A sailing hydrofoil 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. This article is about marine engineering. ... Diagram of Sailboat, in this case a typical monohull sloop with a bermuda or marconi rig. ... For the kite, see foil kite. ... A hull is the body or frame of a ship or boat. ... The lift force, or simply lift, is a mechanical force, generated by a solid object as it moves through a fluid, directed perpendicular to the flow direction. ... This is a sailboat term for the area of the hull which is immersed in water. ... An object moving through a gas or liquid experiences a force in direction opposite to its motion. ...

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. A monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another. ... A multihull is a ship or boat with more than one hull. ... A planform or plan view is a vertical orthographic projection of an object on a horizontal plane, like a map. ... It has been suggested that Catamaran History be merged into this article or section. ... Photograph of an Orma 60 trimaran in Sandhamn before the Round Gotland Race 2005 A trimaran is a multihull boat consisting of a main hull (vaka) and two smaller outrigger hulls (amas), attached to the main hull with lateral struts (akas). ...

Typical configurations

Some multihulls use three foils; two main forward foils provide lift so that the boat "flies" while a horizontal foil on the rudder is trimmed to drive and control attitude. On catamarans, a single main foil can be attached between the hulls just in front of the center of gravity and at 2 degrees of incidence, spanning the tunnel with supporting struts. Hydrofoil catamarans are also called foilcats. This article or section may contain original research or unverified claims. ...

Multihull sailboats can also employ hydrofoils only to assist performance. Just as daggerboards and rudders are foils that enhance the control of a boat, assisting hydrofoils provide lift to the hull to reduce the wetted area without actually lifting the boat completely out of the water. A daggerboard is a type of centreboard used by various sailing craft. ...

Monohull boats typically employ a "ladder" arrangement of hydrofoils splayed out with a dihedral angle of 50 degrees, with a stabilizing rudder foil. One of the earliest examples is the Monitor boat from 1957. This design offers the advantages of maximum lifting foil area at slow speeds and less at higher speeds, with rolling resistance arising from the dihedral support of the outboard ladder foils.

Production designs

TriFoiler

In the 1990s the Hobie Cat company manufactured the TriFoiler (no longer in production), a twin-sail trimaran with a mainsail on each outrigger capable of 30-knot speeds in typical sailing conditions. The prototype of the Hobie TriFoiler, called Longshot, was developed by Dan and Greg Ketterman in conjunction with Russell Long. Though more streamlined than the Trifoiler and having smaller hydrofoils, Longshot still holds the Class A speedsailing record of 43.55 knots on a 500 meter course, set in Tarrifa Spain in 1993. Until recently, it was the only existing speedsailing record held by a hydrofoil, but the recent records of L'Hydroptere have added it to the list with record breaking runs across the English Channel.^[1] Hobie Cats are small racing catamarans used for racing and personal use. ... Hobie Cats are small racing catamarans used for racing and personal use. ... A mainsail is the most important sail raised from the main (or only) mast of a sailing vessel. ... In a canoe or bangca, an outrigger is a thin, long, solid, hull used to stabilise an inherently unstable main hull. ...

Rave

In 1998, Windrider LLC introduced the Rave hydrofoil, a popular two-person trimaran capable of lifting off in as little as 12-13 knots of wind. The Rave is capable of sailing between 1.5 to 2 times wind speed.^[2] The boat's mainsail has no boom. Although the Rave broke new ground in the development of flapped foils and control systems, its weight limited the Rave's light air foiling performance, and its boomless rig was not especially efficient.^{[citation needed]}

International Moth

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 International Moth. John's Prowler design, superseded in 2008 by the F-Zero, features a carbon-fiber hull, inverted "T" foils on the centerboard and rudder, and it can reach speeds of over 27 knots. Fastacraft has since been joined in producing hydrofoil moths by several other companies, including Bladerider,Velociraptor, Aardvark's Axiom design and of course the Prowler F-Zero. The Moth Class is the name for three different classes, although all three have similar boats. ... A centreboard is a form of removable keel on a small sailing boat or dinghy which can be removed to lower the draught (or depth) of the vessel. ... Stern-mounted steering oar of an Egyptian riverboat depicted in the Tomb of Menna (c. ...

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 foil in as little as six knots of breeze with an experienced helm 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.

Experimental designs

L'hydroptère experimental hydrofoil.

Many non-production experimental designs have been built. Some examples of notable designs are:

• The French experimental Hydroptère.
• A Hobie 18 foilcat prototype called Kangalope with foil kits attached.^[3]
• Rich Miller's hydrofoil sailboard.^[4]

Experimental sailing craft Hydroptère The Hydroptère is a French designed experimental sailboat. ... Hobie Cats are small racing catamarans used for racing and personal use. ...

See also

• Hydrofoil
• Hydrofoil board
• Hydroptère
• Hobie TriFoiler

This article is about marine engineering. ... Experimental sailing craft Hydroptère The Hydroptère is a French designed experimental sailboat. ... Hobie Cats are small racing catamarans used for racing and personal use. ...

References

External links

• Foils.org gallery of sailing hydrofoils
• Miller Hydrofoil Sailboard - a hydrofoil windsurfer experiment
• Sailing Cat with Foils
• Trimaran Foil Assisted
• Aspects of a Foiled Multihull
• Design Forum and information exchange
• Windrider Rave