Ing. Marcelo Fornaso wrote:
> Yes. Lots of different shapes can be used to generate lift.
> I'm sure you understood I was referring to efficient airfoils.
> And what I wanted to stress in may bad english is that the effects
> produced in the top (upper camber?) are far more important than those
> produced in the lower camber.
> Of course all the effects (even at the top of the wings) result in
> air moving down.

OK, I can agree with all that.  For most airfoils actually in use, the
descriptions I've seen do show more upwards force on the wing from the top
surface than from the bottom surface.  So a wing is "sucked" up more from
the top than it is "pushed" up from the bottom.  However, as you say, all
this is only a implementation detail and doesn't change the fact that the
plane must produce a net downward push on the air as it goes by.

I've occasionaly mused about a different mechanism than a airfoil to keep a
plane up.  Think of how a pitcher attempts to manipulate the path of a
baseball by spinning it.  The classic curve ball rises more than a purely
ballistic path would.  A baseball certainly isn't a airfoil.  It generates
this lift by changing the angle of its wake due to its spinning.

Let's say you're viewing a pitch in crossection with the pitcher on the
right throwing towards home plate on the left.  In this view, a curve ball
is rotating clockwise.  The wake behind the ball has a downward angle.
Since the ball is imparting downward momentum on the air, it is receives a
net upwards force.

Now imagine a plane that instead of wings has long rotating cylinders, with
the rotation axis along the length of these cylenders, which is left to
right with respect to the plane.  Small lateral grooves in the cylinders
would probably help, just like a baseball pitcher gets different effects
depending on how he orients the spin axis relative to the laces (laces are
roughness and more laces around the equator makes a stronger lift effect).

I'm not saying any of this is a good idea or that it would be useful, but i=
t
is fun to think about.  Maybe even fun enough to build a prototype merely t=
o
prove the point.


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