![RoofFlapCarlEdwardNationwideRoadAmerica](https://upload.wikimedia.org/wikipedia/commons/0/08/RoofFlapCarlEdwardNationwideRoadAmerica.jpg)
A roof flap is an
aerodynamic
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
feature on
race cars, mainly
stock cars
Stock car racing is a form of automobile racing run on oval tracks and road courses measuring approximately . It originally used production-model cars, hence the name "stock car", but is now run using cars specifically built for racing. It ori ...
, which functions as an emergency
spoiler
Spoiler is a security vulnerability on modern computer central processing units that use speculative execution. It exploits side-effects of speculative execution to improve the efficiency of Rowhammer and other related memory and cache attacks. Ac ...
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, particularly if it is facing backwards, the flaps deploy to disrupt the air flow over the roof and reduce the
lift
Lift or LIFT may refer to:
Physical devices
* Elevator, or lift, a device used for raising and lowering people or goods
** Paternoster lift, a type of lift using a continuous chain of cars which do not stop
** Patient lift, or Hoyer lift, mobile ...
force on the vehicle.
First required in 1994,
NASCAR
The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
now mandates that cars in the
Cup
A cup is an open-top used to hold hot or cold liquids for pouring or drinking; while mainly used for drinking, it also can be used to store solids for pouring (e.g., sugar, flour, grains, salt). Cups may be made of glass, metal, china, clay, ...
and
Xfinity
Comcast Cable Communications, LLC, doing business as Xfinity, is an American telecommunications company and division of Comcast Corporation used to market consumer cable television, internet, telephone, and wireless services provided by the com ...
series have two roof flaps 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° counter-clockwise (when looking downward) from the left flap.
Trucks in the
Camping World Truck Series
The NASCAR Craftsman Truck Series is a pickup truck racing series owned and operated by the National Association for Stock Car Auto Racing, and is the only series in NASCAR to race production pickup truck based stock cars. The series is one of th ...
only have the angled flap, due to the smaller roof area of the
pickup truck
A pickup truck or pickup is a light-duty truck that has an enclosed cabin, and a back end made up of a cargo bed that is enclosed by three low walls with no roof (this cargo bed back end sometimes consists of a tailgate and removable covering) ...
type greenhouse and lower overall lift potential of the body shape.
Originally, the flaps each measured wide by tall.
Following several incidents where cars became airborne in Sprint Cup races in preceding years, NASCAR mandated new, larger flaps to increase their effectiveness, introduced with the "
Car of Tomorrow
The Car of Tomorrow (abbreviated as CoT) was the common name used for the chassis of the NASCAR Cup Series (2007 –2012) and Xfinity Series (since 2011 full-time) race cars. The car was part of a five-year project to create a safer vehicle ...
" fifth generation body style in 2007. Flap specs were enlarged again for the "Generation 6" body styles which debuted in 2013. For the 2013 season, the flaps measured tall by tall on the left side, and by on the right.
The new flaps are designed to deploy more quickly than the previous design, and include canvas "parachutes" on their underside to further disrupt airflow when deployed.
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,
Rusty Wallace
Russell William "Rusty" Wallace Jr. (born August 14, 1956) is an American former NASCAR racing driver. He has won the 1984 NASCAR Cup series Rookie of the Year and the 1989 NASCAR Winston Cup Championship. Over the course of his successful care ...
barrel-rolled through the infield of
Talladega Superspeedway
Talladega Superspeedway, nicknamed “'Dega”, and formerly named Alabama International Motor Speedway (AIMS) from 1969 to 1989, is a motorsports complex located north of Talladega, Alabama. It is located on the former Anniston Air Force Base ...
in
1993
File:1993 Events Collage.png, From left, clockwise: The Oslo I Accord is signed in an attempt to resolve the Israeli–Palestinian conflict; The Russian White House is shelled during the 1993 Russian constitutional crisis; Czechoslovakia is peace ...
after being tagged by
Dale Earnhardt
Ralph Dale Earnhardt Sr. (; April 29, 1951February 18, 2001) was an American professional stock car driver and team owner, who raced from 1975 to 2001 in the former NASCAR Winston Cup Series (now called the NASCAR Cup Series), most notably dri ...
exiting the tri-oval. Wallace's car spun backwards, and lifted off the ground. The car landed in a grassy area of the track and his car tumbled violently down the front stretch. In August of that same year,
Johnny Benson Jr. spun off turn two at
Michigan International Speedway
Michigan International Speedway (MIS) is a moderate-banked D-shaped speedway located off U.S. Highway 12 on more than approximately south of the village of Brooklyn, in the scenic Irish Hills area of southeastern Michigan. The track is ...
and flipped down the backstretch.
NASCAR tested a
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 (e.g., motorcycles) for insurance purposes, but mainly in automobile racing, to li ...
at
Charlotte Motor Speedway
Charlotte Motor Speedway (previously known as Lowe's Motor Speedway from 1999 to 2009) is a motorsport complex located in Concord, North Carolina, outside Charlotte. The complex features a quad oval track that hosts NASCAR racing including th ...
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 (born Jackson Earnest Roush on April 19, 1942) is the founder, CEO, and co-owner of Roush Fenway Keselowski Racing, a NASCAR team headquartered in Concord, North Carolina, and is chairman of Roush Enterprises.
Roush Enterprises is the ...
.
Following
Matt Crafton
Matthew Justin Crafton (born June 11, 1976) is an American professional stock car racing driver. He is a three-time champion of the NASCAR Camping World Truck Series (2013, 2014, 2019), in which he competes full-time, driving the No. 88 Ford F-150 ...
's flip while practicing for a
pickup truck race at
Daytona International Speedway
Daytona International Speedway is a race track in Daytona Beach, Florida, United States. Since opening in 1959, it has been the home of the Daytona 500, the most prestigious race in NASCAR as well as its season opening event. In addition to NA ...
in 2017, NASCAR developed flaps that are located on the decklid of the trucks used in their
Truck Series, meant to keep the trucks from getting airborne due to their tendency to do so despite the angled flap on their roofs. These flaps are designed to deploy as the truck goes around, venting the air through the decklid, which often acted as a parachute before. However, upon introduction at Talladega that fall, it was found that the center flap would often deploy on track as the trucks qualified or raced. This was likely due to the positioning of the flap, being close to the rear windshield on the trucks. The pocket of low pressure caused by turbulence of the air coming around the trucks' cabs is likely what caused it to deploy. This resulted in stunted qualifying runs and the inability to keep the trucks grouped in packs during racing as a result of how vastly it changed the flow of air around the trucks. They did prove effective in their purpose later in the race when
Cody Coughlin
Cody Coughlin (born December 11, 1995) is an American professional stock car racing driver who competes part-time in the ARCA Menards Series, driving the No. 72 Ford Fusion, and part-time in the ARCA/CRA Super Series and CARS Pro Late Model Tour ...
wrecked with others during the Talladega race, when his truck threatened to go airborne upon turning backwards, but set back down, although on top of another truck in the process.
References
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Automotive technologies
Auto racing equipment
Motorsport terminology