I don't hate to say it but you and PIM are BOTH incorrect.

You both have only a laymans idea of how a sail works.

Fact: Venturi effect is proven and accepted
Fact: Venturi effect causes lower pressure in the area of the venturi.
Fact: Lower pressure is cause by the lower density of the gas molecules
in the area.
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.

THAT is how a sail works. All that other crap is extraneous to the situation
at hand aboard a sailboat. There is no high-horsepower motor available to
make the sail act as a plane like PIM suggests. All the force is generated
by a difference in pressure between the leeward and windward sides of
the sail which force acts against the foil in the water and the planeform
of the hull to produce forward motion.


"jlrogers" wrote in message .com...
I hate to be the one to tell you this, but PIM is correct. Lift is to air as buoyancy is to water.

"Simple Simon" wrote in message ...
I think you should do a little research into Bernouilli and Venturi.


"PIM" wrote in message ...

"Simple Simon" wrote
The convex side of the sail or the leeward side directs the air
over a longer path. This longer path for the air lowers the pressure
because said air must move faster to cover the increased cord.
Faster flow equals lower pressure. This low pressure combined
with the normal or slightly increased pressure on the windward
side is what creates lift.

Dear Simon,
I am not neglecting what happens on the leeward of the sail,
the leeward of the sail is also deflecting air and thereby creating lift.
as I am explaining in www.sailtheory.com/sail.html

According the "longer path theory" you use it would not matter how
much you pull your sail in, since there is always the same difference
in pathlength between windward and leeward.
Please read www.sailtheory.com/wrongtheory.html for more examples
why it is wrong.

The "longer path theory" is not easy to use and is wrong.
It is the reason I started my site.
Clearly I am not clear enough at this point

Many agree with me that the longer path theory is wrong:
jeff raskin:
http://tinylink.com/?RD9ntJyTuz
university frankfurt (under 2.2)
http://www.informatik.uni-frankfurt..../MIS/mis6.html
University of washinton:
http://www.aa.washington.edu/faculty/eberhardt/lift.htm
Bill beaty:
http://www.amasci.com/miscon/miscon4.html#wing

And so do the most aerodynamicists as far as I know.

I tried to adjust above theories from a wing into a sail.

Best Regards

Pim






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