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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!
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