Abstract: A wingsail assembly in which the pivoting mounting is situated in line with a strengthened portion of the sail assembly such as a strengthened leading edge of a sail element while still retaining the alignment of the axis of pivoting and the center of pressure. A sail assembly is also described in which a locating mechanism, typically in the form of wire stays, a mechanical linkage or a hydraulic system, is arranged to act on opposite sides of a balancing mass, carried by a boom attached to the wingsail assembly and arranged to locate the mass in an approximately horizontal plane. Where the wing or wing section is constructed from spars and ribs where the latter define the aerofoil section of the wing and lie in the direction of air flow, the ribs are conveniently formed from moulded GRP material and include flanges which in selected regions of the periphery of the rib subtend an angle of greater than 90.degree.

Abstract: A wingsail has two rigid symmetrical aerofoil section sail sections (10, 12) which are mounted one downstream of the other, the trailing sail section (12) being freely pivotally mounted to the center line of the leading sail section (10) so that its leading edge just clears the trailing edge of leading sail section.