Comments interspersed.

"Jan-Olov Newborg" wrote in message om...
Dear Simple Simon!

NASA Glenn Research shows on their website that you are totally wrong
about Lift due to "Longer pathlenght and Half Venturi lift theory"!:

http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

Not a good example. The simulator uses a symetrical, double-surface
wing and talks of powered flight.

We are talking about a sail which is a single-surface foil here.
Proof that the Venturi effect is what provides the lion's share
of the lift in the system is the fact that the sail is shaped
by the pressures on either side. Because the sail's convex side is
always facing the area of lowest pressure proves the venturi effect
is in action. (This is not true only on a dead run where the shape is
caused by wind action on the windward side of the sail)


Professor em. of Physics Weltner shows here how misunderstood
Bernoulli equation can be:

http://www.rz.uni-frankfurt.de/~weltner/Mis6/mis6.html

The good professor is confusing a descriptive term (longer path)
for a causative agent (lower pressure). The longer path is not the
cause of the lower pressure. The lower pressure is caused by the
speeding up of the air molecules because of the SHAPE of the path.
Use the wrong shape and you will not get lowered pressure. The
shape is the key to lowering the pressure efficiently and without
excess drag - not the longer path.

Because the shape confers a longer path does not mean it is the longer
path that is the cause. The shape of the foil is important not the longer
path. The so-called longer path descriptor is ONLY a descriptor.
This seems to go over the heads of so many professorial types who
are all too involved with nomenclature.


Aerodynamist Martin Ingelman-Sundberg ownsite with articles :

http://www.marv.nu/undersajtm.html

And, this chap is talking only of airplanes and probably has never
sailed in his life and is also unfamiliar with single-sided foils that
are shaped by the wind.

Thanks for the links but I still know I'm right when it comes to
sailboats.

Capt. Neal
http://www.homestead.com/captneal/index.html

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