Aerofoil sail

An aerofoil sail assembly for providing motive power to a cargo vessel, comprising three aerofoil sails, each aerofoil sail comprising a leading aerofoil portion and a trailing aerofoil portion, and the aerofoil sail assembly comprising a spar defining a longitudinal axis and a height along the longitudinal axis, at least one of the aerofoil portions rotatably positionable, wherein an angular position of at least one of the aerofoil portions controllable relative to the spar, and the spar rotationally positionable about the longitudinal axis, and each of a leading portion and a trailing portion comprising a respective external aerofoil surface and wherein a distance between distal end regions of the external aerofoil surface of the leading portion in a direction transverse to the height of the spar is longer than a distance between distal end regions of the aerofoil surface of the trailing portion in the direction transverse to the height of the spar, and a gap is provided between the leading portion and the trailing portion, and wherein the three aerofoil sails provided in a side-by-side spaced apart relationship, and a leading aerofoil portion of a central aerofoil sail of said three aerofoil sails having a height, and the spar extending internally of said leading aerofoil portion of said central aerofoil sail and for the height of said leading aerofoil portion of said central aerofoil sail, and the spar comprising an internal volume sized to allow operative access for a major portion of a length of the spar.