Let's Go Fly a Kite!

Introduction

Did you know that one of the most famous kite flyers of all time was a 10 year-old boy? His name was Homan Walsh, and with out him the Niagara Falls Bridge would not have been built in 1847. Before building of the bridge could begin, someone needed to get a line from one side of the gorge to the other. Homan successfully flew a kite from one side of the gorge to the other, and his kite line was the first to span the gorge. After securing Homan's initial kite string, heavier and heavier line was fed across until a steel cable could be connected across the gorge so that bridge construction could begin. Homan Walsh was rewarded with a ten-dollar cash prize, which was a lot of money in 1847!

Another famous kite flying duo were the Wright brothers, Orville and Wilbur Wright. Before building the first successful airplanes, they experimented with various designs by using kites. By making many different kite models of their airplanes, they eventually came up with a design that worked, and the rest is history.

There are many different kite designs. Some kite designs are very old, like traditional Chinese and Japanese kites. Some designs are very new, like the dynamic stunt kites used in sport kite flying competitions. These kites are made with modern materials and designs which make them ultra maneuverable. Kites come in all shapes and sizes, as you can see in Figure 1.

Figure 1. This image shows several different kinds of kites.

How does a kite fly, allowing Homan and the Wright brothers to accomplish their feats? As someone runs with a kite, the wind going head-on into the kite creates a force that pushes up on the kite. This force is called lift. This lift force goes perpendicular to the wind and it pushes the kite up into the air. At the same time, another force pulls the kite back. This force is called drag and is caused by the wind catching on the kite itself, pushing the kite back in the direction that the wind is going (see Figure 2). Altogether, these forces cause the kite to go back and up when you fly it.

Figure 2. This diagram shows lift and drag on a kite.

In this aerodynamics science project you will make your own kite for testing how different variables affect flight. The type of kite you will make is called a sled kite, and is very simple to build. After you build the kite you will use it for a series of experiments, testing different variables such as speed, line length, tail length, and any other variable you want to test. Will you be able to figure out the best way to fly a kite?

Terms and Concepts

• Forces
• Force of lift
• Force of drag
• Variables
• Flight
• Sled kite

Questions

• How do you make a kite?
• What forces allow a kite to fly?
• What variables affect the flight of a kite?
• Why do kites have tails? What do the tails do?

Bibliography

On this webpage you will find instructions to make a simple sled kite using drinking straws and a paper bag from the Dryden Flight Research Center at NASA:

• National Aeronautics and Space Administration (NASA). (2004). Sled Kite. Dryden Flight Research Center. Retrieved August 22, 2012, from http://www.nasa.gov/pdf/205712main_Sled_Kite.pdf

From different webpages on the NASA website, you can read about the aerodynamics of kite flying:

• Benson, T. (2008, July 11). Kites. Glenn Research Center: National Aeronautics and Space Administration (NASA). Retrieved October 24, 2006 from http://www.grc.nasa.gov/WWW/K-12/airplane/kite1.html
• Benson, T. (2008, July 11). Forces on a Kite. Glen Research Center: National Aeronautics and Space Administration (NASA). Retrieved August 22, 2012, from http://www.grc.nasa.gov/WWW/k-12/airplane/kitefor.html

Materials and Equipment

• Printer
• Paper
• Scissors
• Optional: Crayons and markers
• Drinking straws (2)
• Tape
• Hole punch
• Kite string (6 m long)
• Meter stick, metric measuring tape, or metric ruler
• Paper clip
• Plastic grocery bag or other thin plastic bag
• Lab notebook

Experimental Procedure

1. Download the Sled Kite Template and print it out on a normal sheet of 8 1/2-inch by 11-inch paper.
2. Carefully cut out the sled kite.
   1. You can decorate the kite using crayons, markers, or other media.
3. Trim the length of the two drinking straws so they will fit in the area marked for the straws.
4. Tape the straws into place.
5. Place two or three pieces of tape in the marked areas covering the black circles.
   1. The tape will help reinforce the holes for the kite string.
6. Using the hole punch, carefully punch the two holes marked by the black circles.
7. Cut two pieces of kite string 45 centimeters (cm) long each. Tie a string through each hole.
   1. Tie them tight, but not so tight that you tear the paper.
8. Tie the opposite end of both strings together to one end of a paper clip.
9. Cut a 1 meter (m) long piece of string.
10. Tie one end of this string to the other end of the paper clip. Your sled kite should look like Figure 2 and is now ready to fly!

Figure 3. This is an image of a sled kite from the Dryden Flight Research Center at NASA (NASA, 2004).

11. Before flying your kite, make some tails to test on your kite. You can make kite tails out of old grocery bags or other thin plastic bags by cutting the bag into loops and then connecting these loops. For a visual guide on how to do this, see the webpage by My Best Kite titled "Making Kite Tails" in the Bibliography.
    1. Lay the bag completely flat.
    2. If the bag has handles, cut straight across using scissors to remove the handles.
    3. Then keep cutting the bag this way to create thin rings (which will look like strips when flat). Make each ring about 3 cm wide.
    4. Cut up the whole bag this way.
    5. Discard the handles but save the rings.
    6. To make kite tails, you can either use individual rings (for a short tail) or loop two rings together and gently pull them tight. Attach more rings to the tail this way to make it longer.
12. The variables you will be testing are tail length, number of tails, flier speed, and string length. In your lab notebook, for each variable make a data table to record your results, such as Tables 1, 2, 3, and 4 shown.

Variable: Tail Length	10 cm	100 cm	500 cm
Result:

Table 1. In your lab notebook, make a data table like this one to record your tail length observations in.

Variable: Number of Tails	No Tail	One Tail	Two Tails
Result:

Table 2. In your lab notebook, make a data table like this one to record your observations in when changing the number of tails on your kite.

Variable: Flier Speed	Standing	Walking	Running
Result:

Table 3. In your lab notebook, make a data table like this one to record your flier speed observations in.

Variable: String Length	1 m	3 m	5 m
Result:

Table 4. In your lab notebook, make a data table like this one to record your string length observations in.

13. Outside in a clear area, use your kite to test the following variables. As you test these variables, record your observations and results in your lab notebook in your data tables. Use a scale to rate the quality of flight under each different condition. For example, a scale of 0-10 where 0 is no flight and 10 is the best flight.
    1. Tail Length:
       1. Try flying the kite with a 10 cm tail make out of the plastic bag rings (you may need less than one ring to do this). Tape the tail to the bottom center of your kite, as shown in Figure 3. How well does the kite fly? What does the kite do? In your lab notebook, record your observations in your tail length data table.
       2. Make the tail have a 100 cm tail by looping rings together and gently pulling them tight. Carefully attach them to the 10 cm tail that is already on the kite. How does the kite with the 100 cm tail fly? Record your observations in your data table.
       3. Make the tail have a 500 cm tail by gently looping more rings together. How well does the kite fly now? Record your observations.
       4. With which tail length does your kite fly the best? Why do you think one tail worked better than the others?
       

       Figure 4. When you attach a tail to your kite, attach it to the bottom center of the kite, as shown here with a 10 cm-long tail. If you attach more than one tail to your kite, attach the tails symmetrically on the bottom of the kite.
    2. Number of tails:
       1. Try flying the kite without a tail. What does it do? In your lab notebook, record your observations in your data table on number of tails.
       2. Attach one tail to your kite, as you did in step 13 a. How does the kite fly now? Again, record your observations.
       3. Remove the tail and add two tails symmetrically to the lower back of your kite. How does the kite fly now? Again, record your observations.
       4. With what number of tails did your kite fly best? Why do you think this is?
    3. Flier Speed:
       1. Try standing still with your kite. What does it do? In your lab notebook, record your observations in your data table on flier speed.
       2. Try walking with your kite. What does it do? Again, record your observations.
       3. Try running with your kite. What does it do? Again, record your observations.
       4. With what flier speed did your kite fly best? Why do you think this is?
    4. String Length:
       1. Fly your kite with the 1 m of kite string already attached to it. How well does it fly? What does it do? In your lab notebook, record your observations in your data table on string length.
       2. Make your kite string 3 m long. How well does the kite fly now? Again, record your observations.
       3. Make your kite string 5 m long. How well does the kite fly now? Again, record your observations.
       4. With what string length did your kite fly best? Why do you think this is?
14. Based on your results, what do you think is the best tail length, number of tails, flier speed, and string length for flying your kite? Why do you think this is? Can you relate your results to the forces of lift and drag on the kite?