Originally posted by Al Stein
For an interesting insight on how much you can straighten )or twist) a wing with the covering, check the instructions for a PT-40. (I think you can find them at the Great Planes site.) Its wing is supposed to have 3/4" of washout and it was originally built with none and twisted entirely by the covering. The newer versions are supposed to be built with the twist already glued in, but They've cut the parts so precisely that even if you build in the twist they recommend, almost all of it pops out when you take a wing panel off the building board... so you're still stuck twisting in most of its huge wash-out with the covering!
For what it's worth, I have just completed a PT-40. The washout is buit in by the
sheeting and not the covering. Take the wing skeleton, support the Trailing edge of the wing-tips so that the trailing edge at the wing root is 1" off the work surface. Add weight to the wing root so that there is "twist". Sheet the wing with the 1/16 balsa. Viola! Washout-enabled.
gus