How long has it been since you looked up into a breezy springtime sky and watched a brightly colored kite skating along in front of some puffy white clouds? Have you ever considered the reasons that kites are able to fly?
It may surprise you, but kites are governed by exactly the same set of aerodynamic principles that allows airplanes to fly. In short, the lift imparted by the action of the wind on the kite’s skin must be greater than the weight of the materials the kite is made of. While kites don’t typically feature the classic airfoil shape of an airplane’s wing, the force of wind acting on the kite’s skin does produce greater pressure on the lower surface of the kite than on the upper surface, resulting in a net upward force on the kite, so it flies upward in the air.
The primary influences on a kite’s lift and ability to fly are the angle of attack—that is, the angle at which the line holds the body of the kite relative to the direction of the wind, and the velocity of the wind. I’m sure you’ve seen the effects of both of these. You change the angle of attack by moving the line up or down where it’s attached to the kite. Get it just right, and the kite flies proudly. Get it wrong, and the kite only flutters or won’t fly at all. You can increase the relative wind velocity by running into the wind with your kite, or by pulling on the line; both increase relative wind velocity and lift. Move with the wind or slacken the line, relative velocity declines, and the kite will lose lift and altitude.
The Wright brothers even used kites in their early experiments when designing their first airplane. An excellent website to learn more about kite aerodynamics is www.grc.nasa.gov/WWW/K-12/airplane/kite1.html.
(And don’t forget: Join the Santa Maria Valley Discovery Museum and Santa Maria’s Parks and Recreation Department at Rotary Centennial Park on April 17 to watch amazing kite flying, participate in kite games, and fly your own kite as a family.)
Roy Reed is a board member with the Santa Maria Valley Discovery Museum at 705 S. McClelland in Santa Maria. Discovery Corner is a weekly column in the Sun, highlighting events, science activities, and more. Send comments to discoverycorner@santamariasun.com.
This article appears in Apr 14-21, 2011.