Marine propellers for hydrofoil craft have to satisfy operating conditions that are different from those of displacement vessels. A hydrofoil propeller must produce a large thrust at the desired low take-off speed of the craft, and has to transmit the maximum propulsive power to permit the craft to run at its designed cruising speed on foils. Moreover, the cruising speeds are mostly higher than those of comparable conventional vessels.\nThe above-mentioned operating conditions could be satisfied with variable pitch propellers. However, hydrofoil propellers will mostly form part of the foil system and the complexities associated with variable pitch mechanisms, together with the difficulties that anyway exist on account of the drive through the struts, or hydraulic drives in the propeller hub, do not make such a design very attractive.
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