Ask Fuzzy: How does a Frisbee fly?

Although a Frisbee is almost the simplest possible flying device, the physics of flight is quite complicated.

The shape is crudely aerodynamic. Being curved, air passing over the top travels a shorter distance than it does along the bottom. That creates a higher pressure above, which you could say, "sucks" the Frisbee upwards.

If you execute a perfectly neat throw, the Frisbee will fly almost flat and, as it nears the end of its trajectory, drag takes over and it drops rapidly. Mathematical modelling suggests the optimum angle of launch is about 10 degrees. The world record is 338 metres!

Then maybe you have a kelpie that will leap off the ground to snatch it out of the air. The kelpie has the aerodynamics of, well, a kelpie.

A perfect throw is fairly difficult, and more likely, the Frisbee will veer off course. If you're right-handed, it usually steers right.

That gives clue to the flight dynamics. While spinning stabilises the Frisbee, it also introduces the effect of gyroscopic precession. You will have felt this effect riding a bicycle. When you turn the bars right, the bike tips left. If the leading edge of a Frisbee tilts up, it twists the Frisbee right (if you're right-handed), and instead of a stylish flight, it spears into the ground.

Commercial Frisbees have a few tricks that help them fly better. One is they're heavier around the edge, increasing stability. Some have small ridges around the top which break up the air flow to prevent vortexes from sticking to the surface during flight.

The Frisbee has much in common with the boomerang which, as Australians know, was invented many thousands of years ago. We found one in our backyard in Duntroon, and were delighted when Professor John Mulvaney came to collect it.