The advances in sailing boat races have been greatly proven in the recent America’s Cup competition. Sailing boats have reached speeds above 40 knots with a simple concept: the wetted surface of the hull is minimized and the required displacement is obtained through a lifting force produced by submerged hydrofoils working at very high speeds. This is a well-known concept in naval architecture that has been exploited since the beginning of the 20th Century. Hydrofoils used in sailing boat races are yet not designed for cavitating flow, but major changes in the design will be needed in case speed increases above 50 knots. When highspeed crafts (including fast sailing boats) operate significantly above the planing threshold speed, the convenience of completely or partially supporting their weight by lifting hydrofoils is evident (Du Cane (1964)). A very low pressure field induced by high in flow speed triggers water vaporization at ambient temperature: cavitation cannot be avoided and foil shape has to be designed with the goal of maintaining a stable flow regime eventually com-promising the lift. When craft speed arise above 50 knots, the de-sign philosophy for the basic section of the lifting hydrofoil has to radically change and turn to super-cavitating hydrofoils (Auslaender [1962]) being the final goal addressed towards the delay and stabilization of the cavity shape over the hydrofoil surface. In super-cavitating regimes the suction surface of the hydrofoil is fully enveloped in the cavity which (typically) detaches at the leading edge of the foil and closes in the wake well aft the trailing edge. The pressure side of the hydrofoil is the only responsible for lift generation thus the main design target is represented by the shape of the foil surface. Several simplified theories assuming steady state potential flow (mentioned later in this introduction) were developed in the past to deal with this essential design problem.

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