Roof flap
Encyclopedia
A roof flap is an aerodynamic
feature on race cars
, mainly stock cars
, which functions as an emergency spoiler
to prevent the vehicle from lifting off the ground. The flaps are stowed during normal vehicle operation; however, in certain situations, e.g., if the vehicle goes into a spin, the flaps deploy to disrupt the air flow over the roof and reduce the lift
force on the vehicle.
NASCAR
mandates that vehicles have two roof flaps, each measuring 12 inches (30.5 cm) wide by 8 inches (20.3 cm)tall, positioned near the rear of the vehicle, with the left flap oriented perpendicular to the length of the car and the right flap angled 45° anti-clockwise (when looking downward) from the left flap.
A race car's body is designed to optimize downforce, but if that body is spun so air is flowing in reverse, lift is generated instead of countered. The roof flaps' job is to disrupt that airflow and prevent lift.
The decision to implement a safety device to keep cars on the ground came after two crashes in 1993. In the first, 1989 NASCAR champion Rusty Wallace
tumbled across the stripe at Talladega Superspeedway
in 1993 after Dale Earnhardt
spun him off the tri-oval; Wallace's Pontiac was hammered, spun around, and lifted off the ground. The car landed in a grassy area of the track and his car tumbled violently down the frontstretch. In August Johnny Benson, Jr. spun off Turn Two at Michigan International Speedway
and flipped down the backstretch.
NASCAR tested a restrictor plate
at Charlotte that September but driver lobbying led to development of the roof flaps. "We developed them so NASCAR would not slow the cars down more," said the devices' primary engineer, Jack Roush
.
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
feature on race cars
Auto racing
Auto racing is a motorsport involving the racing of cars for competition. It is one of the world's most watched televised sports.-The beginning of racing:...
, mainly stock cars
Stock car racing
Stock car racing is a form of automobile racing found mainly in the United States, Canada, New Zealand, Great Britain, Brazil and Argentina. Traditionally, races are run on oval tracks measuring approximately in length...
, which functions as an emergency spoiler
Spoiler (automotive)
A spoiler is an automotive aerodynamic device whose intended design function is to 'spoil' unfavorable air movement across a body of a vehicle in motion. Spoilers on the front of a vehicle are often called air dams, because in addition to directing air flow they also reduce the amount of air...
to prevent the vehicle from lifting off the ground. The flaps are stowed during normal vehicle operation; however, in certain situations, e.g., if the vehicle goes into a spin, the flaps deploy to disrupt the air flow over the roof and reduce the lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
force on the vehicle.
NASCAR
NASCAR
The National Association for Stock Car Auto Racing is a family-owned and -operated business venture that sanctions and governs multiple auto racing sports events. It was founded by Bill France Sr. in 1947–48. As of 2009, the CEO for the company is Brian France, grandson of the late Bill France Sr...
mandates that vehicles have two roof flaps, each measuring 12 inches (30.5 cm) wide by 8 inches (20.3 cm)tall, positioned near the rear of the vehicle, with the left flap oriented perpendicular to the length of the car and the right flap angled 45° anti-clockwise (when looking downward) from the left flap.
A race car's body is designed to optimize downforce, but if that body is spun so air is flowing in reverse, lift is generated instead of countered. The roof flaps' job is to disrupt that airflow and prevent lift.
The decision to implement a safety device to keep cars on the ground came after two crashes in 1993. In the first, 1989 NASCAR champion Rusty Wallace
Rusty Wallace
Russell William Wallace, Jr. is a past NASCAR Winston Cup Champion, currently a broadcaster on ESPN, car owner in the Nationwide Series, and a co-host of NASCAR Angels.-Early racing career:...
tumbled across the stripe at Talladega Superspeedway
Talladega Superspeedway
Talladega Superspeedway is a motorsports complex located north of Talladega, Alabama, United States. It is located on the former Anniston Air Force Base just outside the small city of Lincoln. It was constructed by International Speedway Corporation, a business controlled by the France Family, in...
in 1993 after Dale Earnhardt
Dale Earnhardt
Ralph Dale Earnhardt, Sr. was an American race car driver, best known for his involvement in stock car racing for NASCAR...
spun him off the tri-oval; Wallace's Pontiac was hammered, spun around, and lifted off the ground. The car landed in a grassy area of the track and his car tumbled violently down the frontstretch. In August Johnny Benson, Jr. spun off Turn Two at Michigan International Speedway
Michigan International Speedway
Michigan International Speedway is a two-mile moderate-banked D-shaped superspeedway located off U.S. Highway 12 on more than in Brooklyn, in the scenic Irish Hills area of southeastern Michigan. The track is used primarily for NASCAR events. It is sometimes known as a "sister track" to Texas...
and flipped down the backstretch.
NASCAR tested a restrictor plate
Restrictor plate
A restrictor plate or air restrictor is a device installed at the intake of an engine to limit its power. This kind of system is occasionally used in road vehicles for insurance purposes, but mainly in automobile racing, to limit top speed and thus increase safety, to provide equal level of...
at Charlotte that September but driver lobbying led to development of the roof flaps. "We developed them so NASCAR would not slow the cars down more," said the devices' primary engineer, Jack Roush
Jack Roush
Jack Roush is the founder, CEO, and co-owner along with John Henry of Roush Fenway Racing, a NASCAR team headquartered in Concord, North Carolina, and is Chairman of the Board of Roush Enterprises....
.