Perhaps you've built one of the Ornithopter Zone's flapping-wing model kits, available in our online store. Here are some simple experiments to help you learn more about how an ornithopter works. You could use these experiments for a science fair or school project. Or just to increase your ornithopter skills! These experiments are easiest to perform with rubber-band-powered ornithopters, but they could be performed with electric ornithopters with a little more work.

The wings and body were lengthened to make this ornithopter. It has a 30-inch wingspan, and it needs a thick rubber band to flap the huge wings!		Ornithopters at two different scales. Both ornithopters fly nicely.

Vary the size of the wings: Try making the wing spars longer. Larger wings will cause the rubber band to unwind more slowly. This could give you longer flights, but it also means your ornithopter won't be getting as much power. Experiment to find out the best size! You can also try making the wings broader at their base, by lengthening the motor stick. How would you compare the effects of these two modifications?

Vary the wing tension: The basic ornithopter kits all use membrane wings consisting of a plastic film or tissue paper attached to a rigid leading edge spar. Normally there is no tension on the wing material. You can change this by pulling back on the spars while attaching them to the wing material. When released, the spars will pull forward on the wing material and hold it in tension. How does this affect the flight of your ornithopter? (For the opposite effect, try splicing some extra material into the wing, so it has more room to flop back and forth.)

Vary the flapping angle: Interesting things happen when you change the size of the crank on your ornithopter. This changes the angle through which the wings flap. It also changes the flapping rate and the amount of power expended by the rubber band. Try several different crank sizes, and see how it affects the flight of your ornithopter. You can also try adjusting the thickness of the rubber band so that the wing speed (degrees per second) remains the same. This holds the power output somewhat constant so you can determine the optimum flapping angle.

Change the length of the connecting rods: This moves the wing arc higher or lower. It changes the thrust line and also the amount of "dihedral effect", which is important for ornithopter stability and flight control. By varying the connecting rod length, you can see what effect these two things have on how your ornithopter flies.

Lock one wing in place: Slide the rear connecting rod all the way back against the crank bearing so the left wing doesn't move when the crank rotates. With only one wing flapping, your ornithopter should turn sharply to the left. Now add weight to the right wingtip until the ornithopter flies straight! This will show you how important inertial effects are in the ornithopter.

Get Competitive: See what modifications you can perform to get the longest possible flight time from your ornithopter. In addition to the suggestions made previously, you can try reducing overall weight and determining the best length and thickness of rubber band to get the longest flights under a particular ceiling. Use a winder for the longest possible flights.