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Date: Fri, 02 Feb 2007 16:43:49 -0500
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From: "Mark Sletten" <marknlisa@hometel.com>
References: <list-1806133@logan.com>
Subject: Re: Wing positive pressure
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In-Reply-To: <list-1806133@logan.com>

Ladies and Gents,

All Paul is saying is that to view lower pressure on the top surface of the
upper wing skin as *PULLING UP* on the wing is wrong. It's more accurate to
say the higher pressure air inside the wing is *PUSHING UP* on it (the upper
wing skin) as regards the forces necessary to fly.

In other words, there's no such thing as suction force -- vacuum doesn't
generate force. It isn't the vacuum that causes a can to collapse as the air
is evacuated from within, it's the ambient pressure of the surrounding air
that does so. The force required to crush the can comes not from the vacuum,
but from the surrounding air.

Another poster has already suggested the idea that deflected air, rather
than pressure differential, produces lift... Now there's an argument still
waging among the true geniuses among aerodynamicists!

I had a great deal of difficulty understanding the idea of lift (to my
satisfaction at least, there is argument that no one *COMPLETELY*
understands it as yet) until I read Wolfgang Langewiesche's masterpiece
"Stick and Rudder." 

http://www.pilotsbooks.com/stick_rudder.htm

If you haven't read this book, I highly recommend it. It is arguably the
most complete description -- in easy to understand laymen's terms -- of how
and why a wing produces lift, and how a pilot can best control it.

Mark Sletten