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Re: [Phys-L] Impossible vehicles.


The physics of sailing upwind is the same as sailing downwind faster than
the wind.
This is discussed in some detail, using a couple of different approaches, at

Some useful diagrams are included.

JD's discussion in his above link and the Donald E. Simanek reference therein are quite valuable. Of course a cute implication of all this is it's quite possible to sail both upstream in a river in perfectly calm air (relative to the ground), and to sail downstream faster than the current in the same calm conditions. The first situation is a form of sailing downwind faster than the wind, and the 2nd is a form of sailing directly upwind.

David Bowman