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 may b ...

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

snow Snow consists of 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 througho ...

and

ice Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...

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 Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

This allows them to sail upwind by tacking. A power kite 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, snow, sand, or other surface. It combines the aspects of paragliding, surfing, windsurfing, skateboarding, snow ...

. Kiteboating is done in boats with kite rigs. On land, kite landboarding 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 skis 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 aircraft flight control system#Hydro-mechanical, manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic sig ...

controls. The SkySails propulsion system consists of a large foil kite, an electronic control system for the kite, and an automatic system to retract the kite. The kite, while 1–2

orders of magnitude In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are wi ...

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 Geography of the European Union, located primarily in Europe. The u ...

-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