Patent ID: 9731802
Date: 2017-08-15
CPC Classifications: B63H

Claim:
1. A watercraft having propulsion means extending below the water line comprising a pair of flexible fins each having a leading edge, a trailing edge, a top end and a lower end, said fin being adapted to oscillate through an arcuate path in a generally transverse direction across the central longitudinal dimension of said watercraft, and means operatively associated with said propulsion means comprising foot pedals for applying input force to said propulsion means whereby as input force is applied said flexible fins can twist to form an angle of attack for providing forward thrust with respect to the longitudinal dimension of the watercraft while moving in both directions along said arcuate path; wherein each of said fins is firmly restrained along its leading edge and restrained at its lower end near its trailing edge to provide less restraint at said trailing edge, and each said fin is provided with an essentially square top end to provide enhanced fin twist and more efficient propulsion; wherein the fin has a generally peripheral area which is harder and less flexible than the inner area whereby the cordwise stiffness of the fin itself increases in the direction of the trailing edge.