Resistances due to hull friction, appendage friction, wavemaking, heel and side force, and sea waves are considered. Comparative values of each of these resis­tance components for four boats, including one with two different sets of appendages, are shown. Most of the resistance components are accurately determined by a combination of theory, numerical computation or model testing. An exception is the resistance due to sea waves for which nonlinear effects not accounted for in present theories appear to be significant. Some de­sign features which increase resistance have associated speed-increasing effects. An example is increasing the vessel beam which increases wetted surface, and there­fore the frictional resistance, but has an associated in­crease in potential sail power. This demonstrates the necessity of evaluating the entire system with a good velocity prediction program rather than using an eval­uation based on a few resistance components.

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