Is there a formula relating boat sail area, wind speed, and
horsepower?

The best I can find at the public library are some ranges, ie
hp/sq ft of sail area = 0.015 @ 7-10 kt
0.020 @ 11-16 kt
0.040 @ 17-21 kt
0.070 @ 22-27 kt

I'm trying to get a better idea of how much sail I'd have to put
on a light 15 foot plywood cabin cruiser with appropriate
underwater shape, whose total weight with one occupant and a
week's gear (including accumulated human waste) is 630 lb., to get
it to plane in less than a full gale. TF Jones says 1 hp to plane
each 40-50 pounds.

For comparison, the above table applied to an Albacore racing
dingy (250 lb) with two people aboard (300 lb) and 125 sq ft of
sail says the wind has to be off the above scale for the boat to
plane.

I also found general wind power formulae in books at the library for
generating electicity but there are constants in the formulae, eg
efficiency, which I don't know for boat sails.

I've looked at numbers for several racing boats of about the same
displacement in library books to compare sail sizes but I'd like
to do the calculation for this boat if I can manage it.


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