It slices through air with the greatest of ease. It sails so far that it holds the world record for the longest flight — 1,046 feet, 11 inches — by a thrown, heavier-than-air object. It makes a Frisbee look like a tired dinner plate.
This newly invented flying ring, called the Aerobie, is quickly spinning into the hands of aerodynamics fans throughout the United States. What makes the Aerobie go, says inventor Alan Adler, who lives in Palo alto, Calif., and lectures in electrical engineering at Stanford University, is a special rim along the ring’s outer edge. “The trick was to make the ring aerodynamically stable so that it would fly straight,” he says. “The challenge was to design an airfoil section that had one characteristic flying forward and a different characteristic flying backward.” When Adler began this project a year ago, no one knew whether such a design was feasible. For stability, the ring’s center of lift had to be over its center of gravity.
This perfect balance could be achieved if the trailing half of the ring had a higher lift-slope (the ratio of a change in lift to a change in the angle of attack) than the leading half. But because the ring would be spinning, no known airfoil had the right characteristics to work as both a leading edge and a trailing edge. “I nearly abandoned the quest on several occasions,” says Adler, “but kept going and eventually tested an outer rim design which had a spoiler lip on the upper edge to reduce the lift-slope of the leading half. The model was more stable than anything I had seen before.” He tried different rim heights and angles before he came up with his thin, flat, record-setting ring.
With this design, says Adler, “the Aerobie works over an amazingly broad range of speeds.” And even a 6-year-old can quickly and easily learn to toss it.