Gurney Flap

A Gurney Flap is a small vertical tab attached to the back edge of a race car's wing that helps push the car down onto the track for better grip and faster cornering.

Named after legendary American race car driver and engineer Dan Gurney, who invented it in 1971, this simple device has become one of the most widely used aerodynamic tools in motorsport. The flap is typically a small strip of aluminum or carbon fiber, usually only a few centimeters tall, mounted at a right angle to the wing's surface. Despite its modest size, it makes a significant difference in how air flows around the wing.

The primary purpose of a Gurney Flap is to increase downforce, which is the aerodynamic force that pushes a race car down onto the track. More downforce means the tires grip the road better, allowing drivers to take corners at higher speeds without losing control. Think of it like pressing down on a toy car with your hand—the harder you press, the better it sticks to the surface.

The flap works by disrupting the smooth flow of air as it leaves the wing. This creates a small area of turbulent, swirling air right behind the wing, which changes the air pressure above and below the wing surfaces. The increased pressure difference generates additional downforce across the entire wing, not just at the trailing edge where the flap sits. This effect also helps prevent airflow separation, which is when air stops flowing smoothly over the wing and causes it to lose effectiveness.

Race teams use Gurney Flaps as a tuning tool to adjust their car's aerodynamic balance. By changing the flap's height or adding and removing flaps from different parts of the car, engineers can fine-tune performance for specific track conditions. You'll find these flaps on rear wings, front wings, and other aerodynamic components across various racing series including Formula 1, IndyCar, NASCAR, and sports car racing.

The invention story is quite interesting. During testing in 1971, driver Bobby Unser challenged Dan Gurney to improve their USAC race car's performance. Gurney experimented with adding a small lip to the rear wing's trailing edge, and the results were immediately positive. The device became known as the Gurney Flap and quickly spread throughout motorsport.

While Gurney Flaps primarily increase downforce, they do have a tradeoff. The turbulent air they create also adds some aerodynamic drag, which can slow the car down on straightaways. Teams must carefully balance the grip benefits in corners against the potential speed loss on straights. The optimal setup varies depending on whether a track has many tight corners or long straight sections.

Beyond motorsport, Gurney Flaps have found applications in aviation. Commercial aircraft like the McDonnell Douglas MD-11 use them across their wings to improve efficiency, and helicopters employ similar devices on their rotor blades. This crossover demonstrates how effective this simple invention truly is at improving aerodynamic performance across different applications.