For several years, Hull Vane has been researching and testing the effect on fast-planing vessels of a hydrofoil positioned amidships beneath the hull, the Foil Assist. The underlying principle wasn’t to achieve full hydrofoiling, but partial hydrofoiling in order to improve performance and seakeeping.

With the Foil Assist, the company aims to support a major portion of the vessel’s weight on the foil rather than on its hull at the waterline. The small, passive, wing-shaped device made of solid stainless steel is attached amidships beneath a vessel’s hull. It was 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 (predictability) than a fully hydrofoiling vessel (stringent weight requirements).

Wajer 32 S test

In partnership with Wajer Yachts, Hull Vane fitted a Foil Assist to a Wajer 32 S – a fast-planing hull. Combining computational fluid dynamics (CFD) and hydrodynamics, the design was optimised further.

The combination of Wajer 32 S and Foil Assist makes for a far more comfortable ride, as it virtually flies over the waves, even though its aft is still planing. This reduces slamming and spray considerably and increases stability and speed due to less resistance.

Reduced fuel consumption

Initial research has shown that the Foil Assist reduces fuel consumption by 10 to 20 per cent while reaching top speeds of 45 to 48 knots with a 3 to 6 per cent power reduction. Hull Vane sees the Foil Assist as a next step in increasing speed and efficiency while reducing power requirements for high-speed yachts, fast patrol boats, naval interceptors, sea rescue boats and pilot boats.

Hull Vane BV has years of experience with other submerged foil appendages, including the custom Hull Vane, semi-custom Hull Vane and Dynamic Hull Vane. The patent for the Foil Assist is pending.