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Kites | |
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Where did kites originate (begin)? There are are differing claims. Some say China, others say South Pacific Islanders, even the Balinese have their own story! Nevertheless we are left with a heritage of wonderful stories, designs and techniques for flying kites. Kites have been used for many purposes:
Later kites were used for scientific purposes and maybe just for fun too! Benjamin Franklin flew kites for the fun of it. Later, in 1752, he used a kite for his now famous experiment to find out if there was an electrical charge in clouds. Kites are used by meteorologists (weathermen) to lift measuring instruments into the air. In 1750 Dr. Alexander Wilson of Edinburgh put a thermometer on a kite and sent the kite up to test air temperatures at different altitudes. Later, wind speeds at different altitudes were measured too. We do the same thing today using weather balloons! Dr. Alexander Graham Bell, Otto Lilienthal, Octave Chanute and the Wright Brothers all used kites to learn more about the possibility of people flying. A special kite using the "tetrahedral cell" was developed by Dr. Bell which enabled people to be carried into the air on a kite. Other people used kites to put on special shows. Samuel Cody (Buffalo Bill) became known for his "Wild West Shows" in England. There, Samuel and his son Leon developed larger and larger kites. They competed against each other by using kites to tow boats across the English Channel! They went on to help the French and Russians develop observation kite systems for war time. These same designs are used today for kite festivals and competitions. HOW DO KITES FLY? Let's explore the aerodynamics of kites. Kites are heavier than-air-devices. They weigh more than the volume of air they displace. They are flown at the end of a string, line or rope. Kites are aerodynes. In other words, they overcome the force of gravity and are kept in the air by the force of the wind or the forces of wind pressure on the kite. This force is called lift. Lift is exerted in an upward direction thereby opposing the pull of gravity on the kite. There are two principles involved in the aerodynamics of kite flight. First, the kite exerts a downward force upon the air. The air passes over the top edge of the kite and goes down the upper surface of the kite. As the kite pushes downward, it gets an equal push upward by the air. As this happens, the kite gets an upward counter force and it flies! Newton's law states that for every action there is an equal and opposite reaction. The second principle comes from a Swiss mathematician named Bernoulli. Bernoulli stated that as air passes above a surface (such as a wing or a kite) the air on top moves a longer distance. The air moves faster and reduces the pressure . The air below the surface moves more slowly and the pressure is increased. It is the change in relative pressures above and below the kite surface that allows the kite to lift. For a kite to fly, lift must be greater than the weight of the kite. Knowing the basic principles can help us learn how to fly a kite and how to design a kite. Also, knowing the strength of the wind and wind direction are useful in developing a knowledge of the basic moves and tricks in kite flying. There are many different kinds of kites. They are designed for various purposes and therefore must include the proper "angle of attack" and "flying angle" in relation to the wind. Angle of attack is the angle by which the kite is inclined in relation to the direction of the air moving toward it. This angle can be altered both by the design and by the angle the kite is presented to the wind, such as by string or cord control. If the string is anchored to the ground, the higher the kite rises the less the angle of attack. The flying angle of a kite can also be changed by making adjustments to things attached to the kite, such as the "bridle" or the tail. All these adjustments will add or subtract to the ability of the kite to maintain angle of attack, balance and stability. Because, in reality, kites do not have perfect balance and stability. Therefore, we need to consider some of the ways to add those qualities. A kite does pitch forward, backward and side to side. It does stall and dive. All these qualities make kites fun and a thrill to fly but it is also a challenge to design the kite so it will fly the way it is intended. The tail of a kite adds to its stability and balance. It also acts as a drag and for some kites will put a limit on the maximum altitude that can be reached by a particular kite. In designing kites one must consider the pros and cons to each element of design. For example, one can eliminate the tail, but bow out (curve) the design for stability and thus achieve greater altitude. Other ways to achieve stability may be in the cover material, the sticks or frames, addition of wings or keels or using shaped wing surfaces. Rudders, airfoil-shaped surfaces and tapering are some other design possibilities. HOW DO YOU CONSTRUCT A KITE?
When you get ready to launch your kite, make sure you are in an area that is open and free from trees, electrical and telephone lines buildings and automobile traffic. Stand with your back to the wind. Hold the kite with one hand and the reel of string with the other. Let the wind lift the kite and as it does, feed out the line to the height you wish. Walk in the direction of the wind as you feed out the line. If the kite won't climb you can reduce the bridle angle. To land the kite, walk toward it winding the line on the reel as you walk. More expertise (skill) with kites can lead to investigations of stunt or novelty kites. Another challenge is sending climbers up the kite string or dropping small parachutes, balloons, confetti or messages from kites. Kites can also carry balloons, banners, and other decorations. Attach a camera to a kite and with time shutter release, take a picture. Fly kites in tandem (hooked to each other) or like the people of the Solomon Islands, try fishing with a kite. The possibilities are endless. Visit the kite festivals in your area. Join a kite club or start one in your school or community. There are a wide variety of kite society and associations and some of them are on the internet. You can learn everything from kite safety to the basics to first aid for your kite to some of the more technical skills for flying fighter and stunt kites. Because there is no one right way to design or fly a kite, a success in kite flying is possible for everyone. Even Charlie Brown can fly a kite. Trial and error. After all, isn't that the way great inventors did it? They kept working and experimenting until they learned what worked. They learned from failure. That is the essence of invention and progress. What a great lesson for all of us to learn. Now, go fly a kite!
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