There is a Faustian Bargain to be made regarding the Proa's Prismatic Coefficient. Boats with a lower Cp (finer bow entry) are faster in light air and boats with a higher Cp (fuller ends) are faster in heavier winds. The problem is that higher Cp bows are slower in light conditions and lower Cp Bows are are slower in heavier winds.
Of course this is also directly tied to the sail area/displacement ratio.
To make a long story short, the Prismatic Coefficient determines the amount of Sails and the speed of the vessel.
For a speed to length (square root) ratio of 1 or less the Cp should be .525.
For a boat that matches the Froude 1.34 wavelength speed the Cp should be .63.
The maximum Cp of .7 is for boats expecting to go at 1.8 S/L or higher.
So there you have it, the Prismatic Coefficient of the bows should be .7.
Talador
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Posted by: taladorwood@yahoo.com.au
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