Abstract: A stowable semi rigid airfoil assembly, functions automatically to airflow as a draft adjusting wing sail, or spinnaker sail (19), for use on a mast (17) with a halyard (41) on a wind powered craft. The halyard connected to the heads (83) of port and starboard sail panels (10) surrounding the mast vertically, elongates the airfoil from a “wing chord section shaped boom” (21) attached to the airfoils' foot (57). The sailcloth (12) panels are laminated with rigid foam cored (11) horizontal panel sections (13) set between flexible sailcloth spaces (14), for folding the rigid panels down over the wing shaped boom. The top of the panel sections above the boom are outward folding (22) spaces, and every other one of the spaces up the sail are outward folding, and every other one of the other spaces are inward folding (16) and are increased in separation (20) between the rigid panels. The leading edges (27) of the sail panels are joined at the inward folding spaces.

Abstract: A wing sail for wind powered craft and of the type having semi rigid panels (10) which communicate at their base with an airfoil shaped boom (21). The semi rigid panels (10) of the wing sail can be bent along folding grooves (20) that are parallel to the boom (21). In addition, the semi rigid panels (10), and boom (21) of the wing sail are made of flexible materials so that they can be repeatedly bent without fracturing, perpendicular to the boom.