A high angle of attack will enable the kite to "catch" more of the wind in light wind conditions, whereas a low angle of attack will allow more wind to be "spilt" by the kite in strong winds. The cover of the kite is called the sail. The sail is pushed against the spine and the cross-spar, dividing the sail into four areas. The two small areas at the top of the kite are called pilot sails , while the two larger segments are known as driving sails.
The pilot sails partly control the direction in which the kite moves and the driving sails provide most of the lift. The tail of a kite refers to the strips of paper, plastic or fabric which are attached to the bottom of the kite in order to increase the drag of the kite. Tails can be made in a number of different ways, and can also be added to the wingtips of kites.
Kites can be bowed , or bent, in order to give the cross-spar a dihedral angle. When this happens the cross-spar is bent so that the wingtips are at a slight backwards angle to the spine. This helps make the kite stable. If the kite starts to roll to one side the wing on that side presents a greater surface area to the wind and the wing on the opposite side appears to reduce in surface area.
The greater pressure being exerted on the wing with more surface area being exposed to the wind forces it to return to a normal attitude again. Flat kites include all kites that are not bowed in some way. They don't have to be any particular shape, as long as they are flat, or planar. All flat kites need tails in order to fly. Bowed kites are those kites that have a dihedral angle.
Because they are bowed they do not need tails. Parafoils are special sort of kites which are shaped very much like an aeroplane wing. They rely on the wind to hold them open as they generally have no spars. These kites normally do not need tails. Box kites are also called cellular kites. They have many surfaces, some of which normally lie vertically, while others lie horizontally. Because of these surfaces, which act in a similar way to the dihedral angle on bowed kites, this sort of kite does not need a tail.
They are normally a strong wind kite. Compound box kites are basically box kites with wings attached to them. They fly in lighter winds than normal box kites and can pull much harder because of the increased surface area being presented to the wind.
Delta wings are the best kites for very light winds. They tend to be pushed up and forward so that they lie nearly parallel to the wind. Because of this they have a very low angle of attack. Consequently they don't pull very hard at all. The sail forms a billow, and this, combined with a keel in place of a bridle, allows deltas to fly without a tail.
This kite was named the delta because it looked like the letter "delta" in the Greek alphabet, which corresponds to our letter "d". The sled is similar to the parafoil in that it relies on the wind to hold it open. It has several spines running the length of the kite, but no cross-spars.
Sleds often have vents cut in the sail, near the bottom of the kite, instead of using a tail. They pull very hard and fly with a high angle of attack. Never fly a kite in a thunderstorm or while it is raining. The kite, or the flying line, might be hit by lightning. Never fly a kite with wire, or anything that could conduct electricity through the flying line to you, and don't use a wet flying line.
Never fly a kite near power lines, antennae or transmission towers. If your kite does get caught in power lines, do not attempt to retrieve it. Call the S. Never fly a kite above crowds, near public streets, highways, airports or helicopter pads, or other areas where your kite might be a hazard to other people. In Australia kites are legally allowed to be flown up to three hundred feet above ground level, and may not be flown within five kilometers of an airport. Don't climb trees, buildings or power poles to retrieve your kite.
Ask for help from an adult, or make another kite. But the wind can blow the kite up into the air because the kite is at a slight angle to the wind. When the kite is flying there are three forces in action. There is the force from the kite string, the force of the wind and the force of gravity. The kite rises into the air because the wind pushes it upwards more than the kite string and gravity pull it down. When the kite is nearly perpendicular to the wind, the wind pushes it strongly because there is a large area to push.
When the kite is nearly parallel to the wind, the wind pushes it weakly because there is less of an exposed area. You can feel this yourself when you walk against the wind with the kite. It is easiest if you turn the kite with its side towards the wind. As the kite climbs it lies more and more with its side towards the wind. At the exact point where the pushing force of the wind becomes the same as the kite string and gravity, the kite stops climbing.
A kite flies because the wind pushes it The wind exerts a force on the kite. What is happening? The force of the wind pushes the kite upwards and backwards. See the great bow in the line. That's largely due to the weight of the line, making it hang down like a chain between two posts. Air resistance also plays a part in bowing the line. For a given length of line, the more bow, the less height the kite can achieve. Most of my 1-Skewer kites have a lot of bow in the 20 pound Dacron line by the time I let all 60 meters feet out!
In contrast, very large and heavy-pulling show kites have their line strength more closely matched to the pull of the kite. Hence there is usually very little sag in the line. But if you look straight along the line, you'll see what little sag there is. You have probably noticed that your kite doesn't always fly at the same height, even when flown on exactly the same length of line. This is because every kite has it's own optimal wind strength.
If the wind is weaker than this optimal wind strength, then the weight of the kite is a bigger factor in the overall balance of those four forces, and the result is a lower line angle.
To put it another way, the Lift force is still greater than the Weight force, but not by as much, so the kite cannot rise as high.
I've had some delightful kite flights where the kite barely hangs in the air, flying in well below its optimum wind speed! This often happens near sunset. If the wind is stronger than the optimum wind strength, then the Drag force is the factor which forces the line angle back down.
Lift increases too, but not as much as the Drag! I remember a great illustration of this on a windy day at a kite festival. A huge stack of Taiwanese traditional kites was still airborne, but blown down to less than a 45 degree angle by the strength of the wind.
Normally, these stacks reach much higher line angles. More recently, at the Royal Adelaide Show , a giant orange Octopus kite was aloft in a very stiff breeze. The wind was so strong that the kite was blown down to only a 30 degree line angle at times! There's another implication of the weight of the flying line.
How does a kite fly much higher when there are hundreds of meters of line hanging below it. If you continue to let out line, there comes a point where it weighs so much that the kite cannot lift it any higher — not even at the optimum wind strength.
The only way to make the kite fly higher, all other things being equal, is to use a lighter line! With my own MBK kites, this effect is only seen with the tiny 1-Skewer kites. Those 2-Skewer and Dowel kites pop right up to the meter feet legal limit, as it is here in Australia. The only thing preventing them going even higher is my law abiding nature.
Thermals are regions of rising air, which form due to temperature differences on the ground. A giant bubble of air which is just slightly warmer than the surrounding air is less dense. Therefore, it has a tendency to rise. It won't rise indefinitely, but a more complete discussion of thermals is beyond the scope of this page ;-.
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