This article presents a calculator for assisting in determining the hull speed potential of a moderate speed propeller driven planing hull, based on the hull's weight, the horsepower, and a "hull factor." The hull factor is a constant which is used to convert the necessary dimension of weight and power into a convenient speed unit.
Naval architect George Crouch proposed that a useful estimate of the speed of a moderate planing hull could be derived from the boat's weight and horsepower. If the weight is given in pounds and the power is given in horsepower, the hull factor will be a range of 150 to 250 and the speed will be calculated in miles per hour. The variables are related by
MPH = [ ( HP / LBS )^0.5 ] x C where C = a constant that depends on the hull form.
Crouch proposed that C would have a value for various hull types as follows
PLANING HULL SPEED CONSTANTS--MPH C Hull Type 172 Average runabout, cruiser, passenger vessel 218 High-speed runabout, very light high-speed cruiser 240 Race boat types 253 Three-point hydroplanes, stepped hydroplanes 265 Racing power catamarans and sea sleds
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Author: James W. Hebert
This article first appeared April 16, 2006.