Lift-Off: How can a glider be made to fly higher?

From Experiment Central, published by U·X·L

Purpose/Hypothesis

In this experiment you will create an aerodynamic glider capable of moving through the air and modify it so it can soar higher, gaining lift by manipulating the wings. According to Bernoullis principle, force arises from differences in pressure. Pilots change the degree of lift by manipulating the flaps on the wings edges. To understand the effects of air pressure, examine the diagrams illustrated. Before you begin, make an educated guess about the outcome of this experiment based on your knowledge of flight. This educated guess, or prediction, is your hypothesis. A hypothesis should explain these things:

• the topic of the experiment
• the variable you will change
• the variable you will measure
• what you expect to happen

A hypothesis should be brief, specific, and measurable. It must be something you can test through observation. Your experiment will prove or disprove whether your hypothesis is correct. Here is one possible hypothesis for this experiment: "Modifying the wing cross-sectional shape will create more lift under the wing that will allow the glider to fly higher."

In this case the variable you will change is the wing shape of one of the gliders, and the variable you will measure is the distance the gliders fly.

What Are the Variables?

Variables are anything that might affect the results of an experiment. Here are the main variables in this experiment:

• the type of balsa wood glider used (both gliders should be identical, simple, and lightweight)
• the type of modifications made to the wing shape of the second glider

In other words, the variables in this experiment are everything that might affect the flight time of the gliders. If you change more than one variable, you will not be able to tell which variable had the most effect on the gliders flight.

Level of Difficulty:

Easy

Materials Needed

• 2 balsa wood gliders (Styrofoam gliders are acceptable substitutes, but the gliders must have no propellers or landing gear.)
• 1 high power fan, 16 to 24 inches (41 to 61 cm) in diameter
• 2 pieces of string, 18 inches (45 cm) long
• 2 index cards, 4 x 6 inches (10 x 15 cm)
• 1 roll of adhesive tape

Approximate Budget:

$5 for planes.
(Borrow the fan from a family member or teacher.)

Timetable:

30 minutes

How to Experiment Safely

• Use caution handling fans.
• Make sure the fan is unplugged when assembling the experimental apparatus and never touch the blades of the fan when it is operating.

Step-by-Step Instructions

1. Prepare the control and test gliders. Assemble as shown on the packing bag.
2. Tie one string to the nose of each glider. If there is a metal or plastic clip on the nose, use it to attach the string.
3. Modify the wing of the test glider to create lift. Fold the top and bottom of the index card as shown in the diagram.
4. Tape the cards over the tops of the wings of the test glider.
5. Modify the index card. Push forward from the back of the wing so that the bubble shape is toward the front of the wing. Once you bend the index card, it molds into the shape as illustrated.
6. Attach the two strings from the planes to the bottom of the fan or the fan grating. (Remember, use caution. Make sure fan is unplugged at this stage.) Aim the fan slightly down toward the surface the planes are resting on.
7. Turn the fan on low, then medium. Record your observations.

Troubleshooters Guide

Sometimes problems may arise during an experiment. Heres an example of a problem and what may be the cause.

Problem: The gliders will not stay in the air.
Possible cause: Gliders fly only for short periods because of invisible disturbances in the air, known as turbulence. For this reason, a glider cannot be expected to fly long distances.

Summary of Results

Record your results by describing how each glider moves in response to the air currents. The modified-wing glider, or test glider, should jump up and glide in the air. The other, the control glider, should constantly dive into the table and flip over. You can measure how high the gliders lift off the table with a ruler.

Change the Variables

To vary this experiment, use gliders made from different materials, such as Styrofoam or cardboard. Try different fan speeds and change the angle at which the wind hits the glider.