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Model Forum / Radio Controlled / Air Models / May 2004Aero bird challenger wing breakage........... Help
I have been flying the ABC for a while now and have had this problem 3 times now 2 on brand new wings with no... let me say that again NO damage to them at all. It seems that while doing an extreme nose dive and then pulling up into a loop or what ever this plane continues into the ground with a wing buckle. What is the best way to remedy this situation (weak wing) ? I thought that by wraping the wing in monocoat might help?? or that strapping a piece of spruce to the bottom side might help? Help..... this airplane is fun with the exception of this little fo pa Cade > I have been flying the ABC for a while now and have had this problem 3 > times now [quoted text clipped - 12 lines] > > Cade Take a look in the forums on rcgroups.com - there is a 450+ post long thread on the ABC and how to fix it when you hit the ground. As I recall, this is a common problem with high-g turns. James I have a Fireball Commnder - the wing seems to be a foam core with a harder plastic surface layer. I tried all sorts of adhesives including epoxy and and aliphatic resin - they debonded quite easily. I normally don't use standard type cyano because it can melt foam...... but I tried a test patch and it worked fine - ie the outer skin did not dissolve. (Odourless cyano might be OK as well). Then get some very light ply - it the range 1/64 to 1/32 inch and stick it on to the underside of the wing. Not easy but it has worked for me. Otherwise let in a carbon fibre or spuce spar. Just be sure to try a test adhesive patch to check everthing bonds (or does not dissolve !) OK before doing the whole repair. CW >> I have been flying the ABC for a while now and have had this problem 3 >> times now [quoted text clipped - 19 lines] > >James > I have a Fireball Commnder - the wing seems to be a foam core with > a harder plastic surface layer. I tried all sorts of adhesives [quoted text clipped - 11 lines] > > CW Spar failures often start in the top cap. It's in compression in positive G loading, and like most materials other than concrete or brick, wood is stronger in tension than compression. The top strip will buckle, and then the rest of the spar fails. In full-scale aircraft the spar's top cap is usually heavier than the bottom, unless the aircraft is designed for the same negative G loading as it is for positive. Foam wings would act somewhat differently and might be more resistant to compression loading in the top surface. > >> Help..... this airplane is fun with the exception of this little fo pa > >> > >> Cade Pronounciation: fo pa Spelling: faux pas Dan The cracks in my wing were on the underside, with no evident damage on the upper surface skin. Therfore I surmised a tension crack on the bottom, and the foam skin apparently compressing and recovering on the top. CW >> I have a Fireball Commnder - the wing seems to be a foam core with >> a harder plastic surface layer. I tried all sorts of adhesives [quoted text clipped - 29 lines] > > Dan > The cracks in my wing were on the underside, with no evident > damage on the upper surface skin. Therfore I surmised a tension > crack on the bottom, and the foam skin apparently compressing and > recovering on the top. > > CW Reinforcing the bottom may help, but I would suggest finding some way of reinforcing the top surface as well. When the top surface compresses, the fulcrum point (against which the bottom is being put into tension) is moving inward toward the center of the wing's thickness, increasing the leverage forces on the bottom of th wing. Stiffening the top surface keeps the fulcrum point at or near the top surface and makes the wing much stronger. Since foam has no grain, its strength is limited anyway and maybe you are just flying the airplane a bit too radically. There are, of course, many kits and designs that have their weaknesses, and perhaps yours is one of them and a bit of strengthening would improve it. Some guys use a bit of fiberglass packaging tape along the bottom of the wing to increase its tensile strength. dan > >> I have a Fireball Commnder - the wing seems to be a foam core with > >> a harder plastic surface layer. I tried all sorts of adhesives [quoted text clipped - 29 lines] > > > > Dan |
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