# US 10,308,335 B2 · Fin-based watercraft propulsion system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,308,335 B2 - Document ID: US10308335B2 - Status: Granted - Kind: B2 - Application number: 15/101,901 - Filed: 2014-12-04 - Published: 2016-10-20 - Granted: 2019-06-04 - Earliest claimed: 2013-12-04 - Applicants: Martin Spencer Garthwaite - Inventors: Martin Spencer Garthwaite; Nathan Daniel Abell; Stephen Van Rensselaer Hellriegel - Web page: https://patentgrep.com/patent/US10308335B2 ## CPC - B63H 1/36: swinging sideways, e.g. fishtail type - B63B 21/56: Towing or pushing equipment (tugs B63B35/66; towing arrangements for water sports use B63B34/60) - B63B 21/66: Equipment specially adapted for towing underwater objects or vessels, e.g. fairings for tow-cables ({paravanes for dragging fishing nets A01K73/02; } salvaging underwater vessels or objects B63C7/00; towed underwater vessels B63G8/42) - B63B 2035/008: {remotely controlled} - B63H: MARINE PROPULSION OR STEERING (propulsion of air-cushion vehicles B60V1/14; specially adapted for submarines, other than nuclear propulsion, B63G; specially adapted for torpedoes F42B19/00) - B63B: SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING (arrangements of vessel ventilation, heating, cooling, or air-conditioning B63J2/00; floating substructures as supports of dredgers or soil-shifting machines E02F9/06) ## Abstract A watercraft comprises a motor, an inertial mass, and a fin. The motor oscillates the inertial mass about an axis, producing a torque reaction on and oscillation of the motor. Oscillation of the motor is communicated to the fin, producing thrust. ## Claims ### Claim 1 A watercraft comprising a fin, a motor mounted to a hull and an inertial mass, wherein the motor cyclically counter-accelerates the inertial mass and is subject to a torque reaction caused thereby, wherein the torque reaction on the motor from cyclic counter-acceleration of the inertial mass is communicated to the fin via the hull, resulting in a translation of the fin through a surrounding thrust fluid, wherein the translation of the fin though the surrounding thrust fluid produces thrust. ### Claim 2 (depends on 1) The watercraft according to claim 1, wherein the motor rotates the inertial mass about one of a horizontal axis, a vertical axis, and a transverse axis. ### Claim 3 (depends on 1) The watercraft according to claim 1, wherein the motor and inertial mass are inside the hull. ### Claim 4 (depends on 3) The watercraft according to claim 3, wherein the motor is attached to the hull and the inertial mass is supported about an axis by a bearing, wherein the axis is common with a central axis of the motor. ### Claim 5 (depends on 1) The watercraft according to claim 1, wherein the motor is an electric motor. ### Claim 6 (depends on 5) The watercraft according to claim 5, wherein the electric motor is controlled by a circuit to cyclically counter-accelerate the inertial mass, wherein to cyclically counter-accelerate the inertial mass the circuit alternately applies power to accelerate the inertial mass and applies an electronic brake to decelerate the inertial mass. ### Claim 7 (depends on 6) The watercraft according to claim 6, wherein the electronic brake generates power. ### Claim 8 (depends on 7) The watercraft according to claim 7, wherein the circuit further comprises a power reservoir and power generated by the electronic brake is stored in the power reservoir. ### Claim 9 (depends on 6) The watercraft according to claim 6, wherein the circuit further receives a sensor information and wherein the circuit cyclically counter-accelerates the inertial mass at least partially in response to the sensor information. ### Claim 10 (depends on 1) The watercraft according to claim 1, wherein the motor comprises a stator and a rotor, the inertial mass is attached to the rotor, and the stator is attached to the hull. ### Claim 11 (depends on 1) The watercraft according to claim 1, wherein the fin is secured to the motor by a flexible beam. ### Claim 12 (depends on 11) The watercraft according to claim 11, wherein a bending modulus of the flexible beam is adjustable. ### Claim 13 (depends on 1) The watercraft according to claim 1, wherein the inertial mass comprises a battery. ### Claim 14 (depends on 1) The watercraft according to claim 1, further comprising a power source for the motor, wherein the power source is towed by the watercraft. ### Claim 15 (depends on 14) The watercraft according to claim 14, wherein the power source is a generator. ### Claim 16 (depends on 14) The watercraft according to claim 14, wherein the power source is towed on a surface barge or in a submerged vessel. ### Claim 17 (depends on 14) The watercraft according to claim 14, further comprising a hawser, wherein the hawser secures the watercraft and power source. ### Claim 18 (depends on 1) The watercraft according to claim 1, further comprising a steering mechanism and a ballast adjustment mechanism. ### Claim 19 (depends on 18) The watercraft according to claim 18, wherein the steering mechanism biases the angle of attack of the fin relative to the watercraft. ### Claim 20 (depends on 1) The watercraft according to claim 1, further comprising a second fin.