A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes. Boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains speed, the hydrofoils lift the boat's hull out of the water, decreasing drag and allowing greater speeds.


The hydrofoil usually consists of a winglike structure mounted on struts below the hull, or across the keels of a catamaran in a variety of boats (see illustration). As a hydrofoil-equipped watercraft increases in speed, the hydrofoil elements below the hull(s) develop enough lift to raise the hull out of the water, which greatly reduces hull drag. This provides a corresponding increase in speed and fuel efficiency.

Wider adoption of hydrofoils is prevented by the increased complexity of building and maintaining them. Hydrofoils are generally prohibitively more expensive than conventional watercraft above a certain displacement, so most hydrofoil craft are relatively small, and are mainly used as high-speed passenger ferries, where the relatively high passenger fees can offset the high cost of the craft itself. However, the design is simple enough that there are many human-powered hydrofoil designs. Amateur experimentation and development of the concept is popular.[1]

Hydrodynamic mechanics

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The two types of hydrofoils: surface-piercing and fully submerged

Since air and water are governed by similar fluid equations—albeit with different levels of viscosity, density, and compressibility—the hydrofoil and airfoil (both types of foil) create lift in identical ways. The foil shape moves smoothly through the water, deflecting the flow downward, which, following the Euler equations, exerts an upward force on the foil. This turning of the water creates higher pressure on the bottom of the foil and reduced pressure on the top. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle, so the resulting flow field about the foil has a higher average velocity on one side than the other.

When used as a lifting element on a hydrofoil boat, this upward force lifts the body of the vessel, decreasing drag and increasing speed. The lifting force eventually balances with the weight of the craft, reaching a point where the hydrofoil no longer lifts out of the water but remains in equilibrium. Since wave resistance and other impeding forces such as various types of drag (physics) on the hull are eliminated as the hull lifts clear, turbulence and drag act increasingly on the much smaller surface area of the hydrofoil, and decreasingly on the hull, creating a marked increase in speed.[2]

Foil configurations

Early hydrofoils used V-shaped foils. Hydrofoils of this type are known as "surface-piercing" since portions of the V-shape hydrofoils rise above the water surface when foilborne. Some modern hydrofoils use fully submerged inverted T-shape foils. Fully submerged hydrofoils are less subject to the effects of wave action, and, therefore, more stable at sea and more comfortable for crew and passengers. This type of configuration, however, is not self-stabilizing. The angle of attack on the hydrofoils must be adjusted continuously to changing conditions, a control process performed by sensors, a computer, and active surfaces.


Forlanini's hydrofoil over Lake Maggiore, 1906


The first evidence of a hydrofoil on a vessel appears on a British patent granted in 1869 to Emmanuel Denis Farcot, a Parisian. He claimed that "adapting to the sides and bottom of the vessel a series or inclined planes or wedge formed pieces, which as the vessel is driven forward will have the effect of lifting it in the water and reducing the draught.".[3] Italian inventor Enrico Forlanini began work on hydrofoils in 1898 and used a "ladder" foil system. Forlanini obtained patents in Britain and the United States for his ideas and designs.[4][5]

Between 1899 and 1901, British boat designer John Thornycroft worked on a series of models with a stepped hull and single bow foil. In 1909 his company built the full scale 22-foot (6.7 m) long boat, Miranda III. Driven by a 60 hp (45 kW) engine, it rode on a bowfoil and flat stern. The subsequent Miranda IV was credited with a speed of 35 kn (65 km/h; 40 mph).[6]

Alexander Graham Bell's HD-4 on a test run, c. 1919

In May 1904 a hydrofoil boat was described being tested on the River Seine "in the neighbourhood of Paris".[7] This boat was designed by Comte de Lambert.[8] This had 5 variable pitch fins on the hull beneath the water so inclined that when the boat begins to move "the boat rises and the planes come to the surface" with the result that "it skims over the surface with little but the propellers beneath the surface". The boat had twin hulls 18-foot long connected by a single deck 9-foot wide, and was fitted with a 14HP De Dion-Bouton motor, the boat was reported to have reached 20 mph. It was stated that "The boat running practically on its fins resembles an aeroplane".

A March 1906 Scientific American article by American hydrofoil pioneer William E. Meacham explained the basic principle of hydrofoils. Alexander Graham Bell considered the invention of the hydroplane (now regarded as a distinct type, but also employing lift) a very significant achievement, and after reading the article began to sketch concepts of what is now called a hydrofoil boat. With his chief engineer Casey Baldwin, Bell began hydrofoil experiments in the summer of 1908. Baldwin studied the work of the Italian inventor Enrico Forlanini and began testing models based on those designs, which led to the development of hydrofoil watercraft. During Bell's world tour of 1910–1911, Bell and Baldwin met with Forlanini in Italy, where they rode in his hydrofoil boat over Lake Maggiore. Baldwin described it as being as smooth as flying.

On returning to Bell's large laboratory at his Beinn Bhreagh estate near Baddeck, Nova Scotia, they experimented with a number of designs, culminating in Bell's HD-4. Using Renault engines, a top speed of 87 km/h (47 kn; 54 mph) was achieved, accelerating rapidly, taking waves without difficulty, steering well and showing good stability. Bell's report to the United States Navy permitted him to obtain two 260 kW (350 hp) engines. On 9 September 1919 the HD-4 set a world marine speed record of 114 km/h (62 kn; 71 mph), which stood for two decades.[9] A full-scale replica of the HD-4 is viewable at the Alexander Graham Bell National Historic Site museum in Baddeck, Nova Scotia.

In the early 1950s an English couple built the White Hawk, a jet-powered hydrofoil water craft, in an attempt to beat the absolute water speed record.[10] However, in tests, White Hawk could barely top the record breaking speed of the 1919 HD-4. The designers had faced an engineering phenomenon that limits the top speed of even modern hydrofoils: cavitation disturbs the lift created by the foils as they move through the water at speed above 60 kn (110 km/h; 69 mph), bending the lifting foil.[11]

A schematic illustration of self-stabilizing systems for fully submerged hydrofoils. Its computer gathers data for the boom position and current water level to determine the required flap position.

First passenger boats

German engineer Hanns von Schertel worked on hydrofoils prior to and during World War II in Germany. After the war, the Russians captured Schertel's team. As Germany was not authorized to build fast boats, Schertel went to Switzerland, where he established the Supramar company. In 1952, Supramar launched the first commercial hydrofoil, PT10 "Freccia d'Oro" (Golden Arrow), in Lake Maggiore, between Switzerland and Italy. The PT10 is of surface-piercing type, it can carry 32 passengers and travel at 35 knots (65 km/h; 40 mph). In 1968, the Bahraini born banker Hussain Najadi acquired the Supramar AG and expanded its operations into Japan, Hong Kong, Singapore, the UK, Norway and the US. General Dynamics of the United States became its licensee, and the Pentagon awarded its first R&D naval research project in the field of supercavitation. Hitachi Shipbuilding of Osaka, Japan, was another licensee of Supramar, as well as many leading ship owners and shipyards in the OECD countries.

From 1952 to 1971, Supramar designed many models of hydrofoils: PT20, PT50, PT75, PT100 and PT150. All are of surface-piercing type, except the PT150 combining a surface-piercing foil forward with a fully submerged foil in the aft location. Over 200 of Supramar's design were built, most of them by Rodriquez (headed at the time by Engineer Carlo Rodriquez in Sicily, Italy.

During the same period the Soviet Union experimented extensively with hydrofoils, constructing hydrofoil river boats and ferries with streamlined designs during the cold war period and into the 1980s. Such vessels include the Raketa (1957) type, followed by the larger Meteor type and the smaller Voskhod type. One of the most successful Soviet designer/inventor in this area was Rostislav Alexeyev, who some consider the 'father' of the modern hydrofoil due to his 1950s era high speed hydrofoil designs.[citation needed] Later, circa 1970s, Alexeyev combined his hydrofoil experience with the surface effect principle to create the Ekranoplan. Extensive investment in this type of technology in the USSR resulted in the largest civil hydrofoil fleet in the world and the making of the Meteor type, the most successful hydrofoil in history, with more than 400 units built.

In 1961, SRI International issued a study on "The Economic Feasibility of Passenger Hydrofoil Craft in US Domestic and Foreign Commerce".[12] Commercial use of hydrofoils in the US first appeared in 1961 when two commuter vessels were commissioned by Harry Gale Nye, Jr.'s North American Hydrofoils to service the route from Atlantic Highlands, New Jersey to the financial district of Lower Manhattan.[13]

Military usage


A 17-ton German craft VS-6 Hydrofoil was designed and constructed in 1940, completed in 1941 for use as a mine layer,;it was tested in the Baltic Sea, producing speeds of 47 knots. Tested against a standard E-boat over the next three years it performed well but was not brought into production. Being faster it could carry a higher payload and was capable of travelling over minefields but was prone to damage and noisier.[14]


HMCS Bras d'Or, a military concept hydrofoil.

In Canada during World War II, Baldwin worked on an experimental smoke laying hydrofoil (later called the Comox Torpedo) that was later superseded by other smoke-laying technology and an experimental target-towing hydrofoil. The forward two foil assemblies of what is believed to be the latter hydrofoil were salvaged in the mid-1960s from a derelict hulk in Baddeck, Nova Scotia by Colin MacGregor Stevens. These were donated to the Maritime Museum in Halifax, Nova Scotia.

The Canadian Armed Forces built and tested a number of hydrofoils (e.g., Baddeck and two vessels named Bras d'Or), which culminated in the high-speed anti-submarine hydrofoil HMCS Bras d'Or in the late 1960s. However, the program was cancelled in the early 1970s due to a shift away from anti-submarine warfare by the Canadian military. The Bras d'Or was a surface-piercing type that performed well during her trials, reaching a maximum speed of 63 knots (117 km/h).

Soviet Union

A Soviet Project 206M "Shtorm" patrol fast attack craft hydrofoil of the Cuban Navy.

The USSR introduced several hydrofoil-based fast attack craft into their navy, principally:

United States

USS Aquila, a military hydrofoil. The T-shaped foils are visible just below the water.

The US Navy began experiments with hydrofoils in the mid-1950s by funding a sailing vessel that used hydrofoils to reach speeds in the 30 mph range.[15] The XCH-4 (officially, Experimental Craft, Hydrofoil No. 4), designed by William P. Carl, exceeded speeds of 65 mph (56 kn; 105 km/h) and was mistaken for a seaplane due to its shape.[16]

The US Navy implemented a small number of combat hydrofoils, such as the Pegasus class, from 1977 through 1993. These hydrofoils were fast and well armed.[17]


Italian Sparviero class hydrofoil-missile NIBBIO P-421.

The Italian Navy used six hydrofoils of the Sparviero class starting in the late 1970s. These were armed with a 76 mm gun and two missiles, and were capable of speeds up to 50 knots (93 km/h). Three similar boats were built for the Japan Maritime Self-Defense Force.

Sailing and sports

Main article: Sailing hydrofoil

Team New Zealand's AC72 at the 2013 America's Cup, San Francisco Bay.

Several editions of the America's Cup have been raced with foiling yachts. In 2013 and 2017 respectively the AC72 and AC50 classes of catamaran, and in 2021 the AC75 class of foiling monohulls with canting arms.

The French experimental sail powered hydrofoil Hydroptère is the result of a research project that involves advanced engineering skills and technologies. In September 2009, the Hydroptère set new sailcraft world speed records in the 500 m category, with a speed of 51.36 knots (95.12 km/h) and in the 1 nautical mile (1852 m) category with a speed of 50.17 knots (92.91 km/h).[18][19]

The 500 m speed record for sailboats is currently held by the Vestas Sailrocket, an exotic design which operates in effect as a hydrofoil.[20]

Another trimaran sailboat is the Windrider Rave.[21] The Rave is a commercially available 17-foot (5.2 m), two person, hydrofoil trimaran, capable of reaching speeds of 40 kn (74 km/h). The boat was designed by Jim Brown.

The Moth dinghy has evolved into some radical foil configurations.[22]

Hobie Sailboats produced a production foiling trimaran, the Hobie Trifoiler, the fastest production sailboat. Trifoilers have clocked speeds upward of thirty knots.

A new kayak design, called Flyak, has hydrofoils that lift the kayak enough to significantly reduce drag, allowing speeds of up to 27 km/h (17 mph). Some surfers have developed surfboards with hydrofoils called foilboards, specifically aimed at surfing big waves further out to sea.[23]

Quadrofoil Q2 is a two-seater, four-foiled hydrofoil electrical leisure watercraft. Its initial design was set in 2012 and it has been available commercially since the end of 2016. Powered by a 5.2-kWh lithium-ion battery pack and propelled by a 5.5 kW motor, it reaches the top speed of 40 km/h and has 80 km of range.[24][25]

The Manta5 Hydrofoiler XE-1 is a Hydrofoil E-bike, designed and built in New Zealand that has since been available commercially for pre-order since late 2017.[26] Propelled by a 400 watt motor, it can reach speeds exceeding 14 km/h with a weight of 22 kg. A single charge of the battery lasts an hour for a rider weighing 85 kg.[27]

Candela, a Swedish company, is producing a recreational hydrofoil powerboat, making strong claims for efficiency, performance, and range.[28]

Hydrofoils are now widely used with kitesurfing,[29] that is traction kites over water. Hydrofoils are a new trend in windsurfing[30] - including the new Summer Olympic class, the IQFoil,[31] and more recently with Wing foiling, which are essentially a kite with no strings, or a hand-held sail.[32]

Ukrainian-built Voskhod on the North Sea Canal, the Netherlands
TurboJET's Urzela JetFoil on West Lamma Channel, Hong Kong
TurboJET's Barca Foilcat

Modern passenger boats

Flying Poseidon (built 1982[33]) had just berthed at Rhodes from Fethiye when the sister Kometas hydrofoil[34] from Bodrum also arrived from Turkey in 2011.

Soviet-built Voskhods are one of the most successful passenger hydrofoil designs. Manufactured in Soviet and later Ukrainian Crimea, they are in service in more than 20 countries. The most recent model, Voskhod-2M FFF, also known as Eurofoil, was built in Feodosiya for the Dutch public transport operator Connexxion.[35]

The first Kometa 120M, named Chaika (Seagull) after Valentina Tereshkova's callsign, moored in Sevastopol

Mid-2010s saw a Russian governmental program aimed at restoring passenger hydrofoil production. The Kometa 120M [ru], based on the earlier Kometa, Kolhida and Katran models, became the first to enter production,[36] initially on Vympel [ru] factory in Rybinsk, and later on More shipyard in Feodosiya.[37] Since 2018, the ships are running Sevastopol-Yalta and Sochi-Gelenzhik-Novorossiysk, with a Sevastopol-Sochi connection in the immediate plans in 2021.[38] At the same time, the Alekseyev Bureau began building lighter, smaller Valday 45R [ru] hydrofoils, based on a widely successful Polesye [ru] model, at its own plant in Nizhny Novgorod,[39] the relatively shallow-draft boats used on the Ob and the Volga. The Meteor 120R [ru], a development of the Meteor [ru], became the Valday's larger sibling, the first ship launched in Nizhny Novgorod in August 2021.[40]

The Boeing 929 is widely used in Asia for passenger services, between Hong Kong and Macau and between the many islands of Japan, also on the Korean peninsula. The main user is Hong Kong private corp.

Current operation

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Current operators of hydrofoils include:

Hydrofoil high-speed boat Meteor on Lake Ladoga, Russia.
Passenger hydrofoil Flying Dolphin Zeus moving at high speed near Piraeus, Greece.

Currently, the main hydrofoil operator in Italy is Liberty Lines, which operates connections between the smaller Sicilian islands with Sicily and Calabria and between Trieste and some towns on the Croatian coast. SNAV operates connections between Naples and the smaller Campanian islands and - in the summer period - between Naples and the Aeolian Islands. In summer, Aliscost operates a connection between Salerno and some coastal towns of Campania and the Aeolian Islands.

Discontinued operations

See also


  1. ^ hydrofoil design - YouTube.
  2. ^ Rosado, Tina (1999). "Hydrofoils". Reports on How Things Work. Massachusetts Institute of Technology. Retrieved 11 December 2016.
  3. ^ "Early Hydrofoils". histarmar.com.ar. Retrieved 26 February 2019.
  4. ^ Dixon, Malin. "Forlanini". The Hydrofoil Resource Site. International Hydrofoil Society. Archived from the original on 18 January 2017. Retrieved 22 January 2016.
  5. ^ "Italian Hydroplane of Curious Type." Popular Mechanics, December 1911, p. 927.
  6. ^ "Thornycroft Model Collection". Archived from the original on 24 June 2009. Retrieved 9 September 2009.
  7. ^ The Principle of the Aeroplane Applied to the Boat, The Automotor Journal, 21 May 1904, p21
  8. ^ The Hydroplane or Gliding Boat, St James's Gazette, 24 May 1904, p16
  9. ^ "Hydrofoil". The Canadian Encyclopedia. Historica Canada. Archived from the original on 4 May 2012.
  10. ^ "Jet Hydrofoil Shoots At World Record" Popular Mechanics, August 1953, pp. 70-71
  11. ^ The World Water Speed Record by Leo Villa and Kevin Desmond, 1976
  12. ^ SRI International (1961). "The Economic Feasibility of Passenger Hydrofoil Craft in U.S. Domestic and Foreign Commerce". Archived from the original on 1 March 2012. Retrieved 9 September 2009.
  13. ^ Dixon, Malin. "Enterprise". Archived from the original on 28 April 2010. Retrieved 9 September 2009.
  14. ^ Channel Islands Occupation Review No 34. Channel Islands Occupation Society. 2006.
  15. ^ "Sail Boat Stilts Boost Speed." Popular Mechanics, February 1956, p. 136.
  16. ^ "XCH4". International Hydrofoil Society. Archived from the original on 19 August 2014. Retrieved 8 August 2014.
  17. ^ George Jenkins (1 November 2000). "Patrol Combatant Missile (Hydrofoil): PHM History 1973–1995" (PDF). Foils.org. Archived from the original (PDF) on 17 August 2017. Retrieved 16 August 2017.
  18. ^ "World Sailing Speed Record Council". sailspeedrecords.com.
  19. ^ "World Sailing Speed Record Council". sailspeedrecords.com.
  20. ^ Fisher, Adam. "How a Boat-Plane Hybrid Shattered the Sound Barrier of Sailing". Wired. Retrieved 10 May 2021.
  21. ^ Windrider. "Windrider Wave". Archived from the original on 9 May 2007. Retrieved 7 September 2009.
  22. ^ Branigan, David (20 September 2013). "Gliding on top of the water is still sailing but not as we know it". The Irish Times.
  23. ^ Scott Bass (2009). "Laird Hamilton: A Surfermag.com exclusive interview". Surfer Magazine. Retrieved 2 December 2010.
  24. ^ Stu Robarts (15 December 2016). "Electric hydrofoil finally ready to skim the waves". New Atlas. Archived from the original on 17 August 2017. Retrieved 16 August 2017.
  25. ^ Fred Lambert (22 December 2016). "All-electric Quadrofoil will soon allow you to fly on water – production is ready, says CEO". Electrek. Archived from the original on 17 August 2017. Retrieved 16 August 2017.
  26. ^ "Hydrofoil water bike to launch before Christmas". 2017.
  27. ^ "Ride on water: Pre-sale reservations now available for Manta5 hydrofoiling e-bike". 2018.
  28. ^ Toll, Micah (25 August 2020). "Watch the world's first electric hydrofoil boat in action". Elektrek. Retrieved 10 May 2021.
  29. ^ "The bright and dark sides of kite foilboarding". Surfer Today. 28 January 2014.
  30. ^ Jourdan, Romain (21 January 2021). "Windfoiling vs Windsurfing – Is Foil is the Future?". Wind Foil Zone.
  31. ^ Morgan, Liam (1 November 2019). "World Sailing Council approve Starboard iFoil as windsurfing equipment at Paris 2024". Inside the Games. Retrieved 21 August 2020.
  32. ^ Clothier, Chris (18 June 2021). "The only way is up: the irresistible rise of wing foiling". Financial Times. Archived from the original on 10 December 2022.
  33. ^ "Flying Poseidon". Marinetraffic.com. Archived from the original on 9 October 2013.
  34. ^ "Russian Hydrofoil Page".
  35. ^ Connexxion. "Fast Flying Ferry". Archived from the original on 23 August 2009. Retrieved 9 September 2009.
  36. ^ "Комета взяла курс на полуостров" [Kometa has set course for the peninsula]. vm.ru (in Russian). Вечерняя Москва. Retrieved 10 August 2021.
  37. ^ "В Крыму приступили к постройке двух скоростных "Комет" для пассажирских перевозок" [Production of two high-speed "Komets" has started in Crimea]. tass.ru (in Russian). TASS. Retrieved 10 August 2021.
  38. ^ "Сочи и Севастополь свяжут морские пассажирские "Кометы"" [Sea-going passenger "Komets" will link Sochi and Sevastopol] (in Russian). korabel.ru. Retrieved 10 August 2021.
  39. ^ ""Валдай 45Р" превзошел ожидания создателей" ["Valday 45R" has surpassed its creators' expectations] (in Russian). korabel.ru. Retrieved 10 August 2021.
  40. ^ "Первый "Метеор 120Р" нового поколения спустили на воду в Нижегородской области" [The first new-generation «Meteor 120R» has been launched in Nizhny Novgorod oblast]. morvesti.ru (in Russian). Морские вести России. Retrieved 10 August 2021.
  41. ^ Днепр отныне можно преодолеть на ракете. - dnepr.news
  42. ^ "Fast Flying Ferry ends in 2014". Connexxion (in Dutch). 1 March 2013. Archived from the original on 21 July 2013. Retrieved 2 July 2013.
  43. ^ "Red Funnel Hydrofoil Passenger Ferry". Retrieved 5 February 2021.
  44. ^ Večernje novosti. "Beogradske priče: Gliserima do Đerdapa". Retrieved 6 November 2015.
  45. ^ "A History of Roll on". archive.ph. 19 March 2006. Archived from the original on 19 March 2006. Retrieved 4 November 2019.
  46. ^ "Linda Line declared bankrupt by court". ERR. 25 May 2018.