Sit-down hydrofoil

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A sit-down hydrofoil Air Chair 01.jpg
A sit-down hydrofoil

The sit-down hydrofoil , first developed in the late 1980s, is a variation on water skiing, a popular water sport. When towed at speed, by a powerful boat or some other device, the board of the hydrofoil 'flies' above the water surface and generally avoids contact with it, so the ride is largely unaffected by the wake or chop of the water and is relatively smooth. The air board is a modified hydrofoil where the skier stands up.



Hydrofoils date back the early 1900s, however they were not part of a recreational sport. While the first hydrofoil boat was created in 1906 by Italian inventor Enrico Forlanini, [1] the first waterski hydrofoil was invented in the early 1960s by Walter Woodward, an aeronautical engineer, with two skis attached to a bi-wing hydrofoil. [2] In 1972, Mike Murphy and Bob Woolley added a bi-wing hydrofoil to a surfing kneeboard, then reduced the bi-wing to a single wing. [2] Murphy and Bob Woolley then applied the concept to sit-down hydrofoil, with Woolley riding the first "Sit Ski" in 1984. [2] After various material changes, including the addition of a seat belt to keep rider and ride together and prevent separation collisions, they sold their first "Air Chair" in 1990. [2] Advancements in materials and hydrofoil design have created stronger rigs, gentler rides (shock absorbers in the seat), more maneuverability, and boards that combine sit-down and stand-up (air board) for surfing. [2]

Sit-down hydrofoil components

Other equipment


Sit-down hydrofoil rider performing a jump Sky Skier performs jump, 1998.jpg
Sit-down hydrofoil rider performing a jump

Unlike water skiing or wakeboarding, a hydrofoiler's body and the board rise above the water, supported by a pair of front and rear hydrofoil wings which are still under the water. This reduces the drag of the water, allowing for both a smoother ride on rough water and a lesser need for strength. [4]

The rider sits on the seat of the hydrofoil and is strapped in with a seat belt; their feet are strapped into bindings near the front of the board. When the rider is ready the boat will start to tow the skier. The water flowing past the hydrofoil wings generates lift, which can be controlled by the rider to move the board up and down or side to side above the surface of the water. The rider must be centered over the post of the hydrofoil; small body movements will cause great reactions with the hydrofoil. In order to "float" upward the rider leans back while maintaining balance to avoid pitching forward unexpectedly. To go back down the rider leans forward or pushes down with the feet. Turning is accomplished by pointing the knees in the direction desired; the hydrofoil will follow. To jump, the rider leans even farther back. This will give the rider a somewhat stable base to perform aerial tricks for example.


Submerged hazards such as trees can be struck by the hydrofoil as low as 3 feet below the surface of the water, causing the rider to fall without warning. Such a fall can be the same as colliding with an object, with the rider impacting the water or the foil. The tow rope can get tangled around the skier or equipment, creating a hazardous condition. After a fall the skier remains strapped to the board; while it will turn upright quickly, there is always the possibility of drowning.

See also

Related Research Articles

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Wakeboarding Surface water sport

Wakeboarding is a water sport in which the rider, standing on a wakeboard, is towed behind a motorboat across its wake and especially up off the crest in order to perform aerial maneuvers. A hallmark of wakeboarding is the attempted performance of midair tricks. Wakeboarding was developed from a combination of water skiing, snowboarding and surfing techniques.

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Water skiing

Water skiing is a surface water sport in which an individual is pulled behind a boat or a cable ski installation over a body of water, skimming the surface on two skis or one ski. The sport requires sufficient area on a stretch of water, one or two skis, a tow boat with tow rope, two or three people, and a personal flotation device. In addition, the skier must have adequate upper and lower body strength, muscular endurance, and good balance.

Barefoot skiing

Barefoot skiing is water skiing behind a motorboat without the use of water skis, commonly referred to as "barefooting". Barefooting requires the skier to travel at higher speeds (30-45mph/50-70km/h) than conventional water skiing (20-35mph). The necessary speed required to keep the skier upright varies by the weight of the barefooter and can be approximated by the following formula: + 20, where W is the skier's weight in pounds and the result is in miles per hour. It is an act performed in show skiing, and on its own.

Kneeboarding (towsport) Water sport

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Wakeboard boat

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  1. "History of Hydrofoiling". United States Hydrofoil Association. Retrieved Aug 10, 2012.
  2. 1 2 3 4 5 "Hydrofoiling History". United States Hydrofoil Association. Retrieved Aug 10, 2012.
  3. 1 2 "What Is Hydrofoiling". United States Hydrofoil Association. Retrieved Aug 10, 2012.
  4. 1 2 "Wake Zone: High Flyin' Hydrofoilers". The Lake Channel. Retrieved Aug 10, 2012.
  5. "Life jacket wear/Wearing your life jacket". United States Coast Guard. July 30, 2012. Archived from the original on June 23, 2012. Retrieved Aug 10, 2012.