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The characteristics of surface piercing propeller (SSPA, picth ratios, 1.6, 1.3 and 1.0) with shaft horizontally raked are investigated experimentally. The directions of lift forces on blades of usual submerged propellers do not coincide with the advance direction and there is unavailable rotative flow in the wake. These may cause the reduction of propeller efficiency. The present propeller system is proposed to solve them and the conditions of vanishing angle between the direction of lift force and that of advance are introduced. In the present experiment the exact, thrust force is not measured but only torque and shaft force and the propeller efficiency modified from the measured torque is adopted. The above conditions give effective estimations compared with the experimental results and the present propeller system is shown to be superior in the propeller efficiency.
