Do winglets produce thrust?

"Bob Salvo" wrote in message
...
Anyone?
Bob

Do winglets produce thrust? (CAN winglets produce thrust?)
All non-believers should read the NACA report by Whitcome, the inventor of
winglets. Winglets are an airfoil and therefore produce lift. If the cord
of the winglet is oriented properly, the lift vector will be angled slightly
forward, hence the use of the term "thrust". Since the angle of attack of
the winglet is influenced by the lift coefficient of the main wing, a
significant amount of "thrust" is only produced at a very narrow range of
angle of attack (aircraft speed). A significant amount of "thrust" is
defined as when the forward component of lift of the winglet is greater than
the drag of the winglet. Since sailplanes are flying at either a slow speed
of near stall or very fast speed, the concept would not seem to be of much
use for sailplanes.

The winglets used on sailplanes seem to use an airfoil which has a large low
drag bucket and are designed more to diminish wing tip vortices. This
results in lower sailplane drag, sometimes better aileron control, and
perhaps at some angle of attack of the main wing some "thrust".

Duane