RE: How does an aerobie fly?

Remarkably well, by all reports!

When I first got the message, and eventually discovered the very short question lurking there, it prompted a question in my mind: "What on earth is an aerobie?"

A web search soon told me. We are talking about a throwing ring - like a frisbee, but open in the centre, and without most of the lip around the rim. I have had dealings with such a device, but did not know it under that name. I uncovered a useful bibliography of references to flying rings. The most useful and accessible reference seemed to be to

New Scientist; Jul 28, 1990, v127n1727, p. 37-40;

but there are also others that may be worth checking.

The aerodynamics of such things as flying rings is very complicated, but the following considerations are always important:

(i) The spin about a vertical axis imparted when throwing gives the ring stability. Conservation of angular momentum ensures that this axis is kept near vertical, in the same orientation the flight started. It does not, however provide horizontal stability -- torques produced by air currents (or gravitation, if the throwing axis is not precisely vertical) will cause the ring to veer off to one side.

(ii) An airfoil surface to give lift is usually an important part of the flight. It is easy to check -- see how the ring flies "upside down". A frisbee certainly will not! Some aerobies look nearly symmetrical, in that they have a sharp leading edge rather than the large rim of a frisbee. But even these usually have a distinct curved "top" and flat "bottom".

(iii) Boundary layer effects are important and very complicated. For this sort of device, they usually put an upper limit on the effective launch speed at which a smooth flight can be achieved. It is much higher for an aerobie of appropriate design than for a frisbee.

The aerobie flies faster, further, and somewhat truer than a frisbee - this can mainly be attributed to less air resistance on the sharp leading edge, more lift from the exaggerated airfoil shape of a frisbee, and the extra air resistance from the central part of the frisbee. The propensity of the frisbee to curve, hover, suddenly dart off to one side, makes it my view more fun to play with in the park, and one's throwing partner is within talking, rather than shouting distance!