Hydrofoil sailboats

From Boat Design Wiki

An overview of hydrofoil sailboats

Hydrofoil sailboats can be broken down into two main categories:

1)multifoilers (boats using hydrofoils for lift that have two or more hulls), and

2) monofoilers (boats using hydrofoils for lift with just a single hull).

Multifoilers

These boats have been around for years at least from the early seventies and have mostly used three or more foils or sets of foils. Within this group are multifoilers that use fully submerged foils and those that use surface piercing foils. Relatively current examples include the Rave, 40' Skat and Hobie trifoiler for boats using fully submerged foils and Hydroptere (a serious contender for the current world sailing speed record) and Spitfire using surface piercing foils. Of the current examples, the fully submerged foilers develop all their righting moment from the action of the foils in addition to lift. The surface piercing foilers (generally) use ballast + the weight of the boat for righting moment.

Monofoilers

One of the earliest(1950's) sailing foilers of all was designed, built and sailed in the US and called Monitor. It was a monofoiler using three sets of "ladder" foils to generate lift and rightng moment. Since the early days there are records of a 470, an FD and finally an International Moth being fitted with three sets of surface piercing foils to various degrees of success. The latest monofoilers-International Moths- began a new phase in 1999 by using just two foils to develop lift with all righting moment coming from the crew(plus windward heel) . These bi-foil monofoilers have proven quite fast and successful in racing.

Cross over

Up to now the breakdown of types is about like portrayed above however one brilliant Japanese designer has built a small full flying trimaran bi-foiler that may be the first example ever of a multifoiler using just two lifting foils to fly the whole boat. This can be seen in the boatdesign.net "Multihulls" forum.

Foil Assist

This is a concept whereby the hydrofoil is used to reduce the wetted surface of a hull but not fly it completely free of the water. Current examples include the 60'Orma Tri's, the Catri Trimaran,and the 23' Exploder Trimaran.