Kite rigs are wind-assisted propulsion systems for propelling a vehicle. They differ from conventional

sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails ma ...

s in that they are flown from kite control lines, not supported by masts. Vehicles driven by kites include

boats A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...

, buggies, and vehicles with

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughou ...

and ice runners. They may be as simple as a person flying a kite while standing on a specialized skateboard, or be large, complex systems fixed to the vehicle, with powered and automated controls. They have recreational and commercial uses.

Structure

Current kite rigs can be sailed within 50 degrees of the wind.Skysails
Captain John Konrad, Mariner's Weather Log, April 2009, Volume 53, No. 1,

National Weather Service The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...

This allows them to sail upwind by tacking. A

power kite A power kite or traction kite is a large kite designed to provide significant pull to the user. Types The two most common forms are the foil, and the leading edge inflatable. There are also other less common types of power kite including rig ...

is held at an angle to the wind using control lines. Like any other sail, the kite develops lift and drag, pulling the vessel. The vector of the kite's pull is added to the forces produced by the vessel (water resistance against the hull, force of wheels against the ground, etc.) to move the vessel in the desired direction. Windspeed increases with height, allowing kites to develop substantially more thrust per unit area than a conventional sail. Winds are also steadier and less turbulent higher up. Kites may be adjusted with respect to the wind, manually or by an automated system. A kite cannot stay aloft when there is no wind, and must be re-launched.

Applications

Solo sports

Kite rigs power a variety of recreational conveyances on water and land. On water, kites are used to power surf-board-like boards in the sport of

kitesurfing Kiteboarding or kitesurfing is a sport that involves using wind power with a large power kite to pull a rider across a water, land, or snow surface. It combines aspects of paragliding, surfing, windsurfing, skateboarding, snowboarding, and wak ...

. Kiteboating is done in boats with kite rigs. On land,

kite landboarding Kite landboarding, also known as land kiteboarding or flyboarding, is based on the sport of kitesurfing, where a rider on a surf-style board is pulled over water by a kite. Kite landboarding involves the use of a mountain board or landboard, whic ...

derives the same mode of power for skate-board-like boards. Over snow, kites power

snowboard Snowboards are boards where the user places both feet, usually secured, to the same board. The board itself is wider than most skis, with the ability to glide on snow."snowboarding." Dictionary.com Unabridged (v 1.1). Random House, Inc. 17 Mar ...

s or

ski A ski is a narrow strip of semi-rigid material worn underfoot to glide over snow. Substantially longer than wide and characteristically employed in pairs, skis are attached to ski boots with ski bindings, with either a free, lockable, or partia ...

s in the sport of snowkiting. Traction kites for solosports generally have an area of 1-16 square meters, with anything over ~5 square meters being a big kite that requires expertise.

Ships

Ship-pulling kites run to hundreds of square meters of area and require a special attachment points, a launch and recovery system, and

fly-by-wire Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires, and flight control ...

controls. The SkySails

propulsion system Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...

consists of a large

foil kite Foil kites are soft kites based on the design of the parafoil. They consist of a number of cells running fore to aft, some or all of which are open at the front to allow air to inflate the kite so it takes on an aerofoil section. Due to the amou ...

, an

electronic Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...

control Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controlli ...

system for the kite, and an automatic system to retract the kite. The kite, while 1–2

orders of magnitude An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic dis ...

larger, bears similarities to the arc kites used in

. However, the kite is an inflatable rather than a ram-air kite. Additionally, a control pod is used rather than direct tension on multiple kite control lines; only one line runs the full distance from kite to ship, with the bridle lines running from kite to control pod. Power to the pod is provided by cables embedded in the line; the same line also carries commands to the control pod from the ship.Airborne Wind Energy Systems, a review of the technologies
A. cherubini, A. Papini, R. Vertechy, M.Fontana, Renewable and Sustainable Energy Reviews, 2015 The kite is launched and recovered by an animated mast or arm, which grips the kite by its leading edge. The mast also inflates and deflates the kite. When not in use, mast and deflated kite fold away.

Use

A commercial cargo ship, the MS ''Beluga Skysails'', was built, and launched in 2007, with a kite rig supplementing conventional propulsion. A

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...

-funded four-year study of wind propulsion, using the MS ''Beluga Skysails'', reported that the ship attained 5% fuel savings overall, which translated into of CO₂ for a typical year and itinerary. The study concluded that 25,000 similarly equipped ships could reduce fuel consumption by and save of CO₂, of NO_x. The return on investment for installing a kite sail was estimated to be about two-three years. On her maiden voyage, MS ''Beluga Skysails'' saved an estimated 10–15% fuel, $1,000 to $1,500 per day, while the kite was in use. ''Maartje Theadora'', a large fishing trawler, was retrofitted with a kite rig in 2010.

Companies

Skysails and KiteShip both made kite rigs.

References

External links

Skysails GMBH description of kite sail propulsion
{{Kites Kites Sailing rigs and rigging Marine propulsion Sailboat components