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Contest Flying Tips

Here are some tips for contest flying with rubber-band-powered ornithopters or flying bird models. This information will help you get better flight times in the Science Olympiad Flying Bird event, or in school contests using similar rules. (Our Teachers Guide contains suggested rules for school contests, and they are similar to the Science Olympiad rules.)

The most important advice would be to start out with a simple model before trying to build a really hot competition design. This way, you will develop the experience and skills you need to be more successful when you start to build and fly more advanced flying bird models. Several kits are available, but you should choose the easiest one for your first model, to increase you chances of success. Then you will work your way up by building a more challenging, higher-performing kit. After you've done that, you might be ready to build your own unique design, much lighter than the commercially available kits and capable of much longer flight times. It would be a mistake to jump right into such a difficult project without getting some experience with simpler models first.

When flying any rubber-band-powered aircraft, it is very important to lubricate the rubber band. Use the commercially available lubricant for best results. If you don't have any, you can use vegetable oil. The lubricant prevents tearing of the rubber band and allows you to wind it up about 50% more turns and get much longer flight times. You can fly your rubber-powered ornithopters without lubricating the rubber band, but it would be foolish not to lubricate the rubber band if you're flying in a contest.

Another trick for extended flying times is to use a winder. This is a special device that allows you to put more turns into the rubber band. Leave the front end of the rubber band hooked onto the ornithopter crank wire. Hook the other end of the rubber band onto the winder hook. One person holds the ornithopter tightly, while the other takes the winder and stretches the motor out, several times its normal length. Then turn the winder handle to wind the rubber band. The winder is geared so that each turn of the handle puts several turns into the rubber band. You should know the gear ratio of your particular winder so you can keep track of turns. As you wind up the rubber band, walk the winder back toward the model, very slowly at first and then faster as dictated by the amount of tension. (With practice, you will get a sense of when the rubber band is about to break.) Then hook the rubber band back onto the model. This last step is made easier if you get some little black rubber o-rings at the hardware store. Thread the rubber motor through one of the o-rings before you tie it off. The o-ring is much easier to hook back onto the model than the rubber motor itself. The winder not only allows you to put more turns into the rubber band, it also allows you to use a longer loop of rubber, which might give you longer flight times.

Making a lot of test flights before contest day will help you get better results. Always record the size of the rubber band, the number of turns, and the flight time for each of your test flights. Be aware that two models can perform much differently from each other, because of subtle differences like the size of the crank or the age of the rubber band.

Another important consideration for indoor models is that they should circle consistently in one direction. Otherwise, your bird will probably be flying off into the wall and that would end the flight prematurely. If your bird has a habit of reversing its turning direction half way through the flight, there are two possible solutions. One would be to launch the model in a banked orientation so that its gets into its preferred turning direction from the beginning. The other would be to add some weight to one wingtip. For example, if the bird wants to turn right in the beginning of the flight, you would add weight to the left wingtip, hopefully causing it to turn left throughout the flight.

Finally, the other thing to keep in mind is weight reduction. If you build your ornithopter from a kit, you can reduce weight by tapering the wing spars. If you design your own ornithopter for contest flying, you should make it as light as possible. The commercial kits are designed for ease of construction and not for light weight. Therefore you should be able to get the weight much lower by building your own ornithopter. Keep in mind though, if the wings are too flexible, the ornithopter will not fly properly.