Hydrofoils are boats with hulls that lift up above the water when traveling at high speeds.
The hydrofoils are wings attached to the hull by struts that move underwater like airplane wings and lift the boat up.
Because only the foils dip in the water, hydrofoils avoid water resistance, so can travel faster with less power.
Surface-piercing hydrofoils are used in calm inland waters and skim across the surface.
Fully submerged hydrofoils dip deep into the water to provide stability in seagoing boats.
The foils are usually in two sets, bow and stern.
The bow and stern foils are in one of three arrangements. ‘Canard’ means the stern foil is bigger. ‘Airplane’ means the bow foil is bigger. ‘Tandem’ means they are both the same size.
The first successful hydrofoil was built by Italian Enrico Forlanini in 1906.
In 1918 Alexander Graham Bell, inventor of the telephone, built a hydrofoil that set a world water speed record at 61.6 knots (114 km/h). The record was not beaten until the American Fresh 1, another hydrofoil, set a new record of 84 knots (155 km/h) in 1963.