Eco-Foil: a sustainable racing hydrofoil

The SuMoth Challenge asks student teams to build a foiling Moth dinghy with as small an environmental impact as possible. Every material has a price in a fictional 10,000 SuMoth$ budget, and carbon fibre, the usual choice for foils, is expensive. Chalmers Formula Sailing needed a new main foil that could still take the competition's structural test: 80 kg hanging from the foil with the boat upside down.

We compared three concepts and ran a structured material evaluation on strength, sustainability and manufacturability. The winner was a load-bearing S355J2 steel beam inside a hydrodynamic profile of ash wood, laminated with glass fibre. The foil shape came from foil experts at RISE.

I worked on the design of the mechanical parts and the material selection. We sized the beam with hand calculations and checked it with FEM in Fusion, refining the mesh until stresses at the mast joint converged. The joints were prototyped with 3D printing before production, and the beam was water jet cut and CNC milled.

A life cycle comparison showed the Eco-Foil emits 15.7 kg CO₂e against 49.6 kg for a conventional carbon fibre foil, or 32%. The foil was finished after the thesis and raced on the team's Moth at the SuMoth Challenge 2025 during Foiling Week on Lake Garda, where the team placed 2nd in upgraded boat design.

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