So far I've actually built both kinds of wings.
I personally haven't broken a spar or only slightly damaged a wing. I recently destroyed one in a beautiful crash filled with bits and pieces of coro and pvc littering the field, but that required a complete rebuild. Whe I cause damage I do it right......
If you want a flat bottom wing then the bottom drawing is the way to go. Make sure the the flutes for the top piece run from front to back though. Check out the wing on the "Das Plas Stik" at
www.spadtothebone.com for an excellent example (and great flying wing). I've built several of them. Easy AND Fast, too
So far though I'm starting to lean toward the one piece of coro, flutes running fron to back, scored and folded with 2 glued in pieces for the 'rons. It allows me to make a more symmetrical wing with greater strength for "lunatic stunt flying"
I'm gonna post pics of my latest wing later today - right now the sun is shining and I hear the sound of 2 stroke engines......
DB