A rotor of an outer rotor type motor is coupled to an outside of a stator, and is provided with a shaft coupler, for being connected with a shaft of a drum, fixed at its center portion by an injected material, and a plurality of radiation holes formed therein continuously in a radial direction. In the above formula, A, B, x, y and z are as follows: 0. The aft or back end of the bowsprit is clipped to the mast and may be unclipped therefrom and secured to the deck so as to position the bowsprit at an angle to the boat to present the spinnaker sail to the wind.