PURPOSE: To improve a reliability of a light mast at low cost by forming the front mast having longitudinal grooves for hoisting a sail of a composite material including a continuous fabric impregnated with a resin.

CONSTITUTION: A hollow front mast S comprises a front element 10 formed of cabler fibers and acryl IPN resin by a drawing molding and a rear element 12 composed of polyvinyl chloride by an extrusion molding. In this case, the front element 10 may include 60 wt.% of reinforced fibers. The front element 10 forms a rear recessed surface 10a. A dovetail shaped longitudinally extending spline 13 is disposed on the center of the surface. The rear element 12 forms a dovetail shaped rib 12a which is fitted to the spline 13 and attached to the front element 10. The flat rear surface 12b is provided with two longitudinal grooves 14 for stage warping of a front sail.