Kite
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.
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. With the invention of paper in the Han dynasty, kites made of paper became popular, and kites were called zhiyuan. 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 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, 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".
In the 20th century, many new kite designs are developed. 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. Kites are now mostly used for recreation. Lightweight synthetic materials are used for kite making. Synthetic rope and cord 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, 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 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
Kites have been used for human flight, military applications, science and meteorology, photography, lifting radio antennas, generating power, aerodynamics experiments, and much more.Military applications
Kites have been used for military purposes in the past, such as signaling, delivery of ammunition, and for observation, both by lifting an observer above the field of battle and by using kite aerial photography.Kites were first used in warfare by the Chinese. During the Song dynasty the Fire Crow, a kite carrying incendiary powder, a fuse, and a burning stick of incense was developed as a weapon.
According to Samguk Sagi, in 647 Kim Yu-sin, a Korean general of Silla, rallied his troops to defeat rebels by using flaming kites which also frightened the enemy.
Russian chronicles mention Prince Oleg of Novgorod use of kites during the siege of Constantinople in 906: "and he crafted horses and men of paper, armed and gilded, and lifted them into the air over the city; the Greeks saw them and feared them".
Walter de Milemete's 1326 De nobilitatibus, sapientiis, et prudentiis regum treatise depicts a group of knights flying kite laden with a black-powder filled firebomb over the wall of city.
Kites were also used by Admiral Yi of the Joseon dynasty of Korea. During the Japanese invasions of Korea, Admiral Yi commanded his navy using kites. His kites had specific markings directing his fleet to perform various orders.
In the modern era the British Army used kites to haul human lookouts into the air for observation purposes, using the kites developed by Samuel Franklin Cody. Barrage kites were used to protect shipping during the Second World War. Kites were also used for anti-aircraft target practice.
Kites and kytoons were used for lofting communications antenna. Submarines lofted observers in rotary kites.
Palestinians from the Gaza Strip have flown firebomb kites over the Israel–Gaza barrier, setting fires on the Israeli side of the border. Hundreds of dunams of Israeli crop fields were burned by firebomb kites launched from Gaza, with an estimated economic loss of several millions of shekels.
Science and meteorology
Kites have been used for scientific purposes, such as Benjamin Franklin's famous experiment proving that lightning is electricity. Kites were the precursors to the traditional aircraft, and were instrumental in the development of early flying craft. Alexander Graham Bell experimented with very large man-lifting kites, as did the Wright brothers and Lawrence Hargrave. Kites had a historical role in lifting scientific instruments to measure atmospheric conditions for weather forecasting. Francis Ronalds and William Radcliffe Birt described a very stable kite at Kew Observatory as early as 1847 that was trialled for the purpose of supporting self-registering meteorological instruments at height.Radio aerials and light beacons
Kites can be used for radio purposes, by kites carrying antennas for MF, LF or VLF-transmitters. This method was used for the reception station of the first transatlantic transmission by Marconi. Captive balloons may be more convenient for such experiments, because kite-carried antennas require a lot of wind, which may be not always possible with heavy equipment and a ground conductor. It must be taken into account during experiments, that a conductor carried by a kite can lead to high voltage toward ground, which can endanger people and equipment, if suitable precautions are not taken.Kites can be used to carry light effects such as lightsticks or battery powered lights.
Kite traction
Kites can be used to pull people and vehicles downwind. Efficient foil-type kites such as power kites can also be used to sail upwind under the same principles as used by other sailing craft, provided that lateral forces on the ground or in the water are redirected as with the keels, center boards, wheels and ice blades of traditional sailing craft. In the last two decades several kite sailing sports have become popular, such as kite buggying, kite land boarding, kite boating and kite surfing. Snow kiting has also become popular in recent years.Kite sailing opens several possibilities not available in traditional sailing:
- Wind speeds are greater at higher altitudes
- Kites may be maneuvered dynamically which increases the force available dramatically
- There is no need for mechanical structures to withstand bending forces; vehicles or hulls can be very light or dispensed with all together