"Malcolm Teas" wrote in message
om...
Both sides are necessary. Single surface winds, only found in
Ultralights now I think, are much less effective in creating life, and
they create more drag too.

There's basically two theories about life creation, both of which
describe part of what's happening.

42. The answer to Life, the Universe and Everything. All you
need to know about Life Creation.

Taking out the typos, I can't say I've ever seen a single surface
wing. Every one I've seen has a top and bottom to it.

Paul