The Hybrid Hydrofoil Stepped Hull

Abstract

A hybrid hydrofoil is a vehicle combining the dynamic lift of hydrofoils with a significant amount of lift from some other source, generally planing lift. The attraction of hybrid hydrofoils is the desire to meld the advantages of two technologies in an attempt to gain a synthesis that is better than either one alone. They offer a performance and cost that would be appropriate for some ferries, light cargo, and recreational vessels. The stepped hybrid hydrofoil configuration made its appearance in the high-speed boat scene in the late nineteen thirties, but never was widely used. It is a solution to the problems of instability and inefficiency that has limited other type of hybrids. Their current status may be due to being eclipsed by the pure hydrofoil or by problems in takeoff stall, roll instability, or propulsion matching. But it should not be viewed as a partial step to the hydrofoil, and there are solutions to other problems. It is a valid concept with its own special characteristics and capabilities and merits consideration. Hybrid hydrofoils especially merit consideration for high-speed ferry service for partially sheltered runs, where seakeeping is a consideration but not an overriding one, there are factors limiting size on a given run, such as traffic dispersion, and moderately high speeds are required.