A hydrofoil is a boat with wing-like foils mounted on struts below the hull. As the craft increases its speed the hydrofoils develop enough lift for the boat to become foilborne - i.e. to raise the hull up and out of the water. This results in a great reduction in drag and a corresponding increase in speed.
Early hydrofoils used U-shape foils. Hydrofoils of this type are known as surface-piercing since portions of the U-shape hydrofoils will rise above the water surface when foilborne. Modern hydrofoils use T-shape foils which are fully submerged. Fully submerged hydrofoils are less subjected to the effects of wave action, and are therefore more stable at sea and are more comfortable for the crew and passengers. This type of configuration, however, is not self-stabilizing. The angle of attack on the hydrofoils needs to be adjusted continuously in accordance to the changing conditions, a control process that is performed by computers. Failure to make the proper adjustments will result in the foilborne hull dropping violently back into the sea.
Some operators of hydrofoil include:
TurboJET service, which speeds passengers across the Pearl River Delta between Hong Kong and Macau in less than an hour, with an average speed of 45 knots (83km/h), mainly using Boeing's Jetfoil. Also services Shenzhen, Guangzhou and Kowloon. Operated by Shun Tak-China Travel Ship Management Limited.
Meteor service between St. Petersburg, Russia and the Peterhof, a summer palace of Russian tsars.
Meteor service between St. Petersburg, Russia and the Kronstadt, a strongly fortified Russian seaport town, located on Kotlin Island, near the head of the Gulf of Finland. It lies thirty kilometers west of Saint Petersburg.
Meteor, Raketa and Voskhod hydrofoil types operate all over Volga, Don and Kama Rivers in Russia.
Meteor hydrofoils are operated by a number of tour operators in Croatia, mostly for packaged tours, but there are also some scheduled services to islands in Adriatic.
Linda Line between Tallinn and Helsinki, using two Morye's Olympias, Ukrainian built and Mercedes-Benz powered hydrofoils.
Hydrofoils are regularly operated on the three major Italian Lakes by branches of Ministry Of Transportation: Navigazione Lago Maggiore services routes on the Lake Maggiore between Locarno and Arona, Navigazione Lago di Como services routes on the Lake Como and Navigazione Lago di Garda services routes on the Lake Garda. Three units of the Rodriquez RHS150 type operate on each lake, for a total of nine hydrofoils. Navigazione Lago di Como still operates the last Rodriquez RHS70 in active service in Italy.
Former Russian hydrofoils are used in southern Italy for connection with islands of Lazio and Campania.
Beetle service between Pusan, South Korea and Fukuoka, Japan, it services five times a day, mainly using Boeing's Jetfoil.
Regular hydrofoil service from Istanbul to Yalova
Fast Flying Ferries operated by Connexxion, provides a regular public transport service over the North Sea Canal between Amsterdam Central Station and Velsen-Zuid in The Netherlands, using Voskhod 2M hydrofoils.
Flying Dolfins operate in many lines in the Aegean, between the Cycladic islands and Athens.
Meteor, Polesye and Voskhod hydrofoil types operate in Hungary. MAHART PassNave Ltd. operates scheduled hydrofoil liners between Budapest, Bratislava and Vienna, inland liners between Budapest and the Danube Bend, and theme cruises to Komarom, Solt, Kalocsa and Mohacs.