|
Message
Paul Lipps wrote...
A
strongly held concept is that the bottom of a wing has positive pressure and the
top of the wing has reduced pressure, and this is where lift comes from. Any
wing with curvature on the bottom, such as the NLF1 0215F on Lancair 235,320,360 has reduced pressure both
on the top and on the bottom; its just that the reduced pressure on top is
lower than on the bottom, so the there is a net upward force. Since lift is a
force due to a pressure difference across a surface, it may come as a shock
to most of you that the pressure difference is across the top skin and the
bottom skin. That's right, Ladies and germs, lift on a hollow wing is due to the
air inside pushing up on the top skin and
pushing down on the bottom skin, but the top skin wins, hopefully! Unless it's
not attached properly, as Steve Whitman found out. Suction is not a force; it's
a human's subjective misunderstanding of things physical, such as hot and cold.
Suction doesn't pull open a canopy in flight; the air in the cockpit pushes it
open. Did you know that there are hundreds of pounds of pressure differential on
your canopy which makes up a significant part of your aircraft's overall lift
force, and slowing down the plane to close a half-latched canopy doesn't make
the force go away? Please, if you can't grasp or understand this
apparently un-orthodox concept that flies in the face of all you've been
taught, lets not do an aerodynamic battle on these posts!
So,
let's see if I have this right..... the lift on a wing is
actually the air inside the wing pushing up on the top skin of the wing (in
excess of the air pushing down on the lower skin of the wing)---that is what is
causing the lift. If that is so, then if we take a air tight
container in the shape of a wing/airfoil, evacuate the air out of it, and
position it in an airstream, that it will not generate lift because there is no
air inside to push against the top skin? Mmmmmm, very interesting
proposition. I'm not a betting man--usually--but I have a twenty that
I'd risk!
Chuck
|