The Equilibrium

A series of polymer fins were designed and made using additive manufacturing techniques, to be tested by the Human Powered Submarine team at UC San Diego in a wet submarine that utilizes a thunniform method of propulsion. A 3D printer was also constructed in order to print these fins efficiently. Designs were inspired by the shape and semi-flexible properties of fish caudal fins. Materials utilized included polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), PC-ABS blends, Nylon, and thermoplastic urethane (TPU) polymers. Of these materials, polycarbonate proved most practical for this application. Factors that were qualitatively considered during the practical testing were the material properties of a specific polymer, the surface area of the propulsive  fin, and the shape of the  fin. The low-cost polycarbonate processing techniques used in this project are also applicable to the additive manufacturing field in general.