Dave Doe writes:

If you are right, I'd expect to see planes with the airfoil upsidedown
(with the increased camber on the bottom), but that's not the case (and
I'm talking about the *wings* here, not the horizontal stabiliser

Actually it is. NASA has tested airfoils with a camber on the bottom, and they
fly just as well as airfoils with a camber on the top. I don't know what
became of the research, though. As a I recall, they had some airfoils that
were very good at preventing stalls, but I suppose they had other
disadvantages (drag problems?).

I think you have explained though, that the Bernoulli effect occurs with
a barn door too at an angle of attack - however it is a lot less
*efficient* without that camber (which will continue to 'suck' air down
- as the camber continues to change direction - and therefore drag the
viscous air around it with it). I hope you'll agree with that.

Good airfoil designs can reduce drag and improve stall characteristics, but
generating lift requires only a positive angle of attack.