Saturday, June 19, 2010

one dollar flight

I bought five of these Chinese-made kites at the dollar store.

I was attracted to the design, which is similar to the Indian fighter kite or the Nagasaki Hata. The kite is made from very light-weight materials, including small-diameter plastic spars.

Everything needed came in the package, including the winder, the kite string, a plastic ribbon tail, and a nice little clip for attaching the line easily to the kite bridle. This type of kite needs no bow string; the pressure of the wind on the surface forms the airfoil.

A lot of cheap kites look good, but are poorly made and unflyable. This one was designed and produced by people who understand kites and how they must be made to fly properly. A well-balanced fighter kite is very maneuverable. Letting out a bit of string allows the kite surface to flatten, and the kite begins to oscillate back and forth. When the nose is pointed in the desired direction, a strong pull on the line bows the horizontal spar, forms the kite surface into a lifting shape, and the kite moves briskly in the direction it is pointing.

I also picked up the Mini Copter and the four-inch Spiderman kite, which flew better than I expected.

One of the neat things about kites is that they demonstrate the capacity of humans for intuitively deducing very complex laws of physics. Kites were invented thousands of years ago, probably in China. While the disciplines of mathematics and physics were little developed then, the kite makers nevertheless were able to solve some extremely complex design problems, and to achieve a working understanding of the principles of flight. Because of the flexibility of kites which responds to variable wind pressure, their flight resembles that of birds more than it does modern fixed-wing aircraft.

To get an idea of the variables and the formal calculations required for the design of a kite, take a look at the on line Kite Modeler program posted on the web site of the National Aeronautics and Space Administration.

Some useful thoughts about inductive reasoning can be found in a posting at Slashdot.

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