President Lincoln
Learns to Fly

Objective

The objective is to get a piece of paper, taped to a table top, to lift weight when airflow is introduced over the curved surface.   The weight in this case will be pennies taped to the underside.  Hey, it's interesting, cheap, and above all, it's fun for cadets.

Time Requirement

About 30 minutes.  More time for discussion and further experimentation is good.

Materials

This activity may be done at one central point for a small group, or divided into "teams" for larger groups to allow for more hands-on time.  The materials list below is for each group.

• A Hair Dryer (the kind that blows, not the kind that fits over your head!)
  
• A sheet of paper
  
• Scotch Tape
  
• A supply of pennies (ten or so per group is good)

Background

This is a fun way to teach Bernoulli's Principle, and illustrate how much lift a wing can produce.  Using a piece of regular typing or computer paper, you can show that enough aerodynamic force will be generated to lift weight.  So many times when Bernoulli's principle is taught, cadets don't understand what a venturi is and how a change in the direction of airflow will create a lowered pressure.

In simplified terms, Bernoulli stated that a fluid in motion will have a pressure change when the velocity increases.  In the example of a wing, air flows faster over the upper curved surface than it does flowing over the underside.  As the air going over the upper surface accelerates, the pressure drops by quite a measure.  Relative to the upper portion of a wing, the lower pressure doesn't change that much.  This difference in pressure causes the wing to react by rising towards the area of lower pressure.  If the are is flowing fast enough and the surface of the wing is curved enough, it will move upward.

Procedure

1. Fold a piece of paper with a straight fold about one inch from the edge.  Then "curl" the paper slightly by drawing it over the edge of the table.  This should result in somewhat of a "wing" shape with a flat surface in front.

2. Tape the leading edge of the wing to the table top along its entire length.

3. Using the air flow from a hair dryer, blow on the "gentle" setting over the top of the paper.  Notice that instead of being flattened to the table top, the paper will lift up.  See Illustration below.
   

4. The higher setting of airflow from the hair dryer, the faster the paper will rise...

5. Now, demonstrate that this force can actually lift weight.  Tape a penny to the underside of the paper, about two inches from the trailing edge.  Is there enough lift to raise the penny from the table top?

6. How many pennies can be lifted on each setting of the hair dryer?  Does larger paper work better?  What differences in lift can be observed by comparing the same size sheets of paper in "portrait" versus "landscape" mode?  Does more curl or less work better?

The variations and experimentation possibilities are wide open here.  If time permits, allow the cadets to experiment and predict what behaviors they expect to see.

Discussion

Ask the cadets ahead of time what they expect as you blow air over the top of the curved paper.  See how many think that by blowing over the top the paper will be forced flat onto the table top.   If none of them come up with this theory, offer it yourself.  You can argue "I am going to be blowing a lot of air over the top of this paper.  The pressure of that air should force the paper to flatten out onto the table."  This makes sense, but it is exactly the opposite of what will happen.  Watching the cadets observe the forces of lift in action can be fascinating.  With some, you can almost see the "light bulb" go off in their heads as they finally "get it."

Safety Concerns

This is a pretty safe activity.  There are common concerns about not tripping over cords, and not standing in water when using electrical appliances.  Also, if the hair dryers have a "cold" versus "hot" setting, use the "cold" - not only is it safer, it works better!

Adapted from: Aerospace 2000, Volume 1
Published by the Aerospace Education Training Directorate
National Headquarters, Civil Air Patrol.