Flying toys are popular amusement devices that include boomerangs, flying discs, kites, model airplanes, and ring airfoils. The popularity of flying toys arises in part because flying toys generate lift as they move through the air, giving them interesting and engaging flight characteristics.
Ring airfoils are relatively obscure flying toys that generally resemble hollow cylinders having open ends. The walls of these cylinders may have an airfoil shape. Ring airfoils "fly" when they generate lift by moving through the air in a flying orientation. Lift generated in flying orientations, combined with low aerodynamic drag, causes ring airfoils to follow nearly level trajectories. In contrast, nonflying toys, such as balls, follow parabolic ballistic trajectories. Nearly level trajectories ensure greater flight times than ballistic trajectories, enhancing the fun of playing with ring airfoils.
In a preferred flying orientation, a leading end of the ring airfoil points generally forward, in the direction of motion, and a trailing end points generally backward, away from the direction of motion. This orientation may be gyro-stabilized by imparting spin to the ring airfoil about a longitudinal symmetry axis connecting the leading and trailing ends.
Although known for many years, ring airfoils have failed to achieve the popularity of other flying toys. This failure may be due in part to difficulties inherent in inducing ring airfoils to move through the air in a flying orientation. In particular, because ring airfoils generally are launched by hand, they typically do not begin their trajectory in a flying orientation. Moreover, even if ring airfoils do begin their trajectory in a flying orientation, they typically do not have sufficient spin to gyro-stabilize that orientation, leaving them susceptible to pitching, yawing, wobbling, and/or tumbling during flight. The skill level necessary to overcome these difficulties effectively may place the use of ring airfoils outside the ability of casual players, or of children in general.
Previous attempts to improve the flight characteristics of ring airfoils have included adjusting the dimensions and mass distribution of the ring airfoils to improve lift. Yet, such improved lift cannot be exploited fully unless the ring airfoil is in a flying Orientation.