T-Rex electric build thread

[bob branch]

Alan

Do you think Brad might take offense if I called it "Dog Food" ?

 
bob

[Alan Hahn]

It's funny, but only after I posted my comment did that thought cross my mind!

[bob branch]

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

[bob branch]

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

[Bradley Walker]

Do you have an airbrush?

[bob branch]

Brad

I do but I hate the think. Why?

bob

[bob branch]

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

[bob branch]

Head rest installed.

[Bradley Walker]

Brad

I do but I hate the think. Why?

bob

Lightly spray the canopy with your favorite color.  It will smoke it.

[bob branch]

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

[William DeMauro]

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

[Crist Rigotti]

Bob,
Very informative thread!  Thanks.

[bob branch]

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

[William DeMauro]

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

[bob branch]

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 

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

[bob branch]

more pics

[bob branch]

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

[Dennis Adamisin]

Outstanding Bob! 

[William DeMauro]

FANTASTIC!!!!!!! Thanks so much for this thread. I know it will be helpful to me as I assemble mine.
William

[Crist Rigotti]

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.

[RickS]

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

[bob branch]

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

[bob branch]

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

[Dennis Adamisin]

...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...

[TDM]

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.

[bob branch]

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

[TDM]

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

[bob branch]

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. 

[bob branch]

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

[bob branch]

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 

Oh, and the 2826/12 with 12X6EP? Pulls it with authority.

bob branch

[Ron Heckler]

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 

[bob branch]

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

[bob branch]

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 

[Alan Hahn]

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 

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!   

[Crist Rigotti]

Very nice Bob, very nice.

[Bradley Walker]

Could you please take some photos of the completed ship out in the sun?  For my archives...

I wanna fly it...

[SteveMoon]

Great looking plane Bob, and thanks for all the invaluable info.

Steve

[bob branch]

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.

[Bradley Walker]

Great looking plane Bob, and thanks for all the invaluable info.

Steve

No joke...

[Roger Anderson]

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.

[Rudy Taube]

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, 

[Roger Anderson]

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

[bob branch]

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

[Roger Anderson]

Hey Bob,

Thanks so much for the update.  Do you think that the 3000mah 5S battery has enough mah headroom for this airplane?

Roger

[bob branch]

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

[Rudy Taube]

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!  )

Warm Regards, 

[Dennis Adamisin]

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!  )

Warm Regards, 

grrrrrrrrr

[bob branch]

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

[Rudy Taube]

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! 

Warm Regards, 

[Dennis Adamisin]

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! 

Warm Regards, 

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.     

...and YES I am jealous!  Would gladly trade building season for a January sunburn.