An A frame mast is pivoted relative to a sailboat hull and supports a lateen yard. A boom is coupled to the yard and to the sailboat hull at the bow. The A frame mast is supported in all positions by struts that lead from each leg of the A frame mast to slidable connections on the hull which permits the mast to be raised and lowered. In other forms, a foldable mast assembly for a sailboat uses a rotatable stub mast and a boom mounted at the upper end thereof. An A frame mast is pivoted relative to the boom and carries a lateen yard that can be raised and lowered by a halyard at the top of the mast structure. To raise and lower the mast, a pair of struts are pivoted thereto and are slidably connected to the sailboat hull or boom so that by using mechanical advantage coupled to the slidable connection, the mast be raised and lowered.