Hydrofoils Design and Multifidelity Optimization for a Flax Fiber Moth

Abstract Can sustainability enter the world of high-performance sailing? This paper explores the use of flax fiber composite as a feasible alternative to traditional materials in the design of sailboat components, focusing on an International Moth prototype. A hydrofoil design process was developed, integrating flax fiber composite in proportions exceeding 50% by weight—an approach that represents one of the first attempts of its kind. A multifidelity strategy was adopted and embedded within a concurrent engineering workflow tailored to the project. Starting with accessible design tools such as XFOIL and XFLR5, both two and three dimensional analyses were conducted to define the initial configuration. A Static Velocity Prediction Program was also implemented to evaluate hydrofoil performance in realistic conditions, accounting for finite wing effects, hull drag, and sail thrust. The preliminary design was further refined using a design exploration software (modeFRONTIER), enabling the evaluation of thousands of combinations of key geometric parameters through a multi-objective optimization process which included structural constraints. A high-fidelity optimization phase followed, using CFD simulations on parametric foil models, focusing only on the most promising parameter ranges to reduce computational cost. The resulting workflow proved effective in delivering a set of hydrofoils that demonstrate the feasibility of sustainable composites for competitive, high-performance sailing applications. Keywords hydrofoil, parametric design, multifidelity optimization, CFD, flax fiber composite, moth