Stability and maneuvering of hybrid hydrofoil/SWATH in foilborne mode

Abstract

The hybrid hydrofoil/SWATH, designed and patented by Stefano Brizzolara, is a novel vehicle design that is optimized to operate in both a high speed foilborne mode and a displacement mode. The retractable hydrofoils on the vehicle take on a unique four surface piercing anhedral foil configuration. This foilborne design is previously unassessed for stability and maneuvering characteristics. A six degree of freedom model of the foilborne vehicle dynamics is introduced as a framework to study vehicle stability and maneuvering. Linearized models of the vehicle dynamics are compared to the six degree of freedom results in both the vertical and horizontal planes. Foil configuration design criteria are derived for pitch equilibrium as well as pitch and directional stability. A method for turning the vehicle by rotationally actuating the foil dihedral angles is introduced, and the vehicle state in the unsteady and steady portion of the turn is simulated.