Re: Misconceptions: Physics of Flight

[William Beaty <billb@ESKIMO.COM>]

On Thu, 12 Aug 1999, Glenn A. Carlson wrote:

> Surely not the case for zero angle of attack.

True.   Since "Bernoulli" applies both to cambered and uncambered
airfoils, then the lifting force should be proportional to the difference
in velocity between upper and lower surfaces.

The big question is, if a cambered airfoil is generating lift, is its
angle of attack truely zero?  Perhaps we should think in terms of an
*effective* angle of attack, rather than determining the AOA of the wing
through geometry and then fighting over the fact that this determination
of attack-angle allows cambered airfoils to generate lift at zero AOA.

If the fundamental process behind the lifting force is that mass is
deflected, then maybe we have it backwards, and "attack angle" should not
be determined by drawing chords through airfoil crossections.  Perhaps
instead we should measure the force, and then adjust the airfoil to give
zero lift, and declare this setting to be the "true" zero AOA.

A spinning cylinder can be used as a wing.  It certainly has no particular
attack-angle, so geometrical determination of AOA doesn't apply in every
situation.


> (Is it even possible to have a symmetrical *cambered* airfoil?)

Make a symmetrical streamlined shape, then give it a camber?  What should
we call an asymmetrical streamlined shape which has zero net camber?  If
we give such a shape an overall camber, I'd call that an asymmetrical
cambered airfoil, but perhaps there is a conventional term for such a
thing.



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