The most widespread use of hydrofoils in sailboats to date has been in the International Moth class. Andy Paterson of Bloodaxe boats on the Isle of Wight is widely considered to have developed the first functional foiling Moth, though his boat had three foils in a tripod arrangement. Brett Burvill sailed a narrow skiff Moth with inclined surface-piercing hydrofoils to a race win at the Moth World Championships in 2001 in
Australia, which was the first time a hydrofoil Moth had won a race at a World Championship. This hydrofoil configuration was later declared illegal by the class, as it was felt to constitute a multihull, which is prohibited by class rules. Subsequently, Garth and John Ilett in Perth, Australia developed a two-hydrofoil system for the Moth with active flap control for the main foil via a surface sensor. John's company Fastacraft was the first to produce a commercially available hydrofoil
International Moth. Fasta Craft's Prowler design, superseded in 2008 by the F-Zero, features a
carbon-fiber hull, inverted "T" foils on the
centerboard and
rudder, and can reach speeds of over 27 knots. Fasta Craft has since been joined in producing hydrofoil Moths by several other companies, including Bladerider, Assassin, Exocet, and Aardvark Technologies. Although initially debated fiercely within the class, the adoption of hydrofoils has proven a success for the International Moth class, with rapid fleet growth in the years since 2001. All World Championships since 2004 have been won by hydrofoil-equipped Moths, which can become foilborne in as little as six knots of breeze when steered by an experienced sailor of lighter weight. The class rule remains open to development of all boat components including hydrofoil systems, and development within the class continues to be spurred by both commercial and individual/amateur efforts.
A
sailing hydrofoil,
hydrofoil sailboat, or
hydrosail is a
sailboat with wing-like
foils mounted under the
hull. As the craft increases its speed the hydrofoils
lift the hull up and out of the water, greatly reducing
wetted area, resulting in decreased
drag and increased speed. A sailing hydrofoil can achieve speeds exceeding two times the wind speed.
Both
monohull and
multihull sailboats can be retrofitted with hydrofoils, although greater stability can be achieved by using the wider
planform of a
catamaran or
trimaran.