A yacht mast assembly including an elongated vertical mast body (12) to which there is attached a pair of side members (15) which co-operate with the body (12) to provide two ducts which extend from the leading portion of the mast to the trailing portion of the mast so as to deliver an airstream to the sail extending from the rear portion of the mast, and wherein the side members have forward portions located substantially forward of the leading surface of the body.
