Ship with sail propulsion

A double airfoil for a ship, said double airfoil mounted on a structure controlled angularly around a generally vertical axis by a controller depending on conditions, where the double airfoil comprises a fore flap and an aft flap at least one of which has a fore-to-aft asymmetry and separated by a slit, where each flap comprises a series of shape members distributed in height, wherein said structure comprises a fore mast and an aft mast connected by a boom member and by a gaff member, wherein the shape members of the fore flap are traversed by the fore mast while being able to turn around an axis defined thereby, wherein the shape members of the aft flap are traversed by the aft mast while being able to turn around an axis defined thereby, and wherein said structure is capable of turning on an axis of rotation formed by the fore mast, wherein each of the fore and aft flaps comprise a top member capable of sliding along its respective mast independently of the other, and in that it further comprises two halyards capable, in use, of independently hoisting, hauling down and reefing the fore and aft flaps.