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.
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👉 Hydrofoil in the context of Sailing hydrofoil
A sailing hydrofoil, hydrofoil sailboat, or hydrosail is a sailboat with wing-like foils mounted under the hull. As the craft increases its speed the hydrofoils lift the hull up and out of the water, greatly reducing wetted area, resulting in decreased drag and increased speed. A sailing hydrofoil can achieve speeds exceeding double and in some cases triple the wind speed.
Both monohull and multihull sailboats can be retrofitted with hydrofoils, although greater stability can be achieved by using the wider planform of a catamaran or trimaran.
In this Dossier
- ⭐ Core Definition: Hydrofoil
- 👉 Hydrofoil in the context of Sailing hydrofoil
- Hydrofoil in the context of Wing
- Hydrofoil in the context of Airfoil
- Hydrofoil in the context of Yakushima
- Hydrofoil in the context of Planing (boat)
- Hydrofoil in the context of Drag coefficient
- Hydrofoil in the context of Foil (fluid mechanics)
Hydrofoil in the context of Wing
A wing is a type of fin that produces both lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform. Wing efficiency is expressed as lift-to-drag ratio, which compares the benefit of lift with the air resistance of a given wing shape, as it flies. Aerodynamics includes the study of wing performance in air.
Equivalent foils that move through water are found on hydrofoil power vessels and foiling sailboats that lift out of the water at speed and on submarines that use diving planes to point the boat upwards or downwards, while running submerged. The study of foil performance in water is a subfield of Hydrodynamics.
Hydrofoil in the context of Airfoil
An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more lift than drag. Wings, sails and propeller blades are examples of airfoils. Foils of similar function designed with water as the working fluid are called hydrofoils.
When oriented at a suitable angle, a solid body moving through a fluid deflects the oncoming fluid (for fixed-wing aircraft, a downward force), resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift (perpendicular to the remote freestream velocity) and drag (parallel to the freestream velocity).
Hydrofoil in the context of Yakushima
Yakushima (屋久島) is one of the Ōsumi Islands in Kagoshima Prefecture, Japan. The island, 504.88 km (194.94 sq mi) in area, has a population of 11,858. It is accessible by hydrofoil ferry, car ferry, or by air to Yakushima Airport.
The island is part of the town (chō) of Yakushima, which includes the neighbouring island of Kuchinoerabujima. 42% of the island is within the borders of the Yakushima National Park.
Hydrofoil in the context of Planing (boat)
Planing (/ˈpleɪnɪŋ/ PLAY-ning) is the mode of operation for a waterborne craft in which its weight is predominantly supported by hydrodynamic lift, rather than hydrostatic lift (buoyancy).
Many forms of marine transport make use of planing, including fast ferries, racing boats, seaplanes, and water skis. Most surfboards are planing or semi-planing hulls. Beyond planing, fast vessel designs have seen a transition to hydrofoil designs.
Hydrofoil in the context of Drag coefficient
In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area.
The drag coefficient of any object comprises the effects of the two basic contributors to fluid dynamic drag: skin friction and form drag. The drag coefficient of a lifting airfoil or hydrofoil also includes the effects of lift-induced drag. The drag coefficient of a complete structure such as an aircraft also includes the effects of interference drag.
Hydrofoil in the context of Foil (fluid mechanics)
A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift (force generated perpendicular to the fluid flow) is substantially larger than the drag (force generated parallel to the fluid flow). If the fluid is a gas, the foil is called an airfoil or aerofoil, and if the fluid is water the foil is called a hydrofoil.