How do kites work
Gravity pulls everything towards the centre of the earth. Anything on the ground can't get pulled down any further than that, but things in the air can get pulled down to ground level.
The heavier a kite is the harder it will be to fly. Kites are generally made from lightweight materials so that they will fly easily. If gravity is a force that pulls everything towards the centre of the earth, why don't kites get pulled down to earth? The force that stops a kite from falling down is called lift.
Lift is the force pushing the kite away from the surface of the earth. It is produced by air moving over the top of the kite at a faster speed than the air that is moving over the bottom of the kite. Daniel Bernoulli, a scientist in the eighteenth century, discovered that the pressure of air becomes lower when it is moving.
The faster the air is moving the lower the pressure becomes. A kite is shaped so that air will be slowed down if it is travelling under the lower surface of a kite and will speed up if it is travelling over the upper surface of the kite.
The faster the air moves over the upper surface of the kite the lower the pressure of that air becomes. As the air pressure above the kite becomes lower, the air pressure below the kite pushes the kite up in order to equalize the pressures above and below the wing.
The greater the difference between the low pressure above the wing and the higher pressure below the wing, the greater is the amount of lift produced. In order for all this to happen, air needs to be moving over the kite. So what makes the air flow over the kite?
When we fly kites we use a string to hold on to the kite, and to prevent it from being blown away by the wind.
Birds move through the air by flapping their wings, while powered aircraft use an engine to push the air towards the back of the plane fast enough to make the aeroplane move forward. The force that makes something move forward through the air is called thrust. Birds use muscle power to develop thrust, and except for gliders, aeroplanes use motors. A kite cannot produce its own thrust, and instead must rely on being held in place while the wind moves past it.
So the thrust that acts on a kite is produced because the kite is being held in one place by its string while the wind flows around the kite.
If there was no wind a kite would only fly if the person holding the kite string started running, making their own wind as air started flowing around the kite. What stops a kite from flying straight over your head and into the ground on the other side?
As the air flows over the surfaces of a kite the wind gets held back a little bit by the roughness of the fabric and the sticks. This friction is called drag. Any kite will always have some drag, and some kites are not able to fly without some extra drag being exerted on them. This additional drag is usually created by the tail of the kite, and allows us to make the kite point in the correct direction.
Air flowing through the tail pulls the bottom of the kite in the direction that the wind is blowing. If more drag is caused by the tail than by the rest of the kite then the kite will always point into the wind. A single, long tail causes a certain amount of drag, but the same tail, cut into several lengths will produce much more drag, because the air is slowed down even more when it has to pass around several strips rather than just one.
When the top of a kite turns to one side, the bottom of the kite pivots in the opposite direction. The drag caused by the tail tries to pull the bottom of the kite back to the centre again. The drag caused by the tail of a kite stops the kite from turning too much to one side or the other.
A tail gives a kite lateral stability. If a kite has too little tail it will not be laterally stable, and will move around a lot, and might even start spinning. If the kite has too much tail the kite will be stable, but may be hard to keep flying because of the extra weight caused by the excess tail. A spar is the name for any of the sticks which act as the "skeleton" of the kite.
The spine is the spar that runs from the top to the bottom of the kite. The cross-spar is the spar that runs from wingtip to wingtip. The leading edges of the kite are the edges which the wind flows over first. The trailing edges are the edges which the wind flows around last.
The bridle is the line that connects the kite with the flying line. It is usually connected to the kite in two places, but some kites use bridles that are attached to the kite in many places. The point where the flying line attaches to the bridle is called the bridling point. Each piece of the bridle running from the bridling point to the surface of the kite is called a leg. The force of the wind pushes the kite upwards and backwards. The force of the kite string pushes the kite forwards and downwards.
The force of gravity pulls the kite straight down to the ground. The kite stands still in the air when: The wind pushes the kite backwards as much as the kite string pushes it forwards The wind pushes the kite up as much as gravity and the kite string pull it down. When the kite stops still in the air, it is said to be in equilibrium. How does the kite rise into the air?
Why does the kite stop rising in the air? How is a volcano formed? Read more. The universe. Take a trip through our universe. How does a Segway work? Moving the tow point up or down on the bridle can change the flight angle at which the kite faces the oncoming wind, allowing the kite to fly in a wide variety of winds.
Particularly evident with maneuverable kites dual-line, quad-line, fighter, or power kites , the wind window is an important aspect of kite flying — the angle of wind on your kite changes as you fly around the wind window, decreasing or increasing the power and control depending on a number of other factors such as the weight of your kite or lines. Images below by reeddesign.
Wind Window Particularly evident with maneuverable kites dual-line, quad-line, fighter, or power kites , the wind window is an important aspect of kite flying — the angle of wind on your kite changes as you fly around the wind window, decreasing or increasing the power and control depending on a number of other factors such as the weight of your kite or lines.
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