Kites are among the oldest flying machines. The first documents about them are found several centuries before the start of the new era. Chinese manuscripts say that kites were flown during folk festivals. The Chinese built snakes in the shape of birds, fish, butterflies, beetles, and human figures, which they painted in the brightest colors (Fig. 1).
The most common type of Chinese serpent was the dragon, a fantastic winged serpent. A huge dragon raised into the air was a symbol of supernatural powers. In a number of places in China, until recently, traces of the custom of mass kite flying on the ninth day of the ninth month, Kite Day, remained.
The flying dragon is structurally complex. Two or three dozen light paper cones formed a long round body of a monster, wriggling picturesquely in flight. The serpent-dragon had a large head with a bared mouth. Through the mouth the wind penetrated into the empty body and, inflating it, supported it in the air. Sometimes, instead of cones, the design of the dragon's frame included gradually smaller round disks, which were connected with each other by cords. Each disc was crossed by a thin bamboo strip, at the end of which large feathers were attached (Fig. 2).
To enhance the effect, special “snake music” was invented, reminiscent of the howling of the wind in a chimney. The device that produced these sounds was made from dry poppy heads into which reed pipes were inserted. A rail was attached to the dragon's mouth, and two long silk ribbons were attached to the tail, which wriggled in the air along with the kite.
An interesting sight was presented by lanterns made from thin colored paper (Fig. 3) and fireworks (Fig. 4) attached to snakes.
Kites became widespread in Korea. At first, their use was purely religious in nature, and then flying kites became a fascinating form of activity and spectacle.
Japanese kite "Kero"
In ancient Japanese drawings you can also find images of kites, which were significantly different in shape from Chinese ones (Fig. 5).
Japanese snakes: a - “butterfly”; b - “Yatsuhana”; c - "Gonbo"; g - from the Nagasaki area; d - "Bozo"; e - "Ato"
A typical Malayan kite (Fig. 6) has the shape of a curvilinear symmetrical triangle. Its frame consists of three intersecting rods, the covering is made of coarse fabric.
European historians attribute the invention of the serpent, regardless of what existed in the countries of the East, to the ancient Greek scientist Archytas of Tarentum (IV century BC).
The ancient records of the first practical applications of kites are interesting. One of them says that in the 9th century. The Byzantines allegedly lifted a warrior on a kite, who from a height threw incendiary substances into the enemy camp. In 906, the Kiev prince Oleg used kites during the capture of Constantinople. The chronicle says that “horses and people made of paper, armed and gilded” appeared in the air above the enemy. And in 1066, William the Conqueror used kites for military signaling during the conquest of England.
But, unfortunately, no data has been preserved about the shape of ancient European kites, their structural and flight properties.
Kite "blinds" design Raqqa
For a long time, European scientists underestimated the importance of the kite for science. Only from the middle of the 18th century. The kite begins to be used in scientific work. In 1749, A. Wilson (England) used a kite to raise a thermometer to determine the air temperature at altitude. In 1752, physicist W. Franklin used a kite to study lightning. Having discovered the electrical nature of lightning with the help of a kite, Franklin invented the lightning rod.
Kites were used to study atmospheric electricity by the great Russian scientist M. V. Lomonosov and the English physicist I. Newton.
The serpent begins to provide valuable services to science. Therefore, it is not surprising that in 1756 the famous mathematician L. Euler wrote the following lines: “A kite, this toy of children, despised by scientists, can, however, make you think deeply about yourself.”
The kite was significantly improved by the Australian scientist L. Hargrave in the 90s. last century. Taking advantage of the work of the first glider pilot, the German engineer O. Lilienthal, Hargrave was the first to use two through boxes connected to each other as a kite. Lilienthal, when designing his gliders, noticed that such devices had good stability in the air. Hargrave patiently searched for the best proportions for his boxes. Eventually, the first box kite appeared, no longer requiring a tail for stability in flight (Fig. 7).
Hargrave's flying boxes were not only a greater impetus for the development of the kite business, but also undoubtedly helped in the design of the first airplanes. This position is confirmed by the similarity with the two-box kite of the biplanes of Voisin, Santos-Duman, Farman and the devices of other early aircraft designers.
The first human ascent on box kites was also accomplished by Hargrave. The passenger was lifted on four kites with a total area of 22 m2.
Frameless "monk"
Since 1894, kites have been systematically used to study the upper atmosphere. In 1895, the first snake station was established at the Washington Weather Bureau. In 1896, at the Boston Observatory, the box kite was raised to a height of 2000 m, and in 1900, the kite was raised to a height of 4600 m.
In 1897, work with kites began in Russia. They were conducted at the Pavlovsk Magnetic Meteorological Observatory, where a special snake department was opened in 1902.
The kite was widely used in meteorological observatories in Germany, France and Japan. The kite (rose to a very high altitude. For example, at the Linderberg Observatory (Germany) they achieved the rise of a kite to more than 7000 m. The first radio communication across the Atlantic Ocean was established using a box-shaped kite. The Italian engineer G. Marconi launched it in 1901. on New Foundlain Island, a large kite that flew on a wire that served as a receiving antenna.
The British military department became interested in Hargrave's box kite. Lieutenant Cody of the English army modified Hargrave's snakes. He increased its area by adding side wings placed on all corners of the boxes, increased the strength of the structure and introduced a completely new principle for assembling and disassembling the kite. Military observers began to take to the air on such kites.
At the beginning of the 20th century. Cody's work on snakes was continued by the captain of the French army, Sacconey. He created an even more advanced kite design, which is one of the best to this day. Sacconeus, taking advantage of rich subsidies from the military department, had the opportunity to carry out his experiments on a wide scale. He thoroughly developed the principle of towing kites: one group of kites lifted the main rail (cable) into the air, the other towed the load along the cable. Sacconei set the first records for the height and carrying capacity of kites.
The works of Sacconaeus found their successors in many armies of Europe. In Russia, Colonel Ulyanin created a special kite for the army (Fig. 8 and 9). A valuable and ingenious innovation in the kites of his design were articulated wings, which automatically increased the area of the kite when the wind weakened. In addition to Ulyanin, Kuznetsov, Prakhov and others were fond of snakes, and they created successful designs. During the Russo-Japanese War of 1904-1905. in the Russian army there were special snake units.
In parallel with Cody’s work in Europe, mainly in France, other designers also carried out their experiments. Of these, we should mention Plotter, who changed the place of attachment of the bridle and created kites with keel planes that increased the carrying capacity.
An interesting design of the original single-box kite was proposed by the French engineer Lecornu. He created a snake whose box resembles a honeycomb (Fig. 10). Lecornu justified the idea of building his kite by observing the flight of birds. If you look at a flying bird, you will notice that the planes of the body and wings form a certain angle. Lecornu made the same installation angle of 30° at the horizontal planes of the kite.
During the First World War, troops from various countries, and especially Germany, used tethered balloons for observation posts, the lifting height of which, depending on the battle conditions, reached 2000 m. They made it possible to observe the location of the enemy deep in the front and direct artillery fire through telephone communications. When the wind became too strong, box kites were used instead of balloons. Depending on the strength of the wind, a train was made up of 5-10 large box-shaped kites, which were attached to a cable at a certain distance from each other on long wires. A basket for an observer was tied to the cable. In a strong but fairly uniform wind, the observer rose in the basket to a height of up to 800 m.
This method of observation had the advantage that it made it possible to get closer to the enemy's forward positions. Kites were not as easily shot as hot air balloons, which were a very large target. In addition, the failure of an individual kite affected the observer's ascent height, but did not cause him to fall. A single incendiary rocket hitting the ball was enough to kill it, since it was filled with flammable hydrogen.
Monoblock kite designed by Roche-Donzel
During the First World War, kites were also used to protect important military installations from attack by enemy aircraft by constructing barriers consisting of small tethered balloons and kites that rose to a height of 3000 m. Wire ropes were lowered from the balloons and kites, which were created for the aircraft the enemy is in great danger. Germany has used such barriers to protect submarine yards and hangars in Belgium.
For the snake barriers of hangars near Brussels, large snakes were made in the form of tethered aircraft. The snakes copied the outlines of aircraft of various designs (monoplanes, biplanes) in order to mislead enemy pilots.
In the spring of 1915, an interesting incident occurred in Germany when a tethered aircraft misled not enemy pilots, but its own anti-aircraft battery. One day, early in the morning, a tethered biplane was lifted into the air. Soon after rising, he disappeared into the clouds. When the clouds cleared towards noon, this plane suddenly appeared in their gap. German observers had the impression that the clouds were motionless and that the biplane was flying at fairly high speed. Soon he disappeared into a cloud, only to reappear immediately in the next gap. Air surveillance and communications posts reported: “Enemy aircraft.” Anti-aircraft batteries opened barrage fire. Guns thundered around the airfield, trying to destroy the air enemy. The plane disappeared into the clouds, then reappeared, and the barrage continued until the Germans finally realized that they had fired at their own tethered plane. The latter was not shot down only because when firing an adjustment was made for the imaginary speed of the aircraft and the shells invariably ended up ahead of the stationary target.
Kite making in Europe reached its peak towards the end of the war, in 1918. After this, interest in kites waned. The rapid development of aviation began to displace snakes from military affairs.
Many designers who were previously interested in making kites switched to working on airplanes. But their experience in building kites did not pass without a trace. It certainly played a role in aviation history during the first stage of aircraft development.
Kite "star" design by Babyuk
In the Soviet Union, the hobby for kites began almost simultaneously with aircraft modeling. Already at the first all-Union flying model competitions in 1926, fairly well-flying box kites built by Kyiv aircraft modelers under the leadership of I. Babyuk were presented. Eleven canvas kites with a total working area of 42.5 m2 were launched on a 3 mm thick steel cable from a special balloon winch. The design of these kites is a modified classic Sacconeus type.
The number of box kite trains submitted to all-Union aircraft modeling competitions increased. Eight trains took part in the 1935 competition. Then, for the first time, the various uses of kites were most fully demonstrated. “Air mailmen” ran up and down the railing, with the help of which “paratrooper” dolls jumped, “bombs” and leaflets were dropped, and a smoke screen was demonstrated. The “parachutist” dolls made long jumps following the dropped live “landing party” - white mice in a cage. Dropping model gliders from kites has become commonplace. From a high-altitude launch, many glider models flew several kilometers away.
In pioneer camps, kites were increasingly used for signaling during war games. It was not uncommon in winter to see a skier, towed by a kite, easily gliding across the snow.
Kite making became one of the sections of the initial aviation training of pioneers and schoolchildren, and kites became full-fledged aircraft along with models of airplanes and gliders.
At the Serpukhov House of Pioneers in 1931, a children's snake station was created and successfully operated. The leaders of this station were annually invited with their kite team to the All-Union aircraft modeling competitions.
Soon the experience of the Serpukhovites became widely known. All-Union competitions began to be held independently every year. The snake stations of Saratov, Kyiv, Tula, Stalingrad and other cities represented their teams at the competition.
The leaders of children's kite stations and young "snake riders" with great enthusiasm designed kites and launched them, and carried out work among pioneers and schoolchildren.
In 1937, in Zvenigorod, the Central Council of Osoaviakhim of the USSR organized the First All-Union Box Kite Competition. Unfavorable meteorological conditions (lack of the necessary wind) did not make it possible to achieve record-breaking kite flights. But still, although at a low altitude, it was possible to test their design features.
In 1938, in the village of Shcherbinka (now a city in the Moscow region), the Second All-Union Box Kite Competition was held, at which designs of exceptional interest were shown. For example, the Serpukhov children's kite station presented kites of a modified "Grund" design with a load-bearing area of 20 m 2. The kite lifted a load weighing up to 60 kg. A kite parachute, a kite glider and others were shown.
At the III All-Union Box Kite Competitions, which took place in 1939 in Serpukhov, records were set for kite flight to altitude. A single kite, designed by the Kyiv aircraft modeller (that’s what the creators of kites came to be called) Gromov, was raised to a height of 1550 m. A train, made up of box-shaped kites designed by the Saratov aircraft modeller Grigorenko, was raised to a height of 1800 m. During the Great Patriotic War (1943 .) A. Grigorenko was awarded for the combat use of box kites.
At the IV All-Union competitions, the technical requirements for the design of kites were clearly defined. For example, each kite had to be kept in the air at a wind speed of no more than 4-5 m/s at the ground, the load-bearing area of each kite should be at least 5 m 2, the total area of the kite train should be such that with a wind of no more than 7 m/s it was possible to lift a load weighing at least 80 kg. The number of kites should be no more than 10 pieces. The head snake could have a large area, the configuration and color of the kites was arbitrary.
On each snake train it was asked to install various devices and mechanisms, for example, “air mailmen” capable of lifting a load weighing up to 2 kg, locks for composing a snake train (with a rail diameter of at least 3 mm), devices for aerial photography and others.
According to the terms of the competition, each team had to present a game scenario, during which they were supposed to launch a snake train. The scenario could include, for example, bombing, i.e. dropping “bombs” on some previously planned target, an “airborne assault” (dropping dolls), ski racing, transporting a wounded person on a sleigh pulled by a kite, sound, light and other types of alarms from the kite, dropping reports and leaflets.
Competitions were held for the flight altitude of a single kite, the launch height of a kite train, the maximum load capacity of a kite train, and the speed of assembling and launching a single kite.
To ensure success in competitions, many groups of circles made various auxiliary means. For example, in the Serpukhov House of Pioneers, model airplane schoolchildren made a dynamometer to test the strength of a handrail. A dynamometer mounted on the snake turned on a red light at critical voltage. The same team made an anemometer from an old alarm clock, and with the help of this device changes in wind strength were recorded.
Schoolchildren installed a barograph on the snake, a device for dropping a single “parachutist” or ground “landing” doll to a given point.
Young aircraft modelers at the Kolomna Station for Young Technicians (Moscow region) built box-shaped kites with wing flaps, which provided the kite with greater stability at an angle of about 50°. Aircraft modelers at the Voronezh Station for Young Technicians built profiled box kites.
Saratov aircraft modelers brought a kite train of five box-shaped kites to the competition. Each snake weighs up to 9 kg. The head snake had a total area of 17 m2. There was a camera installed on the snake train that took 12 photographs. The train was capable of towing one skier.
A team of Kyiv aircraft modelers brought a kite train of six kites to the competition. It was possible to drop a large “parachutist” doll from it (up to 70 cm, while the parachute dome was 4 m in diameter).
Young aircraft modelers worked hard, preparing for new starts. In Leningrad, more than 150 participants took part in the city kite competition in the spring of 1941.
After the Great Patriotic War, competitions were not held.
Nowadays, the construction of kites can have neither defense nor scientific significance. However, as a simple, very accessible and exciting activity, creating and flying kites has not lost and will not lose its importance.
Abroad, especially in socialist countries, kites are extremely popular among children and youth. They are especially popular in Cuba. You can often see how Cuban children, even while on the beach, do not part with their favorite pastime - kites of the most varied designs and the brightest colors hover in the air above the sea.
YUT For skillful hands 1977 No. 7
Who among you has not flown a kite? But does everyone know what they are? When did they appear?
The first time a kite flew into the sky was 25 centuries ago. At that time, no one could explain why the kite takes off and what forces act on it in flight.
At first, kites were flown for fun and entertainment. In Eastern countries, for example, kite battles were held. Two kites were launched into the sky, having previously been smeared with glue and sprinkled with crushed glass on the strings holding them on a leash. The winner was the one who was the first to saw through the enemy's string.
Later, kites began to be used for scientific purposes. In his experiments on atmospheric electricity, American physicist Benjamin Franklin used very large kites. The lifting force of some of them was so great that the scientist had difficulty keeping them on a leash. Kites helped Franklin prove the electrical origin of lightning, establish the presence of two charges, positive and negative, and test the idea of a lightning rod,
And at the end of the last century and the beginning of this one, snakes were widely used for meteorological research. With their help, scientists raised instruments to a height of more than 1000 m and measured wind speed, air temperature and humidity, atmospheric pressure...
Nowadays, interest in kites has not been lost.
The creative thought of inventors in many countries gives birth to more and more new designs of kites: disc planes, flywheels, etc.
Today we will talk about twenty-three snakes. The selection includes simple, non-labor-intensive models, as well as more complex ones. Among them, no two are alike: all kites differ from each other either in their flight qualities, or in their design, or in their manufacturing technology.
Any snake from this collection can be made at a pioneer camp or in the yard. We have selected four designs especially for beginning modelers. We talk about them in more detail (they are combined in the figure).
So kites...
WHY DOES THE KITE FLY?
A simplified drawing will help us answer this question (Fig. 1). Let line AB represent the cut of a flat kite. Let's assume that our imaginary kite flies from right to left at an angle A to the horizon or the oncoming wind flow. Let's consider what forces act on the model in flight.
During takeoff, a dense mass of air impedes the kite's movement, in other words, puts some pressure on it. Let's denote this pressure F1. Now let's construct a so-called parallelogram of forces and decompose the force F1 into two components - F2 and F3. The F2 force pushes the kite away from us, which means that as it rises, it reduces its initial horizontal speed. Therefore, it is a resistance force. Another force (F3) carries the kite upward, so let’s call it lifting.
So, we have determined that there are two forces acting on the kite: the drag force F2 and the lift force F3.
By lifting the model into the air (towing it by the handrail), we artificially increase the force of pressure on the surface of the kite, that is, the force F1. And the faster we run, the more this force increases. But the force F1, as you already know, is divided into two components: F2 and F3. The weight of the model is constant, and the action of force F2 is prevented by the handrail. This means that the lifting force increases - the kite takes off.
It is known that wind speed increases with height. That is why, when launching a kite, they try to raise it to such a height where the wind could support the model at one point. In flight, the kite is always at a certain angle to the direction of the wind. Let's try to determine this angle.
Let's take a rectangular sheet of cardboard (Fig. 2). Exactly in the center we will attach it to the O-O axis. Let us assume that the sheet rotates around an axis without friction and that in any position it is in a state of equilibrium. Let's say the wind blows with constant force perpendicular to the plane of the sheet. Naturally, in this case he will not be able to rotate the sheet around the O-O axis, since his action is distributed evenly over the entire sheet. Now let's try to install the sheet at some angle to the wind. We will see how the air flow will immediately return it to its original position, that is, put it under direct
angle to the wind direction. From this experiment it follows: half of the sheet tilted towards the wind experiences greater pressure than the one on the opposite side. Therefore, in order for the sheet plane to remain in an inclined position, it is necessary to raise the O-O rotation axis. The smaller the angle of inclination of the sheet, the higher the axis needs to be moved. This is how the center of pressure is determined. And the wind force that maintains the plane in an inclined position is the lifting force applied at the center of pressure. But the angle of the kite does not remain constant: after all, the wind never blows at the same speed. That is why, if we tied a string to the kite at one point, for example, at the point where the center of pressure and the center of gravity coincide, it would simply begin to somersault in the air. As you understand, the position of the center of pressure depends on the angle a, and with gusty winds this point is constantly shifting. Therefore, to make the model more stable, a bridle of two or three or more strings is tied to it. Let's do one more experiment.
Let's take a stick AB (Fig. A). Let it also symbolize the cross section of a flat serpent. We hang it by a thread in the center so that it takes a horizontal position. Then we attach a weight P, not far from its center of gravity, simulating the center of pressure. The stick will immediately lose its balance and assume an almost vertical position. Now let’s try to hang this stick (Fig. 3b) on two threads and tie the same weight to it again: the stick will maintain balance in any position of the weight. This example clearly demonstrates the importance of a bridle, which allows the center of pressure to move freely without disturbing balance.
SIMPLE CALCULATION
We figured out why the kite takes off. Now let's try to calculate its lifting force.
The lifting force of a kite is determined by the formula:
Fз=K*S*V*N*cos(a), where
K=0.096 (coefficient),
S - load-bearing surface (m2),
V - wind speed (m/s),
N - normal pressure coefficient (see table) and
a is the angle of inclination.
Example. Initial data: S=0.5 m2; V=6 m/s, a=45°.
We find the normal pressure coefficient in the table: N = 4.87 kg/m 2. Substituting the values into the formula, we get:
Fз=0.096*0.5*6*4.87*0.707=1 kg.
The calculation showed that this kite will rise upward only if its weight does not exceed 1 kg.
The flight qualities of a kite largely depend on the ratio of its weight to the bearing surface: the smaller the ratio of these values, the better the model flies.
WHAT TO MAKE SNAKES FROM
To build models, use light and durable materials. Remember: the lighter the kite, the easier it is to launch, the better it will fly. Glue the frame from thin, even shingles - pine, linden or bamboo. Cover small models with thin paper (preferably colored), foil or, in extreme cases, newspaper, and larger snakes with fabric, plastic or lavsan film, or even thin cardboard. Connect individual units and parts together with threads, thin wire, and glue. Be sure to lubricate the threads wound around the part with glue. For bridles and lifelines, choose a thin, strong thread.
SIMPLE SNAKES
These are paper models for beginners. Some can be done in an hour or two, while others can be done in just a few minutes. Such kites fly well and do not require complex controls. So first...
Paper birds
The experience of many researchers has shown that the curved surface of a kite has greater lifting force and stability than a flat one of the same size.
The simplest snakes of the American engineer Raymond Ninney are surprisingly similar to small birds. They fly well, demonstrating excellent stability in flight. There are several of them in Figure 1 (see a, b, c). In just two or three minutes, the inventor cuts out a rectangle (aspect ratio 4:5) from thick paper or thin cardboard, veneer, and foil and bends a bird out of it. Then he attaches a bridle to the body in one or two places - and the kite is ready. In this way, you can make models of any size - it all depends on the strength of the material.
The following design (Fig. 2a) was developed by the American inventor Daniel Karian. Isn't it true that she is somewhat reminiscent of Ninney's birds? Please note that this kite is given rigidity by a frame made of pine or spruce sticks and wings closed in a semi-ring. To cover the frame, the author suggests using fabric: silk, twill, thin linen. Those interested can experiment with a two- or three-wing design. The inventor believes that if you attach several geometrically similar wings to a long rod, you will get a very funny kite (Fig. 26).
Both Raymond Ninney's birds and Daniel Karian's snakes will fly even in large rooms and corridors, but with one condition: the person launching them must move at a constant speed.
Snakes are flat...
At first, all kites were equipped with wet tails. But... Once the Canadian meteorologist Eddie, who worked a lot with kites, noticed that the residents of a Malay village were flying tailless kites of irregular quadrangular shape. Observations helped the meteorologist construct his kite, which you see in Figure 3. This quadrilateral with pairs of equal sides resembles a parallelogram. This figure is obtained when two triangles are added with their bases, one of which, ABD, is equilateral, and the other, ASV, is isosceles, with AB:SD as 4:5. Side AB is tied at the ends with a slightly smaller metal string. Therefore it is slightly curved. The bridle is attached at points O and D, and the fabric (covering) is stretched in the upper part, where it forms two small folds. Under the influence of the wind, the kite bends and takes the shape of a blunt wedge. In flight, its leading edges seem to reject the incoming air flow in both directions, so the kite is stable.
Forty years later, the Englishman G. Irvine improved the Eddie design (Fig. 4).
It is known that the disruption of air flow behind the leading edge leads to the formation of a region of vortices above an obtuse-angled kite. As a result, stability is disrupted in gusty winds. Irwin did it simply - he cut out two triangular windows in the casing, and the oncoming flow began to rush into these windows. The kite's position in flight has stabilized.
The model shown in Figure 5 was proposed by the Frenchman A. Millier. It consists of a wooden strip AB, pulled together by a string into an arc (the chord AB is 9/10 of the length of the strip). At points O and O1, two identical strips SD and EF are attached to the rail (AO1=OB=0.2*AB). Like the AB lath, the slats are also pulled together by a string into an arc and form an equilateral hexagon in plan. The ends of all the slats are fastened with another string passing through the vertices of the hexagon.
The snake you see in Figure 6 is well known in Korea. Its rectangular frame, glued together from bamboo sticks, is covered with fabric. If the size of two sides is taken to be 800, and the other two - 700, then the diameter of the hole in the middle should be 300 mm.
Look at Figure 7. This model, similar to a bird of prey, was invented by the American Sandy Langa. The inventor first tried to test on it the principles of flight, borrowed from nature. Lang made the fuselage and tail from a single wooden strip. He split it at one end and inserted round slats of the supporting wings into the holes of the wooden sleeve. I tied the split part of the tail, the ends of the wings and the nose with thick fishing line - the result was a very flexible structure. And the wing slats were also sprung with rubber shock absorbers. Lang's snake is sensitive to the slightest gusts of wind. In flight, like a butterfly, it flaps its wings, thereby changing the amount of lift, the force of resistance, and stability.
...And box-shaped
Figure 8 shows one of the options for a box-shaped kite. It is stable in flight because its load-bearing planes are oriented towards the oncoming flow at an optimal angle of attack (the lift force generated on them is greater). In addition, its cross-section can be not only square, but also rhombic. For a rhombic, the ratio between the vertical and horizontal diagonals is 2:3. The depth of the box is 0.7 times the length of the larger side of the kite.
The frame consists of four longitudinal and four spacer slats of rectangular cross-section. The figure shows how the spacer and longitudinal rail are connected.
But the Russian inventor Ivan Konin proposed the design of a box-shaped kite, somewhat reminiscent of an airplane. It has two wings (Fig. 9). Thanks to them, the kite rises faster, remains stable in flight and does not tip over in sudden side gusts of wind.
...AND THE SNAKES ARE MORE COMPLEX
Both in design, in the use of materials, and in the time of manufacture, these aircraft differ from previous ones. They are more modern and sophisticated. But, probably, it will be all the more pleasant for experienced modellers to tinker with them: to understand the scheme, understand the principle of flight, and grasp some features.
Jet-powered
Many of you have probably observed that if a river floods widely, its flow rate becomes much slower. And vice versa: in a bottleneck, the flow speed increases sharply. In air, as in water, this physical law also applies. Try to direct the air flow into the wide end of a conical pipe (tapering diffuser), and you will see how the air speed changes: it will be greater at the outlet than at the inlet. In order to obtain jet thrust in practice (and this is how the change in flow velocity in a pipe can be assessed), one condition is required: fix the diffuser on a large plate.
When a flat kite is in the air, a zone of high pressure is created below it, and a zone of low pressure above it. Under the influence of the pressure difference, the air flow breaks into the diffuser and passes through the pipe. But the diffuser is conical, so the speed of the outgoing flow will be greater than the incoming flow (remember a river). This means that the diffuser works like a jet engine.
In Figure 1 (see page 6) you see a kite by the Englishman Frederic Benson, whose design uses the diffuser effect. The inventor claims that jet thrust not only increases the speed of the kite's rise, but also gives it additional stability in flight.
The design of a jet kite is quite simple. Two rectangular crossbars are fastened crosswise in the center and tied at the edges with a strong thread. A diffuser bent from thick paper or foil is installed on this frame. The covering is ordinary: paper, fabric...
According to the WUA principle
It is known that air-cushioned vehicles (AHVs) rise due to the pressure difference: the pressure under the bottom is always greater than at the top. And the stability of the device is created by a special device that evenly distributes the gas flow along the entire perimeter.
American engineer Franklin Bell proved that devices similar to AVPs can fly in the air. Fantasy? No. The kite model is a witness to this (Fig. 3 on page 7).
Smooth bottom and sides, small keel, smooth hull contours - a complex design. But the incoming air flow flows around the body without disruptions or turbulence and easily lifts the kite. It is easy to see that these aerodynamic advantages are effective not only during climb. The curved sides of the hull do a good job of stabilizing the kite’s position in the air at high altitudes. And one last thing. Take a closer look: isn’t it true that in the longitudinal section the model somehow resembles a high-speed motor boat?
A parachute takes off
It is generally accepted that people can only go down with a parachute. A parachute cannot lift a person up, even in an updraft. But a group of Polish engineers tried to refute this opinion. They proved that under certain conditions the parachute can rise upward.
Let's remember a game familiar from childhood. If you blow on a small parachute - a dandelion seed - from below, it will rise up. Of course, a comparison between a dandelion and a modern parachute can be made only conditionally - Polish inventors create a vertically ascending stream of air using powerful fans. But even ordinary wind cannot be discounted, says American Jack Carman and offers a toy - a kite parachute (Fig. 4).
The air flow hits the slightly inclined canopy of the parachute and lifts it up. Structurally, the model is no different from the well-known children's parachutes (we already wrote about one of them in Appendix No. 4, 1974). But there are also differences. For example, to stabilize the flight, a tail is attached to the kite parachute, and a telescopic tube is fixed in the center under the dome. It serves both as a rigid frame and as a regulator of the position of the model’s center of gravity.
Disk in flight
The device will acquire good stability in flight if it is given the shape of a disk. One of the variants of a flying disc is shown in Figure 2 (see page 6). The model is very similar to two low cones folded together. But the cones will not fly well, says inventor Wilbur Bodel from Switzerland, so he supplements the design with a keel, as well as a small weight that shifts the center of gravity down (thus increasing the stability of the device), and a hole in the lower part of the skin. But what is this hole for?
At altitude the wind blows stronger than at ground level. This means that not only its speed changes, but also its pressure. Is it possible to use pressure differences to create additional jet thrust? It turns out that it is possible. When there is a strong gust of wind, the internal cavity of the kite is filled with a slightly larger amount of air. This means that excess pressure is created inside the kite. When the gust weakens, the pressure outside drops and the air from inside rushes out through the hole in the casing. A jet stream, albeit weak, appears. This is what creates additional lift. A characteristic feature of this kite is that it can be flown at night. To do this, instead of a weight, Bodel installs a miniature flashlight with a reflector, a light bulb and a 1.5 V battery.
In the figure “Side View” you can see that the kite frame is assembled from many slats rigidly fastened together. Pay attention to the characteristic nodes connecting the slats with the outer ring-rim, hub and keel.
But the disc plane of the French engineer Jean Bortier already has three keels. It takes off well, maneuvers smoothly in the air, even in strong winds, and hangs motionless on a leash in light winds. Let's tell you in more detail how to make it (see figure on page 10).
Like many other kites, its frame is made of thin wooden slats, fastened with a wire rim and covered with thin paper. So, everything in order.
Prepare four even slats with a cross-section of 3x3 mm for the frame, fold them together as shown in the “Top View” figure, glue them in the center, tie them with threads and coat them with glue. Along the perimeter of the frame, bend a rim of steel wire with a diameter of 0.4-0.5 mm and tie it with threads and glue to the ends of the slats (see figure). Connect the ends of the rim together and wrap them with threads and glue. It is most convenient to dock them in front, in the area of the central rail “a”. If you do not have suitable wire, then make a rim from a thick thread. Don't forget to glue it to the slats.
Cover the disk and keels with tissue paper or newsprint. Glue the skin to the disk from below - this will significantly reduce the resistance of the model. But you can also put paper on top. True, then the skin will have to be glued to all the slats and the rim, otherwise a strong gust of wind will tear it off.
Install three keels on the lower surface of the disk (you can get by with one or two, but then the size of the keels will have to be increased) - The rims of the keels are easiest to make from thin bamboo or pine slats - these materials bend easily, and you can get smooth contours.
If you want to make a large kite, then do not forget to strengthen its frame with two or three more slats.
Tie a bridle to the finished kite - three short threads. They hold the model at the required angle of attack. Cut the central thread of the bridle in half and tie its ends to a rubber compensator ring. This ring, stretching during strong gusts of wind and unexpected jerks, removes part of the load from the frame. Tie a handrail to the bridle. For a small kite, harsh threads (cord line) are suitable. Test the finished model.
As we have already said, a disc kite can be flown even in light winds. And if there is none at all, try to launch the model, towing it behind you while running.
Be prepared for any surprises. If the kite suddenly flies in loops or begins to descend sharply, do not hesitate to release the handrail from your hands - the model will not break when it hits the ground. Pick up the kite and examine it carefully; correct distortions; if necessary, reduce the angle of attack (increase the length of the center line) and fly the kite again. If it cannot be adjusted, it means that the plane of the disk is irreparably skewed. Try attaching a tail to the model from a strip of paper, or a bundle of threads a meter and a half long, or from a lump of paper on a thread.
Instead of a frame... air
Many inventors use not slats and paper to make their models, but... air.
Look at Figure 5. This is an inflatable kite by Canadian inventor Paul Russell (see page 7). In the picture it only looks complicated on the outside. Very simple indeed: two sheets of airtight material were all Russell needed to make the model. Longitudinal and transverse weld seams divide the internal volume into several interconnected inflatable cavities. The seams give the entire structure the necessary volumetric strength. And one more thing. The inflated body has no sharp protruding edges. This means that there will be no turbulence on the surface of the inflatable kite, and therefore the model will be stable in flight. But making such a kite is not easy - certain working conditions are required.
The model of the Finnish engineer S. Ketola (see figure on page 11) is much easier to manufacture.
Is it possible to think of anything simpler? I took two pieces of plastic film, welded them along the edges and in the middle with a hot iron or soldering iron - and the kite was ready. But how many of you know how to weld film so that the seams are airtight? We warn novice modelers in advance: this operation is not easy. Before you start making a kite, try welding several seams on some plastic bag and test them for leaks. Use an iron with a temperature regulator. Do not forget to degrease the polyethylene blanks before welding.
According to the dimensions indicated in the figure, cut out two blanks from the film. Place them together and, stepping back from the edge by 10-15 mm, slowly run the edge of a hot iron or soldering iron along the entire perimeter of the workpieces. In three places of the resulting seam: on the sides - at the bottom and at the top anywhere - leave small holes. Through them you will pump up the snakes. Then weld the workpieces diagonally. And so that you can rest assured that the seams are tight, melt the edges of the workpieces over a candle fire. Do this in the device shown in the figure.
To attach the bridles and tail, burn six holes with a diameter of 1-2 mm in the seams. Do this with a very cool nail or the tip of a candle flame.
Inflate the finished model and weld the holes in the outer seam with a candle or, folding the edges of the skin in half, fasten them with paper clips, after wetting the holes with water or lubricating them with technical oil.
Once you learn how to make small inflatable kites, try making and flying a larger model - one meter or two meters long. But are you strong enough to hold her?
Here is a model (Fig. 7, p. 8). But which one? “Helicopter,” some of us will probably think when they see the rotors. “A kite,” others will say, noticing the model’s bridle and rail.
The incoming air flow hits the plane of the kite (in this case, the rotor), a lifting force arises, and the model rises. This could have happened if the rotor had stood still. But it rotates, which means that lifting force also arises on its blades. Consequently, in flight the kite receives an additional impulse of energy, pushing the model upward. As you can see, there are obvious advantages over other types of kites.
And this helicopter kite was made in Brazil by R. Fugest (Fig. on page 10). In our opinion, the Brazilian model is the most interesting of the subclass of helicopter-type aircraft. This kite has three rotors: two rotors and one tail. The main rotors, rotating in different directions, create lift, and the tail rotors stabilize the position of the model during takeoff and keep it at altitude. The design of the kite is extremely simple.
The frame is assembled from two longitudinal ones, glued at an angle, and two transverse slats. The slats are glued together and reinforced with threads and glue for greater rigidity. The main rotors are installed on the transverse rack, and the tail rotors are installed on the longitudinal ones. To ensure that all rotors rotate easily, they are mounted on wire axles.
Manufacturing rotors is the most critical operation. You need to glue the parts carefully, without rushing. The lifting force of the kite depends on how well you make the rotor.
We offer you two rotor options, but there may be more. Try to design a rotor yourself. Try it out. In the meantime, let's talk about those shown in the figure.
First option. This rotor is most suitable for large models. A kite with four, six or eight blades takes off well and stays well at altitude. The rotor is made like this.
Glue two pine or bamboo slats crosswise and cover them with whatman paper or linden (birch) veneer. In the center of the rotor on both sides, stick a washer made of thin plywood, veneer or celluloid and drill a through hole for the axle.
Second option. This rotor resembles a child's pinwheel. It is good for a small lightweight kite.
Such a rotor is assembled from thin bamboo slats (3x3 cross-section in the center and 1.5x1.5 mm at the ends), tissue or newsprint paper, two washers (veneer, celluloid) and strong thread. Glue the slats together as shown in the figure and pull their ends to the base of the blades with threads.
Snake or pinwheel?
While observing the flight of an artillery shell, Gustav Magnus discovered a strange phenomenon: when there was a side wind, the shell deviated up or down from the target. The assumption arose that this could not be done without aerodynamic forces. But which ones? Neither Magnus himself nor other physicists could explain this, and perhaps that is why the Magnus effect did not find practical application for a long time. Football players were the first to find use for it, although they did not know about the existence of this effect. Probably every boy knows what a “dry leaf” is, and has heard about the masters of this blow: Salnikov, Lobanovsky and others.
Today, the physics of the Magnus effect is explained simply (for more information, see "Young Technician", 1977, No. 7). Now there is even a whole independent subclass of kites, the principle of flight of which is based on the Magnus effect. One of them is in front of you (Fig. 6 on page 8). Its author is American inventor Joy Edwards. This kite is somewhat reminiscent of a pinwheel. In flight, the body of the kite, like the artillery shell observed by the German physicist, rotates around its axis. At the same time, the wing-blades convert the wind pressure into lifting force, and the stability of the kites is maintained due to the symmetrical streamlined body and round keel.
This is how a snake is designed. The central rod of rectangular cross-section, the round keel and the wing-blades form a fairly strong body, which rotates on two axes attached to the ends of the rod. The ears and bridle connect the body to the rail. It should be emphasized that kites of this type are an almost untouched area of inventive creativity.
Now try to make the model that was invented by the American S. Albertson (Fig. on page 11). The principle of operation of the Magnus serpent (as the author calls his model) is clearly visible from the figure.
The semi-cylinders, mounted on slats and closed at the ends with disks, rotate around their axes under the pressure of the incoming air flow. If you hook a bridle onto these axles and tie them to the rail, the device will easily take off.
The kite consists of a frame with axles, two half-cylinders, four half-discs and a bridle. The frame is made up of four longitudinal and two transverse slats (pine, bamboo). Start with that.
Glue the slats together, and wrap the joints tightly with thread and glue. Bend the ends of the central longitudinal slats on a soldering iron, as shown in the figure, glue and tie with threads. Then attach the wire axles to them (the attachment is the same as for the helicopter kite). Tie the bridles to the same axes.
Bend the half-cylinders from whatman paper and glue them to the longitudinal slats of the frame. Lastly, install the keels on the frame. (Each of them is made of two half-disks.) Glue them onto the cross slats from the inside so that the slats are on the outside.
So you've built and flown Magnus' kites. What's next? Try experimenting with this aircraft. For example, increase the size of the half cylinders and the body of the kite. Or make a flying garland of several kites (see picture). Test the model. Let us know about the results of the experiment.
V. ZAVOROTOV, engineer, A. VIKTORCHIK, engineer, master of sports of the USSR
Fig. N. KIRSANOV and V. SKUMPE
Age: 13 years
Place of study: MBOU “School-gymnasium No. 10” named after. E.K. Pokrovsky, Simferopol, Republic of Crimea, Russian Federation
Head: Roman Vitalievich Krivoshchekov, methodologist of the physics and mathematics department of PDO GBOU DO Republic of Crimea MAN “Iskatel”, Simferopol
Historical research work on the topic:
Kites: children's fun or practical aeronautics?
Plan
1 Introduction
2 History of the emergence and use of kites
3 Why and how does a kite fly?
4 Types of kites
6 List of used literature
Introduction
Many parents, when buying a kite for their children, do not even realize that making and flying kites, on the one hand, is children's fun that attracts people of all ages, and on the other hand, it is a hobby that promotes the development of observation, ingenuity and creative potential. And at first glance, such a simple and common toy for us, is not quite as simple as it might seem.
Purpose of the work- study the kite as an aircraft, identify areas of application, design and fly the kite.
Tasks:- study the history of kites;
Find out the types and areas of their application;
Find out why and how a kite flies;
Design a kite and test it.
History of the origin and use of kites
The history of kites dates back to ancient China and dates back at least 2,000 years. The history of the origin of the kite is based primarily on traditions and legends, because the materials from which the kites were made (wood, paper, fabric, leaves and tree branches) were destroyed quite quickly. The oldest archaeological finds date back about 200 years.
The snakes were built in the form of butterflies, birds, fish, and beetles, which were painted in bright colors. The most common was the dragon snake, which looked like a half-crocodile - half-snake.
At a later time, kites began to be built in the form of flat frames covered with paper or fabric. They no longer resembled the fairy-tale snake, but the name has survived to this day.
From the very beginning of its existence, the kite was used in three main areas - military operations, rituals and everyday life. The use of a kite for military purposes was primarily limited to measuring the distance to enemy objects and intimidating enemies. In the history of Russia there are also references to kites: in 906, during the capture of Constantinople, Prince Oleg ordered many kites to be made in the form of horsemen and foot soldiers in order to instill terror in the defenders of the city: they suddenly saw that countless Russian army.
Kites were also used in rituals. It was believed that by getting a little closer to the sky, where the gods lived, and by attracting their attention with your bright appearance, there was a greater chance of drawing the attention of the gods to the prayers of people. So, for example, by flying a kite, they scared away evil spirits and protected from evil forces, diseases, and asked for a rich harvest.
Kites were also used in Asia to catch fish, scare birds away from crops, to lift building materials to the tops of buildings, and of course, as toys.
Scientists also took a closer look at this children's toy. The famous physicist, mathematician and astronomer Leonhard Euler wrote: “The kite, a child’s toy neglected by adults, will someday be the subject of deep research.” And he was not mistaken. Back in 1749, Scottish astronomer A. Wilson raised a thermometer on a snake to measure air temperature at altitude. The famous American scientist B. Franklin, using kites, conducted research on atmospheric electricity and proved that lightning during a thunderstorm is nothing more than an electrical discharge of enormous force. Having discovered the electrical nature of lightning as a result of these studies, Franklin invented the lightning rod.
The great Russian scientist Mikhail Lomonosov also built kites to study electricity in the atmosphere. On June 26, 1753, Lomonosov “with the help of a kite extracted lightning from the clouds.” He flew a kite into a thunderstorm and released a discharge of static electricity along the string used as a conductor. These experiments almost cost him his life, but his follower, Academician Richman, was killed by a discharge of electricity.
In the 19th century, kites were also widely used for meteorological observations. At the beginning of the 20th century, kites contributed to the creation of radio. A.S. Popov used snakes to raise the antennas to a considerable height. It is important to note the use of kites in the development of early aircraft. In particular, A.F. Mozhaisky, before starting construction of his aircraft, conducted a series of tests with kites. Based on the results of these tests, the dimensions of the aircraft were chosen, which should provide it with sufficient lifting force.
The practical capabilities of the kite attracted the attention of the military. In 1848 K.I. Konstantinov developed a system for rescuing ships in distress near the shore using kites. During the First World War, troops from various countries used kites to raise observers to spot artillery fire and reconnaissance of enemy positions. Kites were also used on the fronts of the Great Patriotic War. For example, with their help our soldiers scattered leaflets.
In the post-war years, kites became an exciting activity for schoolchildren. But along with this, they are also often used in the field of meteorology for research and observation of the lower layers of the atmosphere. Box kites lift instruments that record temperature, pressure, humidity and wind direction at altitude. In distant Antarctica, our scientists widely used snakes to study the atmosphere up to an altitude of approximately 1000 m.
Nowadays, kites are not forgotten; they live full, active lives. Kites help meteorologists study the upper atmosphere. You can attach not only a barometer and thermometer to the snake, but also photo and video equipment, subsequently using the obtained data for topographic maps. Using a kite for such purposes is much more profitable, simpler and cheaper than using heavy flying equipment. Also, radio amateurs, just like 100 years ago, still use a kite to receive a stable signal.
The kite also has its own holiday. Every year on the second Sunday of October, World Kite Day is celebrated all over the world.
Why and how does a kite fly?
A kite belongs to a heavier-than-air flying machine. Why does the serpent rise and what keeps it on top? The main condition for this is the movement of air relative to the kite. Wind speed and direction are constantly changing. Not only mountains, but also houses, bridges, buildings, and trees deflect the wind at the surface of the earth from its horizontal direction. So how does a kite fly? A simplified drawing will help answer this question. Let the line AB represent the cut of a flat kite, and let the angle to the oncoming wind flow. Let's consider what forces act on snakes in flight. During takeoff, a dense mass of air prevents the kite from moving, that is, it puts some pressure on it. Let's denote the pressure force F1. Now let's construct a parallelogram of forces and decompose the force F1 into two components - F2 and F3. The F2 force pushes the kite towards us, which means that as it rises it reduces its initial horizontal speed. Therefore, it is a resistance force. Another force F3 pulls the kites upward, this is the lifting force.
By lifting the kites into the air, we artificially increase the force of pressure F1 on the surface of the kite. But the force F1, as we already know, is divided into two components: F2 and F3. The mass of the model is constant, and the action of force F2 is prevented by the handrail. This means that the lifting force increases - the kite takes off. It is known that wind speed increases with height, because the higher you are from the ground, the fewer objects that would impede its movement. That is why, when launching, they try to raise the kite to a height where the wind could support it.
Types of kites
All kites can be divided into two main groups: uncontrolled and controlled.
Uncontrollable kites include the familiar kites, which, being raised into the sky, are there at approximately the same point, and the movement of which can only be influenced by the incoming air flow.
The simplest uncontrollable snakes are flat. The ancestors of all kites, they have a flat frame. Stabilization is achieved due to the shape of the kite, air flows in the sail, and tails. Examples include the Russian kite, Indian kite, star kite, and delta wing kite.
Curved kites have a transverse bend in their design that allows them to be more stable than flat kites, eliminating the need for a tail for stabilization, therefore improving the kite's wind range. Bending in the structure is achieved either by a specially curved connecting element, or by pulling the transverse elements of the frame like a bow.
Having become acquainted with the designs of flat kites, we learned that neither the length nor the width of most flat kites exceed 1 m. Why is this so? To answer this question, we need to consider two important parameters: lift and strength of the kite. It is difficult to make a flat kite with a large wingspan without significantly increasing the strength of its elements. But an increase in strength leads to an increase in the width and thickness of the structural elements of the frame, which affects the mass of the kite. It is impossible to increase the mass indefinitely; a moment comes when the lifting force is no longer sufficient for the kite to take off. Inventors tried to get around this contradiction. This is how box-shaped kites appeared, the strength of which is much higher than the strength of flat kites.
Box snakes. Kites of this group have a spatial frame, they are truly three-dimensional, and due to the frame, stability increases even more, and an increase in working planes entails an increase in lifting force. Everyone knows well such kites, named after their designers, such as the Haragrav kite and Potter's kite.
Non-rigid snakes. This is a hybrid group of kites, the main difference of which is that the shape is taken by the incoming air flow. At the same time, the design still uses separate rigid and semi-rigid frame elements.
Frameless snakes. The shape taken by the air penetrating inside the kite and the complete absence of a frame as such are the distinctive features of this group. The main advantages are complete freedom in the size and shape of the kite and low weight.
Controlled kites include kites whose flight can be controlled by the presence of two or more lines.
Double-line. Aircraft, so-called sports or aerobatic kites, are usually triangular (delta-shaped) in shape with two lines, one in each hand. Due to the lines, it is possible to control the direction of flight of this kite. In addition, due to its design, the kite is capable of maneuvering not only in two planes relative to the pilot, but also in a third plane.
Four-line. Four lines attached to two handles allow you to completely control the angle of attack of these kites. Under the control of the pilot, the kite is able to fly in any direction, rotate and stop at any point in the wind window.
Frameless. In this category of controlled kites there are kites designed for towing; they can be two- or four-line. The sail takes its shape both due to the oncoming flow and due to the frame formed by compressed air. The main purpose is to tow a person.
We have looked at the main types of kites, but there are kites that differ from them in design and materials used. Let's look at some of them.
Snakes according to the WUA principle. It is known that air-cushioned vehicles (AHVs) rise due to the pressure difference: the pressure under the bottom is always greater than at the top. And the stability of the device is created by a special device that evenly distributes the gas flow along the entire perimeter. Snakes can also fly using this principle.
The kite is a parachute. The air flow hits the slightly inclined canopy of the parachute and lifts it up. To stabilize the flight, a tail is attached to the kite parachute, and a telescopic tube is fixed in the center under the dome. It serves both as a rigid frame and as a regulator of the position of the model’s center of gravity.
Serpent-disk. The shape of such a kite gives good stability in flight. The model is very similar to two low cones folded together. The design is complemented by a keel, as well as a small weight that shifts the center of gravity down and thus increases the stability of the apparatus, and a hole in the lower part of the casing. This hole allows you to use the pressure differences that are created during strong gusts of wind.
Pinwheel snakes. The spinners, rotating under the influence of the oncoming air flow, create not only a surface that plays the same role as the plane of a box-shaped or flat kite, but also, thanks to the angle of attack, they create additional lifting force. This allows, other things being equal, to make smaller kites.
Snake helicopter. In the city it can be difficult to find a large open area where you can freely run around with a kite. A kite helicopter does not require much space for its launch, and bad weather is not a hindrance to it.
Snakes with diffusers. We decided to build and test this type of kite. The design of such a kite is very simple. The two slats are fastened crosswise in the center and tied at the edges with a strong thread. The kite is covered with windproof raincoat fabric, to which a diffuser made of the same fabric is attached (photo 1). We flew our kite at the school stadium. (photo 2). Air moving through the diffuser at an ever-increasing speed increases the speed of the kite, and what is more significant, gives it additional stability in flight (photo 3,4,5).
photo 1 
photo 2
photo 3 
photo 4 
photo 5
Conclusions
Based on my research, I came to the following conclusions:
1 The kite has a long history. They were built from different materials and given different shapes.
2 The use and use of a kite was very diverse: in military operations, rituals, everyday life, as well as for the study of physical phenomena. And of course, it was always used as a children's toy.
3 Nowadays, the kite is not used for defense purposes and its role in scientific research is not very significant, but for people interested in aeronautics, it helps to understand the basic principles of flight of all aircraft.
Therefore, we can confidently say that such a children's fun as a kite is, first of all, an example of practical aeronautics.
List of used literature
- www.kite.ru/news/kitestaff/the-kite-story.php
Ermakov A.M. The simplest aircraft models: A book for students in grades 5-8. - M.: Education, 1984. - 160 p.: ill.
Zavorotov V.A. From idea to model: A book for students in grades 4-8. - M., Prosveshchenie, 1988. - 160 pp.: ill. - (Do it yourself).
Perelman Ya.I. Entertaining physics. Book one. - M.: Nauka, 1976. - 224 pp.: ill.
prokite.ru/kites/tipyi-vozdushnyih-zmeev/
O. BULANOVA
Kites were invented in China even before historians began to write their chronicles. The Chinese began making the first kites from bamboo and plant leaves. After the invention of silk in 2600 BC. The Chinese began making kites from bamboo and silk.
Chinese manuscripts tell of kites in the shape of birds, fish, butterflies, beetles, and human figures, which were painted in the brightest colors.
The most common type of Chinese serpent was the dragon, a fantastic winged serpent. A huge dragon raised into the air was a symbol of supernatural powers.
There are many stories in Chinese folklore about kites being flown for both pleasure and business. They were most often used for military purposes. In addition, the Chinese used kites to measure the distance between their army and the walls of the enemy’s castle.
They say that the commander Han Xin, trying to rescue the emperor, launched a kite from his camp and, using the length of the rope, determined the exact distance to the wall of the besieged capital, thanks to which he was able to create a tunnel.
Also, with the help of kites, scouts and observers were lifted into the sky.
There is a legend that in 202 BC. General Huang Teng and his army were surrounded by opponents and were in danger of complete destruction. It is said that a random gust of wind blew the general's hat off his head, and then the idea came to him to create a large number of kites equipped with sound devices.
According to Chinese chronicles, the Chinese Emperor Liu Bang, besieged in his capital, launched them over the rebel camp. Supposedly invisible at night, the snakes equipped with whistles made terrible sounds, demoralizing enemy soldiers.
In the dead of night, these kites flew right over the heads of the enemy army, who, hearing mysterious howls in the sky, panicked and ran away.
However, in Southeast Asia and New Zealand, a device that can float in the air was apparently invented independently of China. It was made from palm leaves and used for fishing by hanging hooks from a thread floating above the water. In addition, it was used by peasants as a garden scarecrow.
We should not forget about the religious significance of kites: in most cultures of the Far East, a thread extending into the sky served as a symbol of connection with the gods of the air and the souls of ancestors. In Thailand, it was designed to drive away monsoon rains.
In the 7th century The kite flew to Japan. Perhaps they were brought to the country by Buddhist missionaries in ancient times, around 618-907.
In Japan, kites gained popularity; they began to give them the shape of a crane, fish, and turtle. Kites began to appear in the form of colorfully painted canvases.
In ancient Japanese drawings you can also find images of kites, which were significantly different in shape from Chinese ones.
Kites in this country served as a connecting link between man and the gods. Kites were flown in order to scare away evil forces, protect against misfortunes, and ensure a good harvest and health.
Stories about how these devices lifted “crackers,” building materials, and even people into the air are very numerous. For example, the samurai Tamemoto and his son were exiled to Hachijo Island. This Japanese Daedalus built a giant kite, on which his son managed to fly away from the island.
The plot is apparently a fairy tale, but the “Van-Van” snakes with a wingspan of 24 m and a tail length of 146 m are historically attested. Such a colossus weighing about 3 tons could easily lift a person into the air.
In India, kite fights have gained popularity; they still attract huge crowds of spectators during the Makar Sankranti holiday.
Kites became widespread in Korea. At first, their use was purely religious in nature, and then flying kites became a fascinating form of activity and spectacle.
In Malaysia, kites were also popular. A typical Malayan kite has the shape of a curvilinear, symmetrical triangle. Its frame consists of three intersecting rods, the covering is made of coarse fabric.
In Europe, of course, they also had an idea of the lifting force of the wind. Surely, Greek sailors more than once had their sails torn off and fluttered in the air, while Roman simpletons had their hat blown off by a gust and it flew up on its strings.
No special ingenuity is required to create a kite. And yet the fact remains: the only thing the West has come up with is “dragon” (the Greek word for snake).
So from about 100 AD. called a Roman cavalry banner in the shape of a modern butterfly net, only longer. The “dragon” swelled with the wind (indicating its direction to the archers), wriggled and frightened the enemy with its whistle. The flowing cylindrical tail of the weather vane, made of fabric that twisted like the body of a dragon, gave the riders self-confidence and created a menacing appearance that instilled fear in the enemy.
Weather vanes also indicated to the archers the direction and strength of the wind. But a short shaft is not a thread going up. Compared to oriental masterpieces, the idea of a “dragon” should be considered very mundane.
In general, according to European traditions, the invention of kites is attributed to the Greek mathematician Arcitas of Tarentum, who around 400 BC. designed a wooden bird based on research on bird flight. It is believed that he was inspired by the sight of a Chinese bird kite.
The ancient records about the first practical applications of kites are interesting; one of them says that in the 9th century. The Byzantines allegedly lifted a warrior on a kite, who from a height threw incendiary substances into the enemy camp.
In 906, the Kiev prince Oleg used kites during the capture of Constantinople. The chronicle says that “horses and people made of paper, armed and gilded” appeared in the air above the enemy.
And in 1066, William the Conqueror used kites for military signaling during the conquest of England. But, unfortunately, no data has been preserved about the shape of ancient European kites, their structural and flight properties.
The restless Marco Polo, who returned from China in 1295, introduced his fellow countrymen to the soaring kite. I liked the toy, but it didn’t become popular. The first (unfinished) European drawing of a “Thai cobra” type kite dates back to 1326.
In 1405, the first correct description of a kite appeared - in a treatise on military technology. And in a picture from 1618 depicting life in the Dutch city of Middelburg, we see boys flying kites of the diamond-shaped shape that is familiar to us today.
But only by the 17th century. kites became common in Europe. At the beginning of the 18th century. the hobby of kite flying was already extremely popular. Kites were used in mesmerizing spectacles and various shows, and not just as a harmless toy for children.
Thus, in Europe this item acquired neither mystical nor religious significance. But I acquired scientific knowledge, although not immediately. In 1749, Scottish meteorologist Alexander Wilson raised a thermometer to an altitude of 3,000 feet.
Three years later, Benjamin Franklin conducted a famous experiment with electricity in Philadelphia: during a thunderstorm, he flew a kite with a piece of wire attached to it. Everything immediately got wet from the rain. Result: the metal key in Franklin's hands sparkled. Having discovered the electrical nature of lightning with the help of a kite, Franklin invented the lightning rod.
Kites were used to study atmospheric electricity by the great Russian scientist Mikhail Lomonosov and the English physicist Isaac Newton.
Newton, when he was still a schoolboy, conducted several virtually unrecorded experiments regarding the most economical form of a kite.
In 1826, George Pocock patented a cart driven by a kite: it reached speeds of up to 30 km/h, and Pocock scared the peasants by driving around the outskirts of Bristol in a cart without horses.
In 1847, when they were crossing Niagara Falls, the first rope was thrown from bank to bank (250 m) using a kite.
Many other ideas arose: for example, using kites to rescue people from a sinking ship. Researchers have done many experiments related to lifting all kinds of loads, as well as people. Since 1894, kites have been systematically used to study the upper atmosphere.
The kite was significantly improved by the Australian scientist Lawrence Hargrave in the 90s. XIX century In 1893, Hargrave created a kite in the form of a box without a bottom. This was the first fundamental improvement in design since ancient times.
Hargrave's flying boxes were not only a great impetus for the development of the “snake” business, but also undoubtedly helped in the design of the first aircraft.
But soon the era of airplanes began and snakes were forgotten. Although during both world wars they were used - on submarines to improve visibility and in pilots' rescue kits to raise the radio antenna.
The kite was widely used in meteorological observatories in Germany, France and Japan. 3may rose to a very great height.
For example, at the Linderberg Observatory (Germany) they achieved a kite lift of more than 7000 m.
The first radio communication across the Atlantic Ocean was made using a box kite. The Italian engineer G. Marconi launched in 1901 on the island of New Foundlain a large kite that flew on a wire that served as a receiving antenna.
At the beginning of the 20th century. The work on the snakes was continued by the captain of the French army, Sacconey. He created an even more advanced kite design, which is one of the best to this day.
The new life of the kite began in the 50s, when Francis Rogallo invented a design without bars - the wind held it spread out in the air. It was a paraglider that blurred the line between a parachute, a hang glider and a kite.
Municipal government institution, education department of the administration of the urban district of Neftekamsk, Republic of Bashkortostan
Municipal educational budgetary institution
secondary school No. 8
urban district city of Neftekamsk
Republic of Bashkortostan
Historical research work
"Kite:
child's play or practical aeronautics?
Completed by: Vinokurov Anton 7A class
MOBU secondary school No. 8
Head: Nasipova G.U.
physics teacher.
Neftekamsk, 2014
Content
Introduction …………………………………………………………………… .3-5
History of the kite ………………………………………………. .6-8
Classification (types) of kites ………………………… …9-15
16-19
Conclusion …………………………………………………………………..20
References …………………………………………………………21
Introduction
From early childhood we know what a kite is: how to fly it and how to control it. We are accustomed to its shape and colorfulness, but have you ever wondered when and why snakes were invented? What were they used for and why do they fly? Did you know that a kite, without exaggeration, can be called the fundamental principle of all flying machines and that the aerodynamics of an airplane wing is based on the aerodynamics of a kite? The main feature of a kite is its simplicity. It is easy to make and use, but what experience does a child gain by playing with a kite! Also, interest in snakes does not decrease with a person’s age. Over the many years since the first kite appeared, they have acquired a new look, and now a new generation of kites has appeared - kites. Kitesurfing and kitesurfing have long been popular among fans of extreme sports.
Kites - this is a whole world with different facets, the world of creativity, the world of science, the world of art. Everyone knows from early childhood what it is
kite: how to fly it and how to control it. Their shape and color are amazing, but have you ever wondered when and why snakes were invented? Having studied the history of kites, we learn that kites were used in scientific research, in meteorology for studying the upper layers of the atmosphere and aerial photography, for dropping loads. Kites play an active role in aircraft modeling, signaling, namely in orienteering, entertainment and sports games.
The German company SkySails has used kites as an additional power source for cargo ships, first testing it in January 2008 on the MS BelugaSkysails. Tests on this 55-meter ship have shown that under favorable conditions, fuel consumption is reduced by 30%.
Without exaggeration, a kite can be called the fundamental principle of all flying machines.
The topic of my work is “Kite flying: children's fun or practical aeronautics?”
What is aeronautics? Aeronautics (aeronautics) is the name of the art of rising into the air with the help of known devices and moving in a certain direction.
The relevance of my chosen topic is obvious. On the one hand, this is children's fun, which requires a lot of imagination and helps broaden one's horizons. On the other hand, designing and flying kites for people who do not view this as an exciting activity makes it possible to understand the basic principles of flight of all aircraft combined. Study the laws of physics and aerodynamics, as well as their practical application.
The first mentions of kites date back to the 2nd century BC, in China (the so-called dragon kite).
For a long time, snakes did not find practical use. From the second half of the 18th century. they are beginning to be widely used in atmospheric scientific research. In 1749, A. Wilson used a kite to measure air temperature at altitude. In 1752, B. Franklin conducted an experiment in which, with the help of a kite, he discovered the electrical nature of lightning and subsequently, thanks to the results obtained, invented a lightning rod. M.V. Lomonosov conducted similar experiments and, independently of Franklin, came to the same results.
Research topic : Kite flying: child's play or practical aeronautics?
Purpose of the study : Identify the factors affecting the launch and flight of a kite.
Object of study : Model of the kite, terrain and weather conditions affecting the flight of the kite.
Subject of research : Qualitative characteristics of kite flight.
Research hypothesis : Using improvised means you can create heavier-than-air aircraft.
Tasks:
Studying the history of kites;
Consideration of types of kites;
Study of the principles of kite flight.
Research methods : work with scientific literature, Internet resources, selection of illustrative material, its design, research, conducting test flights with kite models.
History of the kite
Kites are among the oldest heavier-than-air flying machines invented by humans. It is impossible to say with certainty who and when invented the kite, and when they first took to the air. Ancient Greek sources claim that this happened in the 4th century BC, and that the honor of their invention belongs to Archytas of Tarentum. But one thing is known for certain - in the 4th century BC, kites were widespread in China. It is believed that the first Chinese kites were made of wood. They were built in the shape of fish, birds, beetles, and painted in different colors. The most common figure was that of a serpent - a dragon. This is probably where the name “kite” came from.
They quickly spread throughout East Asia. They began to be used to solve military problems. There is a legend that in 202 BC, General Huang Teng and his army were surrounded by opponents and were in danger of complete destruction. It is said that a random gust of wind blew the general's hat off his head, and then the idea came to him to create a large number of kites equipped with rattles and pipes. The enemy fled in fear from the battlefield amid howls and deafening crashes. The ancient records of the first practical applications of kites are interesting. One of them says that in the 9th century. The Byzantines allegedly lifted a warrior on a kite, who from a height threw incendiary substances into the enemy camp. Also in 559, a man flying a kite was documented in the kingdom of Northern Wei.
In Rus' in 906, Prince Oleg, during the siege of Constantinople, used a kite to intimidate the enemy. And in 1066, William the Conqueror used kites for military signaling during the conquest of England. But, unfortunately, no data has been preserved about the shape of ancient European kites, their structural and flight properties. For a long time, European scientists underestimated the importance of the kite for science. Only from the middle of the 18th century. The kite begins to be used in scientific work. In 1749, A. Wilson (England) used a kite to raise a thermometer to determine the air temperature at altitude. In 1752, physicist W. Franklin used a kite to study lightning. Having discovered the electrical nature of lightning with the help of a kite, Franklin invented the lightning rod.
Kites were used to study atmospheric electricity by the great Russian scientist M. V. Lomonosov and the English physicist I. Newton. In 1804, thanks to a kite, Sir J. Keil was able to formulate the basic laws of aerodynamics. The first manned kite flight took place in 1825. This was done by the English scientist D. Pocock, who lifted his daughter Martha on a snake to a height of several tens of meters. In 1873 A.F. Mozhaisky climbed on a kite towed by three horses. Since 1894, kites have been systematically used to study the upper atmosphere. In 1895, the first snake station was established at the Washington Weather Bureau. In 1896, at the Boston Observatory, a box kite lifting height of 2000 m was reached, and in 1900, the kite was raised there to a height of 4600 m. In 1897, work with kites began in Russia. They were conducted at the Pavlovsk Magnetic Meteorological Observatory, where in 1902 a special snake department was opened.
The kite was widely used in meteorological observatories in Germany, France and Japan. 3may rose to a very great height. For example, at the Linderberg Observatory (Germany) they achieved a kite lift of more than 7000 m. The first radio communication across the Atlantic Ocean was established using a box-shaped kite. The Italian engineer G. Marconi launched a large kite on New Founden Island in 1901, which flew on a wire that served as a receiving antenna. In 1902, successful experiments were carried out on the cruiser “Lieutenant Ilyin” to lift an observer to a height of up to 300 meters using a train of kites. In this case, box-shaped snakes were used, the designs of which were developed by L. Hargrave in 1892. In 1905-1910, the Russian army was armed with a kite of an original design created by Sergei Ulyanin. Entire platoons of snake nauts were part of both ground and naval units, including the Black Sea Fleet. During the First World War, troops of various countries and especially Germany used tethered balloons for observation posts, the lifting height of which, depending on the battle conditions, reached 2000 m. They made it possible to observe the enemy’s position deep in the front and direct artillery fire through telephone communications. When the wind became too strong, box kites were used instead of balloons. Depending on the strength of the wind, a train was made up of 5-10 large box-shaped kites, which were attached to a cable at a certain distance from each other on long wires. A basket for an observer was tied to the cable. In a strong but fairly uniform wind, the observer rose in a basket to a height of up to 800 m. This method of observation had the advantage that it made it possible to get closer to the enemy’s advanced positions. Kites were not as easily shot as hot air balloons, which were a very large target. In addition, the failure of an individual kite affected the observer's ascent height, but did not cause him to fall.
During the First World War, kites were also used to protect important military installations from attack by enemy aircraft by constructing barriers consisting of small tethered balloons and kites that rose to a height of 3000 m. Wire ropes were lowered from the balloons and kites, which were created for the aircraft the enemy is in great danger.
Nowadays, building a kite is an exciting activity; creating and flying them has not lost and will not lose its importance. The theoretical thought of inventors in many countries gives rise to more and more new designs of kites: flat and box-shaped. Inflatable and rotary. Among the kites you will meet, no two are alike - they all differ from each other in appearance, flight performance or manufacturing technology.
Classification of kites
The classification of kites is not precisely defined. Kites can be big or not very big. There is a very wide variety of kite shapes. Ancient snakes were made using wooden frames and sheets of silk or paper stretched over them. Almost all modern kites are made from carbon fiber plastics and synthetic fabrics.
Flat kites are divided into two types according to their aerodynamic design:
Flat - flat kites. The oldest form of kite flying. And the simplest one. They are figuratively a flat plate of a rectangular or any other shape (star, triangle in the form of a projection of a bird, etc.), to which a handrail is tied using a bridle.
Bowed is a category of kites that look very similar to flat kites from the ground. However, this type of kite is a further development of flat kites in terms of stability. To give stability, these snakes have a bend or kink in the longitudinal axis, which, as it were, lifts the ends of the wing and creates a v-shaped wing. This solution provides a significant margin of stability. William Eddy patented this kite design in 1900.
In shape: flat snakes in plan can be made in all sorts of shapes, from square to the artist’s imagination. Let's consider the main ones:
The rectangular kite is the most common textbook example of a kite, but it is not very stable compared to its larger cousins. The snake has three strips: two of them serve as diagonals (“cross”), and the third is at the top and fastens the diagonals. A strong thread is pulled along the contour of the future kite, connecting all the corners, and a cover made of paper or fabric is glued on. The kite must be equipped with a long and fairly heavy tail to give it stability in flight. Snakes of a similar design were common in Japan; images of dragons were applied to the rectangular canvas.
Diamond (bowed diamond) –diamond-shapedsnake. The frame is made in the form of intersecting slats. Belongs to the bowed category. There are many schemes for making a kite concave, such as using a central cross where the cross-staffs run at an angle, or stringing a bowstring on a cross-staff, which gives the cross-staff a bow-like bend. With a large v-shape, such a kite does not need a tail, however, with a significant increase in the v-shape, the kite loses lifting force. The bridle is most often tied to the longitudinal rail in two places.
Delta (delta, bowed delta) is a snake, in plan resembling a delta wing. The frame is somewhat more complicated, since it requires at least three slats, which are rigidly fixed in the form of a triangle (two cantilever and one transverse). The peculiarity of the design is that during flight, wind pressure bends the cantilever slats and the kite takes on a v-shape. The domed structure of the cladding also gives additional stability. Moreover, the stronger the wind blows, the more stable the kite behaves. Models of sports controlled kites received this form. The ability to control is achieved using a two-layer scheme. The pilot holds both rails in his hands. By changing the tension of the rails, controlled flight is achieved.
Rokkaku - This hexagonal Japanese snake (hence its name) is native to the central Japanese region of Niigata on the coast of the Sea of Japan. It has a central rail and two transverse ones. The transverse slats are given a curved shape (bowed shape), due to this, rokkaku type snakes are very stable even without tails. This is a very common form of kite as it is easy to make.
Bermuda (Bermuda) - a kite is usually hexagonal in shape, but can have the shape of an octagon and even a more multifaceted figure. The design consists of several flat slats intersecting in the center. A bowstring is stretched along the perimeter of the slats, imparting rigidity to the structure. The sail is already stretched between the slats and the bowstring. Very often, each side of the kite is made of different colors to obtain a more variegated color. Requires a long tail. The snake shares the same name with the island where they were traditionally flown on Easter as a symbol of the ascension of Christ.
Box kites
Box snakes appeared as a result of the development of flat snakes. People have noticed that vertical surfaces greatly affect the stability of a kite's flight. This is how the first box-shaped kite appeared. Box snakes generally do not require a tail.
The rhombic kite is the simplest box-shaped kite, it is not complicated in design, is stable in flight and is easy to launch. It is based on four
longitudinal slats (spars). Two crosses are inserted between them, each of which consists of two spacer slats. The kite cover is made of two strips of paper or synthetic fabric. This creates two boxes - front and back. This kite design was invented by Australian explorer Lawrence Hargrave in 1893 while trying to build a manned aircraft.
Potter's is a box-shaped kite that has special flaps to increase lifting force. It consists of four longitudinal slats (spars) and four paired transverse slats-crosses, two boxes and two flaps.
Frameless kites
Frameless snakes are snakes that do not have hard parts. It takes the form of a snake by inflating due to the oncoming air flow. Hence the two advantages of these kites - the probability of breakage when dropped is zero and compactness during transportation. The second advantage allows you to make kites of very large sizes.
Sled (sleigh) is a kite with a non-rigid frame. In flight, its shell maintains its shape due to the wind, as if inflated. Only two longitudinal slats are used, sewn into the shell, which are not connected to each other. These slats maintain the shape of the shell and prevent it from crumpling. This type of kite behaves quite capriciously in gusty winds. For stable flight, a kite requires a long tail. The advantages of such a kite include ease of manufacture and compactness during transportation, since it can be rolled into a tube without the need for assembly and disassembly.
Sled foil is a further development of the kite of the previous model. There are no rigid elements in this design at all. The rigidity of the dome is given by cylinders inflated by the oncoming air flow. The pressure created in the cylinders tapering towards the rear edge of the kite is quite enough to keep the canopy straightened in flight. However, a kite of this design also has disadvantages, for example, the dome can easily crumple when the wind subsides and this will lead to the kite falling, even if the wind rises again, the dome can no longer straighten out on its own. It also has certain starting difficulties. But the undeniable advantage of the fact that snakes cannot be broken allowed this design to continue its development.
Super Sled foil is another development of the “sled”. Three inflatable sections make this kite more resistant to collapse. It also allows you to make this kite of considerable size and obtain significant traction. Can be used to lift objects, including a camera.
FlowForm is a very common kite design as it is one of the most stable frameless single line kites. With proper training, in a steady wind it can fly without a tail. However, in strong and gusty winds, the use of the tail is still recommended. They can be made in truly gigantic sizes; an area of 3 sq.m is considered the most common. They are also manufactured with a large number of sections, six, eight and even more.
The Nasa Para Wing kite is the result of research by the US National Space Agency, which brought to light quite interesting single-layer frameless kites. Developments were carried out in search of optimal systems for launching spacecraft. As a “by-product”, a kite is built by people all over the world. A number of original solutions make this model easy to manufacture. Some models are controllable. Despite many advantages (low material consumption, high thrust, etc.), these kites have a significant drawback - relatively low aerodynamic quality, which, however, is steadily increasing due to further improvement of the kite design.
Parafoil is a special subclass of frameless kites. This type of kite is made of airtight fabric with closed internal spaces and an air intake facing the oncoming flow. Air, penetrating into the air intake hole, creates excess pressure inside the enclosed space of the kite and inflates the kite like a balloon. However, the design of the kite is such that when inflated, the kite takes on a certain aerodynamic shape, which is capable of creating the lifting force of the kite. There are many types of kites - parafoils: single-line, double-line controlled, four-line controlled. Double-line kites are mainly aerobatic kites, or kites with an area of up to 3 sq.m. Four-line kites are kites with a fairly large area from 4 sq.m., used in sports as a motive force (kiteing). Single-line snakes are for entertainment, come in a variety of designs and shapes, and can even depict all sorts of objects and animals.
Inflatable - another interesting model is an attempt to combine the advantages of parafoils and frame models. There is also a shell, but now it is inflated not by the wind, but by means of a pump on the ground (like rubber rings). The kite also does not have a frame, but due to the excess pressure inside the shell, it already has a flying shape on the ground. Again, by analogy with an inflatable ring - the kite does not sink in the water when it falls, for this reason it is used in kiting when riding on the water surface.
Why do kites fly?
The ability of kites to stay in the air and lift loads is due to the fact that they have lifting force. Let us give the following experience. If you stick your hand out of the window of a moving bus or carriage with a plate (a piece of cardboard or plywood), placing it vertically, you will feel that your hand is being carried back with some force. This force arises because a stream of air flows onto the plate and exerts pressure on it. This pressure will be greater if the size of the plate or the speed of movement is increased; At high speed, this force can be so great that sticking your hand out will be dangerous. The force of pressure on the counterflow plate can be reduced many times if the plate is placed with its edge facing the air flow. If the plate is placed at a slight angle, the hand will begin to tilt not only back, but also upward. The angle relative to the air flow is called the angle of attack (usually denoted α - alpha). Snakes fly at an average angle of attack of 10-20°.
So why does a kite fly?
There are four forces acting on a kite: drag, lift, gravity and lift. A B α F 2 F 3 F 1 (see figure).
In a simplified drawing, line AB represents a cross-section of a flat kite. Let's assume that our imaginary kite flies from right to left at an angle α - alpha to the horizon or the oncoming wind flow. Let's consider what forces act on a kite in flight.
A dense mass of air impedes the movement of the kite during takeoff, in other words, it exerts some pressure on it, let's denote it F1. Now let's construct a so-called parallelogram of forces and decompose the force F1 into two components - F2 and F3. The force F2 pushes the kite away from us, which means that as it rises it reduces its initial horizontal speed. Therefore, it is a resistance force. The other force (F3) carries the kite upward, so let’s call it lifting. We have determined that there are two forces acting on the kite: the drag force F2 and the lift force F3.
By lifting the kite into the air (towing it by the rail), we artificially increase the force of pressure on the surface of the kite, that is, the force F1. And the faster we run, the more this force increases. But the force F1, as we have determined, is decomposed into two components: F2 and F3. The weight of the kite is constant, but the action of force F2 is prevented by the handrail, the lifting force increases - the kite takes off.
Wind speed increases with height, which is why when launching a kite, they try to raise it to such a height where the wind could support the model at one point. In flight, the kite is always at a certain angle to the direction of the wind.
The drag force is created by the movement of air that flows around the kite.
Lift is the portion of drag that turns into upward force.
The force of attraction is due to the weight of the kite and is applied at a point called the center of gravity.
The driving force is imparted to the kite by a lifeline that acts as a motor. The kite will fly if the lines of action of all these forces intersect at the center of gravity. Otherwise, the kite's flight will be unstable. To meet these requirements, the surface of the kite must be inclined to the wind at the correct angle. The longitudinal stability of the kite is ensured by the tail or the shape of the aerodynamic surface, the transverse stability is ensured by the keel planes installed parallel to the rail, or by the curvature and symmetry of the aerodynamic surface. When making kites, these factors should not be forgotten. The stability of a kite's flight also depends on the position of the kite's center of gravity. The tail shifts the kite's center of gravity down and slows down the kite's oscillations if the wind is gusty or uneven.
Let's calculate the lifting force of a kite using the formula:
Fh=K*S*V*N*cos(a),Where
K=0.096 (coefficient),
S - load-bearing surface (m2),
V - wind speed (m/s),
N - normal pressure coefficient (see table)
Wind speed, V, m/s 1 2 4 6 7 8 9 10 12 15
Normal pressure coefficient N, kg/m2
0,14 0,54 2,17 4,87 6,64 8,67 10,97 13,54 19,5 30,47
a is the angle of inclination.
Example.
Initial data:
S=0.5 m2;
V=6 m/s,
a=45°.
N=4.87 kg/m2. (see table)
Substituting the values into the formula, we get:
Fз=0.096*0.5*6*4.87*0.707=1 kg.
The calculation showed that this kite will rise upward only if its weight does not exceed 1 kg. We calculated the lifting force in the old system of units (kg*s, kilogram-force), and not in the SI system (N, Newton). The fact is that in everyday life it is easier for us to evaluate force in kilograms rather than in newtons, i.e. we know how much effort we need to put in to lift a bag of 5 kg of potatoes. The same is true with kites. To be fair, let’s translate the kilogram-force into the SI system: 1 kg*s = 9.81 N. But not everything is as simple as it looks from the outside. It is very difficult to know the wind speed, even if you fly a kite while holding an anemometer in your hands, the results will not be true. Wind speed changes with height. And the angle of inclination changes slightly during the flight. Only practice will help you fly a kite.
Thus, having considered the basic principles of kite flight, we can safely say that a kite, which is simpler to design and control, is the prototype of more complex aircraft.
Many designers who were previously interested in making kites switched to working on airplanes. But their experience in building kites did not pass without a trace. It certainly played a role in aviation history during the first stage of aircraft development.
CONCLUSION
Having considered the history of the kite, having studied the main types and design, and conducting a comparative analysis, I came to the following conclusion.
Nowadays, kite flying, being a child's play, requires a lot of imagination and helps broaden one's horizons. In the process of choosing the type and shape of the kite, design inclinations develop, the designer has the opportunity for artistic expression in the process of inventing emblems and other decorative elements, so the flight of a kite is always an exciting spectacle.
For others it is an exciting sport. Clubs and communities are being created all over the world, uniting kite lovers - both designers and those simply flying them. One of the famous ones is KONE - the Kite Club of New England, part of the Kite Flying Association of America. Some people consider kite flying as a good tradition, for example in Japan.
Abroad, kites are extremely popular among children and youth. They are especially popular in Cuba, Fr. Bali. You can often see how children, even while on the beach, do not part with their favorite pastime - kites of the most varied designs and the brightest colors soar in the air above the sea. Nowadays, the construction of kites can have neither defense nor scientific significance. Since with the development of aviation their role in these areas has decreased.
Designing and flying kites for people who do not view it as entertainment helps to understand the basic principles of flight of all aircraft combined. Kite making has become one of the sections of initial aviation training for schoolchildren, and kites have become full-fledged aircraft along with models of airplanes and gliders, as they allow one to study the laws of physics, aerodynamics and their practical application.
This approach to kites is the initial step for children who plan to connect their lives in the future with the design or operation of aircraft. Without knowledge of calculations, without taking into account the features of the lower layers of the atmosphere, wind direction, etc. do not fly either a kite or a model glider or airplane
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