For several years, Hull Vane has been researching and testing the effect of a hydrofoil positioned amidships beneath the hull on fast-planing vessels. The aim was to support a major portion of the vessel’s weight on the foil rather than on its hull at the waterline. The underlying principle wasn’t to achieve full hydrofoiling, but partial hydrofoiling, in order to improve performance and seakeeping.

The Foil Assist is a small, passive, wing-shaped device made of solid stainless steel that is attached amidships beneath a vessel’s hull. It is designed to withstand cornering forces and to damp pitching motions in choppy conditions.

Partially supporting the vessel’s weight on the submerged wing, rather than at the waterline, helps reduce the effect waves have on performance. And because the Foil Assist only partially lifts its hull out of the water, the vessel handles much more like a normal planing vessel than a fully hydrofoiling vessel.

In partnership with Wajer Yachts, Hull Vane fitted a Foil Assist to a Wajer 38S – a fast-planing hull. Combining computational fluid dynamics (CFD) and hydrodynamics expertise, the design was successfully optimised further. The combination of Wajer 38 S and Foil Assist makes for a more comfortable ride, as the boat virtually flies over the waves, even though the aft is still planing. This reduces slamming and spray considerably and increases stability and speed due to less resistance.Initial research has shown that the Foil Assist reduces fuel consumption by 10-20 per cent, while reaching top speeds of 45-48 knots with a 3-6 per cent power reduction.


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