DIY Aerodynamics: The Gurney Flap

Enjoy, as I have, this tale of the creation of the “Gurney Flap,” a small piece of metal—usually aluminum—that is bolted on to sports cars’ wings to provide downforce. It is a solution that is both effective and cheap, rare in the world of aerodynamics. The Gurney Flap was invented on the race track by Dan Gurney, who was at the time managing a race team, although he is also a legendary driver.

Towards the end of the third and last day of testing, driver Bobby Unser challenged ‘the boss’ to come up with a solution, and Gurney suggested the flap. He’d seen the success Richie Ginther had had experimenting with spoilers on Ferrari sportscars and wondered what would happen if a small spoiler was fitted along a wing’s trailing edge.

In 45 minutes or so, the first Gurney Flap was fabricated and attached to the car’s rear wing, and Unser went out again. Within a couple of laps it was clear he was circulating no faster than before and everyone in the pit assumed the flap was a failure. But when Unser came in he called Gurney over and quietly asked him whether anyone was around to spy on what they were doing. Once Gurney had confirmed they were alone, Unser told him the rear was now so well planted that the car was pushing (understeering) badly, hence the poor lap times. All they needed to do was restore the aerodynamic balance by adding more front-end downforce and the car would be transformed.

The Gurney Flap [AllAmericanRacers.com]