Fred the Red Shirt wrote:

Nyal Williams wrote in message ...

Now, I'm confused! An airfoil cannot produce thrust
-- only 'lift.' But if an airfoil has a reverse counterpart,
the two are joined at the center and rotated about
an axis in a vertical plane, they are then a propeller;
this produces 'thrust.'


Well if that last statement is true then the earlier one
is false. Do propellers produce thrust?

The first poster is confusing a wing and an airfoil. It's a _wing_ that
cannot produce thrust in the aerodynamic sense, by the definitions used.
A propeller can produce thrust. They both use airfoils.
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Eric Greenwell
Washington State
USA