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Building Tips and technical articles. => Building techniques => Topic started by: Peter Nevai on July 07, 2011, 11:38:20 AM
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Hi every one I will be placing the step by step construction process of the Pathfinder LE kit by RSA (Gordon Delany Design) in this tread. The process shall be a long one due to business travel and my limited shop tools and building space.
I like to start of with the small stuff that I can knock out fairly quickly by hand. I had the wife mail me the hardware pack from the kit via APO so I could get my hands on something. So I'll start off with the bellcrank. The kit comes with a nice 4 inch carbon fiber bellcrank as shown in the pictures below. But being one for not leaving well enough alone, I modified it. Using some stuff laying around I fabricated the mod to the bellcrank as shown. I used a piece of powder coated aluminum electronics chassis hole cover left over from some equipment we were installing it was roughly 1.25 X 5 inches by roughly 1/16 th inch thick and using a hacksaw blade wrapped with a rag I cut it to the approximate shape shown, using a file I then got it to the final shape. Next I bent in the Z bends and drilled two holes in the aluminum using pin vice and a drill bit large enough to fit the pin vice and to accept the two phillips head screws that came on the plate, and the proper width to fit into the two eyelets in the bellcrank.
I did not want the Leadout grommets to ride on the bare screw threads so I scavenged two electronic D connector nuts (The ones that secure VGA / DB-9 etc cables on to the PC ports) Threading the nuts onto the two phillips screws I used a file to file down the nut corners and reduce the diameter enough so they fit into the leadout grommets freely. You can see these hand made bushing in the photo they are the two round threaded brass pieces.
I did not like the bellcrank bushing that came with the Carbon crank. It is a soft plastic that seemed to me would get heavy wear from the raw surface of the hole in the carbon crank. Besides I never much cared for plastic bellcrank bushings. So I figured if I was going to replace it I might as well replace it with something worth while. Long ago I discovered the tons of neat miniature parts you can scavenge from old obsolete computer hard drives. So I pulled a discarded one from a refuse pile. This was an old 60 gigabyte 5.25 Maxtor Hard drive. I opened it up and found what I was after. The heads on most of these drives ride on a sealed shoulder mount ball bearing assembly. I popped of the heads and salvaged the bearing along with the sealed motor bearings. With the nice stainless shoulder bearing assembly in hand I enlarged the hole in the bellcrank and fitted the Bearing, It is secured with a Snap ring explicitly for this purpose as it is used to hold the bearing in place in the Hard Drive.
You can see the bearing in the photos as the round stainless item with the circlip below it. Final assembly is inserting the phillips screws into the aluminum plate, Threading and tightening the two brass ferrules on the screws then inserting the aluminum plate assembly into the holes in the bellcrank arms. Secure the screws to the bellcrank with nuts as shown, insert the bearing and secure that with the circlip.
There you have it a customized Ball bearing precision Composite bellcrank assembly. A bonus is that the hole in the bearing is a perfect fit for the metal bellcrank post supplied in the kit. The bearing make the bellcrank rotation smooth as silk, the bushed leadout scheme does helps with this also. It places no angular or twisting forces on the leadouts without any binding.
While there is no absolute need to modify the kit bellcrank in this way, It is a part of my process so I include it. The biggest drawback to this part is my finger tips are raw and sore as hell. But if you have more than a 6 inch ruler, a pair of pliers, a set of jewlers files and access to some power tools (dremel) etc then so long as you have all the raw materials you can knock this out in 2 hours. It took me almost 8.
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whilst I like the concept you are adding complexity and additional weight for no real gain......
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whilst I like the concept you are adding complexity and additional weight for no real gain......
It is no more complex than other split arm bellcranks out there (The tom morris Brett Buck Bellcrank or some of Windy's units) I like using that type of leadout attachment, it binds less, wears less and the leadouts always have a straight pull no matter the orientation of the bellcrank. The motion of the bellcrank is silky smooth low friction, no matter what amount of tension is placed upon the leadouts. ( comes in real handy when you have minimal line tension, it can make the difference between loosing the model or not) Which is the result of the ball bearing pivot. The added weight is located in the best place possible (very close to the CG) and can be more than than compensted for by selecting lighter weight components in other (Asthetic) places like wheel selection, spinner selection, etc. Of all the elements in a CLPA model, The control system, next to the engine the control system is the most critical. The last model I gave this treatment to (A Vector 40 kit) had control surfaces that were so free and smooth that they would flutter in the mildest breeze.
Note: The bellcrank as is in the kit is more than adaquate and is of better quality than most, but if you are going to the trouble and expense of retrofitting the kit with CF pushrods, Titainium ball links and adjustability up the wahzoo, this happens to be one spot that could stand some improvement. Until you try a control system using a ball bearing bellcrank pivot, you can't make a comparison. Also with this system there is no noticable chnage in control geometry as there is no wear on the bellcrank bushing or bellcrank pivot hole. There is no play either vertical, horizontal, or lateral in the bellcrank. While I did not measure it play in any direction of the bellcrank at the bellcrank pivot is undetectible without a dial gauge.
Besides, I had the time, I was bored as hell (You think Muncie has nothing to do? Try Kabul... Well avoiding potential terrorist, insurgents, road side and suicide bombs can lend a bit of excitement to life).
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Peter, did your wife also send you any other parts or sub assemblies from the kit?
I like your approach to building so far. Personally, I like to construct all the smaller sub-assemblies before the wing and fuselage. I don't know about others, but for me, I get slowed down building the small stuff if I've got the wing and fuse built. It seems to take forever for me to get them done at that time, whilst, if I build them right up front, they're waiting for me to install when I've finished the bigger stuff.
Whatever way you decide to go, keep us informed, and watch your backside.
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what do you intend securing the nuts with? Loctite? mechanincal means? I would like to see you have those fixed for good on there - pretty easy otehrwise for one to come loose.....even nylocks may do the trick.
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what do you intend securing the nuts with? Loctite? mechanincal means? I would like to see you have those fixed for good on there - pretty easy otehrwise for one to come loose.....even nylocks may do the trick.
I am of two minds on this, I can either loctite or epoxy the nuts or mushroom the screw ends so they can not spin off. Mushrooming the ends is the most secure method but makes it really difficult to take apart should a leadout need changing. Loctite or epoxy is easier to get apart but is not as secure.
Note, the brass bushings are threaded, they thread up on the screws and are tightened against the aluminum plate. Even if the nuts come off the screws will not fall out because they are still attached to the aluminum plate (held in place by the threaded bushings). Remember the brass bushings started out life as brass nuts that fit the screws. The aluminum plate is also secured to the bellcrank by the C clip that holds the bearing in place, there is zero chance that the clip will come off accidentally. (It is a real bear to get off with tools). So even if the nuts should fall off the screws attached to the aluminum plate still act as pins to retain the leadouts and the C clip now keeps the plate securely attached to the bellcrank proper and the screws still seated within the holes in the arms.
Because of this redundancy I think I will use loctite to afix the nuts to the screw threads, perhaps with a drop of epoxy to be safe.
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Everybody has their way of doing things. I like your bellcrank set up. H^^
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Yep, whatever works for you. I do it completely differently and it works for me. This seems like a good method.
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The box it comes in. Much smaller than expected
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The Stab and elevators.
This is where I ran into the first problem with the contents of the kit. The stab requires over 90 inches of 3/8th X 1/2 inch balsa stick to complete. The Kit is packaged with 2 36 inch pieces for a total of 72 inches. This is only enough material to complete the stab and one elevator half. Also the balsa strips that make up the ribs should be 3/32 X 3/8 inch strips. Mine was packed with 3/32 X 1/2. I contacted Eric and he promptly sent replacement pieces. He is going to make a change in the kit contents to include a third piece of 3/8th X 1/2 for the stab and elevator construction. But if you already have one of these kits Please note that you may also be a little short on the material.
Otherwise the Stab and elevators build up exactly like on the plans. When cutting the pieces try to use the top view of it that is on the Fuselage sheet. This one has the horn clips shown and you get a more accurate measurement. The view on the Wing sheet of the plans does not show the Horn clips and using that one your elevators will come out a tad on the long side. At least mine did. No matter as it is negligible and can easily be sanded to size.
The laser cutting on mine was OK, which means not great but not bad either. Many parts had to be cut free with the aid of a xacto knife while some of the thicker parts has significant burns. Nothing that made the parts unusable though.
The snapple bottles filled with water are used to weigh stuff down, like when laminating the ply parts to the ribs etc, and to hold stuff flat.
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I just figured you liked Snapple. The box looks fine except that it does have Gordy's picture on it.
Have fun.
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I just figured you liked Snapple. The box looks fine except that it does have Gordy's picture on it.
Have fun.
I do like snapple it's the best stuff on earth. But as for a cheap way to weigh stuff down, you can't beat water. And as the building surface is a mirror on a 3/4 mdf back board (Old head board) I can't pin things down. So bottles of various sizes. Wait till I start jigging the fuse with the gallon containers.
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I am glad you mentioned the mirror. I was going crazy trying to figure out the gap down the middle of the 2 piece ribs. Whats the mojo you installing?
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This is the Motor Mount crutch assembly. This is where I think I made a big mistake. The Plans and the FM construction article are very vague. I could not discern how far the engine bearers extended forward. It is not clearly shown on the plans and not discussed in the article. I made a guess that the maple mounts ended at the very front end of the plywood doublers. But now I think I was wrong. The supplied mounts are 10 inches long and if the mounts end at the front of the doublers they do not extend as far back as shown on the plans. They fall about 3/4 of a inch short. As you can see mine only extend past the rear bulkhead by about a half inch. They should extend about 1 inch further. I will fix this by cutting about 3/4 inch off the front of the mounts and splicing some back at the rear, to strengthen the fuse at this critical spot right over the wing.
When assembling your version use the Maple mount location on the plan starting from the rear end of the maple mounts lined up with the rear of the maple mount shown on the plans. Measure forward from that point. Do not try to estimate the locations of the parts from the front backward. This makes positioning the engine a bit more troublesome (As engine dimensions vary) but you will avoid the mistake I made. Also the balsa blocks provided with the kit are not referenced to the plan or called out on the plans or the construction article. Right now I have no Idea which balsa block is to be used where. The dimensions of the block do not seem to match with any of the outlines on the plans and the FM article is mute on this aspect of construction.
We will get to that problem later in this thread, and I hope one of the designers can shed some light on this subject. Otherwise the crutch squares up nicely and is straight forward in construction. It goes faster if you do all the plywood balsa laminating before hand and have the pieces all laminated and ready to go. The bulkheads are 1/8th ply with thin ply lamination's front and back. The nose ring gets the same treatment. At first these items feel too light and soft for this use, but I'll defer to the designers that this method is as strong as traditional engine mounting using solid PLY bulkheads and nose ring.
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Hi Peter, I'm not one of the designers, just the draftsman who worked closely with Gordan on the design. I took a look at the plan for the fuselage, and the top view shows the motor mount ending at the doubler. The Motor mount shows being slightly longer than 11 inches to conform to the shape shown on the side view.
Did you notice that the down thrust is built into the motor mount crutch?
I'm not in possesion of one of the kits, so I don't know about the balsa blocks supplied in the kit.
It's been our experience that the laminated nose ring, and forward bulkheads are as strong , or stronger than lite ply, and weigh less. Never seemed to have a problem with the laminations except in the case of my Bipe, where due to space considerations, i felt I neede a more solid nose ring, and went with birch ply for the part.
I'm sure Gordy will have a few comments to add, and correct me if I'm in error on any of this information. H^^
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Hi Peter, I'm not one of the designers, just the draftsman who worked closely with Gordan on the design. I took a look at the plan for the fuselage, and the top view shows the motor mount ending at the doubler. The Motor mount shows being slightly longer than 11 inches to conform to the shape shown on the side view.
Did you notice that the down thrust is built into the motor mount crutch?
I'm not in possesion of one of the kits, so I don't know about the balsa blocks supplied in the kit.
It's been our experience that the laminated nose ring, and forward bulkheads are as strong , or stronger than lite ply, and weigh less. Never seemed to have a problem with the laminations except in the case of my Bipe, where due to space considerations, i felt I neede a more solid nose ring, and went with birch ply for the part.
I'm sure Gordy will have a few comments to add, and correct me if I'm in error on any of this information. H^^
Hee Hee, Don't want to take any of the heat? ;)
Yes, I did notice the down thrust built in to the crutch design. It is slight but evident when the crutch is upside down as shown in the photo. When the tops of the bulheads are lined up with the tops of the fuse sides, It will have a degree or so of down angle relative to the centerline. I was unsure if the aluminum pads were to be inset into the maple mounts or laid on top. I opted to use some thinner material and epoxy them to the tops of the bearers. They are 1/6th aluminum pads and sufficent to prevent crushing the wood underneath.
You don't know what joy is until you have to use a loose hacksaw blade to rip saw maple motor mounts 8 or so inches, and keep the cut straight.
Thanks for taking the time to look the problem over. My Motor crutch mistake is not a serious issue, just an inconvenience. And was one of the reasons I started this thread so future builders of the Model will have a good reference to work from, one that may fill in the blanks in the FM article and potential discrepancies in the kit. The readers will note that I am assembling this model in sub assemblies. The Stab and elevators are one. The engine crutch is another. The vertical stab and rudder assembly is also sub assembled. This is how I am staging this build. You will notice that finishing touches such as sanding final shapes and small detail work has not been attempted yet. I like to group those tasks together so when that stage is reached it can be all done in one sequence. Also this way components can gather some hangar rash that won't impact the final stages while the sub components are awaiting assembly. For example If I ding the edges of the rudder before it is ready for assembly, no big deal, it remains in its rough form until right before it gets installed on the Fuse.
The next sub assembly will be the fuselage sides, they will be assembled and laminated then set aside until they are needed. Each fuse side is comprised of 5 pieces that have to be joined or laminated together in the kit. The plan shows the fuse sides being a single length.
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The Vertical Stab and Rudder Subassembly. This went together without a hitch. Everything is at Zero (No offset in the rudder part). Historically when I ever put any offset it would be either sanding in a asymmetrical airfoil shape into the subassembly or installing the whole thing with a minute offset. Like my last model the Vector 40 there is no offset shown on the plans so this will be installed on the fuse also with Zero offset. One note however. This is a 6 piece unit. There is a little triangular piece that fits at the base of the vertical stab back where the rudder section joins it. I could not find this little piece anywhere, I fear it may have ended up in the pile of the scrap pieces. No worry though as there is enough scrap balsa left in the kit to build a entire 1/2A airplane. I just found a scrap piece with a right angle and trimmed it to fit the space.
I ended up gluing this sub assembly to the mirror work surface with CA and had to pry it up using a spatula.
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Peter,
I tape saran wrap to the glass to prevent parts from sticking to the surface when gluing them up. NOT the peal and stick kind, it seems a bit porous.
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The vertical stab and rudder are laidout this way to wind up with a stiff, warp resistant, structure. D>K
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I guess that Eric of RSM Dist needs to put a disclaimer in his site about his kits being builders kits. I wonder at times how he keeps track of all this stuff. Have built several of his kits and am glad I had some experience behing me. Have the parts to build another HumBug and it will be powered right this time. Looking good on your build so far. H^^
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I guess that Eric of RSM Dist needs to put a disclaimer in his site about his kits being builders kits. I wonder at times how he keeps track of all this stuff. Have built several of his kits and am glad I had some experience behind me. Have the parts to build another HumBug and it will be powered right this time. Looking good on your build so far. H^^
I knew from the beginning that this was not going to be a traditional kit (Like Brodak or Sig Kits) Brodak kits which are excellent by the way. I was told that the FM article would be absolutely necessary and it really is. But that is the purpose of this thread. To bridge the gap between a builders kit and one like Brodak puts together. Hopefully between the FM article and the Info contained within this thread a future builder will have a clearer path to successfully build this kit. It even supplements any info for people scratch building just from laser cut short kits. While it's not a step by step Glue this piece to that piece instruction it will fill in the gaps between the FM article and the Plans that are available from FM or supplied in the kit.
So far the construction process did not require much in the way of detailed explanation. But that will change when it comes to the adjustable leadout installation and construction. The adjustable leadouts supplied in the kit differ a good deal from the way Gordon installed and designed his on the plans. The Cowl construction is another area. I will note now, and again later.
The control system shown on the plans are Tom Morris components. They are not what is packaged in the kit. If you want to have the same setup as shown on the plans then you need to contact Tom Morris and order a set of controls for the Pathfinder LE. This is what I will be doing. The hardware supplied in the kit is good stuff, just it is not the same stuff as shown on the plans. I have verified this info from Tom Him self.
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Here is the latest installment of photos. We have the Ribs that support the landing gear laminated with 1/32 ply ready to go. And you can see also the fuselage as it comes out of the kit. There are 5 pieces to each fuse side. The side doubler for the engine crutch, the side doubler for the stab mount area, the rear half 1/8th inch fuse side, the front half fuse half and a long thin triangular strip at the bottom (hidden by the tape)
Note: This is the method most use to but join sheet balsa. You true up the edges and then but them up against each other. Take tape and run it down the entire edge, taping the two pieces together. Flip over and run a bead of glue down the seam. Scrape off any excess then weigh down flat till it dries. Works like a charm every time. The tape keeps glue seapage to the un-taped side which you can face to the inside of the airframe. The little seepage on the taped side can be readily sanded out.
Here you can see first hand the SNIT Jig. (SN.apple I.ce T.ea) Hey you use what you have on hand! I put a small patch of Saran wrap on the underside of the bottles to give them good sticktion on the mirror surface. As long as the glass is clean the plastic wrap really clings to the smooth glass. While not as rigid as professional or task specific jigs, it works very well is infinitely adjustable and refreshing to boot.
I still have not figured out the balsa block configuration for the nose and cowl. I wish Gordy would comment on this thread and clear it up. It is completely neglected on the plans and has me scratching my head on how the top of the fuse under the canopy is supposed to go together. The plans only show the outline but no supporting description or detail.
NOTE: There are cutouts in the bulkheads for two balsa extension strips along the sides of the fuse. These are there to support the upper fuse sheeting and upper fuse bulkheads. The plans call out for two strips of 1/8th X 1/4 balsa stick to use as the extension strips. The cutouts in the bulkheads are too narrow for this. You can squeeze in a 3/32 balsa strip but I had to enlarge the notches to accept the 1/8th X 1/4 inch strips. I do not know if this is an error in the laser cutting, a miscommunication or some mod that was implemented later but never made it to the plans. At any rate it is a trivial modification that has to be made so prepare for it.
In addition the fuse bulkheads seem really fragile. Some being a mere skeleton's worth of balsa to form the fuselage shape. By that I mean rather wide and quite narrow with the grain not runnig in the optimum direction. I will highlight this in later photographs. I am seriously considering beefing up some of these bulkheads but of course that will mean additional weight.
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Greetings Peter. I took a look at the plans to try and figure out what was giving you questions in the nose,cowl area.
The cowl is pretty straight forward, with 4 pieces of 1/4" balsa that are identical, except for a relief for the nose wheel mount plywood. The idea was to capture the plywood by having the cowl parts laminated so that the relief makes a pocket that the edges of the nose gear plywood fits into.
As for the area on top of the fuselage, under the canopy, I formed mine so that the top of the balsa crutch, between the motor mounts, became the bottom of the cockpit, and where I mounted the pilot figure on mine.
Does this help? H^^
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Greetings Peter. I took a look at the plans to try and figure out what was giving you questions in the nose,cowl area.
The cowl is pretty straight forward, with 4 pieces of 1/4" balsa that are identical, except for a relief for the nose wheel mount plywood. The idea was to capture the plywood by having the cowl parts laminated so that the relief makes a pocket that the edges of the nose gear plywood fits into.
As for the area on top of the fuselage, under the canopy, I formed mine so that the top of the balsa crutch, between the motor mounts, became the bottom of the cockpit, and where I mounted the pilot figure on mine.
Does this help? H^^
I'll have to post a close up photo of this part of the plans. Hi John!
I understand the area you speak of. I am confused about the area just above that and the section extending to the nose ring. This area is comprised I think by the nose block at the front shaped into what appears to be the instrument panel under the canopy. But then extends just above the fuse sides all the way back to Bulkhead 3. This piece is not part of the fuse side but some structure that sits right atop the fuse sides adjacent to the engine bearers. As the photo of the fuse shows the engine bearers and the balsa stiffener between them. I am confused as to what is used to fill the space between the engine bearers and the bottom of the canopy, from BH3 all the way forward to the nose ring. This mystery is complicated by the fact that there is no balsa block in the kit long enough to fulfill this area.
I understand the double 1/4 inch cowl sides, it is the front of the cowl (air inlet and venturi area) that concerns me, again complicated by the fact that there is no balsa block supplied that seems to fit the space up front between the cowl sides.
The plans show the cowl extending right up against the nose ring. The nose ring is not thick enough to support the dowels recommended in the article to secure the front of the cowl.
Note: The cowl width when assembled is a really tight fit over the OS 46 VF cylinder head. Much inside carving will have to be done so there is enough clearance around the cylinder head.
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Here is the close up photo of the plans and the areas under question. Sorry about the quality. But it gets the point across.
The trouble with allocating kit materials to these areas is that I do not want to use up a piece of balsa block to this area only to find out later that, that particular piece was meant to be used elsewhere.
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OK, I better understand your questions.
In the area under the canopy, the block actually ends where the angle would make the base for the instrument panel. The small amounts of material going back to the back of the canopy are made fro scrap, and I should have marked it soo. I believe Gordy had a soft balsa block that went from the nose to the back of the canopy. He painted his canopy so it's all under wraps.
There should be a small block to fit between the cowl sides , behind the spinner ring. If it's not in the kit, be sure and make one out of scrap. You are correct, without it, the front of the cowl cannot be mounted as shown. H^^
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Starting on the wing. The great thing is are the guides and the built in tabs that allow the wing to be built without a jig. I followed the instructions in the FM article on how to set this up. The really really bad thing is that the bellcrank mounts are not cut properly in the kit. They are too narrow! I discovered this only after gluing the lower bellcrank mount on to the center ribs with epoxy. Because the mounts are cut improperly there will be insufficient contact area between the mounts and the upper and lower spar that caps the mounts!
I am upset that this error was make in the kit fabrication at such a critical part of the model. I am uncertain how I can now fix this deficiency, I can not afford for the bellcrank mounts nor the center section of the wing to structurally fail. As the parts have already been glued to the rear shear web spar and then glued to the 4 ribs, I would have to trash the entire assembly and cut new bellcrank supports as shown on the plan in the photo below. The supplied plywood supports are no where close to the parts shown on the plans.
This is a major fault please note this when constructing your kit!
I can probably fill in the space left by the too narrow supports but I fear that it will never have the structural integrity that a proper width pieces would offer. The killer thing is that the way the bellcrank mounting is designed there is not much in the way I can satisfactorily reinforce this area.
NOTE: In the photos you can see just how narrow the supplied laser cut bellcrank supports are compared with the drawing.
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The plan drawing
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Darn Peter, that's a headache, but shouldn't be too hard to fix, even in place. Cut as shown on the plan, it's supposed to fit onto the spar, and put the joint in shear, but you know that.
I'm glad you like the self jigging features of the wing. Gordan tells me that goes back to Ed Southwick's Skylark construction. H^^
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Make the bellcrank pivot long enough to extend past the surfaces of the center section. Then make ply pads to go over the pivet and butt up to the fuselage side. 1/8th inch steel wire/shaft should be enough to hold. I have a couple of wings in which there is no ply inside the wing itself. Also if you think that is not enough ply by itself, don't build an I-Beam wing. VD~
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Make the bellcrank pivot long enough to extend past the surfaces of the center section. Then make ply pads to go over the pivot and butt up to the fuselage side. 1/8th inch steel wire/shaft should be enough to hold. I have a couple of wings in which there is no ply inside the wing itself. Also if you think that is not enough ply by itself, don't build an I-Beam wing. VD~
Read my mind John, Since I already epoxied all those parts in place and glued the ribs to the shear web spar at the back, I needed to come up with a alternate plan, else I would have to make new ribs, Spar etc. I took some of the scrap Ply and fashioned a couple of square pieces that filled up the empty places in the rib slot where the ply supports go. That taken care of I will do as you say. I was already planning to make ply pads on top and bottom extending to the fuse sides to help reinforce that area and in light of Matt Colans problems with his TP with the pull test I thought that would be prudent.
As the construction comes along I post photos of the fix.
Builders of this Kit should note this in their build process. The ply bellcrank supports are tapered far too much!! n1 :X DO NOT USE THE wing drawing itself to see if it conforms!!!!! n1 :X If you check it against the wing plan, then it would look like the part is laser cut correctly, HB~> THIS IS WRONG HB~>. y1 Use the separate section drawing located above the Wing Plan for the proper shape of this part!!!
I posted a picture of this part of the plan that shows the actual part outline!
Somehow when the parts were laser cut the part outline that is on the wing plan drawing was used for this and it leaves the part tapered much too thin at the ends. The Rib slots are correct however.
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As a side note. Upon looking through the kit contents I think that the kit is short the necessary blocks to fabricate the wing tip blocks. According to the FM article there should be bocks hollowed at the leating edge of the wing tips. I only have one piece of 4 inch X 1 inch X 8 inch balsa block. And that would be needed to form the upper fuse nose block. (The area highlighted in the plans earlier in this thread) there is no significant left overs from this piece to make the wing tips.
I also have a block that is 2 inches X 1 inch X 6 inch block for the tail between the stab and elevator. I figure I would still need 4 pieces of 3 X 3 X 3/4 or 1 inch balsa block to fabricate the wing tips.
Am I correct in this assumption John? (John Miller) Please Confirm.
If so The kit is short these items and they do not even show up in the kits part list. I hate to hammer Eric on this sort of stuff, I have already found other balsa that was short in this kit and he shipped me those, so this would be another oversight. Perhaps George Delany needs to go over the kit contents and materials with Eric on this kits item by item so others do not have these issues. I find it weird that so far I have been the only one to report these irregularities.
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Greetings Peter.
I checked the parts you asked about. First, it appears that the plywood BC mounts were cut using the wing view, where the part of the mount is under the spar. The part shown on the smaller detail drawing, above the wing, shows thwe part in it's entirity.
The supplied block used at the tail would be fine, if it were 2 inches longer. The actual size that would work best would be, 1" x 1 1/4" x 8".
The wing tips will require 4 pieces of 1" x 3" x 3" balsa to make the tips.
I don't really know if any of the kits have been built yet, probably why you are finding these little problems. HB~>
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I have one of the Pathfinder LE kits that I bought last year, yet to be built. I also have the magazine article for reference. I am very interested in this thread because I will face the same issues when mine goes from bones to bird.
It is also a bit disappointing to read that an expensive high end kit like this has its flaws. I was under the impression that laser cut kits were preceded by a prototype build to insure that all the parts were included and fit as designed.
Still, I think the Pathfinder is a gorgeous plane and well worth the effort required to overcome any shortcomings.
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I agree Dick. Peter is providing potential builders of this design with a great service. There were two prototypes built from the original plans, and cutfiles, but, there were some apparent minor changes going into kit production. Peter is also providing a service to Eric at RSM, by reporting these items to him. Eric's a class act, and will bend over backwards to make his products conform to his standards.
Here's some pictures attached of the two prototypes. I own one of them, and they do fly very good.
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This is the shot of the wing under construction. The Shear web spar and the built in tabs work like a charm. Set it up exactly like the FM article says. The article says that you can install just about everything without removing the wing from the board except for the center sheeting. Although you would have to have the skills of s surgeon to apply the cap stripping and other components to the top side of the wing (REMEMBER THE WING IS BUILT UPSIDE DOWN) On advantage of building on a mirror you can see all stuff on the underside. This will make installing the top spars much easier since you can see reflected where the rib cut outs are and where you are smearing the epoxy on the center section components.
Also easy to spot if there are any gaps between items on the back side. Use a sharpie marker to draw your reference lines on the glass. In the kit the landing gear mounts are 1/8th ply. Study the assembly order subsection on the plans before you start sticking the pieces in. There is a very specific order to how the several pieces fit together. There are a total of 4 ply pieces for each main gear and 1 balsa filler piece. These are installed between ribs 3 and 4 (ply doubled) and then the main spar caps them. There is no detail on the meathod to construct the vertical section of the landing gear mounts. But this should be a simple task using some of the scrap plywood to fabricate it. Did I mention there is enough scrap balsa left over to construct a fleet Of 1/2a planes?
Also in the photo you will see the cowl, I'll get into more detail on that later, however it is best to mention that the nose gear wire is not bent according to plans. I did not sweat this detail but it does take a little tweaking to fit properly within the cowl. It does not conform to the outline etched into the plywood mounting pad. Since the nose gear is not bent according to plan you will need to create a bigger hole to pass the gear through the cowl bottom. This is because the angle at which it exits the cowl will cause the gear to deflect more upon landing. If the hole is too small the gear wire will smack into the hole sides and possibly cause your cowl to crack. I'll cover this more later. But be prepared for this or bend a new nose gear according to the plan.
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Here's some pictures attached of the two prototypes. I own one of them, and they do fly very good.
John, I absolutely love the paint job on the original yellow one that was featured in the article. Did Gordan by chance sketch up a layout of the graphics, so a copy could be made?
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Hi Dick
As far as I know, he did not, but there are enough pictures available to let someone easily duplicate his trim scheme. I'm sure that he'll be pleased by your comments. H^^
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One of the things that are annoying me is that I have not yet settled on a graphics theme. Usually at this point in the construction process I have some inspiration as to where I want to go with it. Did the transparent thing with the vector and once I've been there I usually don't want to re visit it. The Pathfinder speaks to me of something else, although what that may be I have no idea. One thig is certain, it won't be a racing theme aka Gordon or similar. I have just not settled upon whether it should be a soft theme or a hard one. (Soft being curvy shapes, Gradient colors) Hard being angular and high tech. I was pondering military but that's been soooooo done already. Oh well something will come to me after I stare at the finished airframe for a while.
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The great Tip debate.
The wing was coming along great. The included Rib spacing templates are a huge help. They get the ribs spaced and aligned properly. As you can see there are a ton of ribs and riblets (Sounds like a Sonny's BBQ menu) When I assembled the wing I got installed all of the ribs to the rear shearweb spar, and using the templates got the correct spacing and glued the rib tabs to the surface.
NOTE*** This wing has unequal wing panels the inboard side of the wing is longer than the outboard half. This is why the shear web and the templates are marked inboard and outboard. Keep this in mind and use the the correct spacing template on the correct side! I do not recall reading this in the FM article.
After getting the ribs fixed into position I attached the bottom spar (Top in this case as the wing is built upside down) I used slow cure epoxy to glue the spar from the center of the wing out to Rib #4 the second ply reinforced rib. I let this cure overnight and then I carefully glued the spar to the rest of the ribs using CA. This makes the whole process easier to manage, as this allows you to lift the spar up and glue each rib separately rather than trying to do them all at the same time before the CA kicks off.
I repeated the process then on the left half the top and bottom. With the spars installed it was time to add the riblets.
Not you will have to shim RBH 3 as the notch is too long. Something different between that half rib and the LG mounting blocks. Did you remember to install the PLY LG mounts to the ribs before installing the spars??? You need to install the block first the spar goes over them.
I had to trim a notch or two here and then on the half ribs but all in all they went in without a hitch. Here the Spacing templates come in really handy. Once the riblets were in I set the oven to 450 degrees and the cooking time........................... Oops wrong topic. With the half ribs installed I added the leading edge reinforcement strips. What seemed to be a spidery fragile wing now became a rigid structure. At first I had my doubts about the strength of this wing but after all the spars were installed it became solid as a rock. Looks like it will be really light weight too. Kudos Gordon.
Everything was going along swimmingly until I got to the tips. To accommodate my building surface I glued the tip plates to R 11 before adding Rib 11 to the ends of the wing. It just made it easier to square up the tip plate to the rib. Once done I popped them on the wing ends. This is where I ran into the problem, I started looking for the material to attach to the wing tip plates. Shown on the plans and in the FM article there were supposed to be some blocks for this purpose. Well no such blocks in the box. I contacted Eric and got a long response which I won't get into here about how Gordon changed the design. so the blocks were not necessary and that no block for this purpose were going to be supplied.
In my opinion this was a song and dance. Clearly all of the wing tip parts that are laser cut match the plans and the FM article exactly. Using the laser cut parts supplied you requires that the Blocks shown in the plans be used! The tip plates alone are not sturdy enough to make up the assembly and leaves you no way to mount the adjustable leadout guide. Not using the blocks requires you to completely redesign the way the tips are constructed.
To make a long story short as of this writting you have to order a piece of 1" X 3" X 12" long minimum balsa block to finish the wing tips as detailed in the FM article and illustrated on the plans. The photos I've attached validate this. You can use thinner balsa sheet and use a laminating technique with the layers pre-cut, simulating the hollowing process as well. This is how the Brodak Vector 40 wing tips are constructed. Up until this point I've been relatively happy with the quality of the kit. But the deficiencies have accumulated to the point where I caution that this kit is ONLY! for experienced builders with balsa stock and ply stock on hand. First it was the shortage of 3/8 X 1/2 stock, then the kit did not have any 3/32 X 3/8th stock, Then the bellcrank supports were cut wrong, the nose gear not bent correctly, 1/8 dia horns when the Flap and elevator ply mounting clips are designed and cut for 3/32" for starters.
Compared to the Brodak Vector 40 kit I last built the Brodak kit was a 10 this kit is down at a 5 at nearly twice the price. The best features of this kit is not really the kit but the design kitted, The consideration and forethought that Gordon put in when making the model easy to construct, strong and light. So far the execution of the kit it's self has been not more than OK.
Anyway, back to the construction, I am rapidly approaching the point where I am will have to form the leading edge sheeting. I dread this, as I still have not found a way to construct the forming buc's with the tools at hand. As I have to wait on the order of the balsa block for the wing tips, I guess I'll have time to figure a way to make those darn BUC's.
BTW. You will find a weird duplication. In the kit you get 4 ply landing gear pieces marked LG-1, a wider ones and a slightly narrower ones. USE the WIDER ones that's supplied. I think the narrower LG-1 piece is a error as I can not seem to figure out how it would be useful
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More wing
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All righty then,
Spent most of the weekend trying to figure out the wing tips with the material on hand. I do have a solution that works considering the lack if included blocks for the task. There is enough scrap 3/8th balsa sheet left (from the flap cut out) that can be edge joined and then used to laminate the leading edge blocks. The lamination technique should be familiar to those who have built the Brodak Vector 40. You cut the sheet to simulate the hollowing process while building up the height needed for the block. Then all you have to do is sand the outer contour. No actual hollowing needed as you fro cut the lamination's to mimic this. If you wish to carve and hollow the solution I have found has enough material for this. It is enough for 8 pieces of 3/8 inch wing tip that can be laminated into the four blocks that are required for the tips.
I'll post photos tomorrow. So make sure you save ALL of the scrap 3/8ths stock from the kit you'll need it.
I have yet to figure out how to mount the adjustable leadout guide, it is the one thing on the plan and the FM article that is not covered in any detail and the plan is very vague on this. Also vague is exactly where the leadout exit slot is to be. Is it above the leadout plate? Below? if it is vertically centered as shown on the side view the most of the Wingtip plate has to be cut away, leaving a bare minimum of support of the wing tip. Even as it is (un cut) the inboard wintip is very unstable and flexes a great deal. I can not imagine that cutting half of it away will help any.
Another item is that rib 8 through 11 are not laser cut correctly. The plan shows those ribs slotted almost the span of the rib with a 1/2 inch slot. This slot is for the adjustable leadout clearance. The ribs as supplied are cut the same as all the other ribs which have a central support (between the spars as seen on the pictures) and minimal material at the tops and bottoms. If the central supports are cut away then only a tiny portion of the rib would be left. I will have to reinsert the balsa knock outs back in these ribs and try to slot them while installed in the wing.
The problem with this is the Half ribs, If you examine the plan then it looks as if the leadouts would saw through the half ribs closest to the tip. The leadout spacing shown on the plans allows for only a tiny amount of adjustability if contact with the vertical parts of the half ribs is to be avoided.
In the end I think that the adjustable leadout solution shown on the plan and in the design will turn out unacceptable. Either the line spacing would have to increase or the limits of adjustability is far less than suggested on the plans. I am rather surprised that Gordon has remained so quiet and not made any comments on this thread at all. Makes one wonder.
The rest of you DO NOT remove the knock outs from the inboard ribs 8 through 11 glue them in and slot them as shown on the plans.
Note**** the provided Leadout guide has to be modified to resemble the one on the plans. You may wish to just fabricate a new one, it may be easier.
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I have yet to figure out how to mount the adjustable leadout guide, it is the one thing on the plan and the FM article that is not covered in any detail and the plan is very vague on this. Also vague is exactly where the leadout exit slot is to be. Is it above the leadout plate? Below? if it is vertically centered as shown on the side view the most of the Wingtip plate has to be cut away, leaving a bare minimum of support of the wing tip. Even as it is (un cut) the inboard wintip is very unstable and flexes a great deal. I can not imagine that cutting half of it away will help any.
I regret that the plan and artical seem vague on the installation of the adjustable leadout assy. It's one of those things that one does almost by instinct, but that isn't how everyone does the same thing.
The inboard wing tip shows a notation to laminate 1/64" plywood, and shows the hidden dotted lines, where the 1/8" balsa was removed to create a 1/8" wide slot for the leadouts. There's a 1/4" X 3/8" balsa fairing strip attached on the top and bottom of the 1/8" balsa wing tip, between the trailing edge sheeting, and the tip block. In practise, it's easiest to laminate one side, leaving the area to be removed, glue free, and then remove the 1/8" balsa. Then attach the opposite 1/64" lamination. next, attachethe 1/4" tip fairing strips, on top of the 1/64" plywood laminations, so the tip becomes quite rigid once all assembled.
Another item is that rib 8 through 11 are not laser cut correctly. The plan shows those ribs slotted almost the span of the rib with a 1/2 inch slot. This slot is for the adjustable leadout clearance. The ribs as supplied are cut the same as all the other ribs which have a central support (between the spars as seen on the pictures) and minimal material at the tops and bottoms. If the central supports are cut away then only a tiny portion of the rib would be left. I will have to reinsert the balsa knock outs back in these ribs and try to slot them while installed in the wing.
The problem with this is the Half ribs, If you examine the plan then it looks as if the leadouts would saw through the half ribs closest to the tip. The leadout spacing shown on the plans allows for only a tiny amount of adjustability if contact with the vertical parts of the half ribs is to be avoided.
Mea Culpa, This was an oversite on my part. After several changes being asked for, I made the changes on the plans, but overlooked making the changes to the cut files. In my defense, I can only say that few people realize how many changes need to be made for what, on the surface, appears to be a simple minor change.
Before the change was made on the plans, when I built my version of the prototype, the ribs were lazer cut as they are presently supplied in the kit. When it was realized that the center supprt would interfere with the leadouts near the tips, I removed the center support on the interfering ribs, and added a 1/16" X 1/4" support further back where it would not interfere with the leadouts. Due to the fact that the grain runs 90 degrees o the rib, it seemed to make the affected ribs stronger in resisting the crush.
In the end I think that the adjustable leadout solution shown on the plan and in the design will turn out unacceptable. Either the line spacing would have to increase or the limits of adjustability is far less than suggested on the plans. I am rather surprised that Gordon has remained so quiet and not made any comments on this thread at all. Makes one wonder.
Gordan has had a death in his family, and is not paying a lot of attention to the internet at this time.
Actually Peter, the adjustable leadouts, as designed, work very well, and result in a strong and stable tip.
Note**** the provided Leadout guide has to be modified to resemble the one on the plans. You may wish to just fabricate a new one, it may be easier.
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I took another look at my files, and found that I had indeed made the changes on the cutfiles. What I cannot be sure of is which file was used to make the kit, or even if the changed file was sent to Eric. Because of a lot of changes being asked for, there were a lot of files flying back and forth, and I feared that the wrong ones may be used. I can see how it could easily happen, and I have to admit, that I may not have sent out the file with those changes. It's been a few years. It is what I feared and warned about, asking that older files be removed.
The simplest solution is either to do as you suggest, or use the solution I did.
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Attached are the Photos of the inboard wing tip. I did the ply lamination's to the tip plate as suggested I applied them to the entire outside edge rather than just the spot shown on the plans. This keeps all of the balsa pieces the glued to them at the same base level. I did surmise that I would have to cut away the tip plate to slot for the leadouts. I'll do that when I flip the wing over. Here you can see the alternate solution to using one piece tip blocks. I edge glued the left over scrap from the Flap sheet to get sufficient width and marked the tip outlines on this piece. You may ask why am I doing this before installing the leading edge sheeting?
Because for me the leading edge sheeting is still a problem, and I want to get as much done before I beat my self silly with that. It is also easier to make the rib clearance modifications for the leadouts before the sheeting is in place. I want to make sure I have as much leadout adjustment possible without sawing ribs in half with the leadout wire.
NOTE:
The trailing edge sheeting supplied with the kit is not wide enough to cover the shear web! it is only wide enough if you but up against it. Wile this is not a issue with the top side of the wing. On the bottom the sear web does not extend past the ribs to but up against it. Either you ignore gluing the trailing edge sheeting to the shear web on the bottom of the wing or position it so it covers the shear web. That is what I did, so you will see in the photo that a portion of the trailing edge is uncovered by the sheeting. The sheeting still overlaps the trailing edge enough to get a good box structure with the sheeting glued to the shear web, ribs and trailing edge. I'll just use some scrap to fill in the 1/8th space where the trailing edge sheeting does not cover the trailing edge completely.
At the top of the wing you should be able to butt up against the shear web and retain the box structure along the trailing edge. We shall see if this is true when I flip the wing over and do the other side.
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Pretty creative us of scrap balsa to make the tip blocks. I like the idea.
As for the trailing edge sheeting, Gordan prefered having the sheeting cap the shear web, top and bottom. In my case, I butted the sheeting to the shear web on what will become the top of the wing, (bottom when jigged up) and capped the shear web on the other side. I installed both sides of the trailing edge sheeting, while still jigged up. My thinking was that It gave a better chance of keeping the trailing edge straight that way. It also made it easy to glue the sheeting on doing it that way.
I don't know if it really matters, as Gordan's wing came out just as straight as mine.
You did the tip as I did mine. It comes out pretty neat that way. H^^
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Hey Peter:
Been following your build here with interest, because I have the same kit, not yet started it. I dont understand why you have a delima with the LE sheeting. Does the plan / design require a buck to mold the top and bottom sheets into one piece ? If so could you not just wet the bottom sheet, glue it in place from spar to LE using weights, flip wing over and do the same for top sheet ? Maybe I should just get the plan out for review. Not sure what materials and tools you have available where you are, but if I had to make a buck, I would make it from foam glued to base of something rigid, the same shape as the spar web, with root and tip half ribs for a carving / cutting guide.
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I use a straight edge all the time to make sure things are running straight. I checked the TE on both the horizontal and vertical to make sure they remain straight throughout the building process, before gluing and after. Having done mainly Foam Wings in the past I am especially paranoid about warps. The mindset is that Foam Wings are inherently warp free and builtup's are inherently warp prone. This may not be true of built up wings but it helps to think that way.
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Hey Peter:
Been following your build here with interest, because I have the same kit, not yet started it. I don't understand why you have a dilema with the LE sheeting. Does the plan / design require a buck to mold the top and bottom sheets into one piece ? If so could you not just wet the bottom sheet, glue it in place from spar to LE using weights, flip wing over and do the same for top sheet ? Maybe I should just get the plan out for review. Not sure what materials and tools you have available where you are, but if I had to make a buck, I would make it from foam glued to base of something rigid, the same shape as the spar web, with root and tip half ribs for a carving / cutting guide.
The dilemma is that, I have no way rough cutting the foam to the shape of the BUC templates. The Leading edge stiffener is only 1/8th wide so there is very little margin for error sheeting it in two half's, and would require attaching wet balsa to the wing skeleton. Now if there is any invitation to warps that is a VIP invitation. Plus as I can not make a mess (I don't own the property) Creating mounds of Styrofoam dust from sanding a BUC to shape is pretty much out of the question.
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I would not anticipate needing to soak balsa to form leading edge skins. They are not fully wrap around are they? I dont think I recall that.
I typically just sheet them with dry wood, at the VERY most I will get it in position , and mist lightly with a spray bottle of water, this swells the outside of the sheet and most times allows it to form right around the ribs
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The dilemma is that, I have no way rough cutting the foam to the shape of the BUC templates. The Leading edge stiffener is only 1/8th wide so there is very little margin for error sheeting it in two half's, and would require attaching wet balsa to the wing skeleton. Now if there is any invitation to warps that is a VIP invitation. Plus as I can not make a mess (I don't own the property) Creating mounds of Styrofoam dust from sanding a BUC to shape is pretty much out of the question.
A good option if you can handle the extra expense would be to have have Bob Hunt cut you a set of LE bucks and ship to you.
All you would have to send him are the root and tip half rib patterns and lengths of each wing panel.
Probably could get by with just a single buck for both LE's.
I will take a look at the plan later tonight and see if I can come up with any bright ideas.
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I would not anticipate needing to soak balsa to form leading edge skins. They are not fully wrap around are they? I dont think I recall that.
I typically just sheet them with dry wood, at the VERY most I will get it in position , and mist lightly with a spray bottle of water, this swells the outside of the sheet and most times allows it to form right around the ribs
I agree that a mist would give enough of a curve, but his issue is the 1/8 thich LE support (think it might just be 1/8 x 1/4 on the flat) which does not give much for pinning or support weights to hold sheet in place while glue drys. Wing does not have the typical 3/8 or 1/2 square diamond to accommodate a 2-piece sheeting.
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Looked at the plans, LE design could have easily been changed to work with a 2-piece sheeting, but the ribs would have had to be modified before assy. So I think you are stuck with the buck. If I had already built my kit I would likely have a buck laying around, I would send it to you for the cost of shipping. But my Pathfinder LE is still about 3 or 4 projects down the road.
Saw the recommendation on the plan about shortening the nose if using engine heavier than PA40UL. Are you going to do that ?
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Peter, I still would recommend using Bob Hunts method. You can read it as it's pinned to the top of this forum. When I did the wings for the Bipe, I used a preformed balsa leading edge as a forming buck.
I know we've spoken about this, and you were concerned that there my be some slight differences that will cause problems. There were slight differences with my wing, but the balsa willingly conformed to the rib shape. Once the leading edge cap was installed, it was easy to add the rest of the sheeting.
A few pics to illustrate:
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Looked at the plans, LE design could have easily been changed to work with a 2-piece sheeting, but the ribs would have had to be modified before assy. So I think you are stuck with the buck. If I had already built my kit I would likely have a buck laying around, I would send it to you for the cost of shipping. But my Pathfinder LE is still about 3 or 4 projects down the road.
Saw the recommendation on the plan about shortening the nose if using engine heavier than PA40UL. Are you going to do that ?
I have moved the engine back about a 1/2 inch from where it is shown on the plans. That leaves me with two choices, use some sort of extension to get the prop out where it should be without blunting the nose a bit or just make the nose infront of the engine shorter and adjust the back of the cowl to fit. I have not yet decided which way to go yet. It may be the latter because I am unaware of any 1/2 inch extensions out there anywhere.
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I would not anticipate needing to soak balsa to form leading edge skins. They are not fully wrap around are they? I don't think I recall that.
I typically just sheet them with dry wood, at the VERY most I will get it in position , and mist lightly with a spray bottle of water, this swells the outside of the sheet and most times allows it to form right around the ribs
Last night I figured out a solution to the leading edge sheeting problem. It requires some precise cutting to the balsa sheet but it will work. Here is how I plan to tackle it.
I have cut to shape and size the leading edge sheeting. I will carefully align the edge of the sheet with the centerline of the leading edge reinforcement strip. I will support the sheet against the leading edge reinforcement with some tape or other means so the sheet is at a 90 degree angle (vertical) to the leading edge strip. Then from the back side I'll attach the edge of the sheet to the LE strip with CA glue along the seam where it meets the LE strip. (Standard Technique allowing the adhesive to wick between the surfaces) Once the CA kicks, the leading edge sheeting will be attached toe the LE strip with the sheet sticking up in the air.
Then I'll use a wetted paper towel and dampen the outside surface of the leading edge sheeting and slowly bend it around the curve of the ribs. (after running some wood glue along all the ribs and spar) Once the sheeting is bent around the ribs and conformed to the wing shape I'll secure the sheeting to the spar using standard spring clips or pins while the slower drying glue dries.
After both the top and the bottom of the wing is done then a 1/2 inch strip of carbon veil covering the seams at the very tip of the leading edge should make it bullet proof. The carbon veil should be invisible under the covering film, it is much thinner than galss tape.
Hows that for a solution???
The hardest part is trimming the sheeting so the angles and the length of each panel is correct at the LE, TE, Root and tip ends of the sheet, as once it's attached with CA to the leading edge reinforcing strip there is no turning back.
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Sounds kind of iffy, you will only have a 1/16 ca glue joint between sheeting and LE support.
Thinking it might break or crack the sheet when you try to curve it down to the spar.
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Sounds kind of iffy, you will only have a 1/16 ca glue joint between sheeting and LE support.
Thinking it might break or crack the sheet when you try to curve it down to the spar.
Not if I get that area damp enough, Balsa gets pretty mushy when wet. And the supplied sheeting is the really light grain low density stuff.
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Maybe I am backwards, but I usually glue leading edge sheeting to the spar first. Using peices of masking tape to hold it in place. Then start gluing to the leading edge peice, also using masking tape to hold it in place. If you use straight grained balsa it bends a lot easier. H^^
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Attached are the photos of the latest progress. Shown is the adjustable leadout assembly I made up. I did not use the one supplied in the kit as it was not acceptable in this design. I made a small modification to the one George Delany has on the plans as I made a alignment plate out of aluminum to fit over the tubes and to provide a greater surface area that clamps the adjuster in position. I did this over the traditional screw and washer set up because I wanted to make sure the extension tubes remain aligned and to prevent crushing of the plywood slider channel that is typical with the screw and washer setup. Once you have all those dents in the slider rail it adjustment becomes notchy as the washer get hung up in the dents.
Also highlighted is my method for attaching the wing sheeting. The pins you see in the photo do not pierce the sheeting they are inserted into the 1/8th leading edge reinforcement strip. They are positioned so the leading edge of the sheeting sits on the pins, keeping the sheeting aligned 1/16 inch centered on the 1/8 wide strip. Then from the back side I applied CA along the length of the sheeting to glue the leading edge of the sheeting to the reinforcement strip. Once this was set I removed the pins and using a paper towel I wet the outside surface of the sheeting. I then applied wood glue to the spars and rib tops. When this was done I gently rolled the sheeting over the ribs and spars, clamping the sheeting to the spar at various points along the wing. I use the scrap ply from the kit to prevent the clips from denting the sheeting.
This worked out very well and the wet sheeting bend without a problem or any splitting. I pre cut the sheeting to size and shape before attaching it. If there turns out to be any gaps between the ribs and the sheet I'll use CA and nail those down when I flip the wing over. I may modify this technique with the top panels to avoid any gaps between the ribs and the sheeting. The other side will be easier because I'll have more material to pin to and I do not have to worry about maintaining that 1/16 inch tolerance.
Note: In the last photo you can see that I joined the trailing edge sheeting with a 45 degreen angle spanning one inboard rib. On the underside I reinforce this joint with 1/8th balsa cut so the grain is 45 degrees in the opposite direction putting the grain of the sheeting and the reinforcing strip at 90 degrees but no joint angle is parallel or aligns with the centerline of the wing.
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The sheeting
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Nice job with the LO guide. Similar to the way I make mine. I use 1/16 phenolic plates on either side of the wood slider. Only thing I would have done different is move the slider as far out to the tip as possible. No reason for it to be buried inside the tip like that.
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The L.O. guide was placed where it was to allow enough movement, fore and aft. If it was moved further out, the forward movement would be lessoned, the further out the less forward movement, unless the leadout is angled to match the angle of the tip. If angled, then the tubing must be mounted angled also, so that the leadouts exit with out binding on the tubing. I've done it both ways.
Gordan Delaney is very particular about such things.
It's looking pretty good Peter. I did the sheeting on another design similarly, but wound up needing to do some additional work to get the radius smooth. It can be done.
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Progress has slowed a bit as I wait for Tom Morris to make up the pushrods and horns. I got the bottom of the wing sheeted and cap strips installed. I cut the wing away from the building surface. Yo need to be careful during that process as it is easy to have the xacto blade to wander. Do not rely on the balsa to seperate evenly along the perforations. Use them as more of a guide where to cut. The wing is alot lighter that it looks.
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I might suggest you will be happier with independently adjustable leadouts.
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A bit late for that as they are now fully imbeded in the wing tip with the tip blocks installed. I'd have to have a real good reason to hack the wing apart to get at them. If you could elaborate please do, before I start covering.
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Peter,
With a Pathfinder in which Gordan has already figured stuff out, just follow the plans. It will be fine.
Independently adjustable leadouts are a trim tool that is worth more than gold. Allows you to fine tune several issues but particularly yaw. I seem to have a propensity for designing planes that want to yaw in hard outside corners. Being able to adjust just the down leadout has allowed me to trim this problem out without causing other problems that moving the up leadout would cause. Nice to have that ability.
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Here is a interesting item. The kit and the plans call for the installation of a tip weight box, which I dutifully installed. (the one in the kit is neat you have to supply your own blind nut and hatch screw though) What I am trying to figure is since there is a tip weight box, why does the plan call for attaching a quarter to half ounce weight permanently to the out board wing tip? And which is it 1/4 or 1/2? Makes little sense to me.
Next I have to cut off the end of the nose by 1/2 inch. I will need to make this a square cut without the aid of a band or Scroll saw. I do not look forward to doing this with my trusty hacksaw blade.
I ended up using 4-40 screws to mount the engine. The 6-32 screws were a much better fit in the engine mount holes but the blind nuts were humongus, easily half again as wide as the engine bearers. On the positive side there is absolutely zero play between the bearers and motor mount pads so I do not have to worry about any engine offset creap.
Note: There is insufficent balsa block to flesh out the cowl or the nose of the model. You will have to piece together scrap balsa to creat blocks to carve the nose and the Cowl to shape. This is very tricky as the plans do not have sufficent detail as to the placement and sizes of the required blocks. You will have to wing it. I hope I have enough wood in the right places to allow mw to shape the nose and cowl without ending up with gaping holes in places. The only guide to this is the photo of the nose and cowl shown in the FM article.
I am awaiting my back orderd spinner from RSM before starting the carving and sanding process. I elected to use a Needle Nose profile spinner as that will let me use a lesser taper to the nose ring on the fuse. A necessity as I have to cut the nose short by 1/2 an inch and that far back there is very litttle in the way of wood to carve due to the location of the motor mounts
and supporting material. By the looks of it I will be sanding into the maple mounts to get the taper I need as it is.
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The tip weight specified being permenently installed is to limit the amount of weight needing to be stuffed into the tip weight box. On both of the prototypes, we wound up with about 3/4 oz of tip weight. Any percentage permenently installed will allow less having to be installed in the box.
The amount , 1/4, or 1/2 oz is specified to let the builder decide how much weight he wants to have for adjustments, and is, of course, a choice left to the builder.
Before you shorten the nose, may I suggest you send Gordan an e-mail. He's currently running a PA .61 I believe. He is running the shorter nose, but he may also have found it necessary to add nose weight. I'm running the stock nose legnth, but my Stalker .51RE is lighter in weight. and I needed no additional trim weight. H^^
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The tip weight specified being permenently installed is to limit the amount of weight needing to be stuffed into the tip weight box. On both of the prototypes, we wound up with about 3/4 oz of tip weight. Any percentage permenently installed will allow less having to be installed in the box.
The amount , 1/4, or 1/2 oz is specified to let the builder decide how much weight he wants to have for adjustments, and is, of course, a choice left to the builder.
Before you shorten the nose, may I suggest you send Gordan an e-mail. He's currently running a PA .61 I believe. He is running the shorter nose, but he may also have found it necessary to add nose weight. I'm running the stock nose legnth, but my Stalker .51RE is lighter in weight. and I needed no additional trim weight. H^^
The VF weighs in at 12 ozs without the RC carb, add the pipe and I think you have a power package that weighs more than the PA. I already relocated the engine around 1/2 inch back from the plans. So I'm kind of commited, unless I want to fill in the holes and drill new ones. I'll try to PM Gordon again and ask, but as you know he has had other things on his mind.
Can we see a photo of the bottom of the plane to see how the pipe tunnel is covered? Is it open on the bottom? Covered? Or builder preference?
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Just a note. Generally, you permanently attach tip weight to balance the outboard wing against the longer inboard wing and leadouts. Just get it so it balances. Then you add tip weight to the weight box as needed to balance the lines.
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Randy has made a better explanation of the fixed tip weight than I did.
Both Gordan's, and my prototypes are running rear exhaust with mufflers, so the bottom is covered. Gordan has one that Jim Tichey had just finished before he died, that has a PA 40 Ultralight with a pipe. I'll try and get some pics of it over the weekend, when I go visit him.
Memory tells me that the pipe is covered to about even with the CG, open on the bottom, from there to the back. It's really builders preference, but keep in mind the heat has to get out before affecting the pipe too much.
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Peter,
With a Pathfinder in which Gordan has already figured stuff out, just follow the plans. It will be fine.
Independently adjustable leadouts are a trim tool that is worth more than gold. Allows you to fine tune several issues but particularly yaw. I seem to have a propensity for designing planes that want to yaw in hard outside corners. Being able to adjust just the down leadout has allowed me to trim this problem out without causing other problems that moving the up leadout would cause. Nice to have that ability.
In the example you have given here, is the up line in the front ?
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Yes the bell crank is inverted, as shown on the plans. This puts the up leadout in the front. I would have done this anyway as I've been doing this forever. Can't recall now who got me started doing it that way or why, but been inverting the bell crank Since the mid 70's.
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Attached are some photos of the nose area and cowl. As you can see I used bits of scrap to build up the areas in question for carving. The plywood mount for the nose gear may need to be trimmed to clear the cylinder head of the engine, I just hope I don not have to cut too much of it away, and compromise the strength of the gear mount. It is going to be close. I am using some of the scrap 1/64 ply and balsa to make a simple treatment for the nose gear wire. The heat shrink tube over the wire makes for a great surface to glue to and as a added benefit allows some give to the assembly. Since the heat shrink can twist and move a little bit over the gear wire it allows the gear treatment to move a tiny bit on the wire hopefully this small amount of give will prevent the gear wire cover from just snapping off should the gear wire flex. I do not think it will be totally grass proof though.
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While I am waiting for my TOM Morris controls I have started shaping the fuselage nose. Lots of sanding and carving. It is wise to go really slow during this process as it is easy to get too enthusiastic and remove too much material amongst all the compound curves and the like. Resist the urge to Grab a knife and start hacking away. Sand and carve in small areas incrementally, lest you carve ro sand flat spots in areas that supposed to have smooth gradual transitions.
The Nose ring is about 1/16 of an inch over size, so if you accidentally sand into it a little you are safe, but be careful there is not much room for error here. I tack glued the cowl to the fuse to facillitate the shaping process and I suggest you do the same. I have not yet figured out the cowel front end attachment. As I cut the nose short (It is cut to 10 inches to compensate for the weight of the OS46 VF) I can not see how to do a dowel anchoring scheme as Gordon suggests. There is nothing to sink the dowls into. Only have the PLY ring north of the cowl front end.
Note. You will need to carve out the insides of the cowl as well. The insides of the cowl as supplied squeeze right up against the cylinder of the OS 46 VF. When sanding the outsides of the cowl you will have to remember that material will have to be removed from the inside as well.
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If you are using a 46VF, I hope you left a lot of room for tank space. Takes a big tank. ;D
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If you are using a 46VF, I hope you left a lot of room for tank space. Takes a big tank. ;D
Using a 6 oz tank Hope that covers it. It is a RSM unifow, and yes it is a big sucker will fill the tank compartment completely, especially as I had to shave a 1/2 inch off the nose. The next size a 7 oz would have been too big no matter what.
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Well, good luck. You may end up needing a smaller venturi. Pete Peterson uses an OS46VF in his Saturn. Uses a bit over 7oz. I used one for a year (a Tom Lay prepped engine) that used 7.5oz. Most other folks that have used them end up around 7oz unless they neck down the venturi. When I told Pete he would need at least 7oz of fuel capacity, he smirked and put in a 6oz tank. Then had to make a new tank with a hopper to get about 7 1/8oz into the compartment. And he has just enough fuel to finish the pattern. I suggested a smaller venturi, but he liked the power.
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I've attached the cowl in the front through dowels in the nose ring, and then putting two screws in the back end of the cowl. You can do it I'd you want, I haven't had a problem using that method.
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I've attached the cowl in the front through dowels in the nose ring, and then putting two screws in the back end of the cowl. You can do it I'd you want, I haven't had a problem using that method.
That's how I mount my cowl. y1
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Well, good luck. You may end up needing a smaller venturi. Pete Peterson uses an OS46VF in his Saturn. Uses a bit over 7oz. I used one for a year (a Tom Lay prepped engine) that used 7.5oz. Most other folks that have used them end up around 7oz unless they neck down the venturi. When I told Pete he would need at least 7oz of fuel capacity, he smirked and put in a 6oz tank. Then had to make a new tank with a hopper to get about 7 1/8oz into the compartment. And he has just enough fuel to finish the pattern. I suggested a smaller venturi, but he liked the power.
Now I'm worried, a 7 oz would not have fit length wise even without a shorter nose. The only available room is down towards the cowl and not much there as thats where the pipe goes. I am going to use a Smith venturi, not sure the dia. But I think it is .275 with a PA needle valve. This plane is quite a bit smaller than the SV11, with a 57 inch span and less squares. Unless any one has any other Ideas I'm stuck with the 6 oz tank.
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Don't worry about it. You can always make an unbalanced tank. One that can cozy up to the pipe (but not touching). If it had greater volume below the pickup than above, no big deal. Worst case, you go with a .260 or .265 and extend the run. The plane is smaller and you can always afford to give up a bit of power for a long run.
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One thing I know, I cant build a tank, even when I am home with all the proper tools. I've tried in the past and they turned out horrible, leaky and obscenly heavy. I know better than try that again. Unless I can find someone who makes a custom tank. I'll have to take my chances. Unbalanced tank conjurs up all sorts of engine run issues in my mind even if I could build my own. I thik I'm screwed.
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What are dimensions of tank compartment ?
Sullivan has several 8 oz tanks.
2 different round tanks in addition to the slant rectangle.
Maybe one of them will fit.
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Allen is right, I am preparing to use a Sullivan RST-8, 8 oz plastic tank in one of my projects. The tank is 4.5" long X 1.875" wide X 2.25" tall, not counting the little blister for the overflow.
By lowering the tank floor a little, this tank will easily fit into the nose pf the Pathfinder L.E.
I've previously posted a diagram showing how I set up my plastic uniflow tanks. I've been using them this way for years, and never a problem.
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Thanks Alan and John,
In the past I have had mixed results using plastic RC tanks. This one will fit and I can push it all the way back against the Rear Bulkhead to keep the weight further back. Especially as all tubes exit forward. On a horizontal plane does the uniflow tube remain on the tank horizontal center line for its entire length? or does it angle up or down? Is a solid oiece of tube inserted between the clunk and the feed tube so the clunk does not fold back on it's self? And dosn't the clunk get hung up on the uniflow tube? I thought I saw years ago a scheme where the uniflow tube was also flexible and was attached to the pickup via a slip arrangement so they both moved in unison. I guess these are the reasons I've had mixed results with clunk tanks. Is there a part number for this tank, so it would be easier to find online?
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Thanks Alan and John,
In the past I have had mixed results using plastic RC tanks. This one will fit and I can push it all the way back against the Rear Bulkhead to keep the weight further back. Especially as all tubes exit forward. On a horizontal plane does the uniflow tube remain on the tank horizontal center line for its entire length? or does it angle up or down? Is a solid oiece of tube inserted between the clunk and the feed tube so the clunk does not fold back on it's self? And dosn't the clunk get hung up on the uniflow tube? I thought I saw years ago a scheme where the uniflow tube was also flexible and was attached to the pickup via a slip arrangement so they both moved in unison. I guess these are the reasons I've had mixed results with clunk tanks. Is there a part number for this tank, so it would be easier to find online?
The Uniflow tube is a solid tube, initially set up on the centerline of the tank. The location of the uniflow being the outermost hole in the stopper precludes interfering with the clunk. It also allows the uniflows height to be adjusted by rotating the uniflow line itself, and is easy to do without taking the tank out of the plane, or disassembling it. You change the apparent height by raising or lowering the end of the uniflow inside the tank.
If you desire, a short legnth of solid plastic, or copper tubing can be placed in the pick up line, so it won't be able to flop forward in a hard landing, or minor crash. I've found the use of the sintered bronze filter,m as a clunk, seems to do a great job of both filtering the fuel, and reducing possible problems with fuel pick up. Virtually all the fuel is gone from the inside of the tank, when the engine quits, and I get little, or usually no surging as the tank is running out of fuel.
The RC tanks I like to use are made by Sullivan, and in the case we're talking about here, is the RST-8. RST relates to the type of tank, the 8 refers to the capacity. The diagram I posted was based on a smaller tank, so to use the larger 8 oz tank, the front view of the tank would be shown with the wider dimension being the to of the tank.
I've used this method of constructing uniflow clunk tanks for over 15 years, and it works great for me. I really like being able to adjust the apparent height so easily.
Others build their uniflows with a clunk on both the uniflow, and the pick up line, or connect things up so the uniflow follows the pickup. It can be made to work, but I do not believe you wind up with the best uniflow tank this way. First, there are two lines that must be flexible enough to allow relatively free movement. Next, the end of the uniflow moving with the pickup, sees varying heights, and pressure differences as both the uniflow, and the pick up move arround. In a hard tank, the unilow does not move around, it stays fixed, and establishes the height of the tank. I think that is why some have problems setting up an RC plastic tank for uniflow in our CL models.
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Not much to do until I get the Tom Morris horns and pushrods. Perhaps they'll arrive this week. So I mucked about and made some cokpit detail. They are just fitted in place in this photo, not glued in. BTW I finished shaping the nose and got it all sanded. What a chore, I am not a fan of sanding at all. You end up looking like you took a dive into a vat of Wheat Flour. Sneeze for an hour afterwards.
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Nice work, Peter.
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I've built a couple of RSM kits. The bellcrank supplied is a SIG Nylon, using a 6-32 thru-bolt. Other than enlarging the holes for bushed leadout cables, I use them stock, and they seem to work just fine.
I must comment that RSM supplies first-grade balsa in the kits. Some was still marked "Bud Nosen AAA Grade"
Floyd
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I prefer 4" composite bellcranks myself.
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Well My aluminum spinner came in along with my Tom Morris controls. They both are lovely. I need to get the same spinner in a 3 Blade. It is a Dave Brown Vortech 2 inch spinner. They will custom cut for a 3 blade for an extra 5 bucks. The spinner was 27.99 and a custom cut is 35.00. So no need to break out the dremel and risk screwing it up. They'll lighten the back plate as well.
Note: You have to order the prop adaptor nut separately, the spinner does not come with one, I wish RSM noted that on their web site.
The ply nose ring is over size it is about 2" 1/8 in diameter. I guess I'll have to get a sacrificial spinner to use for getting the final shape of the nose sanded. I really don't want to risk scratching up the shiny Aluminum spinner sanding the nose ring down. As you can see from the photos the cowl fit is very tight. The only way it can go on is by slipping it straight up onto the bottom of the fuse. There is NO clearance to allow for tilting or angling the cowl in place. The hole for the venturi and the fit at the for and aft end is nice and tight. Also I only have a little over 3/16 of material thickness where the cowl contacts the ply nose ring. Unless I can figure out a way to pin the cowl to the ply nose ring from the front (Before mounting the spinner) then the dowel option is out. I possible could create a socket from CF, Aluminum tube in the cowl front. Then use a removeable pin through the ply nose ring to fit into the socket. I just have not figured a way to make this removable pin flush with the ply nose ring or how to keep it in place so it does not contact the back of the spinner. In the end I may just make mating tabs on the cowl sides and fuse then secure the traditional way using some short screws and blind nuts.
Things should start moving quicker now that I have the control system. All of the sub components are done, Now I can attache the flap rod, horn and finish sheeting the top side of the wing. Then it is assembly time. Oh fun, O joy, without an incidence meter and doing it on the floor.
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Cute thread wrapping on the pushrods.
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This may sound obvious, but wrap several layers of masking tape around your spinner and block sand at a bias to rough it out. Then sand aft toward the tail, one direction only till your just skimming the masking tape.
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Hi Peter, It was good talking to you last night. The plane looks great and I can see I can sure learn from your talent! If she's not ready for Flushing let me know and we will work something out.---LOUIE H^^ D>K
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The real trick will be getting the plane in trim by the 25th. I should be able to get the airframe put together and covered in time. (The advantages of Film Coverings) But getting any trim issues ironed out will be a whole other issue. Got my fingers crossed that it may fly reasonably well off the board. My Brodak vector kit did. Needed the smallest tweaks, mainly engine related. I have a couple of OS 40 FSR's sitting around. Might just build another vector 40 and stuff one of them in it With a MACS tuned muffler system. The biggest challange with the FSR is getting a handle on Run Away. THose motors love to scream.
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The saga continues. I turned my attention to the task of venting heat from the engine compartment. The rule of thumb here is to have a greater area for heat to escape vs the Air inlet area for cool air intake. As I was pondering the layout of the engine pipe configuration it is clear that the items that get the hottest is the engine cylinder, head, and exhaust header. Also heated air tends to rise, I wanted to get some vents more in line with these parts.
Most designers will mainly punch holes in the bottom surface of the cowl, which is great and hides these typically unsightly opening on the bottom of the aircraft. But not necessarily the most efficient solution. I wanted more locations where the hot engine compartment air can exit the cowl. So I decided that a pair of vents in the cowl sides would in order. Now I could just punch holes in the cowl sides but that is kind of ugly. Also I wanted to make sure that air exited these holes and not cause turbulence to hinder the exit of the heated air.
So I borrowed a technique from full size aircraft. As you can see in the photos the holes are not perpendicular to the cowl sides they form more of a tunnel. One that has a greater opening area than the hole is by itself. As air flows across the cowl side it creates a low pressure area across the tunnel opening, the air pressure inside of the cowl would be higher because of the air forced into the cowl front scoop and because hot air expands. The combination of these pressure differentials helps this type of arrangement scavenge the heated air from the engine compartment and the area directly surrounding the exhaust header.
I will add additional opening such as these to the bottom of the cowl as well. To help with the aesthetics I am planning to use some thin wall aluminum tube to line the openings in the cowl sides tapering them to match the shape of the balsa cut out, this will simulate the appearance of turbine exhaust stacks seen on some turbine powered propellor or aircraft.
To create these openings I used a 3/8th aluminum tube sharpened at one end and used it in a rotating cutting dashion to cut the holes, Then some sandpaper rolled into a rod did the clean up.
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Might ask Ted Fancher about exhaust outlets in the cowl on piped planes.
Just sayin'
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My other concern was the cooling of the engine crankcase area. Not much I can do there with the structure as it is. The nose being shortened I had to cut away much of the potential inlet area. The outlets would end up under the forward mounted canopy. I did not choose aluminum spinners only for asthetic reasons. I chose them for their heat sinking qualities as well. Being bolted to the crankshaft and the front thrust washers they will help carry away heat from the crankcase and bearings and anything else that comes in contact with the crankshaft. Will probably apply a little electronics heat conducting compound Between the spinner shell and backplate and between the thrust washer and the Back Plate.
The pipe tunnel will get it's own ventilation treatment. Actually they make little 3v fans I could install to move air out of the engine compartment, it would even run on all day single LI 3v button cell. But I think I'll leave that for another project. They are used in hand held portable electronics devices, weigh a couple of grams, pretty cool actually.
http://www.sunon.com/pro2.php?c1=10&c2=2 (http://www.sunon.com/pro2.php?c1=10&c2=2)
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You don't really need that. Opening in the front of the cowl, relatively smooth inside from cowl opening to end of pipe tunnel and an exit at the end of the pipe tunnel that is 3 times the area of the intake. I usually don't put any more openings in. The large exit area will vacuum air from the inlet all the way down the pipe tunnel and out as long as there aren't too many obstruction in the way. I have used a very small inlet that pours over the crankcase. It doesn't take much as long as there is sufficient exhaust to draw the air through.
Openings along the cowl or the pipe tunnel just serve to create hot spots.
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Peter, it's your build, and ultimately, your plane, but in my opinion, Randy is right. He's basing his remarks from the experiences of Ted Fancher discovering that he had to close up all those cowl outlets on his Trivial Pursuit, because they were allowing the heated pressurized air inside the cowl area to escape before it reached far enough back to cool the header, and the pipe. Ted experienced run problems before he figured it out, and closing the outlets cured them handily, as I recall.
Yes, you could install some small electric fans. Neat as that seems, wouldn't that be making the problem of cooling the power system more complex? There is a proven method that requires no additional energy, works great when the plane is under power, and shuts down when the power does. Both Randy, and now, myself are advocating you consider using it. Of course, it's ultimately your choice.
Speaking of cooling issues, at one time I felt that cooling outlets designed to get cool air to the crankcase would be beneficial. I set up the Legacy I was then building to extract air from the crankcase area. After many many flights, I've come to the realization that crankcase over heating is probably a non-issue.
As I've found out, the air entering the crankcase through the venturii is cooler than the upper part of the engine. This naturally cools the lower end, when the engine is running. The heat is created at the top of the cylinder, and at the exhaust, making these areas the most important to have adequate cooling.
I've also found that the spinner is usually cool right after the engine shuts down. It does heat up as it acts similarly to a heat sink, but the heat reaches a peak, to match the engine, then drops as the engine cools down.
In my experience with this design, the Pathfinder L.E., the cooling air should not be allowed to escape the cowl and tunnel, until after the rear manifold, and coupler when using a pipe.
I also took my version of the prototype down, and took some pictures of the cowl, and the mounting so you can see how the dowels are used at the Front of the cowl. This set up has proven out to be very secure on the prototypes.
Your build is moving along at a good pace, and looks good. I'm looking forward to future installments, and the finishing and trimming flights. H^^
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Sorry, so many irons in the fire, I forgot to attach the pictures of the cowl mounting.
I use two 1/8" dia. dowels mounted towards the sides of the cowl. This puts them where there is plenty of meat to glue into. I also use a plywood half ring mounted to the front of the cowl. This also adds stregnth to the mounting system.
Notice I've only used one allen screw at the rear of the mount. This arrangement has held up well to flight and landing loads impossed where I fly. (Mostly thick grass, very draggy.) H^^
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Peter, it's your build, and ultimately, your plane, but in my opinion, Randy is right. He's basing his remarks from the experiences of Ted Fancher discovering that he had to close up all those cowl outlets on his Trivial Pursuit, because they were allowing the heated pressurized air inside the cowl area to escape before it reached far enough back to cool the header, and the pipe. Ted experienced run problems before he figured it out, and closing the outlets cured them handily, as I recall.
Yes, you could install some small electric fans. Neat as that seems, wouldn't that be making the problem of cooling the power system more complex? There is a prooven method that requires no additional energy, works great when the plane is under power, and shuts down when the power does. Both Randy, and now, myself are advocating you consider using it. Of course, it's ultimately your choice.
Speaking of cooling issues, at one time I felt that cooling outlets designed to get cool air to the crankcase would be beneficial. I set up the Legacy I was then building to extract air from the crankcase area. After many many flights, I've come to the realization that crankcase over heating is probably a non-issue.
As I've found out, the air entering the crankcase through the venturii is cooler than the upper part of the engine. This naturally cools the lower end, when the engine is running. The heat is created at the top of the cylinder, and at the exhaust, making these areas the most important to have adequate cooling.
I've also found that the spinner is usually cool right after the engine shuts down. It does heat up as it acts similarly to a heat sink, but the heat reaches a peak, to match the engine, then drops as the engine cools down.
In my experience with this design, the Pathfinder L.E., the cooling air should not be allowed to escape the cowl and tunnel, until after the rear manifold, and coupler when using a pipe.
I also took my version of the prototype down, and took some pictures of the cowl, and the mounting so you can see how the dowels are used at the Front of the cowl. This set up has proven out to be very secure on the prototypes.
Your build is moving along at a good pace, and looks good. I'm looking forward to future installments, and the finishing and trimming flights. H^^
I am toying with the fan Idea. Something I may play with in the future, not for this project. I sent Ted a PM asking him to add his experience to this thread, we'll see if he responds. I could easily fabricate some sliding shutters inside the cowl to adjust the amount of air that would flow through the openings, that are of less weight than the material removed to create the openings themselves. I find the scoops to add to the overall appearance of the model. I can see the possibility of diverting air away from the engine and header before it has a chance to flow past the components. In that case it becomes more a matter of the placement of the openings as opposed to the total area of the openings themselves. I located the openings on the side of the cowl strategically to be slightly aft and adjacent to where the exhaust header would fall. This in theory should pull more air past the header just before venting it outside.
I can easily test the temperature of the internal components by using small manufacturing / test lab temperature indicator tabs. These are little strips with dots on then. You attach the strip to the object you wish to get the temperature of and perform the test. The you remove the test strip and depending which dots have turned black gives you the a rough idea of the max temp achieved.
http://www.grainger.com/Grainger/WAHL-Temperature-Indicator-6FYY2?Pid=search (http://www.grainger.com/Grainger/WAHL-Temperature-Indicator-6FYY2?Pid=search)
As far as the pipe tunnel goes I was going to treat it as a separate area, with it's own inlet and outlets. I feel that the entire drive train and exhaust path be kept at reasonable temps, as the materials and adhesives we use soften or get brittle when heated past a certain point. It makes me wonder if that is the potential cause of some models using sandwiched carbon veil and balsa as opposed to the traditional ply balsa combo for engine crutches is the overheating of that area. Balsa reflects less heat than Plywood (Balsa is much more porus and has many more internal air spaces, and air heats faster) and perhaps the epoxy used is softening. Could be a contributing factor on Matt Colans structural failures in his TP.
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Sorry, so many irons in the fire, I forgot to attach the pictures of the cowl mounting.
I use two 1/8" dia. dowels mounted towards the sides of the cowl. This puts them where there is plenty of meat to glue into. I also use a plywood half ring mounted to the front of the cowl. This also adds st regnth to the mounting system.
Notice I've only used one allen screw at the rear of the mount. This arrangement has held up well to flight and landing loads imposed where I fly. (Mostly thick grass, very draggy.) H^^
Hi John,
The dowels work if you have the necessary clearance to tilt fit the cowl to the fuse. I did not build in that clearance. The only way I can get the cowl on is by dropping it into place. The cowl has to be exactly flush with the nose ring and the rear fuse cut out for it to fit in place. To make it tilt in back and to have the play to fit the dowels into the nose ring holes, I would have to cut the cowl so there is sufficient gap at the rear so it would be able to swing into place after the dowel pins as inserted into the holes up front. Also I would have to open up the hole for the venturi as it is quite long and has to be able to fit into the cowl before the pins could engaged the holes in the nose ring. I hate gaps in cowl, fuse fits. I also want to keep the engine compartment sealed as best I can to help with the sirflow dynamics in that area. Gaps allow air leakage which mucks with airflow paths, and decrease the effectiveness of air outlet ports.
Thats a pretty tall engine. The VF comes no where near the bottom of the cowl. It falls short by at least .25 inch, so I am not cutting a big round hole for cylinder head clearance. I will have a hidden jack to power the glow plug.
Now if someone would machine a apinner back plate with impellor fins as used in some vacuum cleaners without adding significant weight. We could use some of the engine power is most of our completely over powered beasts to force cool outside air through the engine compartment and pipe tunnel. But I suppose all this is moot as we'll all be flying electric within the next 5 years anyway. Sniffle...........
Did you know that a well engineered Tower or notebook PC run cooler with the case all closed up and panels attached? It's true the electronics will run hotter in a completely open environment as opposed to being sealed up in a properly designed enclosure.
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Good point Peter. My intent for posting the cowl mounting pics was to show how it was done on the plane I built. As you've noted not all are the same, even with the same design. Factors like you've noted, esp. shortening the nose for balance considerations may dictate different solutions. I'm sure that what you come up with will be well thought out, and efficeint. H^^
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Might take a look at Claudio Chacon's Trivial Pursuit (painted like the Voodoo race plane). He set up intake and outlet holes in the cowl then used separate intake and outlets for the pipe tunnel. He tells me it worked OK, but he had to be careful of getting a hot spot between the two.
http://flystunt.com/AIRPLANE/VOODOO.htm
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Now that's sweet. The cooling hole are right in line with what I have in mind. Gotta love paint finishes, they make finishing the openings so much easier than treating them with film. Anyway just an update. I've been working on myriad of detail items of the kit, mainly sanding flaps, shaping and sanding the wingtips, you know getting all the bits an pieces ready for assembly. Nothing really to post photos of as everyone generally knows how to sand, prepare parts.
I just realized that I did not order any hinges for this plane. I will have to get on that right away, as I assemble everything before covering. While sanding the wingtips to shape I noticed that the trailing was not straight. I used a straight edge and checked and only at the trailing edge it wandered from true. Weird, not so much as a warp but a minor wiggle. Well I soaked the trailing edge down at the area of the wiggle, laid a aluminium ruler along the trailing edge and have it weighted down flat against the building surface. That took the wiggle out of the TE and It's now straight. This should be a heads up to all to check the height of the TE at each rib location as it seems that the ribs may not lie at equal heights in spite of the built in Jigging system. The wiggle in my TE spanned the center 4 ribs only, and those are the ones that are assembled first as the basis of the rest of the wing.
Out board of the first 4 the TE was straight and true the rest of the way out on both halves. I now remember why I despise built up wings. It is a real pain sanding a 57 inch wing without accidentally snapping a rib here and there either with the sanding block or by grabbing it too hard in the wrong place to steady it. Wings this size are unwieldy and sheeted foam is just so much more durable, not to mention sanding block friendly. It is turning out rather light though, the wing complete is lighter than (without film covering) than 12 ozs (comparing it against the weight of the VF46). I don't have a scale handy to weigh it, the fuse is quite a bit lighter than the wing. If my guesstimates are correct then I figure that the airframe will come in between 26 and 32 ozs uncovered and be 44 to 50 oz. fully finished. This is using only the wood supplied with the kit. Although this would be the full up weight, I never consider the weight of the engine as a limiting factor except for balance as no matter what engine you put in a plane that item has to be there and you can not really change the weight of the package.
It is a given the VF comes in at 12 ozs in CL trim. And out of any component the engine is usually by far the heaviest single component. I always prefer to gauge how heavy the airframe turns out with it's ancillary components.
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All righty then, I figured I would post an update, just so people don't think I've abandoned this thread. I am at the point of endless sanding, the part of the build process I despise. Hours of getting the everything to the final shapes shown on the plans. Then more sanding to get the surfaces as close to the final condition ready for cover. Here is where covering with film starts to diverge the building process from those who choose to paint and or use silkspan, or other covering materials. As after assembly the next step is the final finish, with no more intermediary steps. The balsa has to be filled and as smooth as it can possible be (Or as filled and smooth as I have patience to make it). As I cover the model after it is completely assembled it is easier to get the lions share of sanding done before any assembly.
Contrary to many who work with film I cover the entire airframe with the material and cover after it is completely assembled. There are reasons for this and I'll touch on a few right now so you can understand the reasoning behind it. There are tricks with film coverings that go a long way to ensure the durability and appearance of a film covered model. I do not like mixing media. While good results can be accomplished the places where the media overlap can and usually does present problems that can take a while to crop up. So I use film exclusively and If I were to paint I would use that exclusively as well. Paint and film just weather and wear at different rates. It does not take long for your wings to start looking different than the fuse if you should to decide to do one in paint and the other in film, also you run into problem areas where the two meet.
Anywho, to get the best all film results you should start on the bottom and work from back to front, meaning that any rearward pieces should underlie those forward of them. The reasoning behind this should be clear so and seams are not facing the airflow. This way they will not loosen and peel backwards (unless you have a peculiar habit of flying backwards) Starting on the bottom and working up also allows you to easier hide or place seams where they are least noticeable.
Of course the thing most of you are thinking about is "What about the Wing to Fuselage joint? Got any smart answers for that part?" Yes, those you cover very first before covering anything else. I have used this white pre mixed stuff sort of like microballoons really light weight and comes premixed in a jar. I use this for the fillet material at the wing joints. You can use just about any material in this location. Run a nice radius fillet between the wing and the fuse and at the stab areas as well. Let what ever material you use completely dry or harden, namely outgass as much as practical.
The nicer and more gradual the radius is at these locations the nicer your film will lay. Cut a strip of covering only a 1/4 inch wider (either side) than the fillet. Just enough to cover over all of the fillet material. Starting from the wing TE attach the covering to the filleted area and gently stretch the film as you iron down the film onto the curve of the fillet. The trick is to heat, stretch, tack, in that order. Focus mainly on the center line of the fillet running from rear to front. You will notice if you are heating and stretching before applying pressure to iron down the film the edges of the film will naturally conform to the curve of the fillet. Keep working forward past and half way around the leading edge. You will have to stretch a bit more to get a good fit around the LE radius. Once it is down you can go back with the iron and a dampened rag and work out any small wrinkles or air bubbles. Heat with the Iron and then attach and cool using the damp rag. A pin and a tiny pinhole for more persistant air bubbles. The trick is to move steadily forward working the length of the strip an inch at a time before moving forward. A bit more finesse is required at the leading edge. The nice thing about working with this narrow strip of film , is that if you totally blow it, you can just heat it up and peel it off and start again. It may take a coupl tries before you get the hang of it to yeild a nice smooth film surface on this part of the airplane. Make the strip quite a bit longer than you need, it make it easier to handle and you just trim off the excess anyway.
Covering the Wing / Fuse and Stab / fuse interfaces in this fashion makes the rest of the process go much smoother. You do not have to try to man handle larger wing or fuse panels to fill this gap. Your seams location is more flexible for both the wing panels and the fuse panels.
So now perhaps you can appreciate one reason to assemble then cover and why you need to get all the wood as smooth as possible before assembly.
NOTE: Take a damp rag or lint free cloth to the area you are about to cover. The surface should be as dust free as possible. Balsa dust should be cleaned off of the surfaces. Otherwise your film will attach mainly to dust and not the airframe. leading to sagging, lift ups and other covering problems down the line.
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Yea, sanding and sanding. Then, more sanding. You have to develop a certain Zen toward it.
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Zen my Butt. Although you do need a great degree of inner calm not to smash the damn thing into kindling when you get the Trailing edge all smooth and integrated into the wing tips only to find that somhow you've managed to sand nice craters into the rib cap strips. Or the real life journey into the laws of dminishing returns whilst trying to get the wing tips symetrical to each other and on each axis. I suppose one of those things that have a zillion moveable rods that trace the contours of an object would help in this regard they are useless when you find that you don't have enough material to sand to shape on one end or the other in the first place.
I think I have set the record in having the number of repaired ribs in a plane that had not even flown yet.
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Well, I have two thought. First is, take the sanding slowly. There's less chance of mistakes. I've certainly pitched many parts away due to sanding mistakes.
The other thought is to remember what Windy always said: no finish is ever completed, only abandoned. Learning the rule of "good enough" is a tough go sometimes.
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Construction Update.
While fitting the custom controls by Tom Morris, I found that there was no way the adjustable elevator horn and ball link assembly would fit in the space between the fuselage sides. I had to cut out the Fuse former that came with the kit and make a new one to increase the spacing between the sides at the horn location. With Tom Morris controls this needs to be significant! It kind of messes with the fuse profile back under the stab but as it is under the stab It is not too obvious. Because of this I had to cut an additional former to fit above the location of the one on the plans as well. If you are bending your own or using a slimmer profile adjustable control horn set up back in this area you may not have clearance issues.
In addition I felt that the fuse bottom under the wing where the pipe tunnel will go has not enough structure. The Fuse bottom in the final will have large areas cut out to fit the pipe. I felt that this area needed more than just the 1/8th in fuse side to 1/4 inch fuse bottom plank interface. After pipe installation quite a bit of strength imparted by the fuse bottom would be compromised basically leaving just the fuse above the wing as the main support structure. Also if I left only the fuse sides tied to the bottom plank at this location, when I cut this section away to install the wing then the balsa sides attached to the bottom sheet would spring out of shape because there is no other support for the fuse sides at this location directly under the wing. What I did was add the 1/4 X 1/4 balsa sticks to the fuse sides as seen in the photo, I used this additional surface area to glue the bottom plank to. This addition will stiffen up the area below the wing and provide additional support when the opening for the pipe has to be cut. It also helps hold the fuse sides in alignment when the bottom section is cut apart to install the wing.
Shown is my method for securing the cowl. I will use some screws and blind nuts to secure the cowl to the 4 plywood posts. I will bush the holes with some delrin tube to prevent the cowl sides from crushing when the cowl is tightened.
NOTE: Check the clearance for you elevator control system BEFORE cementing the horizontal fuse former under the stab!
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Starting on the wing. The great thing is are the guides and the built in tabs that allow the wing to be built without a jig. I followed the instructions in the FM article on how to set this up. The really really bad thing is that the bellcrank mounts are not cut properly in the kit. They are too narrow! I discovered this only after gluing the lower bellcrank mount on to the center ribs with epoxy. Because the mounts are cut improperly there will be insufficient contact area between the mounts and the upper and lower spar that caps the mounts!
I am upset that this error was make in the kit fabrication at such a critical part of the model. I am uncertain how I can now fix this deficiency, I can not afford for the bellcrank mounts nor the center section of the wing to structurally fail. As the parts have already been glued to the rear shear web spar and then glued to the 4 ribs, I would have to trash the entire assembly and cut new bellcrank supports as shown on the plan in the photo below. The supplied plywood supports are no where close to the parts shown on the plans.
This is a major fault please note this when constructing your kit!
I can probably fill in the space left by the too narrow supports but I fear that it will never have the structural integrity that a proper width pieces would offer. The killer thing is that the way the bellcrank mounting is designed there is not much in the way I can satisfactorily reinforce this area.
NOTE: In the photos you can see just how narrow the supplied laser cut bellcrank supports are compared with the drawing.
I know you're way past this point by now, but for future problems like this (parts epoxied together wrong) it is a whole lot easier than you would ever imagine to cut the epoxy joints apart with a hot #11 blade or whatever knife you need to use. I heat the knife up with a combination of my Monokote iron and my heat gun. I also heat the area that I am going to cut apart.
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Hi Peter. It's been A while but how are you doing? The plane is looking awsome! The fits are fantastic. I am just puttering around with flying stuff when I can. We are down in VA. for the holidays, be back in NY next week. I guess the spring will be the next step for flying. The cold bothers this old man unless it is a dead calm day, but I do keep my battery charged just in case. If I can help in some way let me know.---LOUIE H^^ H^^ D>K
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Peter, how about an update?
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Peter
Who is this George Delaney? Is he also known as Gordan Delaney the famous stunt flyer from Utah USA?
Norm Whittle
Infamous stunt flyer from Utah USA
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Peter Nevai has abandoned this build thread and has not been active here since last August. It is a shame that his Pathfinder was never finished, or he chose not to share the completion with us. Does anyone know what happened?
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I don't think he could take the comments that were made. Also when trying to help someone, it pays if they would read and comprhend what is said/written. I am bad about that myself.
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Still a work in progress, Work has been a whirlwind and I get home and all I can think of is zoning out. Not having a real work space here is contributing to my procrastination.
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That looks good! Hope you will post more progress soon.
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The tip weight specified being permenently installed is to limit the amount of weight needing to be stuffed into the tip weight box. On both of the prototypes, we wound up with about 3/4 oz of tip weight. Any percentage permenently installed will allow less having to be installed in the box.
The amount , 1/4, or 1/2 oz is specified to let the builder decide how much weight he wants to have for adjustments, and is, of course, a choice left to the builder.
Before you shorten the nose, may I suggest you send Gordan an e-mail. He's currently running a PA .61 I believe. He is running the shorter nose, but he may also have found it necessary to add nose weight. I'm running the stock nose legnth, but my Stalker .51RE is lighter in weight. and I needed no additional trim weight. H^^
Peter, Some times John get facts and numbers mixed up. The nose moment on my Pathfinder is 10inches. The engine is a PA .51. And I have no nose weight in it. But, I do glue in a half an oz. of tip weight. Hope this helps.
Gordan.
E-mail is gordandelaney@yahoo.com
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Well, ya'll probably thought I dropped off the face of the earth, I have not and nor is the saga of the pathfinder build run it's course. Although little additional progress has been made since the last post, I did get all of the surfaces hinged, fitted and ready for glue. But in the interim because of work and then moving back home to south Florida, the Death of a family member and then moving to a new place in south Florida.....psst a really nice place. I have not had the time to dedicate to modeling. Still have unpacking to do and the garage to put in order. Also sometimes you just get tired of working on the same thing getting bummed out that it seems to take forever to finish. That is the stage I am with the pathfinder, besides the hangar rash it developed from the fist move from NY to Florida and then from one address to another which needs repair. Then I still have to order a tuned pipe and all sorts of other small items to finish it, for me at the moment seems a bridge too far. Anyway what I did do and most likely finish before the Pathfinder is I purchased a Control Line Specialties Forerunner kit. The foam wing version, profile. Got a new LA46 to stick in it. Just need to order a Venturi and needle valve assembly, tank. It should go together rather fast and is a perfect knockabout model to get into the air with. Durable, can be easily be flown off of grass (The pathfinder would have issues taking off of good old Florida Bermuda grass more than an inch high. I flew the heck out of the last one I had. Flew it until from fatigue the wings folded up in mid air. I'll post the construction details in a new thread just for posterity as the model is no longer in production so I do not know how much it will help others unless they also have one to build. Stay Tuned... Now I have to get the garage squared away among a encyclopedia's (Yes, it was a collection of actual Books that had all the stuff worth knowing before the internet) worth of other chores.