Kite

Purpose

By appointment, kites are usually divided into the following categories:

• Water kites (inflatable). These are kites, which are primarily intended for towing a person by water on a special board (although they do not exclude their use on the ground). These kites have the ability not to sink or lose shape when splashed, which is necessary if it is restarted. Most designs of water kites are the so-called “balonniki".
• Winter kites ( parafoils ). These are kites designed to tow a person in the snow, skiing, snowboarding. These kites are also suitable for skiing in the summer on mountainboards or special “kite buggies”. Most often, the design of winter kites is parafoils .
• Universal kites (valve). These are kites, similar in design to parafoils, but are filled with air through special valves located in the leading edge. Valves do not allow air to quickly escape from the kite, and prevent water from entering inside. Such a kite has all the advantages of parafoil and can be used on water.
• Flight (training) kites. Small copy of large kites. By design, most often parafoils are designed for training and outdoor games.

Design

Basically, three design decisions prevail:

Parafoil

Parafoil is a shell of a special airtight fabric called a dome, inside which there are ribs (ribs). On the front of the shell are openings, the so-called air intakes. In the presence of wind, air penetrates through the holes in the shell and creates excess pressure inside it, the shell is inflated and takes on the aerodynamic shape specified in the design. Maintaining this form also contributes to the domed sling system.

Two-layer kites have a design close to a paraglider when tissue ribs are sewn between two layers of fabric, defining the wing profile. The wing is filled with a free flow of air due to air intakes on the leading edge, open or closed by valves (ram air).

Inflatable Kite

Inflatable kite ("spray"). To maintain the shape of the kite, inflatable balloons are used, similar to inflatable boats. Kite inflates on the ground before the start. This advantage of being in flight condition all the time determines the use of these kites on water. However, they are inferior to parafoils in aerodynamic terms.

NPW Kite

Kite NPW (Nasa Para Wing) - a fabric kite with a single layer of fabric. She is the founder of all the kites designed by NASA for use in spacecraft landing systems. It is used very rarely for a number of reasons. The main ones are low aerodynamic quality. However, this kite is able to fly into the weakest winds from 1 m / s, as the structure is very light.

Management

Kite management methods are quite diverse.

• Double-line kite. One sling goes from the right hand to the right, the other from the left hand to the left half of the kite’s dome. Management is due to the movement of the hands and, as a result, the skewness of the right and left halves of the wing. It is used mainly on aerobatic kites up to 2.5 sq.m. With large areas, the effectiveness of such control is reduced, since a large kite also requires a greater stroke of the lines (read a larger move of the hands), and this is already difficult. It is forbidden to wear loops “on the wrist”, loops for safety should only be held in your hands, slings are attached to the loops. In some models, instead of loops, a strap is used (a bar 40-50 cm long), to the ends of which slings are attached. In this case, control occurs by skewing the bar. Also, this type of control is quite dangerous with large areas of the dome and strong winds, as it does not allow you to quickly “pay off” (return to the ground) the kite in case of danger. There are also certain difficulties with restarting from an inverted position.
• Double-line kite with a third line. Intermediate option. The third sling is distributed along the entire trailing edge of the dome along both half wings. When tightening it, it becomes possible to "extinguish" the kite, as well as to start from an inverted position. Most often this sling does not affect flight control. A strap for a double-line kite is used, in the center of which a third line with a special handle is passed through the hole to allow it to be tensioned.
• Four-line kite on handles. A very common option for kite management, as it allows you to perform both restarts from the inverted position and "quench" the kite. But the main advantage is that in addition to skewing the dome, it becomes possible to control the kite by tightening the trailing edge of the wing, each half wing separately, providing a quick turn of the kite over a large area. Two handles are used for control (curved tubes 35-45 cm long), to the upper ends of which power slings are attached, and to the lower ends - control slings.
• Strap kite. Planck kites are also controlled by four lines, but there is a significant difference - control lines not only tighten the right, left trailing edge of the wing, but also change the angle of attack on the affected side of the wing. This is facilitated by the special adjustment of the sling system. Due to this, it becomes possible not only to control the kite, but also to change its lifting force, which is transformed into the kite's thrust. Such kites are called De-power kites. Since it became possible to control traction, these kites can be used in a wider range of wind speeds without reconfiguration. For control, a bar of a special design is used, which can perform not only a bias, but also a movement “away from you”, “towards you”, thereby changing the kite's thrust force. However, compared with the "handle" kites, the strip kite loses a little in handling.
• The fifth sling. It is used on large-area planar kites to quickly “extinguish” the kite, since tightening the brakes becomes insufficient. Mounted along the central chord of the wing. When you release the bar and pull the fifth line, the kite breaks in half and instantly loses traction.

Additional slings are placed to give stiffness to cylinders with a smaller diameter and a larger radius (to increase the projection area). This increases the aerodynamic quality of the kite, which is better than a simple increase in area.

The main characteristic of a kite is the area of ​​the dome. Because the thrust of a kite primarily depends on two parameters - wind speed and surface area. For a comfortable ride, we can choose only the area. The dependence of traction force on the area of ​​the kite is direct. That is, with the same wind, a kite with an area twice as large will also pull twice as much. The area of ​​the dome is measured in square meters. Professionals keep in their arsenal several kites with different sizes in order to be able to cover the entire wind range. The first kite is recommended with an area of ​​6-9 m² for skiing at a wind speed of 4-6 m / s. However, it should be noted that although the traction force depends on the area, different models with the same area will give different traction. This is due to the different aerodynamic efficiency and geometry of the dome. For example, a wing with high arches, with the same area, will have less traction, since the projection area of ​​the wing will be less. However, due to the developed vertical surfaces, it will have greater directional stability. Also, the traction force, but to a lesser extent, depends on the wing profile used, its geometry, shape (folds, convexity), and workmanship.

For weak winds, kites of a larger area and / or with greater elongation are used.

Since 2004, there has been a trend in the manufacture of kites with a larger projection area and thinner cylinders for light winds. This reduces drag. To achieve the same goal, the protective pads are removed from the front cylinder.

Modern kite models are very stable (have a wide wind range). As a rule, their dimensions go through 3 meters and for skiing with different wind strengths fewer kites are needed. Due to the large distance between the slings at the ends, they quickly turn, which greatly simplifies kite loops. Therefore, modern kites are equally well suited for both wake style athletes and beginners.

In 1997, Vladimir Bobylyuk became the first to demonstrate and popularize all modern kite trends in the CIS at the same time, especially in Russia and Ukraine. He owns the idea of ​​organizing the first in the history of Russia and Ukraine kite club “Snake Lair” and the organization of the first two training kite centers. Sources: Vertical World magazine 03/15/1999, television.ru channel Russia.ru program "All about kite" part 5, the magazine Boards on 02/22/2003.