Hydrofoil
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).
[1] 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.
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.
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.
[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.
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.
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.
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.
[9] A full-scale replica of the HD-4 is viewable at the Alexander Graham Bell National Historic Site museum in Baddeck, Nova Scotia.
[11] German engineer Hanns von Schertel worked on hydrofoils prior to and during World War II in Germany.
In 1952, Supramar launched the first commercial hydrofoil, PT10 "Freccia d'Oro" (Golden Arrow), in Lake Maggiore, between Switzerland and Italy.
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.
[citation needed] Later, circa 1970s, Alexeyev combined his hydrofoil experience with the surface effect principle to create the Ekranoplan.
In 1961, SRI International issued a study on "The Economic Feasibility of Passenger Hydrofoil Craft in US Domestic and Foreign Commerce".
[13] 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.
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.
The French experimental sail powered hydrofoil Hydroptère is the result of a research project that involves advanced engineering skills and technologies.
[19][20] The 500 m speed record for sailboats is currently held by the Vestas Sailrocket, an exotic design which operates in effect as a hydrofoil.
Some surfers have developed surfboards with hydrofoils called foilboards, specifically aimed at surfing big waves further out to sea.
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.
[28] Candela, a Swedish company, is producing a recreational hydrofoil powerboat, making strong claims for efficiency, performance, and range.
Hydrofoils are a new trend in windsurfing[31] - including the new Summer Olympic class, the IQFoil,[32] and more recently with Wing foiling, which are essentially a kite with no strings, or a hand-held sail.
