Date of this Version
Published in Transactions of the Nebraska Academy of Sciences, Volume 4 (1977).
Indoor model aircraft are extremely light and fragile, free-flying craft-flown, as the name implies, indoors in large (often unsuitable) buildings with performance measured by flight duration. The model is designed and adjusted to fly a circular path to avoid sidewall collisions, climbing at the outset when the motive power is high and then slowly descending. Model fragility precludes flight under conditions where even very mild atmospheric disturbances could collapse the delicate structure of the ship.
Because reduction in weight results in easily discernible improvement in duration, evolution of these models has been largely empirical, concentrated on weight reduction with only scattered aerodynamic design criteria having been developed. The problem of weight reduction has, in fact, been attacked so enthusiastically for years that now a skilled technician can produce a flyable model having a wing spanning up to three feet but with an overall structural weight less than half that of a dime. The best of these large models will climb two hundred feet or more and fly upwards of forty-five minutes with duration limited not by model but by flying site. These models will be powered by twisted rubber strands of minute cross section, turning a propeller having a diameter roughly two-thirds of the wing span. Even at 100% efficiency, the total amount of energy available from such a motor which normally weighs about as much as the model itself would lift a brick only a strong hand's width, yet it will sustain the model in flight for well over a half hour.