In this investigation you will determine the efficiency of the paper glider you made. A glider's efficiency is measured by its lift-to drag ratio (L/D ratio) which tells how many units forward it goes for every unit it descends. Aeronautics engineers call this L over D. A real glider, or sail plane, may have a L/D ratio of 30:1 which means it glides forward 30 meters (or feet, miles, etc.) for every meter it descends. To find your glider's L/D ratio:

 

1. Measure the height from which the glider is released (vertical distance) and the horizontal distance it travels.
   
   
2.  Divide the horizontal distance by the vertical distance to get the L/D ratio. horizontal distance / vertical distance = L/D

3.  Do several trials and find the average L/D ratio for your glider.

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Extension

1. Cut 1/2 inch off the end of the wings of their glider (be careful to cut the same amount off each wing).
    
   
2. First predict what will happen. Will the glider fly a shorter or longer distance? More or less stably? Record your predictions in your journal.
   
   
3. Fly the glider several times, measuring and recording the distance each time, and calculating an average. Did performance match prediction?

    

	How much distance?	How stable?
1st trial
2nd trial
3rd trial
	Average distance:

4. Keep cutting off 1/2 inch of the wings each time, recording the results, and calculating the average, until the glider no longer flies. Record your results in a new table similar to the above.
   
   
5. Discuss in your groups and try to explain your results. Here are some questions that you may want to consider.
   • Did the glider fly a shorter distance (more drag?) or longer distance (less drag) with each reduction in wingspan? <> 
   • At what point did the glider stop flying altogether (insufficient lift)?
      

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More Flight Characteristics

1. Work in groups and cut out two different wing designs. You can invent the designs, search for them in a paper airplane book or check our List of Resources.
   
   
2. Fly each different airplane design three times from a set point, and record the distance flown and other flight characteristics.
   
   
3. Record the average distance for the three flights. Compare the results with different wings.
   

   Consider the following questions and write a brief report based on them:

   • Which wings provide most lift? Most drag? Longest or highest flight?
   • Share your results with the whole class.
     
     
4. Record the results of comparison flight tests of your gliders, changing other aspects of the design. For instance, you can push the wings far forward or far back and compare the flight characteristics. You can add weight (taping a coin on the nose, fuselage or tail of the glider). You can add drag, placing paper with paper clips (or whatever their imagination dictates) at different points.
   
   
5. For each change, record three flights and calculate average distance flown, and record any other flight characteristics.
   
   
6. Discuss your results with the other research teams in your class.