Power Kites

A power kite or traction kite is a large kite designed to provide significant pull. They come in two main forms: foils and leading edge inflatables. There are also rigid-framed kites and soft single skin kites. There are several different control systems used with these kites which have two to five lines and a bar or handles.

Various types of kites exist, ranging from materials, shape, usage, skill required to operate, and so on. A modified parachute that has a positive lift/drag ratio is a kite. A tethered body that does gain a positive lift/drag ratio upon being towed in some media is a kite. Kites have their wing body and kite line; the kite line is moored to a fixed or moving body which even could be the kite line itself; the moving body could be a falling payload or human pilot as in some hang gliders. Kites of very low stable lift/drag ratio are only rarely treated as kites, but as streamers and flags. Kites may fly in air or fly in water or other media. A deflection off the direction of the ambient stream obtains because of the shape of the kite's wing. New types of kites continue to be invented and designed.

Power kites are generally used in conjunction with a vehicle or board, such as in:
Kite surfing on a kiteboard
Kite buggying on a purpose-built 3-wheeled cart
Kiteskating on all-terrain roller skates
Snow kiting on skis or snowboards
Kiteboarding on an all Terrain Board/Mountainboard/Landboard
Kite jumping, using a power kite for jumping above the ground
Manlifting, where a harnessed kite flier is tethered to the ground or one or more people to provide tension and lift

Bow kites are leading edge inflatable kites that incorporate a bridle on the leading edge. They can be identified by a flat, swept-back profile and concave trailing edge allowing the kite greater depower. Bow kite design was pioneered by Bruno Legaignoux, and have been licensed to many kite manufacturers.

Bow kites have a wider wind range than C-kites (traditional LEI kites), so two kite sizes (such 7m² and 12m²) could form an effective quiver for winds ranging from 10 to 30+ knots for a 75kg rider. This makes bow kites more suitable for beginners to kite sports; however, they are also used by professionals.

Bow kites are used in a varity of kite related sports, including kitesurfing and snowkiting. Because of their depower range, they allow users to combat problems caused by gust, making them safer to use. They are also used by kite surfers for wave riding, as their unique shape lends itself to this discipline.

More on bow kites!

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 amount of power that these kites can generate, they can be used for a number of different activities including kitesurfing, kiteboarding on land, snowkiting, kite buggying and recreational kiting.

Foil kites are flown with various line set-ups that includes 2-, 3- and 4-line systems; 2-line systems comprising of rings, wrist bands or bar compared to depowerable 4-line systems using a bar or handles. (See also: kite control systems)

In order to make them suitable for use on water some foils have limited air inlets in the centre of the leading edge, with valves to keep the air in and (hopefully) the water out. Internal holes in the cell sides allow the whole kite to inflate. These kites are naturally slower to inflate than an open-fronted foil.

Foils are the most efficient of the power kites. The aerofoil section means that they can still provide significant lift when parked overhead, unlike leading edge inflatable kites.

More on foil kites!

A leading edge inflatable kite, LEI or C-Kite is a single skin kite with inflatable bladders providing structure. It is useful as a power or traction kite. These kites are flown using 2, 4 or 5 control lines and a bar. (See also: kite control systems) A LEI is a great kite for water use because the inflated bladders cause it to float on the water surface. A LEI can sit on the water for an indefinite time and still be relaunched because unlike a double skin kite there are no chambers that can fill with water. Generally used for kitesurfing, leading edge inflatable kites come in many different sizes from approximately 5-18 square metres.

The inflatable and Bow kite designs were invented by Dominique and Bruno Legaignoux.

A parafoil is a nonrigid (textile) airfoil with an aerodynamic cell structure which is inflated by the wind. Ram-air inflation forces the parafoil into a classic wing cross-section. Parafoils are most commonly constructed out of ripstop nylon.

The device was developed in 1964 by Domina C. Jalbert (1904-1991). Jalbert had a history of designing kites and was involved in the development of hybrid balloon-kite aerial platforms for carrying scientific instruments. He envisaged the parafoil would be used to suspend an aerial platform or for the recovery of space equipment. A patent was granted in 1966.

Deployment shock prevented the parafoil's immediate acceptance as a parachute. It was not until the addition of a drag canopy on the riser lines (known as a "slider") which slowed their spread that the parafoil became a suitable parachute. Compared to a simple round canopy, a parafoil parachute has greater steerability, will glide further and allows greater control of the rate of descent; the parachute format is mechanically a hang glider of the free-flight kite type and such aspect spawned the paraglider use.

The air flow into the parafoil is coming more from below than the flight path might suggest, so the front most ropes tow against the airflow. When gliding however, the angle of attack is lowered and the airflow meets the parafoil head on. This makes it difficult to achieve an optimum gliding angle without the parafoil deflating.

Paragliding is a recreational and competitive flying sport. A paraglider is a free-flying, foot-launched aircraft. The pilot sits in a harness suspended below a fabric wing, whose shape is formed by the pressure of air entering vents in the front of the wing.

The paraglider wing or canopy is known in aeronautical engineering as a ram-air airfoil, or parafoil. Such wings are comprised of two layers of fabric which are connected to internal supporting material in such a way as to form a row of cells. By leaving most of the cells open only at the leading edge, incoming air (ram-air pressure) keeps the wing inflated, thus maintaining its shape. When inflated, the wing's cross-section has the typical teardrop aerofoil shape.

The pilot is supported underneath the wing by a network of lines. The lines are gathered into two sets as left and right risers. The risers collect the lines in rows from front to back in either 3 or 4 rows. The risers are connected to the pilot's harness by two carabiners.

The pilot is loosely and comfortably buckled into a harness which offers support in both the standing and sitting positions. Modern harnesses are designed to be as comfortable as a lounge chair in the sitting position.

More on paragliding!

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