You are making a mistake: why the air speeds up at leeward.
It has nothing to do with the length difference.

If you do not want to leave your good old theory,
please consider the one I suggest as an extra.
my theory :
"the sail deflects the air (on the windward side as well as on the leeward
side)"
It is very satisfying, it explains a lot.

Any way, all theories are a simplification of the reality.
more theories to describe the same are possible.
The best theory is the one that is the simplest and explains the most.
It does not mean all other theories are rubbish!

By the way, how do you explain that a flatter sail sails
better "pointing" close hauled as a deep(=curved) sail?
The more curve the more force according your theory, so what is the use of
flattening the sail?
(my answer: www.sailtheory.com/sail.html#ch)


In reply of your previous post:

"Simple Simon" wrote in message
Fact: Venturi effect is proven and accepted
Venturi effect is in a pipe, in a venturi, There it is indeed proven and
accepted.
A sail is no venturi.

Fact: Venturi effect causes lower pressure in the area of the venturi.
yes.

Fact: Lower pressure is cause by the lower density of the gas molecules
in the area.
density difference is not of importance. A keel works just as a sail
prducing sideways lift, but
density of water stays the same.

Fact: An object with low pressure on one side and higher pressure on the
other side if free to move will move in the direction of the low pressure.
Yes.


THAT is how a sail works.
There is no venturi. There is a sail. That is the error.

All that other crap is extraneous to the situation
at hand aboard a sailboat.
oh.

There is no high-horsepower motor available to
make the sail act as a plane like PIM suggests.
I do not want to suggest a motor. Sorry if I did.
(with "power" I mean energy/time, or force x speed, so not a motor,
on my site you can read "force" instead of "power" in most places.
It is a small translation error. "power" is in Dutch different from
"motorpower"
thanks for the hint. This helps improving my site )

All the force is generated
by a difference in pressure between the leeward and
windward sides of the sail
yes, and these pressures are created by changing the direction of the wind
locally.

which force acts against the foil in the water and the planeform
of the hull to produce forward motion.
yes.

Best regards,

Pim
www.sailtheory.com






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