"Simple Simon" wrote in message
...


How is measuring the actual length of travel a molecule
takes on its journey across the top of the foil as opposed
to across the bottom of the foil amount to nonsense?

I'm simply pointing out that the air doesn't travel different distances on
both sides of the sail.

The flow of the air gets interrupted by the sail. As the air hits the sail
on the windward side, it gets deflected and slowed down. The energy that
has now been removed from the wind has transferred to the sail. i.e. the
wind is "pushing" the sail.

On the leeward side, the air is trying to flow away from the sail, thus
creating "pull". As the angle of the sail comes close to head on to the
wind, a point is reached where turbulence decreases and the air flows
smoothly across both surfaces, but you still have the "push" and "pull"
forces working. This is the point where the sail is working efficiently.

You don't need complicated formulae to understand this. You certainly don't
need Bernouili.


Regards


Donal
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