Abstract: A reversible aerofoil comprises a central panel (10) with lateral panels (12A,12B) hinged to opposite edges. The lateral panels can be hinged so that either one overlies the central panel while the other is extended, thereby producing alternative mirror-image aerofoils. The lateral panels can be hinged so that they both overlie the central panel, thereby producing a stowed configuration. The shape of the panels is such that in the stowed configuration the profile of the outside surfaces of the lateral flaps match that of the central panel, thereby allowing a cross-section to be produced which edge-on is substantially symmetrical, preferably elliptical, thereby producing a low-drag aerodynamically stable stowed configuration.

Abstract: An aerofoil sail has a rigid main panel (10) pivotally mounted to a hull (17) about a vertical axis (15) with trailing a flap (12A) hinged (14) to one side of the main panel. The trailing flap comprises a series of separate flaps (12A' ,12A" ,12A'") individually settable so that the angle of incidence can differ (.alpha.,.beta.) at different levels on the sail. Alternatively, a single trailing flap can be torsionally flexible so that the angle of incidence can differ along its length. In a preferred form flaps (12A,12B) are provided at opposite edges of main panel (10) and can be alternatively folded in to give a reversible aerofoil section.

Abstract: A reversible aerofoil or hydrofoil has a central panel with lateral panels hinged thereto. The section of the central panel is symmetrical on either side of a central axis and the lateral panels are of similar section to each other. Either of the lateral panels can be folded in to lie against the central panel or the other lateral panel or both, while the other lateral panel is extended, the combined panels thereby forming a non-symmetrical aerofoil or hydrofoil section. By extending the folded-in lateral panel and folding in the extended one, the section is reversed.