The 'Ultimate' Science Fair Project: Flying Disk Aerodynamics

Related Links

• Science Fair Project Guide

Project Summary

Difficulty	6  –  7
Time required	Short (several days)
Prerequisites	You should know the basics of throwing a frisbee (i.e., be able to play catch with a friend).
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	No hazards

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Sponsor

Sponsored by a generous grant from Northrop Grumman Foundation

Weightless Flights of Discovery Program for Teachers

www.northropgrumman.com/ community/weightless.html

Objective

The goal of this project is to use aerodynamic principles to predict the flight direction and distance for a frisbee.

Introduction

Tossing a frisbee with your friends is a great way to have fun in the sun. As you practice your throws and become more accurate, you're learning about the aerodynamics of frisbee flight intuitively. You're learning the body mechanics that will make the frisbee go where you want it to go. This project will get the thinking part of you into your frisbee tossing. Who knows, it might even help you get better!

You should do background research to learn about the concepts of lift and drag. The NASA website listed in the Bibliography is a great place to start. The diagram below shows how lift and drag act on a frisbee.

This diagram shows the forces on a frisbee in flight.The arrow v shows the direction of flight. The downward arrow is the weight of the frisbee (mass times gravity). The backward arrow, d is the force of drag. The upward arrow, L, is the force of lift. It acts perpendicular to the direction of flight. Both lift and drag change as a function of the tilt angle, α, of the disk. (Hubbard and Hummel, 2000)

You'll notice in the diagram above that the frisbee can be thrown at an angle. That is, at the moment when you snap your wrist and let go, the frisbee is tilted with respect to the ground. In this project, we'll call that tilt the "launch angle." The diagram below defines exactly what we mean. This is looking at the frisbee edge-on, for a right-handed thrower. The dotted line is zero degrees, corresponding to a horizontal launch. When the outer edge of the frisbee is above the horizontal, the launch angle is positive. When the outer edge of the frisbee is below the horizontal, the launch angle is negative. There is a second diagram for a left-handed thrower. Note that the definition of positive and negative angles changes.

Definition of launch angle for a right-handed thrower. Outside edge tilted up is positive, outside edge tilted down is negative.

Definition of launch angle for a left-handed thrower. Outside edge tilted up is negative, outside edge tilted down is positive.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• lift,
• drag,
• weight.

Questions

• What are the forces acting on a frisbee in flight?
• How does the tilt of the frisbee affect the direction of flight?

Bibliography

• Discovery Channel video clip on the research of Sarah Hummel, ultimate player and frisbee researcher:
  Discovery Channel of Canada, 2002. "High Flying Frisbee Science," (video clip): http://www.exn.ca/dailyplanet/view.asp?date=11/15/2002.
• Hummel, S.A, 2002, "Frisbee Flight Simulation and Throw Biomechanics", University of CA, Davis, Retrieved April 18, 2008 from http://mae.engr.ucdavis.edu/~biosport/frisbee/frisbee.html
• The Exploratorium, 1997. "What effect does the rim of a frisbee have on its flight?" Sport! Science [accessed February 10, 2006] http://www.exploratorium.edu/sports/ask_us_sports_october.html.
• NASA has a great reference site on Aerodynamics. Even though there is not anything specific on frisbee flight, you can still learn a lot about how frisbees fly by learning about aerodynamic forces on other types of airfoils. Check out the Gliders section, and the Lift Simulator program.
  http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• frisbee,
• tape measure,
• string,
• masking tape,
• marker,
• protractor,
• notebook and pencil,
• helper (for measuring and throwing back the frisbee),
• video camera and a second helper to run it (optional).

Experimental Procedure

Flight measurements diagram. Frisbee is thrown from launch point, aimed along center line. Example landing points indicated in blue. Measure distance from starting point and angle from the center line. Angles to left of center line are negative, angles to right of center line are positive.

1. Do your background research and learn about the forces on the frisbee in flight.
2. To measure the effect of launch angle on frisbee flight, you will need to try your best to keep all other aspects of the flight the same. You'll want to throw with similar arm motion and speed, and impart a similar spin on the frisbee each time. You want to have the same release point, so that your arm is directed along the center line for each launch. The one thing you want to vary is the launch angle (see diagrams in the Introduction section). If you clearly made a mistake on a throw (for example, if the release was way off the center line) then don't include it in your results.
3. Measurements: launch angle, distance, and direction.
   1. Use string or chalk to mark out a 10–15 foot center line for aiming your throws (see Flight measurements diagram, above).
   2. If your tape measure is not as long as your typical frisbee throw, make a longer tape measure using a piece of string. Mark off regular intervals with tape labels and a marker, and you're in business.
   3. If you have a video camera, you can use it to help you analyze the launch angle of the frisbee. Set it up behind you, but at a slightly off the axis of the center line so that your body does not block the view of the frisbee as you throw. Later you can use still images (on your TV or computer) to measure the launch angle of the frisbee with a protractor. Just cover the screen with a piece of plastic wrap, and you can draw the angle right on the plastic. That way you can have a permanent record for each throw.
   4. If you don't use a video camera, then you or one of your helpers will have to watch closely and estimate the launch angle for each throw. Here's one method you can try: Hold one arm out horizontally and use the other arm to try to match the launch angle that you saw. Have a helper use a protractor to measure the angle between your arms.
   5. Measure the flight distance and direction with your measuring tape (or string). Hold one end at the launch point and the have your helper hold the other end at the landing point (where the frisbee first hits). Record the distance of the throw and the angle that the string makes with the center line (use a protractor).
4. Try throwing the frisbee with at least five different launch angles: horizontal, plus two different positive and two different negative angles.
5. Make at least 10 good throws at each launch angle, measure and record the results. If there is wind, note the wind speed and direction in your notebook (make a diagram like the one above, and show the direction of the wind).
6. Average the results (distance and direction) for each launch angle.
7. Do you see a consistent relationship between launch angle and flight direction?
8. Is there a relationship between launch angle and distance?
9. Think of ways for showing your results (both the average and the scatter in the data) using a diagram like the one above.
10. Can you explain your results in terms of the aerodynamic forces on the frisbee?

Variations

• What happens if you include the complication of wind in the equation? How will the flight of the frisbee be affected by throwing into the wind? Across the wind? With the wind? How will launch angle change the flight in each of these conditions?
• Compare frisbee flight with flight of an Aerobie (open ring flying disk). What differences do you notice? Can you explain them in terms of aerodynamic forces?

• For more science project ideas in this area of science, see Aerodynamics & Hydrodynamics Project Ideas

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Credits

Andrew Olson, Ph.D., Science Buddies

Sources

• Diagram of forces on a flying disk from: Hubbard, M. and S.A. Hummel, 2000. "Simulation of Frisbee Flight," presented at the 5th Conference on Mathematics and Computers in Sport, G. Cohen, Editor, University of Technology, Sydney, New South Wales, Australia, 14–16 June, 2000. Online at [accessed February 10, 2006]: http://mae.engr.ucdavis.edu/~biosport/frisbee/5thMACS_Frisbee_Simulation.pdf.

Last edit date: 2006-02-15 15:47:34

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