A kite is a tethered heavier-than-air craft with wing surfaces that react against the air to create lift and drag forces. A kite consists of wings, tethers and anchors. Kites often have a bridle and tail to guide the face of the kite so the wind can lift it. Some kite designs do not need a bridle; box kites can have a single attachment point. A kite may have fixed or moving anchors that can balance the kite. The name is derived from the kite, the hovering bird of prey. There are several kite shapes, including the popular delta kite and diamond kite. The lift that sustains the kite in flight is generated when air moves around the kite's surface, producing low pressure above and high pressure below the wings. The interaction with the wind also generates horizontal drag along the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of one or more of the lines or tethers to which the kite is attached. The anchor point of the kite line may be static or moving (e.g., the towing of a kite by a running person, boat, free-falling anchors as in paragliders and fugitive parakites or vehicle). The same principles of fluid flow apply in liquids, so kites can be used in underwater currents. Paravanes and otter boards operate underwater on an analogous principle. Man-lifting kites were made for reconnaissance, entertainment and during development of the first practical aircraft, the biplane. Kites have a long and varied history and many different types are flown individually and at festivals worldwide. Kites may be flown for recreation, art or other practical uses. Sport kites can be flown in aerial ballet, sometimes as part of a competition. Power kites are multi-line steerable kites designed to generate large forces which can be used to power activities such as kite surfing, kite landboarding, kite buggying and snow kiting.
History
In China, the kite has been claimed as the invention of the 5th-century BC Chinese philosophers Mozi and Lu Ban, who flew wooden kites called muyuan (木鸢). With the invention of paper in the Han dynasty, kites made of paper became popular, and kites were called zhiyuan (纸鸢). Materials ideal for kite building were readily available, including silk fabric for sail material; fine, high-tensile-strength silk for flying line; and resilient bamboo for a strong, lightweight framework. By 549 AD, a kite was used as a message for a rescue mission. Ancient Chinese texts describe kites being used for measuring distances, testing the wind, lifting men, signaling, and communication for military operations. The earliest known Chinese kites were flat (not bowed) and often rectangular. Later, tailless kites incorporated a stabilizing bowline. Kites were decorated with mythological motifs and legendary figures. By the Tang dynasty, bamboo flutes, whistles, and ribbons were attached to kites to create sound, the precursor to the modern fengzheng (风筝), named after the sound the kites made in the wind. After its introduction into India, the kite further evolved into the fighter kite, known as the patang in India, where thousands are flown every year on festivals such as Makar Sankranti. Kites were known throughout Polynesia, as far as New Zealand, with the assumption being that the knowledge diffused from China along with the people. Anthropomorphic kites made from cloth and wood were used in religious ceremonies to send prayers to the gods. Polynesian kite traditions are used by anthropologists to get an idea of early "primitive" Asian traditions that are believed to have at one time existed in Asia. Kites were late to arrive in Europe, although windsock-like banners were known and used by the Romans. Stories of kites were first brought to Europe by Marco Polo towards the end of the 13th century, and kites were brought back by sailors from Japan and Malaysia in the 16th and 17th centuries. Konrad Kyeser described dragon kites in Bellifortis about 1400 AD. Although kites were initially regarded as mere curiosities, by the 18th and 19th centuries they were being used as vehicles for scientific research. In 1752, Benjamin Franklin published an account of a kite experiment to prove that lightning was caused by electricity. Kites were also instrumental in the research of the Wright brothers, and others, as they developed the first airplane in the late 1800s. Several different designs of man-lifting kites were developed. The period from 1860 to about 1910 became the European "golden age of kiting". The 20th century saw the development of many new kite designs. These included Eddy's tailless diamond, the tetrahedral kite, the Rogallo wing, the sled kite, the parafoil, and power kites. Kites were used for scientific purposes, especially in meteorology, aeronautics, wireless communications and photography. The Rogallo wing was adapted for stunt kites and hang gliding and the parafoil was adapted for parachuting and paragliding. The rapid development of mechanically powered aircraft diminished interest in kites. World War II saw a limited use of kites for military purposes (survival radio, Focke Achgelis Fa 330, military radio antenna kites). Kites are now mostly used for recreation. Lightweight synthetic materials (ripstop nylon, plastic film, carbon fiber tube and rod) are used for kite making. Synthetic rope and cord (nylon, polyethylene, kevlar and dyneema) are used as bridle and kite line.
Materials Designs often emulate flying insects, birds, and other beasts, both real and mythical. The finest Chinese kites are made from split bamboo (usually golden bamboo), covered with silk, and hand painted. On larger kites, clever hinges and latches allow the kite to be disassembled and compactly folded for storage or transport. Cheaper mass-produced kites are often made from printed polyester rather than silk. Tails are used for some single-line kite designs to keep the kite's nose pointing into the wind. Spinners and spinsocks can be attached to the flying line for visual effect. There are rotating wind socks which spin like a turbine. On large display kites these tails, spinners and spinsocks can be 50 feet (15 m) long or more. Modern aerobatic kites use two or four lines to allow fine control of the kite's angle to the wind. Traction kites may have an additional line to de-power the kite and quick-release mechanisms to disengage flyer and kite in an emergency.
Practical uses
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