ORIGINAL: Mike Connor
Did you use carbon strips at the high point of the wing on top? I believe the integrity of the wing on top is more important the then the bottom when it comes to folding a wing. Hence the 3/32 balsa on top and 1/16 balsa on bottom. Someone correct me if I am wrong.
It is not the integrity that is in question, it is the failure mode. In a wing failure caused by positive G's (e.g. - a hard pylon turn), the bottom skin is in tension and the top is in compression. Tension is a stable state and the bottom skin and spar will carry a tension load up to the point of the material failing at it's tensile limit. Compression is not a stable state and the top skin and spar are subject to elastic buckling failures. Depending on the skin thickness, rib spacing and other support details, an elastic buckling failure can take place at a small fraction of the actual material failure point. To counter this, a thicker skin is used, which is less prone to a buckling failure.
Mark