PURPOSE: To ease transportation or storage of each body and to increase the bending stiffeness of the float body by forming each float body connected by beams with each other by using a bag body whose form is maintained by air filled therein and also by installing a reinforcing member as one body to each bag body at its forward part.

CONSTITUTION: A pair of float bodies 1 consisting of waterproof canvas material like rubber that is formed into a bag body are connected together by beams 2 and 3 at the fore and aft ends of the body 1. Each of beam 2 and 3 penetrates locking pieces 13 provided at both sides of the float body 1. Sleeves 41 provided at both ends of a connecting rod 42 are fitted around the beams 2 and 3, and the beams 2 and 3 are connected together by a connecting member 4. A mast holder 43 is fixed on the crossing point between the forward sleeve 41 and the connecting rod 42. A mast 6 is inserted into the holder 43, underneath of which a center board 9 is held via a rib 94. In addition, a reinforcing member 7 extending forward beyond the forward beam 2 is installed to each float body 1.