soarski wrote:
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.



PLEASE....Readers of the World! This is not in our textbooks! Did
someone in the USA write the above???

Wings produce Lift!! A by product of lift is drag! Winglets do also
produce lift, and therefore drag. Possibly less than the wing? But
you canot call it thrust!.......

"Thrust", for the winglet question and my remarks about gliders and
sailboats, was used to mean "force in the direction of motion".
Apparently, that was an unusual use of the word for some people.

Here's an expanded expanation:

Gravity is pulling straight down, and so can not propel the glider
forward; drag is pulling the glider back, and so can not propel the
glider forward. So, what is left to counteract the drag? Lift, produced
by the wings. This forward force comes from the lift, which is not
vertical, but tipped forward a bit. Look at any diagram showing the
forces on a glider, and you will see how the lift, drag, and gravity
forces accomplish this.

It is not common to call this force moving the glider forward (without
it, drag would bring it to stop) "thrust", but the word is sometimes
used that way.

I still can't answer the original question about the winglets, though.

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Eric Greenwell
Washington State
USA