Reversing propulsion device for watercraft

1. A novel device adapted to be placed in a watercraft, said device including propulsion means extending below the water line comprising a pair of flexible fins each having leading and trailing edges and adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, and means operatively associated with said propulsion means 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, each said fin being carried at the upper extent of said trailing edge by a fixed pivot and wherein when said leading edge strikes a resistance element, said fin pivots aft to clear the resistance element and rotates forward and resumes producing thrust upon clearing the resistance element.

2. A novel watercraft having propulsion means extending below the water line comprising a pair of flexible fins each having leading and trailing edges and adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, and means operatively associated with said propulsion means 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, each said fin being carried at the upper extent of said trailing edge by a fixed pivot and wherein when said leading edge strikes a resistance element, said fin pivots aft to clear the resistance element and rotates forward and resumes producing thrust upon clearing the resistance element.

3. A novel watercraft having propulsion means extending below the water line comprising a pair of flexible fins each having leading and trailing edges and each adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, means for positioning said propulsion means to propel said watercraft forward and to rotate said propulsion means approximately 180° with respect to the longitudinal dimension of the watercraft to propel said watercraft aft, and means operatively associated with said propulsion means 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 or aft thrust with respect to the longitudinal dimension of the watercraft while moving said flexible fins in both directions along said arcuate path, each said fin being carried at the upper extent of said trailing edges by a fixed pivot and the upper extent of said leading edge by a retainer which is normally engaged while being disengageable when said leading edge strikes a resistance element allowing said fin to pivot aft to clear the resistance element and re-engageable as the fin rotates forward and resumes producing thrust.

4. A novel device adapted to be placed in a watercraft, said device including propulsion means extending below the water line comprising a pair of flexible fins each carried by a mast and adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, and means operatively associated with said propulsion means 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 said fins have essentially hard leading and trailing edges which join to form a thinner tip and the area between said edges being of a softer, flexible material which is flexible in bending and wherein each of said fins having therein a mast receiving opening aligned with and aft of said leading edge, said mast receiving opening receiving said mast, said mast receiving opening comprising a substantially circular opening attached to an aft extending elongated opening to resemble a keyhole in cross-section, wherein said elongated opening provides enhanced torsional flexibility to the fin during motion.

5. The device of claim 4 wherein said leading edge, trailing edge and tip of said fins has a hardness of about 80D, the area between said edges has a hardness of about 40D, and the thinner tip is about 0.06 inches.

6. A novel watercraft having propulsion means extending below the water line comprising a pair of flexible fins each carried by a mast and adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, and means operatively associated with said propulsion means 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 said fins have essentially hard leading and trailing edges which join to form a thinner tip and the area between said edges being of a softer, flexible material which is flexible in bending and wherein each of said fins having therein a mast receiving opening aligned with and aft of said leading edge, said mast receiving opening receiving said mast, said mast receiving opening comprising a substantially circular opening attached to an aft extending elongated opening to resemble a keyhole in cross-section, wherein said elongated opening provides enhanced torsional flexibility to the fin during motion.

7. A novel watercraft having propulsion means extending below the water line comprising a pair of flexible fins each carried by a mast and adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, means for positioning said propulsion means to propel said watercraft forward and to rotate said propulsion means approximately 180° with respect to the longitudinal dimension of the watercraft to propel said watercraft aft, and means operatively associated with said propulsion means 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 or aft thrust with respect to the longitudinal dimension of the watercraft while moving said flexible fins in both directions along said arcuate path, wherein said fins have essentially hard leading and trailing edges which join to form a thinner tip and the area between said edges being of a softer material which is flexible in bending and wherein each of said fins having therein a mast receiving opening aligned with and aft of said leading edge, said mast receiving opening receiving said mast, said mast receiving opening comprising a substantially circular opening attached to an aft extending elongated opening to resemble a keyhole in cross-section, wherein said elongated opening provides enhanced torsional flexibility to the fin during motion.

8. The watercraft of claim 2 , 3 , 6 or 7 wherein the watercraft is a kayak having a hull, keel and a cockpit.