An excellent way for students to gain a feel for aerodynamic forces is to fly a kite.
History of Kites
Kites have been around for thousands of years and they are a part of many different cultures around the world. There is a lot of information available on the web concerning the history of kites, so we will not duplicate that information here. We suggest that you use your favorite search engine to find this information. (Search on the phrase "History of Kites"). From an aerodynamics point of view, two of the most important users of kites were the Wright brothers. In 1899, as they were developing their theories for the control of an aircraft by using wing warping, they built a small maneuverable kite to verify their ideas. Between 1900 and 1903 they would often fly their gliders as unmanned kites at Kitty Hawk, North Carolina. These experiments led directly to their successful 1903 aircraft.
Types of Kites
A wide variety of kite kits and kite accessories are available at department, hobby, and toy stores. You can even design and build your own kites. This slide shows some of the more popular types of kites. (The names for the various kites are not standardized - what I call a diamond kite may be called a two-stick kite at another site, and my "Delta" kite may be called a "bat" somewhere else.) Once again, there is a lot of information available on the web concerning kite design and purchase. (Search on the phrase "Kite Design" with your search engine).
Forces on a Kite
Each of the kites on this slide looks different than another kite, but the forces acting on all the kites is exactly the same. In fact, with the exception of thrust, the forces acting on a kite are also the same forces which act on an airliner or a fighter plane. Like an aircraft, kites are heavier than air and rely on aerodynamic forces to fly. Gas balloons and bubbles, on the other hand, are lighter than air and rely on buoyancy forces to fly. Like an aircraft, kites have a solid frame normally made of wood or plastic, and this frame is covered by a paper, plastic, or cloth "skin" to generate the lift necessary to overcome the kite's weight. A kite must be made as light as possible for good performance, yet be strong enough to withstand high winds. Determining the forces on a kite can be difficult, so we have prepared a kite simulator to let you study these forces. You can use KiteModeler to design your own kites. You can then build a kite based on your design and compare the results with the computer program.
Flying
While the forces on all kites are the same, each kite flies a little differently. Some kites are highly maneuverable and some kites are very stable. There are kites with multiple control lines that can perform stunts, while other kites can be flown to high altitudes. We can use math techniques that you learn in school to determine the altitude of a kite graphically. With a little more knowledge of mathematics, you can actually calculate the altitude at which the kite is flying.
Regardless of the type of kite, the flyer must always fly safely for the protection of others, to protect property, and to insure that the kite can be flown again.
Have Fun!
Forces on a Kite
Kite Flying
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byTom
Benson
Please send suggestions/corrections to: benson@grc.nasa.gov