On 15 Oct, 20:11, "Graham Frankland"
wrote:
"Ian" wrote in message

ups.com...

On 15 Oct, 14:19, (Richard Casady) wrote:

Thrust from the engine, of course.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

But in your example, gravity is still causing you to descend through the
air. Unless converting excess speed to height, you only climb because the
air in which you are flying is rising faster than your sink rate.

Whether in a zoom or a thermal, I can get my glider to rise without
smuch as a millinewon of thrust...

Presumably, if a boat's motion is generating apparent wind from dead ahead
and a fully battened sail (I say fully battened because it's a better
aerofoil shape) could be set far enough out to achieve sufficient angle of
attack to produce some lift, then a keel boat "may" go a little quicker.

Nope. Lift is - by definition - always at right angles to the free
stream air velocity. You might get the boat to go sideways a bit, but
the assoiated drag will always slow you down as you do.

Ian