Inventor finds an aerodynamic flying ring that flings the farthest

Scott Zimmerman is a slender young man who goes to school at Pasadena City College and programs computers at the Jet Propulsion Laboratory. Mr. Zimmerman is also a four-time World Frisbee Champion. It was in this latter role that he went to the Pasadena Rose Bowl on Jan. 12 to set a new Guinness World Record in the category of longest throw of ``any inert object, heavier than air.''

The inert object Zimmerman brought for the attempt was not a familiar Frisbee, but a new flying ring called the Aerobie. Using a backhand throw and spinning something like a discus thrower Zimmerman sailed flying rings down the field over 30 times in front of an official from the United States Disk Sports Association.

His longest throw, 1,046 feet, surpassed the old record by more than 60 yards. In contrast, Zimmerman's record throw for a Frisbee is 456 feet.

The Aerobie is the creation of Alan Adler, a Stanford University lecturer and consulting engineer. Holder of 15 patents of the ``high tech'' type, Dr. Adler several years ago decided to spend some of his time working on things that were less esoteric and more fun.

``I realized I had invented a lot of things, but nothing that I would ever want to buy myself,'' he explains.

Although Adler's career has been in electrical engineering, the inventor had studied aerodynamics through his love of sailing. Thus, it was natural that he be drawn to flying toys.

As he looked into the Frisbee, Adler discovered that no one knew exactly why it flies as well as it does. The thick edges create turbulence which somehow makes the platter fly in a stable fashion (if you throw it correctly). But the edges also create considerable air resistance, or drag. The inventor became intrigued with the idea of inventing a low-drag Frisbee.

To decrease the drag, Adler first tried making thinner disks. These, however, invariably hooked or sliced depending on the direction in which they were spun. The reason for this is that the forward part of the disk acts as a more efficient ``wing'' than the trailing part. If the disk weren't spinning, this imbalance of force would flip the disk over. But because it spins, the disk acts like a gyroscope so that upward pressure causes the disk to tilt to the side instead.

``The only way to fly straight and level is to get the center of lift over the center of the disk,'' Adler says. For some time he was stumped.

But then he got the idea of replacing the flat disk with a shallow cone: a kind of ``China hat.'' With the correct angle, the front part of the disk should fly less efficiently while the back part should fly more efficiently, and so center the lifting force.

After building and testing a few, he found they did fly well, but only when thrown at a one precise speed.

For ease of manufacture, he refined his China hat down to a canted ring with a backbone of rigid, polycarbonate plastic and an outer layer of soft thermoplastic rubber. Some 2 million of these were made and sold in 1980 and '81 by Parker Brothers & Co. Inc. under the name of Skyro. People were thrilled by the Skyro's performance when it was thrown at just the right speed, but frustrated because it was so difficult to achieve, Adler reports.

Using the Skyro, Tom McRann of the Stanford University athletic department set the previous Guinness record for the longest throw of an object at 286 yards, the record just broken by Zimmerman.

Then, about a year ago, the inventor came up with an even better approach. Using an aerodynamics program on his home computer, Adler realized that a more efficient airfoil would be more stable over a wide range of speeds. He did this by giving the ring a cross section that looks a bit like a slender fish.

The fish's tail is a small ridge that runs along the ring's outside edge. When the ring is thrown, this ridge is at the leading edge of the forward section. In this position, the ridge causes turbulence and decreases the amount of lift generated. In the ring's rear section, however, the ridge is at the trailing edge and so does not interfere with the lift being generated nearly as much.

The new flying ring has been on the market since mid-December and sells for seven or eight dollars. So far, Adler says he's sold a total of 3,500.

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