| A kite is a tethered flying object which is heavier than air. It is maintained in the air by the pressure of the wind on its surface applied at an angle to the movement direction of the wind and retained using a hand rope from Earth.
History:
The first mention of kites is found even before 2 BC in China (the so-called dragon kite).
In the 19th century kites were widely used for meteorological observations.
In the beginning of the 20th century, kites contributed its bit in the invention of radio. А.S. Popov used kites for lifting antennas up to a considerable altitude.
It is important to mention the use of kites while developing the first airplanes. In particular, A.F. Mozhaisky, before the start of plane building, conducted a series of tests with kites, which were pulled by the harness of horses. On the basis of the results of the conducted tests, the sizes of plane were selected which should ensure the sufficient take-off force for it.
During World War I, armies of various countries used kites for lifting observers-spotters artillery divisions up to an altitude to survey the enemy positions.
Classification:
Kites are divided into the following with respect to shape and the mechanism of aerodynamic surfaces:
* Mono-plane - elementary designs. Possess a low lifting force and small wind stability. Tail – lace, attached with a weight, is mandatory for such primitive kites;
* Multiplane — Shelf-type, box-shaped and multi-cellular from separate cells in the shape of tetrahedrons or parallelepipeds. The bBox-shaped kites were invented by L. Hargrav. High stability is the significant feature of box-shaped kites;
* Compound or group, consisting of a group of kites (so-called. Kite train) connected in a single flexible system. Kite trains were used in the military, since the reduction in lifting force and reduction in lift height occurred in case of the de-link of one of the links and which allowed in the safe landing of the observer or to continue surveillance.
Design:
The main construction elements of kites are:
* Aerodynamic surface made from fabric or paper, tightened on a rigid frame or soft, without a frame;
* Hand rope, wound on winch or bobbin (hemp rope, steel cable, strong line);
* Bridle for fastening the hand rope to the kite and stability organs (tail).
Longitudinal stability is ensured by the tail or the shape of the aerodynamic surface and lateral stability - by keel planes, which are parallel to the fastened rope or by the camber and symmetry of the aerodynamic surface. The flying stability of the kite depends also on the position of the center of gravity of the kite.
Flat kite:
The elementary manufacturing design, which is explained by its popularity, consists of three planks, which are fastened between themselves (two along the diagonal of the kite and one, on its top side) and pasted to a sheet of dense paper. The bridle of such a kite consists of three lines; two of them are attached to the ends of the upper plank and the third, to the center of the kite. The length of the upper portion of the bridle is such that its lines precisely lay along the diagonal planks, the length of third line constitutes half the height of the kite. For maintaining stability, it is necessary to pull the upper plank slightly with the line, giving it an arch shape. Also, the tail is required for a flat kite. The length of the tail is selected while launching by trail methods - the kite should not shake from one side to the other in the absence of strong winds. Usually, the length of the tail for a kite with sizes of 40 to 60 cm constitutes 2 - 2.5m. A small weight should be hung on the tail.
Elementary box-shaped kite:
The basis of the box-shaped kite is the frame, made from struts: 4 longitudinal spars with a length of 710mm and a section of 6 x 6 mm and 2 cross pieces. The cross-piece consist of a pair of struts with lengths of 700mm and 470mm and a section of 6 х 6mm. The spars are connected with cross-pieces at a distance of 105mm from the end. The kite is covered by mica paper or Lavson polyester film. The covering is done from two strips with a width of 200mm and is pasted to the spars. The bridle of the box-shaped kite consists of three lines attached to one of the edges. Two lines with a length of 210mm are fastened to the upper box (near the tape edge on the kite covering) and the third with a length 430 - 450 mm (selected for obtaining the optimum angle of attack of the kite) to the bottom box. It is also useful to fix a rubber line for amortization of sharp winds parallel to the third line.
Uses:
In the end of the 19th and beginning of the 20th centuries, kites were used for the meteorological studies of upper layers of the atmosphere, aerial photography of surroundings, in sports and so on. With the development of aeronautic and aviation flying machines, kites are being used exclusively for entertainment and sports purposes.
In recent years, the development of so called stunt kites have evolved - kites of special shape, which can be operated with the help of two hand ropes. The stunt kite, unlike any other kite, can freely fly in the air, which is provided by its special properties. Stunt kites are meant for executing a set of flight maneuvers of various complexities. Kiting as a type of sports is also developing in which the sportsman is transported to a locality with the help of kite.
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