In a sailing catamaran provided with a forwardly directed pivoted arm carrying at the free end a third pontoon into alignment in front of either of the catamaran hulls a triangular truss assembly is provided bridging across the hulls. The apex of the truss assembly is then engaged to a point along the length of a mast which has its foot or base resting on the arm. A forestay stretched between the mast and the end of the arm supports a headsail while a mainsail is mounted on the mast.