Eric Greenwell wrote in message ...
K.P. Termaat wrote:
"soarski" schreef in bericht
om...

In my country, our gliders move forward because the wing produces
thrust, and our sailboats move over the water because the sail produces
thrust. Whether we should rule the world is causing much controversy.


In my country (Holland) students will be disqualified from their examination
when they make an "interesting" remark like this. Reducing induced drag is
what winglets do and gravity is the engine of our gliders.

And what produces the "thrust" that moves your sailboats? Gravity?

This may be a simple confusion over the word "thrust", which I used (as
did the original question) in the sense of "force in the direction of
motion". Both the glider and the sailboat are propelled in a forward
direction by lift from the wing or sail.

Not if you _define_ lift as perpendicular to the direction of motion...

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FF