Kite Science

By Amy Cowen on March 31, 2010 11:01 PM

Kites are a great way to explore science at high—and low— altitudes!

A casual walk down a popular beach boardwalk or promenade often affords the chance to watch a kite master at work. While the familiar diamond kite may be the kite of your childhood, today's kites come in a near-dizzying array of shapes and sizes, many with a variety of tails that spin and twirl in the air, creating spirals of color and movement.

Watching a high-flying kite can be deceptive. It spins. It whizzes by. It arcs and circles and loop-the-loops. Maybe it looks easy. It's just a kite, after all. Right?

Harder than it Looks!

My last adventure with a kite was on the Oregon coast. It was harder than I expected to even get the kite airborne. Time after time, I tossed the kite into the air and tried to move against the wind enough to cause the kite to lift. Time after time, I found myself nursing hands in danger of getting cut by the thin standard-issue-weight twine that comes with a basic kite. The wind would play with the kite, pulling against my hands, but time after time the kite fell to the ground.

Once I did get the kite into the air, it was hard to hang on. My then 8-year-old took a spin at navigating, and then he passed the bridle over to his younger brother who was almost immediately lifted off the ground by the winds that wanted to carry the flight—and the brother—away. Photos of him on tiptoes, feet just touching the sand as he struggled to anchor the kite show the lift that was fighting against his body weight. (Okay, maybe I should have run to rescue him rather than stop to snap a photo, but it was an inexpensive kite... I didn't really think he could parasail far!)

As he let go, the kite sailed off, over the hotel and lodged in nearby electrical lines.

If you've flown a kite with kids or students, this scenario might sound familiar. If you've had to go, as I did, to the luxury kite store for replacement string, you might have found yourself faced with questions for which you didn't have answers... and found yourself staring in amazement at spools and spools of kite string in various diameters and materials.

Kite-flying can be serious business.

It can also be serious science!

Thoughts on Design

It's certainly easier to sit back and enjoy the kite masters on the beach than to fly your own, but if you've got ideas about design, structural engineering, or aerodynamics, a kite offers instant gratification and a high-flying step up from what you can test with a paper airplane!

A Kite-Studded History

Ben Franklin, Alexander Graham Bell, and the Wright Brothers all used kites as central vehicles for testing ideas, and it is thanks to the kite of 10-year-old Homan Walsh that construction of the bridge over Niagra Falls was started in 1847.

From exploring ways to alter the design of a kite to examining the forces that operate on a kite during flight, kites offer a variety of angles for creative science projects. The range of established kite designs, including familiar models like diamond, delta wing, and box, offer immediate room for adaptation and exploration. Which shape flies higher? What material works best for the struts that form the frame of support? What ratio of length to width is most effective? What material for the kite itself works best. (Franklin's kite was silk to help keep it up in the inclement weather that he needed for his testing.)

Room to Experiment

You can make a simple sled kite from a sheet of paper. But what happens if you take that same concept and make it from cotton? From silk? From nylon?

Thinking beyond the core construction, you can ask questions about the tail of the kite. How does the flight change if there is no tail or if there are two tails? What impact does the length of the tail have? What length of strength works best? How is the length of string related to the launch of the kite?

As you experiment with kites, you'll find yourself experiencing firsthand the forces that operate upon an airborne kite: lift, weight, tension and drag.

And, of course, you need to deal with and think about wind. What kind of kite flies best in low winds? What modifications can you make to a basic kite to help address changes in wind speed or to facilitate flight in low wind?

There's a lot of room for exploration! These projects can help get you started on a school or Saturday project:

Let's Go Fly a Kite! (Science Buddies' Difficulty Level: 2) This introductory project is perfect for younger students but also offers a good overview of kite dynamics for all ages and raises some important variables that can be explored in more advanced projects.

The Wright Stuff: Using Kites to Study Aerodynamics (Science Buddies' Difficulty Level: 5-6)
This project explores the affect of changing the bridle point—the spot where the string meets the frame. What happens to the angle of flight when the bridle point is altered?

How Low Can It Go? Design a Kite that Flies Best in Low Winds (Science Buddies' Difficulty Level: 5-8)
This project involves testing three different kite styles to evaluate performance in low winds using an anemometer.