FLYING HIGH: The Eternal Wing
The Pathfinder, an unmanned flying wing powered by the sun, attempts to break flight records during the summer of 1995 when it sets off from Edwards Air Force Base in southern California. Using 6,000 watts of solar energy -- equivalent to the amount of electricity needed for just four hair dryers -- the Pathfinder could prove an ideal platform for environmental research. Join FRONTIERS in the Mojave Desert as designer Paul MacCready and the flight team, along with host Alan Alda, prepare for the launch.
Activity 1: A Flying Wing Competition
Activity 2: Design Challenge: The Ultimate Glider
Activity 3: Cambered Wing Glider
For Further Thought
ACTIVITY 1: A FLYING WING COMPETITION
Paper airplanes, like their full-scale commercial counterparts, ride a delicate balance of forces to stay aloft. The mass of any craft (within Earth's gravitational field) creates a downward force known as weight. To counter the weight, the craft's wings produce an upward force called lift. When the lift is greater than the weight, the craft rises. When the weight is greater, the craft dives.
In the following activity, you'll make a basic flying wing. By adjusting the total area of the wing, you can achieve the best balance between weight and lift. Once that is achieved, the craft will glide effortlessly across the room.
- sheet of 8 1/2" x 11" paper
Experiment with lift and weight and then compete for distance with this simple glider.
The Possible Paths of a Classroom Glider:
- Hold a sheet of paper upright (portrait orientation). Draw a horizontal line 1/4" to 1/2" from the bottom edge of the paper to form the leading edge.
- From the top of the paper, draw a vertical line along the center about halfway down the length of the paper. Draw two more vertical lines, each one inch from the center line and extending midway down the paper.
- Fold the leading edge over itself several times, until about half the sheet is folded.
- Fold the glider over along the center line. Make a good crease. To form the wings, fold each side over along the wing lines. The glider should look like the letter "M."
- For your test flight, gently release the glider. If it climbs too steeply, fold the leading edge back. If the craft dives, undo one of the folds. Continue adjusting the craft until you produce the best aerodynamic design. The trick in flying the glider is to release it, not throw it, as you would a traditional paper airplane. Experiment a few times before you compete for distance. You will probably need to make some adjustments.
- Make two 1/2" snips about 1/2" apart in the middle of each wing. Experiment by folding these control tabs up or down. Observe how they affect the flight path of the glider.
- STALL: Too much lift. The glider climbs too steeply and loses control, balance, lift and speed; spirals downward until it crashes.
- DIVE: Too little lift. The weight offsets the lift, resulting in a steep dive that crashes.
- STABLE DOWNWARD SLOPE: The right balance between lift and weight results in a sustained gentle downward slope.
- Try using a heavier stock of paper. What happens?
- The control tabs represent the control surfaces found on an aircraft's wings, rudder and stabilizer. Control surfaces extend or retract to shift the balance of forces. Can you add a control tab that makes the craft travel in a clockwise circle?
- In a paper airplane, the thrust produced by the thrower gives it the faster speed needed to acquire sufficient lift. How is this glider different?
- Heavier paper would require exposing more wing area to achieve the same balance between weight and lift.
- Add a rudder-like tab at the rear of the craft body.
- The glider requires less forward thrust; its design gives it more lift.
ACTIVITY 2: DESIGN CHALLENGE: THE ULTIMATE GLIDER
After you have explored the physics of flight using the basic model in the previous activity, work with a partner to construct a glider using paper, straws, tape and paper clips. The glider does not have to be a flying wing. It can have any shape as long as it glides. Continue improving your design until you have constructed a glider that flies the greatest distance. Then test your designs in a classroom contest. Draw a blueprint of your glider and compose a set of instructions that could be used to construct your model. (You may want to hold the competition in the gym, if possible.)
ACTIVITY 3: CAMBERED-WING GLIDER
Most aircraft wings form a shape called an airfoil (also known as a cambered wing). The airfoil is curved (or "cambered") on top and flat underneath. Air flows differently across these two surfaces, resulting in an additional lifting force (Bernoulli's principle).
- sheet of 8 1/2" x 11" paper
- 2 straws
- index card
This activity demonstrates how an airfoil works.
- Holding a sheet of paper in landscape orientation, fold and crease it so a 1/2" edge extends on the bottom section.
- Slide the longer section back so that the edges align. As you move the paper, a curved surface will form on the longer side. Use a piece of tape to secure the shape along the aligned edges.
- Join two straws by twisting the end of one straw and inserting it into the hollow of a second straw.
- Tape the flat side of the wing to the straw fuselage. The straw fuselage should extend 1" beyond the leading edge of the wing.
- Tape an index card to the rear section of the fuselage. For increased stability bend up the ends of the card by about 1".
- For balance, attach a small lump of clay to the front of the straw fuselage. Gently launch your glider. If it dives, what do you need to do to correct the flight pattern? If it climbs too steeply and stalls, what do you need to do?
If the plane dives, remove some clay. If it climbs too steeply and stalls, add more clay.
FOR FURTHER THOUGHT
- Make a comparison of the leading edges of a glider, the wings of a commercial jet, a boomerang and the wings of a bird. (For more on bird flight, see the activity for the "Bird Man" segment of this show.)
- Brainstorm other applications of the "do more with less" philosophy.
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