A screw propeller is the most typical mechanism for ship propulsion. However, it is well known that some species of aquatic animals such as tuna and dolphin are able to swim at a high speed by powerful fanning of their caudal fins. The swimming motion of these animals is considered to be a combination of the heaving and pitching motion of the tail fin (the oscillating wing). The authors have developed a two-hinge oscillating fin propulsion mechanism which basically follows the swimming motion of aquatic animals'. The propulsion system is driven by a 13 PS motorcycle engine mounted on an experimental ship. The ship is 3.6m in length, 1m in width, and about 160kgf in weight. The wing is flat plate of 3.2mm thickness and 0.27m^2 area, and its aspect ration is 6.3. The wing motion is determined by the balance of forces between a flowing fluid and the torsion of a coiled spring attached to the 2nd hinge at each engine frequency. The maximum ship speed of l.58m/s is obtained in the case of 3.53N・m/deg spring strength and 2.8Hz frequency.
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