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Model Forum / Radio Controlled / Air Models / February 2004Bolt-on wings for a 48" combat foamie
I'm building a 48" combat foamie F-86 from MM Glider Tech (http://www.mmglidertech.com/f86.html). The default wing configuration calls for attaching the swept-back wings to the bottom of the fuselage with Shoe-Goo glue. I'm considering a bolt-on modification for securing the wings to the saddle and am looking for any tips and tricks. The primary reason for considering the modification is to make it easier to transport the glider from site to site. I have a large family, and there just isn't room in our Grand Caravan for 3 kids, a dog, a ton of camping equipment, and a fully-assembled 48" combat foamie. My concerns are as follows: 1. I do NOT want to the wings to shear off when I crash (and I crash a lot!). The whole point of building a foamie is to buy some insurance during crashes, and I've read that the default wing configuration can withstand horrendous cartwheeling crashes without a problem. Will a bolt-on configuration for a foamie end up being less crash proof? 2. Most bolt-on wing configurations use nylon bolts in an effort to promote shearing. Are there lightweight alternatives to nylon bolts? Or are there nylon bolts that don't shear? 3. How should I fabricate the fasteners for the bolts (both on the wing's center line and in the fuselage's saddle)? Most conventional approaches have one or two dowels near the center of the wing with 2 nylon bolts near the trailing edge. I don't like the idea of using dowels and am considering using one bolt near the leading edge and one near the trailing edge. Will this be sufficient? 4. As much as possible, I'm trying to keep this combat foamie relatively light. If I fabricate bolt-on wing fasteners that are at least as strong as the conventional Shoe-Goo approach, how much extra weight am I looking at? Any thoughts or insights would be greatly appreciated. (email address deliberately obscured with digits) Forget bolts - they DO snap and stick in the hole !! Use simple dowel pegs 1/4" [6 mm], across reinforced areas (1/16 th [1.5mm] ply doublers /treblers ?) , fore and aft of wing, then as many elastic bands as required! IMPORTANT >>>> Fit two servos, one IN each wing - one fitted in wing centre/fuz space with torque rods WILL break when used with detachable wings !! (size of servo depends on wing root thickness) K I S S >> Keep It Simple, Stupid Tip - fit two strips of thin plastic sheet on the top and bottom of wing, about 1 inch wider than fuz, full chord ,BEFORE taping up wing - helps stop lacky bands and fuz edges 'digging in' to the foam.... Nice to have you join us sloppy hooligannzzz ................... Young's Modulous >> "If it dont bend, it snaps !" I built a F5 from http://www.combatairmodels.com/ :same problem. There is a construction tip on : http://www.bungymania.com/ -> F5 Tiger Modifications. This is very easy and I used this modif. with two planes . It is a french text...with photos. If you have trouble with the translation, I can help (french is my mother langage) Robert > Forget bolts - they DO snap and stick in the hole !! > Use simple dowel pegs 1/4" [6 mm], across reinforced areas (1/16 th [1.5mm] [quoted text clipped - 13 lines] > > Young's Modulous >> "If it dont bend, it snaps !" > I built a F5 from http://www.combatairmodels.com/ :same problem. > There is a construction tip on : [quoted text clipped - 5 lines] > translation, I can help (french is my mother langage) > Robert There is an ENGLISH button in left hand menu that I found handy ! Nice site - nice ships - could be tempted .................. > I'm building a 48" combat foamie F-86 from MM Glider Tech > (http://www.mmglidertech.com/f86.html). The default wing configuration [quoted text clipped - 14 lines] > horrendous cartwheeling crashes without a problem. Will a bolt-on > configuration for a foamie end up being less crash proof? If anything, I would think that if the plane is that durable, then wings that shear off will stand up even better to crashes. Nylon wing bolts are a cheap and easy item to replace. > 2. Most bolt-on wing configurations use nylon bolts in an effort to promote > shearing. Are there lightweight alternatives to nylon bolts? Or are there > nylon bolts that don't shear? I didn't really think that's why nylon bolts were used - I thought the big attraction was their light weight. I suppose the shearing is an added benefit - it probably saved my GeeBee from a much worse crash! I don't think there are nylon bolts that won't shear under some amount of strain. Steel bolts will shear if enough force is applied :^) > 3. How should I fabricate the fasteners for the bolts (both on the wing's > center line and in the fuselage's saddle)? Most conventional approaches > have one or two dowels near the center of the wing with 2 nylon bolts near > the trailing edge. I don't like the idea of using dowels and am considering > using one bolt near the leading edge and one near the trailing edge. Will > this be sufficient? I think that would work fine, particularly if your wings have a nice, tight fit in the saddle. I have a foam Piper that uses a SINGLE wing bolt, with NO alignment device, except for the fit of the wing in the saddle (which is quite loose after a few crashes). It uses a recessed aluminum collar countersunk and epoxied into the wing (I guess you don't really want a skinny little bolt holding the wing directly by the foam), and a nylon blind nut, also countersunk and epoxied into the fuse. > 4. As much as possible, I'm trying to keep this combat foamie relatively > light. If I fabricate bolt-on wing fasteners that are at least as strong as > the conventional Shoe-Goo approach, how much extra weight am I looking at? Nylon's pretty light. I imagine it won't be much heavier than the glue to replace it. I'm going to use one on a tiny little 21" indoor model I'm building. > Any thoughts or insights would be greatly appreciated. > > (email address deliberately obscured with digits) I've built one already, two things i would change are the way they cut the fuse. to run the rods to the ailerons. On the second rough landing the fuse snaped in half were i cut it out, so go with two micro servos out in the wing, one for each ail. second is what you already figured out that a glued on wing sucks, use two nylon bolt one at the front one at the back. I sunk a one inch by one inch wood dowel piece into the fuse. one at the front, one at the back then used a 1/4x20 tap to tap threads into the center of each. the nylon bolts never sheared on me but the wood did shatter twice on inpacts. i hope this helps you. Good luck and lots of air. > I'm building a 48" combat foamie F-86 from MM Glider Tech > (http://www.mmglidertech.com/f86.html). The default wing configuration [quoted text clipped - 33 lines] > > (email address deliberately obscured with digits) Ken, I have built that plane with bolt on wings. The rubber bands deformed the wings and fuse too much. They crunched the wings and fouled up the trim. 1) Use 1/4" nylon bolts. Pretty tough to shear, but buy extras and carry them with you anyway. If you really don't want them to shear use aluminum or steel. I however use and recommend nylon. Foam doesn't break, but a lot of the plane is not foam.. 2) Glue 1/8" ply plates to the bottom of the fuse in the wing saddle. I went nearly full width and basicly square. "Countersink" the plates. 3) Standard single servo mounted in the wing is fine. 4) Use blind nuts (t-nuts, whatever they are called) in the ply to screw into. 5) Use 1-1/2" square 1/8" thick ply "washers" on the bottom to distribute the bolt load and prevent pull through and wandering. I did not glue mine on, but it might not be a bad idea to keep from misaligning the wings. Countersinking and gluing will definitely be smoother. Cover them the same color as the wing bottom. BTW, I did mine in yellow sign vinyl with black stripes, stars and bars etc and black wing and stab bottoms. Looks good, flies well. A friend of mine recommended against silver after experience with a Mustang.  SignatureTom Koszuta Clarence Sailplane Society (Buffalo) NY > I'm building a 48" combat foamie F-86 from MM Glider Tech > (http://www.mmglidertech.com/f86.html). The default wing configuration > calls for attaching the swept-back wings to the bottom of the fuselage with > Shoe-Goo glue. I'm considering a bolt-on modification for securing the > wings to the saddle and am looking for any tips and tricks. |
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