"Todd Pattist" wrote in message
This is an interesting winter-we-can't-fly debate. The wing
on a glider in steady motion through the air produces a
total aerodynamic force. That total aerodynamic force is
exactly vertical and exactly equal to the gravitational
force. By convention, we resolve this total aerodynamic
force into two components called lift and drag. The lift
component is always perpendicular to the flight path, and
the drag component is always parallel to it. By the usual
convention, "thrust" is either parallel to the flight path,
or is the non-aerodynamic force produced by an engine of
some sort. Thus, "lift" cannot produce "thrust." Either
the lift is perpendicular to the path, while thrust is
parallel, or it's an aerodynamic force and is excluded. For
a glider with winglets attached, when you are talking about
the total lift and drag forces, winglets cannot produce any
"thrust" by the definitions.

Good post Todd,
Isn't that what I said earlier??
Winglets produce lift, with a vector. The vector direction
can be perpendicular to the winglet surface, fwd or aft.
That is dependant on how it is shaped and mounted.
A lift vector facing the nose (fwd) being called thrust
might be a mishmash of terms, but it happens.
I usually think of thrust as a motive force acting on the vehicle.
Winglet vectors are recovery of lost energy by reshaping flow
to our advantage. Good idea, yes, thrust...... probably not
a really good description of what is happening........

Scott.