Rubber-powered
Rubber-powered models are powered by the stored energy of a twisted elastic material. These range from the simple rubber-band powered toys available in many toy stores, up to the open rubber class, examples of which often use 200 g of rubber in their "motor". Rubber does not produce a constant power output; when fully wound a rubber motor produces its maximum torque, but this drops rapidly at first before 'plateau-ing', finally declining again, after which the propeller stops. Using this initial burst efficiently is vital and automatically variable pitch propellers help here, together with timer-operated changes of wing and tailplane incidence and of rudder setting. At the end of the power run the blades fold back alongside the fuselage to minimise drag during the glide.
The FAI rubber class is F1B, also known as Wakefield. Charles Dennis Rushing has written on the history of the Wakefield Cup. F1B models may have a maximum of 30 g of rubber motor, and the empty weight of the airframe must be at least 200 g. The maximum total area of the model must be less than 19 dm2. The mini rubber class is Coupe d'Hiver (also known as F1G). "Coupe" models have no area restrictions. The maximum weight of rubber allowed is 10 g, and the minimum empty weight of the airframe is 70g. . Open rubber is a popular event, featuring large models with enormous amounts of rubber crammed into them. Open models often have 50% of their flying weight composed of rubber.
P-30 is a common beginner's event. A P-30 must use an unmodified commercially available plastic propeller. P-30 has a maximum wingspan and overall length of 30 inches (76.2 cm), and uses maximum 10 g of rubber. The empty airframe must weigh at least 40 g.
The most well known beginner rubber powered models are the AMA Cub (also known in the USA as the "AMA Delta Dart"), Denny Dart, Canarsie Canarie and Squirrel. They are commonly used in workshops or for beginners to learn about construction and flying.
The Squirrel, designed by Darcy Whyte is the easiest to build. Free plans are available for download for a Squirrel.
The smallest rubber powered model aircraft was built in 1931 by a Philadelphia high school student, called the Flying Flea and was one and a quarter inches long and could remain airborne for approximately one minute.
Read more about this topic: Free Flight (model Aircraft)