A Computational Design Framework for Hydrofoil Design Applied to the International Moth

Abstract

The International Moth is a small racing sailboat that can reach top speeds of 35 knots (18 m/s), due to its use of hydrofoils, which lift the entire hull clear of the free surface. The hydrofoils replace the hull as the primary generators of hydrodynamic forces within the vessel system, and in turn, heavily drive the overall performance of the vessel. Optimizing the shape and planform of the foils is a key to achieving race-winning designs. However, hydrofoiling sailboats are highly coupled systems that operate in two simultaneous fluid media, and a change in foil configuration can have cascading effects on the overall vessel state. Thus, a design framework is formulated that allows foil designs to be evaluated within a 6 degree of freedom velocity prediction program (VPP). The framework integrates gradient-based shape optimization tools in 2 and 3 dimensions. Evaluation of the framework demonstrates functionality for design optimization independent of the VPP, but the presented approach to modeling hydrodynamic forces within the VPP requires improvement in order to produce meaningful results that can inform design decisions.