re aircraft thrust/lift, there was a recent dialogue on this in the letters column of Scientific American. Kind of fun, as everyone is, in essence, saying the same thing...differently...

Aircraft get their *unique* thrust from the Venturi effect. Here's the thing: have a friend drive a car along the freeway. Sit in the passenger seat and put your hand out, into the windstream. Tilt your hand at various angles. There is one specific "magic" angle at which your hand is yanked upward. At lower angles, there's some lift. At higher angles, there's quite a lot of lift. But at the one specific angle where the Venturi effect is maximized, there's one WHALE of a lot of lift!

So, yeah, sure, airplanes could fly with wings at 45 degrees up. You'd need a blortload of thrust, but they would fly. But when you set your wings at that "magic" angle, you can fly with much, much less thrust.

*All* lift is supplied by a downward movement of air. But efficient and effective and economical lift is an artifact of the Venturi effect.

Anybody here done any sailing? It's been said that the wind doesn't "push" against the sail, but that it "pulls" around the convex curve of the sail. Another Venturi effect. You could have a perfectly flat, perfectly stiff sail, against which the wind would push. You'd make some progress. But someone with a canvas sail that is bellied to just the right degree will race ahead of you and leave you bobbing in his wake.

Heh... Who says there's no such thing as a free launch?

Silas