Jan,

Your reply, once again, is loaded with errors and show very little depth
of understand of the very things you are discussing.

You say velocity cannot create low pressure. WRONG!! Just think of a
painter's spray gun. The paint is introduced into the air stream by a
low pressure created by the velocity of the air thru a venturi. A hand
pumped bug sprayer creates a low pressure by velocity over the tip
positioned in that high velocity steam. This is something you have to
come to terms with understand the workings of a sail

I asked you "What is the Ground effect have to do with a sail" you
elected to not answer that but you go off half cocked about wings,
sails, rudders, curved roofs etc all working the same. I AGAIN ASK YOU
to explain how ground effect is of importance in the operation of a
Sail?

Even in your use of Newton's Law your understanding is WRONG! You say
deflecting the air thus creating a force. Jan the air flow is the FORCE.
The deflecting is the action, which creates the reaction. Your
understanding of Newton's first law leaves at lot to be desired.

Jan, you better read some of those web sites you are calling up on
Search.

Ole Thom