Wind energy used by a boat

I'm looking at different designs of ocean rowing boat. The boats are moved by a combination of factors

1. Human power
2. Wind acting on the cabins
3. Other elements including currents, wave action etc (that we're not really interested in)

I'm trying to assess the relative proportions of the wind and human power in two different boat designs with different sized cabins. (Essentially looking at the impact of having a larger cabin with a flat surface that could be more easily blown by the wind.)

In both boats,the rowers row all the time, providing a constant power output of 200W.

If we take the average wind speed to be 15mph then the force (lbf) exerted by the wind per square foot is$= 15 \times15\times0.00256 = 0.576 \times$ Coefficient of friction for the area of flat cabin facing the wind (2.0) =1.152 lbf per square foot.

Let us now assume that Boat A has a flat cabin area presented to the wind of 15 square feet and Boat 2 has a flat cabin area presented to the wind of 30 square feet.

Boat A - 17.28 lbf Boat B - 34.56 lbf

How can I turn the lbf of wind load into a unit that I can compare with the output of the rowers to understand the proportional input from each?

Or do I need to make further estimations about each boat's weight, friction with the water etc?

-
Switching to SI units for all variables will already help you a lot. – Bernhard Nov 26 '12 at 14:43
Assuming you are rowing downwind, take the wind force at (wind speed minus boat speed), times the boat speed, and that's the power given by the wind. Don't forget the air resistance of the oar blades on the recovery stroke. – Mike Dunlavey Nov 26 '12 at 21:42