The Swiss Hydros project is delving heavily into the finer detail of foil behaviour, both flying and immersed, with the aim of placing its strong technical team at the forefront of the next wave in high-speed sailing – and power – craft development

Hydros is a multiple-part project based in Lausanne, Switzerland. The programme was born in 2005 when banker and sailing enthusiast Thierry Lombard rescued the financially struggling Hydroptère project, and decided to assemble a whole new design team based on the EPFL (Ecole Polytechnique Fédérale de Lausanne) campus, both to help develop the 60ft l’Hydroptère and also to create a new foiler – Hydroptère.ch – which could then become a full-scale laboratory for future sailing hydrofoil development.

The four-member core design team comprised a CFD expert, a composite engineer, a specialist in structural analysis and a naval architect; this group was then integrated within EPFL’s extensive laboratory resources to begin a range of detailed studies on hydrodynamics, composite properties and assembly methods, and also to develop new video-imaging tools.

Step one – refining l’Hydroptère

The design team first worked on modifications to the foils, rudder and elevator on Alain Thébault’s well-known craft to try to beat the outright sailing speed record. This boat had already proved capable of good performance in strong winds and moderate wave conditions, but the foils then being used could not safely exceed 48kt without the onset of serious cavitation. Cavitation is best explained as a process of vapourisation; due to the very low pressure over areas of the foils the water simply transforms from liquid to vapour (it is not the ‘drawing down’ of air bubbles as is sometimes believed).

Cavitation quickly leads to the generation of large bubbles, decreasing lift and dramatically increasing drag – very bad for performance and also for security, since it was mainly the struggling rear elevator that had been preventing Alain Thébault’s large craft from nosediving.