which I usually do at the Toledo RC show. Actually, what I really like is (I know half of you will nuke the thread now) CA hinges. Say all you want, done right they are less restrictive than most dubro hinges and require less power to flex them, will just fall from the wieght of the control surface and never never pull out or fail. Yea, I know all the arguments but have found the CL arguments to be bogus in my hands. Your milage may differ. That's fine. But for a change the hinges that came with the kit from Brodak did not have any catches in any of them so I used them this time.
The Gorilla glue cleaned up real well.
The plane is now assembled and since the light was dying fast as it set here in Michigan I ran outside to my neighbors little area of bent grass in his lawn where I take my pictures and snapped a few that I'll post now. The only thing not done is the name and numbers. The name and style will be the same as on the Strega in the earlier pictures. It will be in silver on this plane. The Strega has yellow pinstipes on the canopy and turtle deck so the bright yellow fit in. Here it would be too much so I'm pulling the silver from the stripes. The method will be the same as I did on the Strega. I'll use monocote cut with a blade from a pattern from my printer in full size and then transfer it to the wings using the Windex method. Once the windex is dry (24 hours) I'll go over the edges with monocote solvent. I'll shadow the letters with the bright red pin stirpe I have used elsewhere and the bird will be done. I'll post pics when I get there too. But because I am flying it tomorrow the windex would not have its 24 hours to evaporate out and dry so the name and numbers will get applied afterwards.
Oh, I think we electirc fliers can be pretty excited about this bird. If you have noticed the weights coming in on the bird in glow ... mostly mid 60's without fuel of course, I have a suprise. Brad, better tell John to get more coming after I post this. My bird with battery is exactly 60 ouces with a 2200 mah 4 cell turnigy lightmax pack and the heavy ice 50 esc with the heat sink. With a 4 cell 3000 mah lightmax pack it is 63 ounces. Gang, we are now lighter than they are! No more back seat at all.
bob branch
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more pics
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One more pic. I'll post a flight report tomorrow evening if I can get the time. The indoor RC season starts Tuesday and I have to finish building a plane to fly.
I'm glad I was able to share this thread here. I hope its useful to some folks wether in the electric or building or covering areas. Be glad to answer any questions anyone has.
bob branch
Harsens Island, Michigan
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Outstanding Bob!
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FANTASTIC!!!!!!! Thanks so much for this thread. I know it will be helpful to me as I assemble mine.
William
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Bob,
Nice looking airplane. A 4S 2200mah pack for a 60 ounce airplane? I would think that the 3000mah pack would be what you'd need. Keep us posted.
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Hi Crist, Hi Bob,
I agree with you Crist.
I've have been using the same motor/prop combination that Bob has put into his T-Rex ..the AXI 2826/12 with APCE 12/6 in 4 different planes already over the past 5 years. I've kept some extensive records, shared with Bob, and with the above combination I have always been in the 1750 to 2100 usage range (depending on plane size, wind and temps ) on 4 cells. Use of 2200 cells to me is cutting it too tight. Bob and I have discussed this a few times already.
I know Bob is trying to fly it as light as possible but with the T-Rex area of 675 sq in. the plane will not feel the difference the 3000 size pack weighs. For comparision purposes, Bob's T-Rex area and weight fall very close to my 1964 "Trike" (stunt hanger topic about a month ago) that I refitted (from a Fox 35 ) with an AXI 2826/12 earlier this fall. That aircraft has an area of 670 and weights 61 oz with the electric conversion and 4 cell 3000's. The trike is averaging 2050 to 2100 usage for 5.5 minutes. Bobs plane will most likely fall in the same usage range. Unfortunately while 2200 cells might be light, I just don't think they will "cut it" on this size plane and a full pattern usage could jeoperdize battery longivity (if the plane even makes it thru!!).
As Bob mentioned, we plan on test flying it tomorrow so we will know more then...but if they were my batteries I would use larger packs than 2200 (the 3000) and I will suggest that to Bob once again tomorrow morning. I would hate to see Bob hurt his batteries (the 2200 packs).
Rick Sawicki
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Well, that is the beauty of the timer and running the short test run flights. You can see the actual draw on the entire pattern before having flown it. I have been seeing 1800 mah ave draws but on a slightly smaller plane. However, on a larger plane (67 oz) albeit thinner airfoil I was still in the low 1800 mah range. So we shall see. 1800 mah though is only 82% of the 2200 mah packs and if that is the range I am in, then I'll take that. First flights however will be with the 3000 mah packs just to be sure I am in the ballpark balance wise. Interestingly enough the cg of with the two packs is very close due to the longer configuration of the 3000 mah packs and where I can position the 2200's.
Before this summer I was flying with 3700 to 4000 mah packs but from watching the draws saw that I could go down to 3000 mah with no issues and did. Its obvious I don't need to carry 3000 mah either and a 2600 mah 4 cell is not currently available from turnigy so I'll see how this experiement works. Working with the 2826/12 the 20 C pack obviously has more than enough current capacity to drive the motor. We usually static about 28 amps or so and average about 20 in the air.
bob branch
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Ok, after the first day of test flights I can report the following. The blunt airfoil and wide fuse required a few more rpm than expected and reluted in the need to fly with a 3000 mah 4 cell pack. I don't have any 2600 mah packs in my inventory, but they would do the deed. So the all up wieight with the battery onboard is 63 ounces. Very nice stable easy to fly airplane.
bob branch
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...and I can report from the spectating side of the circle that Rex looks great in the air and show some real performance potential. Needs to add a tweak of this and a dollop of that and it will be ready for battle.
Oh yeah, it looks even beter in person than in the pix...
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Congratulations.
It looks like I am going to use the exact same set up on my plane except the prop and I will use a 2650 30c Turnigy battery pack.
This set up weights the same as a 60 size 2 cycle conventional set up.
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Dorin
I think you might be cutting it a little close. I used 2246 mah average for a 5 min 30 sec pattern yesterday withe the 12X6apcEP. If you use a 2650 mah pack that is 85% of the pack. Will probably work, most folks don't like to use over 80% but the packs are not that expensive now. BUT, you have closed yourself off from being able to experiment with many other props. The apcE's have aabout the lowest energy consumption out there, the EP requires a bit more. But lots of props require a good deal more. The weight difference between the 30C 2650 4s pack you are looking at and the 20C 3000 mah 4S pack is negligible for all practical purposes. But there is no need for a 30 C battery with the motor. A 20C 3000 mah pack can be discharged at 60 amps. You will never see 30 with this power system. The extra capacity with the 3000 mah 20C 4S pack will give you the ability to do any kind of prop testing you want with a good margin on the battery. Cutting battery capacity close is best done once you have a good amount of experience in electric. Even with that my estimates did not take into account adequately the drag of the airplane and I am drawing more power than most of my other planes with the same power system including a 67 ounce extra I tested earlier in the year.. Still well within the capacity of the system though as the flight performance showed. But that is one of the reasons you want to do your early flights at the shortest times possible so you can get a reading on the lap times and the power requirements before you risk killing a battery. If you draw one of these things down below minimum charge, you risk not getting it back. And as Rick pointed out previously, the harder you push things the more heat you get and the less time things last. Between myself, the Adamisins and Rick Sawicki yesterday we flew 11 electric airplanes. I have no idea how many flights. I did at least 7 or 8 on mine alone. Two were twins running on one pack as well as all the singles. The temp outside was 65 degrees. No motor at any time was more than a few degrees above air temp and no battery exceeded 89 degrees. We are not pushing the systems at all and getting all the performance the planes require. One of the real keys in electric is the consistency without so much hassle. As you can see folks really have tried to stay conservative for the most part on their setups and it pays benefits in consistant runs and reliability we just don't see in glow. I'm running the same motors I ran 3 years ago and they have spent a lot of time in RC hovering airplanes as well.Rick Sawicki I think said he is on the 6th year with some of his motors. Still no engine failures except one I had from a severe prop strike and that motor had had several crashes and several prop strikes. (not a lot of room under those noblers and smoothies).
Anyway, I offer it not as a criticism but as data for you and food for thought. I know the first year I flew electric when we were still searching props I was stunned to see the huge difference in current draw for different props. Its a wonderful study on a bench test stand. Jjust to take a bunch of same size and pitch props and hook up an amp meter and run them all at the same rpm and record the differences. It will definitely get your attention.
Good luck with your decisions.
bob branch
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I am humble enough to take your advice and go to the 3000 mah pack no problem there.
I make my own carbon props i am not sure if you heard of the Gator Props. Yes I am the guy who developed them. Mike Palko was using them in his Sidewinder. It would be a nice post to share your findings in regards with your testing of different props and the Amp draw. Maybe I get an idea of making my own prop dedicated for electric in the future. I am sure that I have a lot of testing ahead of me. The extra margin in the battery can be used to squeeze more from the system. Maybe a bit more diameter or less pitch whatever so I find this a great idea.
Thanks for the advice. Dorin
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Finally we get down to the name. I live on an Island, get here on a ferry, 365 days a year, in Michigan. Yup, ice and all. The plane's name will be Miss Isle. Yea, I know, two meanings. That's ok too.
The method is the same we have used elsewhere with Windex but here I will show another little addition to the method that can lead to some interesting fun and creativity cause you can do any shape or picture with this even something as complex as an entire skeleton with all the individual bones... yup seen it done.
First I created the lettering. You can do it in any graphics program. I used Microsoft word Pad. Yup, same one that is standard with any windows program. No need to get something else. Zillions of fonts. You can make them bold, italics, you may need to go to Word to create bending letters, not sure, haven't tried it yet. What alot of people do not know is you can do any size font, just just the ones that they give you options for. I think I used 350 or 400 point for the Isle. You can print it out then go see how that size looks on the plane and if you like it or not. You can do positioning and even colors. Same for your numbers in matching Fonts.
Next we will transfer it to monocote in the color of your choice. We are going to cut on glass and use a new blade for every letter and change even more frequently if you are getting drag or non clean cuts. Spray the glass with a very light mist of windex. You do not want to activate all the adhesive like when we put the stuff on the planes. We want to just get the film to stay still. Lay the film down on the glass and rub it down but not real heavily. You just want it to stay still while you work. Tape the pattern to the film (I use blue adhesive tape). Next cut the pattern using a sharp point scalpel. Nothing broad, just a very thin pointed blade so you can get whatever curve you need. Be sure to press hard enough to go thru the pattern and the film in one pass or you will not have a clean cut. If it starts to move, you have to stabilize it with your finger.
Once you have cut the entire pattern, remove the paper pattern and be sure all the cuts were made and went thru the film. Then take some Press and Seal ... its kinda like Glad Wrap but has a very light adhesive on one side. Remove all the excess so the letters alone remain on the glass. Lay the Press and Seal over the letters, sticky side down and press the Press and seal onto the letters. You may not get 100% adhesion but you want to then peal up the Press and Seal and have the letters stay attached to it. They now are ready to be transfered to the airplane.
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Next we will apply the name to the wing. First spray a good coating of Windex on the wing. You want to activate all the adhesive on the monocote and you want to be able to move the trim if you need to adjust the positioning.
Once you position it where you want it, squeege it with a cridit card as before, then peel away the Press and Seal. You need to do this carefully so the lettering doesn't move. Mine did just a bit on one letter and the dot of the "i". But its easy to reposition. If the credit card moves a letter too much use something more rounded. I used the rounded back end of the handle of a plastic handle allen wrench just to have something to rub it down with till it did not move.
Again it now needs to set and dry for 24 hours. I did wipe the excess Windex off around the letters but not on them. They might move. Once it has been dry for 24 hours I'll clean up the edges by scrapping the edge with a scalpel anywhere there is un-niceness with a scalpel and then go around the edges with Monocote Solvent applied with a thin brush. Then I after its set I will buff it clean. I'll be using the trim tape for highlights and when its all done in a day or two I'll post the final pics. If you wanted to use shadow lettering you would just cut the shadow out seperately and apply it sperately by the same method or by just transferring the shadow one piece at a time. The method that works in your hand may vary of using freehand or the Press and Seal. I wanted to show the Press and Seal here because I had not shown it in the previous posts in the thread and don't think I have seen anyone present it on one of the control line forums.
bob branch
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I also might note that the plane has been flown 4 or 5 flights prior to applying the name. I did nothing but wipe it with soap and water before applying. The lettering. I could have waited any number of weeks and flights because there is no oil of course to deal with.... just those slimy electrons n~
Oh, and the 2826/12 with 12X6EP? Pulls it with authority.
bob branch
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Hi Bob,
I'm new to Stunthanger. My friend William DeMauro told me about it. I've been in this hobby since 1975 and that's when I met Willie. Right from the start I have been using monokote to cover all my planes. By experimentation I have learned a lot about its characteristics. I build all my planes from scratch after drawing full size plans then cover all the parts before assembling them. After reading your write-up, I see we both cover planes basically the same. However, I have been putting the trim colors and names of my planes on by ironing them on. If I use trim sheets, after cutting the design I put soapy water on first, move the scheme where I want and then dry everything with a paper towel and let dry overnight. It works like a charm. I did not know about the windex system until I read your article. I guess that does the same thing that soapy water does with trim sheets. I will try it on my next project. I also make monokote hinges in place of standard types and have never had a problem with them. I also found a way of making fillets around the wing and stabilizer. I cut a piece of monokote 1/4" wide and fold it in half face to face. Then place the point of the fold in the fillet area and iron on one half at a time. As I go around the wing area I start at the trailing edge and pull on the fillet gently as I go around the wing and let the heat of the iron do its work. The first time I covered a plane that was partially assembled was when Willie asked me to cover his SV-11. However, we used black baron covering since he electrified the plane and wanted to keep it as light as possible. The next project for us is T-Rex.
Ron
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Ron, I'm off to try your fillet method this weekend! btw, the windex will work as soapy water with trim sheet material and decals as well, but soapy water will not work as windex in the windex method. There are some good threads on the windex method on RCU forums as well. That is where I learned it.
bob branch
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Finally here are some pics of the finished name and numbers. Again I elected to stay simple because of the business of the checkerboard on the fuse. I just picked up the silver color of the pinstripes that are already on the fuse and wings. I decided against doing any shadowing again to avoid business and keep the rest of the plane simple. The plane is still wet and I have not been able to buff it off but I think you can see the idea. To answer Denni's concern in an earlier post about the windex trim staying down, I think you can see I made no effort at all to avoid ribs or to look at what angle the letters pass over ribs or any other structures. They will lay down as long as you are not trying to lay around a severe compound curve. For instance I would not do this on a wingtip contour. Notice I ended all my trim away from wing tips as far as the windex adhered material. The 3M trim tape runs into absolutely no issues on wing tips, even thin ones like the edges of a horizontal stab. I have trimmed a nobler with curved 3M tape contour trailing back to a point on a horizontal stab edge just like you would do with paint with no issues.
So unless anyone has a question this is where I will officially end the thread. Be glad to answer any anytime someone needs it.
bob branch H^^
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Finally here are some pics of the finished name and numbers. Again I elected to stay simple because of the business of the checkerboard on the fuse. I just picked up the silver color of the pinstripes that are already on the fuse and wings. I decided against doing any shadowing again to avoid business and keep the rest of the plane simple. The plane is still wet and I have not been able to buff it off but I think you can see the idea. To answer Denni's concern in an earlier post about the windex trim staying down, I think you can see I made no effort at all to avoid ribs or to look at what angle the letters pass over ribs or any other structures. They will lay down as long as you are not trying to lay around a severe compound curve. For instance I would not do this on a wingtip contour. Notice I ended all my trim away from wing tips as far as the windex adhered material. The 3M trim tape runs into absolutely no issues on wing tips, even thin ones like the edges of a horizontal stab. I have trimmed a nobler with curved 3M tape contour trailing back to a point on a horizontal stab edge just like you would do with paint with no issues.
So unless anyone has a question this is where I will officially end the thread. Be glad to answer any anytime someone needs it.
bob branch H^^
Hey, we expect ski's on the landing gear and a complete flight report! Maybe that's a new thread. Also we expect an entry in the "List your setup". We are a tough bunch. Once you post in the electric forum, you take on obligations! mw~
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Very nice Bob, very nice.
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Could you please take some photos of the completed ship out in the sun? For my archives...
I wanna fly it... ;D
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Great looking plane Bob, and thanks for all the invaluable info.
Steve
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Brad
I'll be glad to get final pics when we get sun. The long range forecasts now call for maybe Sat afternoon, if not then mid next week. But when it does shine again (our wonderful indian summer here in SE Michigan is coming to an end this week it looks like.
Steve
Thank you.
I will file a light report on the open forum tonight.
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Great looking plane Bob, and thanks for all the invaluable info.
Steve
No joke...
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Bob,
Thanks for all of the info posted in your thread. I'm sure it will be helpful with my efforts. I have just ordered my Brodak T-Rex ARF and plane to go electric. I will be using a Castle ICE50 LITE ESC, a Hubin FM-2a timer with the motor and battery to yet be determined. I have several Turnegy motors on order to try on my test electric Pathfinder before I make my motor and battery choice for the T-Rex. I see that your are running an AXI 2826/12 motor using a 4S battery and an APC 12x6 electric pusher prop. I noted that you indicated the need to increase the rpm a bit after your maiden flights but you did not give any lap times or motor rpm settings. If I calculate things correctly, the AXI 2826/12 motor is rated at 760kv which will turn approximately 10,944 rpm at 14.4 volts. To get right at 5 second lap times with my Pathfinder, I need to set the my motor at about 9,300 to 9,500 rpm using an APC 12x6 electric pusher prop. That lap time is necessary to keep good line tension with the heavy Pathfinder. If one needed to run at 9,500 rpm on the T-Rex using the AXI 2826/12 motor, the motor would have to be set at about 86% throttle. That seems it might just be a bit on the high side to me. Please let me know what you think. Also, any data or information you can provide will be very helpful.
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Hi Roger,
I think Bob found out that the 4S battery was not enough "nitro", he went to a 5S and it works fine. The 5S will make all your #s come out better too. ;-) .... I am installing an Orbit and a 5S in mine.
Bob,
Thanks again for your outstanding thread. It helped in many ways. :-)
Regards, H^^
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Hey Rudy,
Nice to hear from you. It looks like several of us are going to be playing in the same electric T-Rex pond before long. The design of the T-Rex seems to be nicely suited for electric conversion. Lots of room under the hood and easy motor mounting. Thanks for the update about Bob changing from a 4S to a 5S battery. I have been using a 4500mah, 5S, 20C battery for all of my testing so far. My power usage numbers have been all over the board but I seem to have gained a lot lately on a workable setup. I have found that the prop selected has a great deal to do with how many amps the motor pulls. APC electric props seem to perform the best with the lowest power use for the performance provided. The APC electric pusher props do seem to give better line tension when the plane is at 45 degrees or more. I have ordered a 4000mah, 4S, 20C battery to try with the Turnigy 35-48 motors. I have ordered the 35-48 motors in 800kv, 900kv and 1100kv versions. I also have a Turnigy 42-50, 650kv motor on order to try. I will experiment with all of these motors before I pick the power package to put in my T-Rex.
Roger
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Roger
Thanks for updating Rude for me.
Rude
What Roger said is correct. I did not post final numbers yet cause I have really not reached that point in my flight tests. I am still in the 2 1/2 minute runs getting basic trim sorted out before i did final current numbers. Was playing with too many things at one time and had to get back to one at a time, but then our Michigan warm early winter weather ran out and we have been snow and wind bound since. In checking the last plot I had on my ICE esc I found I was drawing too high rpm load (% power) on my 3000 mah 20C batteries for the governor to function as I want it too so I went up to 5 cells rather than the weight of a large 4 cell. It was going to give me more range to tune in and the option of low pitch prop experiments as well. Both Rick Sawicki and I just flew ICE controllers the last day out and only really have that one day of data so a lot to discern yet. I have not posted final numbers yet because I am not to a point I want to have someone believe that if they do this set up they will get the result I state till I have the actual numbers. So when we get flyable weather again and I can finalize data I'll do so.
Good luck with your projects guys. Hope you can get ahead of me while I'm waiting for weather..... or maybe that our weather will change..... fat chance... we have had between 2 and 5 icebreakers cutting ice around the island I live on every day for the last week.
bob branch
Harsens Island, MI
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Hey Bob,
Thanks so much for the update. Do you think that the 3000mah 5S battery has enough mah headroom for this airplane?
Roger
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Roger
I just cannot give you an answer to that yet. From Denny's numbers on the 6S strega I think so, but again, I don't want to say so til i do it. I still have some trim issues before I have the plane flying straight so I know I will be decreasing drag some more. I really have not paid much attention to current draws on trimming this yet as the power numbers had to come in first. When I could hear that the governor was not kicking in in maneuvers on 4S I knew I had to change to 5 S even though the line tension was there. All I got was a few flights changing rpm on each on 5S and the last one had me in the ballpark, and in a range that the governor was kicking in the way I like it to, but it was the second flight on the pack so I did not have recharge numbers that are meaningful yet. Then it got dark that day and then cold.... oh yea, there was also something about Archie and Big Art wanting food that afternoon before they had to drive home. Can't remember what all that was about. But Big Art looked pretty contented when we left the restaurant... and he was careful to be sure he had a few beers so Archie had to drive. Wtach out, y1He's still sharp as ever.
bob branch
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Hi Roger,
I'm very glad to see you are getting your ECL plane ready. :-)
1. RE: the mAh needed. ...... I know that some have flown the pattern with very small mAh of energy used (some at the ridiculously low 2,200 mAh?), but my guess is that these are with very light, sleek, relatively thin winged, medium size ECL planes. My experience has been that a higher drag plane like my profile, relatively thick wing, P-40 with everything hanging out in the breeze, uses about 2,850 mAh per a 5:30 min. flight pattern. The T-Rex with a "real" man size looking fuselage and a relatively thick airfoil wing, will tend to use more mAh per pattern than the above sleek, thin, smaller planes. My guess is around 3,000 mAh will be needed. Using the safe 80% rule, this would mean a 5S battery of at least 3,750 mAh would be needed.
I like to have extra headroom everywhere and never make my equipment work too hard. Therefore all my batteries are 4,000 to 4,200 mAh. I would rather have a few extra mAh, even at the cost of a few oz. Our planes can easily handle a few more oz. considering the almost unlimited power we have in ECL. :-)
2. RE: your motors ....... I would go with the 650 Kv with your 5S battery. This gives you a max RPM of 12,000. Using the conservative 80% of max rule you get 9,620 RPM. This is a good sweet spot for us. I feel that 8,500 to 8,800 RPM will even be better because it will be quieter. This is the RPM I hope to prop for.
After watching, and hearing, Paul Walkers beautiful ECL plane, I am convinced that we can fly with unlimited power and still be very quiet. And watching Dave fly many times has made me a true believer in having a LARGE power source that never lets the plane slow down or miss a beat in the pattern. Just the opposite of using a felon fox .35. I have installed an Orbit 25. Paul told me that my Orbit 30 would be too much, he had already tried it. He uses the 25 and I saw it pull his plane like a freight train. BTW, to watch Paul and Dave fly is like watching Michelangelo painting beautiful, perfect figures against a cobalt blue sky with a 70' paint brush. :-)
IMHO: don't be shy about using a lot of power. Dave proved to everyone how well this works. If you like your Turnigy motors then use one that is = to at least a .60 wet engine. The motor, plane, and the pilot will all be much happier with a system that is not always having to run at max speed, heat, etc. ;-)
Bob,
I am very sorry to hear about your WX issues. This puts a damper on your testing I'm sure. Look at the bright side, Your beautiful, green, flower filled MI Spring is just a few short months away, and you have a better "building season" than we do! :-) ..... Last week it was 73 and sunshine with string bikinis worn here at the beach, BUT ..... to make you feel better, it rained all day today, it is a freezing cold 59 degrees and it is forecast to rain all week! This will be my entire years building season, so I better get cracking on my ECL plane ..... removable wing, tail, exact scale paint scheme, YIKES! that means at least 200 hours of work for me ( 180 hours thinking about it and 20 hours of actual work! LL~ )
Warm Regards, H^^
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Bob,
I am very sorry to hear about your WX issues. This puts a damper on your testing I'm sure. Look at the bright side, Your beautiful, green, flower filled MI Spring is just a few short months away, and you have a better "building season" than we do! :-) ..... Last week it was 73 and sunshine with string bikinis worn here at the beach, BUT ..... to make you feel better, it rained all day today, it is a freezing cold 59 degrees and it is forecast to rain all week! This will be my entire years building season, so I better get cracking on my ECL plane ..... removable wing, tail, exact scale paint scheme, YIKES! that means at least 200 hours of work for me ( 180 hours thinking about it and 20 hours of actual work! LL~ )
Warm Regards, H^^
grrrrrrrrr
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Don't get me wrong, I enjoy winter in Michigan. Would not move to Florida for all the money in the world. And you are right, it does give a good building season and when we get a 40 degree day with sun and light wind it's a real treat and I head down the road and fly some electric rc.... just take it out of the car, fly, jump back into the car and stay warm! But the real treat here is when the ice breaks loose in the spring and the ferry cannot run for a few days.... we have an airboat that ferries those of us to work who have to get there and during these weeks most folks leave a car on the mainland and have one on the island.... but the silence when off islanders cannot get on the island.... oh its deafening!
bob
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Hi Dennis,
Your "grrrrrrrrr" ...... I feel your pain. I was born NORTH of you with more cold and snow than any human should have to endure! (that's why I escaped while still in my teens ;-) It was not my intent to sound insensitive by talking about our nice WX, I was trying to use it as an excuse for my lazy building pace. It is just really hard for me to stay indoors when there is such perfectly formed Si-O-Si on display at the beach all year long, not to mention all the other outdoor activities. Out here you don't buy expensive land, you buy very expensive Sunshine! n~
Warm Regards, H^^
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Hi Dennis,
Your "grrrrrrrrr" ...... I feel your pain. I was born NORTH of you with more cold and snow than any human should have to endure! (that's why I escaped while still in my teens ;-) It was not my intent to sound insensitive by talking about our nice WX, I was trying to use it as an excuse for my lazy building pace. It is just really hard for me to stay indoors when there is such perfectly formed Si-O-Si on display at the beach all year long, not to mention all the other outdoor activities. Out here you don't buy expensive land, you buy very expensive Sunshine! n~
Warm Regards, H^^
Well I never figgered out how to abandon snow & cold, but I have learned ow to spread it around. I tried moving to NC. The company that hired me went belly up in six months. While I was there they had a "100 year blizzard" that dumped 14" of snow. One February we took a family vacay to Daytona Beach. The day we got there it was 22 degrees. I'm sure if I wander out to visit you out on the beach, El Nino would turn into El Freezo for my visit. Only Hawaii has escaped my touch... So far. HB~> HB~> HB~>
...and YES I am jealous! Would gladly trade building season for a January sunburn.
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"and YES I am jealous! Would gladly trade building season for a January sunburn."
come down and see me in New Zealand - it has been upward of 30 degrees C for the last couple of weeks too hot to do anything - but pretty sure you will get a sunburn quickly
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Boy do I hate waiting! I'm waiting to go flying, waiting for my T-Rex and waiting for my motors and battery that I ordered from Hobby King. The T-Rex should arrive sometime on Friday but I have no idea when the things from China will arrive. I ordered the items from Hobby King more than two weeks ago and their tracking system really doesn't give much information.
I guess I will just have to learn to be more patient but that is a skill I have not been able to develop as yet.
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After six straight days of rain, things are looking up. We are not supposed to have rain today but it looks as though the rain will return again tomorrow. This kind of extended rain event is very unusual for this neck of the woods. Now that we have our long building season in progress, my T-Rex arrived yesterday along with my TGY 42-50 motor and my Hubin timer. I'm looking forward to putting this dude together and having some circle burning fun!
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Things got even better today. Had some nice sunshine and my three TGY 35-48-800, 35-48-900 & 35-48-1100 motors arrived. I now get to do some serious playing with my electric Pathfinder test bed to find out what will work best for me.
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I got a warning on beginning this post that there had been no post in 120 plus days and a suggestion I should start a new thread. I think though since so many people have referenced this thread that I should include this section as part of the original for completeness. My T-Rex has sustained an inflight wing failure. Fortunately we caught it just before things came apart and modification is being done to solve the issue. What was observed was that the wing began to flex in maneuvers in the air. One inch flex at each wing tip one one flight and two inches on the next. At that point the plane was grounded. Rick Sawicki my flying partner noticed it as did another pilot on the flight it showed up and on the next one when it had increased we decided it had to be addressed. I cancelled my trip to Brodak because this was the Friday before Brodak's and I did not know the nature of the failure of if repair would be possible but I did not want to be limited by time.
Prior to starting any mod I checked with others who have seen the plane fly. Rick Sawicki has seen all but a handful of its flights. No flexing was noted. I checked with the Adamisin Clan because they had all seen its maiden flights. None had noted any wing flex whatsoever. The flex began the day I taped the hinges of both the elevators and the flaps. The issue of major concern is that it progressed and got worse and these were 2 minute flights. It would have separated in a full pattern.
On returning to the shop what I found prior to opening things up was that both wings could be twisted probably 20 degrees by grabbing the tips and applying pressure to the trailing edges. This occurred in both directions and on both wings. When the plane was suspended from the wing tips and not a lot of pressure applied to the fuselage vertically perpendicular to the wing a large wrinkle developed in the covering emanating from the junction of the outboard edge of the centersheeting junction with the trailing edge and progressing outwards and forwards. The leading edge section of the wing flexed as well but the trailing edge flexed badly.
My analysis from MY perspective... and I am not an engineer and will defer to any who have an opinion... was that the trailing edge of the wing was failing in overload. The failure was made more imminent by the added loading from taping the hinge lines. I felt that to correct the problem and allow the plane to return to flying status I had to achieve the following: 1) stiffen the entire wing and eliminate the flexing, 2) Strengthen the trailing edge section, 3) tie the trailing edge to a more rigid structure to eliminate the stress riser that was overcoming the strength of the trailing edge. I think the cause was the wood that was selected for the airplane. It was just not up to the loads.
To correct the problems I did the following: First I opened up the bottom of the wing. Using a scalpel I simply cut the film along the back edge of the leading edge sheeting, the inboard tip rib, the front of the trailing edge and the inboard edge of the center sheeting. This piece was removed in tact and kept for a pattern for the repair film piece. I will enlarge it 1/2 inch in all directions to close up when I'm done. I'll only have to apply the red trim tape along a small portion of the wing. The white section and the silver tape stripes will not be impacted. Secondly on the leading edge I installed vertical grain 1/8 inch balsa spar webs from the top to the bottom spar. I did this from the rib that is at the edge of the center sheeting to one rib outboard of the landing gear and then did the trailing edge mods I'll discuss below and evaluated the result. The leading edge became rigid to the rib beyond the end of the spar webs. But there was still a tad of flex beyond. Granted there is little load there. But on looking at it and evaluating it over the last week I have decided to extend the leading edge spar web one more rib outboard to really lock the leading edge in.
The trailing edge I treated in much the same way but in two stages. First I created the webs placing them between the upper and lower trailing edge sheeting at the front of the trailing edges. The webs do not overlap the edges of the sheeting but set between the sheets. Each one is sanded to fit the contour of the trailing edge sheeting and to fit each rib well. They, like the leading edge webs are CA'd in place. These webs I took out to the next to last bay. The plane is not in my estimation flyable at this point. The stress riser is still there at the junction of the center sheeting and the trailing edge. The wing while now stronger against flex from vertical loads still twists severely. I needed to get rid of the flex stress at the inboard end. The key is already in the wing. The alignment spar box! It is a thick box section tied together from one side of the wing to the other with the alignment spar. The alignment spar box extends out past the rib that the center sheeting ends on and into the rib bay beyond the center sheeting. I started with a piece of balsa essentially a spar web doubler and custom sanded it to fit between the spar web I placed between the trailing edge sheets and the spar box. Once this was fitted and snug I epoxied it in place to both the trailing edge spar web and the alignment spar box. This eliminated the stress riser. There is now no flex from either vertical loads or twisting loads in the inboard section of the wing. I could still detect twist deflection outboard of the spar webs, most notably in the trailing edge. This led me to extend the spar webs to the inboard wingtip rib on the trailing edge and at least one more bay on the leading edge (so two bays outboard of the gear).
I hope to add the additional spar webs tomorrow and will post pictures and results at that point. I'm pretty sure from what I have seen that this will result in an acceptably rigid wing structure.
I should also mention that I reentered the fuselage aft of the cockpit and installed the fuselage doubler to reinforce the area aft of the flap hinge line there. I had noticed flexing occurring there as well. If you will recall however, I had to cut into the structure there to access the flap horn after assembly This doubtless weakened the structure. Not shown in the build thread was a modification I did to the reinforcing member that runs along the top of the fuselage sides and perpendicular to them.To clear the complex flap horn I used I had to relieve these. I think I may have weakened things there as well. To fix this and tie this area and structure into the back of the fuse I fabricated a 1/8 play plate to span the structures I relieved and tie them and the fuse sides together and to the bulkhead at the front of the rear deck. To close up my entry I used replaced the entry cutout and used an epoxy structural fillet with WEST System structural filleting blend added to the epoxy. This tired everything back together there in a very solid manner and the repair was recovered.
One last mod I have done I think was mentioned by someone else, I bent new gear out of music wire. My outboard gear flexed due to wire being soft and I was suffering nose overs on landings due to the gear twisting off. This no longer occurs.
My final power system turned out to be a 4S system. I am currently using 4S Rhino 3700 mah packs with the Axi 2826/12 and turning an APC 12X6EP prop. I found the Rhino batteries to handle the loads much better than the 3000 mah Turnigy packs. 4 cell packs this size were inadequate. 5 cell packs were very borderline. The 3700 mah Rhinos have performed very well and are able to deal with the loads much better. The weight difference does not appear to be an issue... as long as the wing issue is solved.
Again, I apologize for adding this so late on but since so many folks have told me they have referenced this thread I thought this post should be a part of it.
bob branch
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Here are the pictures of my repair. I will show the leading edge mods first.
The leading edge is a normal D tube type construction with half ribs between the full ribs.You can see some are plywood and support the gear. I installed 1/8 inch end grain balsa spar webs connecting the upper and lower spars. This is pretty normal. Same way the Strega is done. I was concerned with the leadout possibly rubbing near the bellcrank so I set the innermost web in front of the spars and the second one within the spars. The rest are aft of the spars. I attached the webs with medium CA and where I did not have a perfect fit to ribs or to segments of the webs I applied thick CA and then kicker to create a fillet. I extended the webs out to about the end of the flaps. The next bay begins to taper and not much load goes out there anyway. Also I found the wing was so stiff by the time extended this far I did not feel I needed to go further. I did, however, notice that going this one bay further than I had done at the time of my previous post, both on the leading and trailing edge webs did stiffen the wing further so for me it was worth the minimal weight gain.
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Now onto the trailing edge modification I have made.
The first pic is of viewing the first bay outboard of the center sheeting. We can see the top and bottom trailing edge sheeting and between them the horizontal trailing edge. It is thicker than the trailing edge sheeting. (focus branch, focus!!!!!!! ::) ) Also visible is the box for the rear alignment spar. This is a really solid construction and it contains the alignment spar itself. This is all epoxied together and will become the load carrier for the trialing edge vertical flex loads on my modification.
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In this pic I have fabricated a vertical grain web from 1/8 inch balsa to fit between the trailing edge top and bottom sheets and to butt against the horizontal trailing edge piece. It is glued in place with thick CA to the horizontal trailing edge and with thin CA to the top and bottom trailing edge sheets. As you can see there is still space present between the web and the alignment spar box. This space is greater than 1/8 inch.
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To connect the trailing edge web to the alignment spar box I next laminated a web doubler from 1/8 inch vertical grain and 1/16 inch horizontal grain balsa. The horizontal grain wood let me sand the thickness easier to precisely match between he web previously attached and the alignment spar box. The view is edge on of this doubler.
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The horizontal grain wood allowed me to custom sand it to thickness more easily so that the web doubler contacts the first web member and the aft side of the alignment spar box. The photo shows this in place at fitting. The doubler was glued to the first trailing edge web on the horizontal wood surface and to the alignment spar box on the vertical grain side with thick CA. After it set thin CA was used to establish bond between the upper and lower trailing edge sheets.
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The last photo shows this accomplished and a filler web spanning to the next rib.
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The rest of the bays from out to the end of the flap all have had vertical grain webs placed as well. I fit all these between the trailing edge sheets as the glue joint is easier and no additional sanding will be required before recovering.
I wound up extending both the leading and trailing edge webs to the end of the flaps as this did provide additional rigidity to the wing, especially in torsion.
The end result has removed the stress riser at the trailing edge sheeting-center sheeting junction. No flex can now be detected on vertical loading of the fuselage. The wing is now as torsionally rigid as any other wing. It should allow my T-Rex to fly on into the future to a normal life expectancy. Final finish only requires application of a section of Ultracote on the bottom of each wing. A much easier repair than if I had painted and I have no concerns now with the taped hinge lines.
Thanks again to Brad and John for this great flying bird. It really is a plane that I can become a markedly better pilot with.
BTW, for completeness, I have finalized flying on a 4S system utilizing the Axi 2826/12, Rhino 3700 mah packs, and APC 12X6EP prop.
I hope this is of help to others who are enjoying this wonderful bird . I know this is not an approved fix, but it is how I solved the problem that developed with this particular airframe.
bob branch
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Hi Everyone,
I can vouch for this powertrain combination that Bob mentions for the T-rex or any other similar size model,
"BTW, for completeness, I have finalized flying on a 4S system utilizing the Axi 2826/12, Rhino 3700 mah packs, and APC 12X6EP prop.'
I had used it on 3 other similar sized airplanes during the past 3 years and I can easily vouch that it is an excellent and well matched "plug and play combination". After Bob played earlier in the year with a few other combinations of mainly battery cell count, sizes and types, I suggested that he go back to "basics" and try this "well tested combination". Well he did..and having seen his plane fly several times with it..I can easily add that it is just about "prefect" for this aircraft , or similar sized ones.
Just adding my confirmation..."it is a system that works".
Rick Sawicki
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Update of the wing mod. It works fine. No unusual flexing noted in test session today.
Update on the power system. Tried a new power system today and will be staying with it. Transferred in teh system I had in the strega. 5S 3000 mah turnigy packs, dualsky 4260CA5. Turning apc 12X6EP at 9315. Flew it today. Awesome power. Gee, like in RC!: Everything needs MORE POWER! Now to start moving the leadouts forward from the axi's position... so I can hold onto the thing!
bob branch y1
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Thanks for a most informative thread - I refer to it constantly as I'm assembling my eT-Rex :)
One thing keeps sticking in my mind which is confusing the heck outta' me - way back on page 2 I read "concerned at the weight it looks like this bird is going to come out at as being too light." Now this may sound stupid and probably highlights ignorance on my part, but I didn't think that was possible. I was brought up on "lighter is better". I understand that bigger aircraft are more inherently stable due to greater weight/momentum, but I didn't think that would extend to adding weight. Could anyone please enlighten me...?
Thankx in advance,
Frank
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Hi Frank. I try to be funny sometimes and can't make it fly. In the past arf's have tended to come out on the heavy side. I was really working to keep the weight as light as I could. Things can get too light if they do not stand up to use. A couple of examples I have found with the T-Rex are the wing mod and the reinforcement of the fuse in the area of the flap horn that I did. The wood was really light. Also as I flew the plane I found I could use the 3000 mah packs but I got better overall motor performance with 3700 mah rhino 4S packs from both a flight performance view and a longevity view. So I could fly it lighter with the 3000 mah packs, but the motor governed better and gave better pack survival not pushing them so hard. I did experience some pack deaths on the 3000 mah. But in big wind the bigger packs gave much better governing and steadier flight speeds. In addition the plane does not appear to be very weight sensitive. I have not noticed any softer corner or decrease in any flight capability at the heavier weight I fly today than the lighter weight I started with. The plane still has the hardest corner of anything in my fleet and is rock solid through the entire pattern. I just could not ask for more.
bob branch
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Ahh - not ignorant, gullible ::) And thankx for your quick reply - I can sleep tonight ! :D
Another question for you if I may - how much engine and/or rudder offset are you using?
Cheers,
Frank
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Frank
Rudder offset has always been zero degrees.
Engine offset, I started out with a lot and have been decreasing it. I did the a lot because on of my glow flying friends who flies the modern p-47 stunters told me he uses a lot now where he used to use not a lot. I found in the T-Rex that engine offset really uses a lot of power mah wise and getting rid of it really lowers mah consumption. I gradually worked it down and now fly the plane with zero degrees of engine offset. I get lots of line tension thru the entire pattern and find it is not needed. As a result of this when I set up my SV-11 arf I also set it up with zero degrees and have no line tension issues either. So I will opt for the lower power consumption.
bob branch
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... Also as I flew the plane I found I could use the 3000 mah packs but I got better overall motor performance with 3700 mah rhino 4S packs from both a flight performance view and a longevity view. So I could fly it lighter with the 3000 mah packs, but the motor governed better and gave better pack survival not pushing them so hard. I did experience some pack deaths on the 3000 mah. But in big wind the bigger packs gave much better governing and steadier flight speeds. ...
bob branch
Hi All,
Bob,
Thanks for the payoff quote which I have excerpted from your post.
This is what properly governed E-power has that nothing else does: the possibility of GOBS of instant torque that can be tapped in just a few critical tenths of a second.
A "stiff" low cell resistance battery that is not overly depleted and with adequate voltage headroom above the motor running voltage is critical.
Okay, I'll be quiet now.
Regards All,
Dean P.
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Thanks HEAPS Bob - your willingness to take the time to share your wisdom to help others is much appreciated...
Regards,
Frank
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Bob
what was the KV of the first set up you had in the plane?
thanks
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Actually...
I will put the T Rex against anything out there... Flying wise...
I see they are back in stock....