"Simple Simon" wrote:
That's precisely why I give more credence to Venturi.

I like to keep it simple as my name suggests. Why
clutter a good physical reality with extra theories
that may or may not be applicable?

In my opinion the theory:
"air tends to follow the sail (also on the leeward),
and thus deflects the air, and for that deflection you need a force,
and that force is the sailforce"

is easier as explaining:
"the path on the leeward is longer, so the air has to move faster"
continued with
"fast moving air has a lower pressure"
"just like in a venturi in a pipe"

Please note that I do not make air molecules bounce of the sail,
I am deflecting a flow of air.
To check if that flow has not separated from the sail I also reccomend
telltales.

Please read www.sailtheory.com/sail.html for more details.

What might be confusing:
Bernoulli never had a theory for a wing. He had a theory for explaining how
high a fountain would spray.
Newton never had a theory for a wing, his theory was about bouncing balls
and planets etc.
Euler, Kutta and Joukofski, and Prandtl all had some theories about flow
around a wing.
For some strange reasons they are not often mentioned.
(I am promoting Ludwigs Prandtl "lifting line theory" if you want to know)

I quit this discussion, I think the "longer path gives higher speed, and
thus lower pressure" theory really sucks.
If you do not need a theory, please do not use a theory. It is better to use
no theory as to use a stupid one.

Thank you for giving your opinion.

Best Regards,
Pim






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