Terry Spragg ) writes:

It's all in the sail trim, lad.

there's none of that stuff on a beam reach


Further, a sailboat in motion in a 10 kt true wind may see an
apparant wind on board of anywhere from say 5 kt when going
downwind, to perhaps 20 kt if really boiling along upwind.

wind speed is wind speed. its a simple matter to calcuate apparent wind
and add it to ambient wind speed and use that in teh formual, in fact it
can be included in the formual, whatever it is.

I would be interested to see a sailboat with a bunch of tall
pipes connected through the hull to a point well above the
waterline, with some sort of sensor in each pipe to measure
airflow, pressure and suction against the hull at speed,
investigating the way a hull's shape can affect hydrostatic
pressure, and co-incidentally, friction against the hull. Could
pumping air under a hull reduce drag? Ask any air hockey puck.

P.C. will expound that Viking boat hull shapes have air tunnels
on either side of the keel, and benefit when air is trapped under
the hull at speed, regardless of how it was constructed.

thanks but I'm not designing a cathedral hull.
in teh 1920's MIt did some tests on sails with primative equipment that
you oudl dupicate if you want. one neat thing they did was to put a smoake
bomb on the end of a pole and stick it out from various parts of the boat.
they made a film of it. you coudl do it with a camcorder. you'd need
someone in a powerboat with a walkie-talkie to record views from outside
the boat.

no, there's got to be a formula relating wind speed, sail area, and
horsepower.
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