Fin propulsion for muscle-powered water craft

摘要

The propulsion system uses a fin which can be moved under the surface of the water, and which is mounted on stems using hinges. The fin has at least twice the flexural rigidity between the hinge points, as in the region 80 mm to 200 mm behind the axis of rotation in the direction of the flow. The fin may be mounted in the stems using a sharp-edged core sheet (9), and the sharp edges may be restricted to notches (10) at the ends of the sheet. Backwards propulsion may be achieved through engaging the rear end of the fin in a claw fitted to the end of a pole, and moving it up and down.