The semifoiled glider : the new sailing hydrofoil-planing-hybride

Abstract

This work deals with the idea of assuring inherent stability of sailing hydrofoils by keeping the ship in a transient phase. Mainly multi-hulls are discussed. A complete take off is avoided while the ship still enjoys the benefits of hydrofoils, namely high efficiency. This concept is implemented by using V shaped foils at the bow and planing surfaces at the stern. Therefore, the ship always stays in close contact with the water surface. The risk of dangerous fall-backs is reduced and longitudinal stability is assured. Due to the foils and the planing surfaces dynamic lift is generated. The immersed volume and the wetted surface are reduced resulting in high efficiency. The planing surface at the stern can establish a virtual pivot by approximation. The freedom of movement is reduced by one degree which can be used for more specific design and optimization. This leads to better seagoing behaviour and higher efficiency. A further concept of this work is to design the hydrofoil in a way that lift and resistance of the hulls and foils together result in a function of the immersion depth without sharp bends or jumps. This is done by integration and fairing of the foils to the hulls. Due to these concepts and due to other constructive measures discussed in this work, the ship should be able to reach high speed while keeping the risk of undesired touch downs and capsizing low. The assets and drawbacks of existing sailing hydrofoils are discussed and several innovative hull geometries are developed. The expected behaviour of the Semifoiled Glider is discussed too. Special attention is paid on calculation methods (analytic and empiric formulae) of the related forces and moments, allowing to design and simulate the behaviour of the Semifoiled Glider.