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Wanted Sky Pup Plans

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ragflyer

Well-Known Member
Joined
Apr 17, 2007
Messages
701
...maybe you should change your name to wantodesign :)...while it can definitely be done its a lot more involved than just adding some carbon bid to the spar web. Almost anything can be engineered, but the question is what is the trade off. I don't want to dissuade you (its experimental aviation after all) but you have some design work to do upfront or you can build as you say and test fly and tweak in the old tradition of the pioneers with some very obvious risk to limb and life. Its been done many times and I believe the UL rules still permit you to do that. Your choice!

A few points:

1. the wing as designed handles some twist (about cm = -0.1) due to the camber in the airfoil. Only symmetrical airfoils induce no twist. Adding ailerons increases this about 3 fold.

2. The wing twisting as designed is reacted by the leading edge wing connection which in turn is reacted by the D nose- 0.8mm nose ply and the back of the shear web which for most part is foam. All these components need to be checked to see if they will take the additional torques. Adding (very stiff) carbon bid to the spar web is only one part of the load chain.

3. Carbon bid is about 10,000 to 30,000 times stiffer than foam and 10 to 30 times stiffer than wood. This means it will take all the shear load in the spar rather than the foam and will need to transfer it to the wood caps. If you wrap it around the spar caps then it will see significant bending stress (Billski has posted this out many times). It may be fine but you will need to do check.
 
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