Winging It Make a Wind Tunnel On the Wings of Insects Quiz

In order to sustain flight, an aircraft must generate a lifting force that is equal to its own weight. If the lift is substantially less than the vehicle weight, then the vehicle cannot maintain level flight. Lift is generated by the inclination of the wing surface to the direction of movement, and its speed of movement. The back of the wing, called the trailing edge, is inclined downwards, so that as the air leaves the wing some of it is traveling in a downwards direction. The air approaching the wing is also affected by this motion at the back, and surprisingly, is deflected upwards before it gets to the wing. Both the upper and lower surface of the wing contributes to the lift, the lower by experiencing higher pressure than atmospheric (pushes it up), and the upper surface by having a lower pressure (sucks it up).

The lift is caused by the reaction of the wing, as it redirects the air from going upwards in the front, called the leading edge of the wing, to downwards at the back. This is exactly the same as though one were to roll a ball along the floor towards a hard wall. The ball hits the wall and bounces back. This collision generates a force by pushing the wall away from you. In fact, if the ball were heavy or fast enough, it would create enough force to knock the wall down! Lift in fluids, air and water, is caused by an identical effect.

A century of clever development has gone into the design of the cross-sectional shape of wings (called the airfoil) to produce airfoils that create lot of lift for a given speed. The airfoil has a characteristic streamline shape - rounded in front and sharp at the back. In the early days, the airfoil was actually modeled on the shape of a trout viewed from above. The main place where the airfoil shaping is important for lift is the upper surface.

A paper glider is a fun model to demonstrate some of the features of lift. The airfoils of these are not streamline shapes, meaning they do not have a teardrop shape, as do the wings of birds and airplanes. The paper wing is much cruder, and consequently does not fly as well as a more refined wing might. A bird with a wing like the one we are going to make wouldn't survive long! We will make two gliders that will demonstrate some of the characteristics of lift.

OBJECTIVE

This activity page will offer an introduction to wings and lift and a hands-on experience in constructing two paper gliders, as well as an opportunity to explore how position of the center of weight and wing size affect flying characteristics.

MATERIALS

• Standard 81/2X11" paper
• Pencil
• Ruler
• Scotch tape
• Scissors

PROCEDURE

PART 1 - MONOPLANE GLIDER

1. Select either of the shorter edges of a sheet of paper. Position your pencil about 1/2 inch from this edge. Use your ruler to draw a parallel line.
2. Make five more parallel lines all about 1/2 inch apart.
3. Fold and crease the paper's edge along the first line your drew. Fold back this creased edge and flatten the "lip" against the sheet.
4. Fold and crease the paper along the second line. Keep the fold direction the same. FYI: Elementary school teachers like to call this a "roll fold" as opposed to the fan-like "accordion fold".
5. Keep folding up the paper until you've folded along the last line. Firmly crease the stack of rolled folds so that it maintains its shape. You may need to secure it with a piece of tape.
6. Imagine a midline that runs from the middle of the folded "leading" edge back to the middle of the trailing edge. Gently fold and crease your paper along this axis. Try not to disturb or warp the leading edge fold.
7. To produce the "fuselage" of the glider, you'll need to fold down each wing from either side of the central crease, as shown.
8. Add stability to the glider by adding a 1" fin that is created by folding up on the tip of both wings as shown here.

9. Hold the glider by the fuselage and throw it gently in a horizontal direction.
10. Experiment with increasing and reducing the number of folds. .
QUESTIONS
1. Why was the folded edge called the leading edge?
2. How did removing a wing fold affect the glider behavior?
3. How did adding an extra fold affect the glider's behavior?

PART 2-Ring Wing Glider

1. Proceed as in steps 1 through 5 of the Monoplane instructions. This time however, mark ten folding lines instead of six.
2. Keep folding up the paper until you've folded along the last line.
3. Gently roll this folded paper into a cylinder that resembles a large bracelet. Both ends of the folded (and leading) edge should align. Slip one of the folded edges into the other so that the pressure of the folds binds them together. You may need to secure this shape with tape.

4. Hold the glider as though it were a football and throw it gently in a horizontal direction.
5. Test fly it again putting some spin in about the axis, as though it were a football. See if there is any difference in flight.

QUESTIONS

1. What part of the glider acted as the wing?
2. How can you increase the lift of this design at a given speed?

Have you ever placed your hand in a stream of rushing water?
If so, what happened as you angled your finger tips in the stream flow.
Why?
Suppose you angled your hand down?
What would happen if you keep your hand level?

WEB CONNECTION

Building Paper Airplanes
Links to several paper airplane sites

Aviation Museums
A comprehensive list of aviation museums worldwide

The activities in this guide were contributed by Michael DiSpezio, a Massachusetts-based science writer and author of "Critical Thinking Puzzles" and "Awesome Experiments in Light & Sound" (Sterling Publishing Co., NY).