page_title: Formula One car
section_title: Ground effect
hierarchical_section_title: Formula One car / Aerodynamics / Ground effect
caption_attribution_description: English: Renault R29 (detail), F1 testing session, Jerez 10-Feb-2009
context_page_description: A Formula One car is a single-seat, open cockpit, open-wheel racing car with substantial front and rear wings, and an engine positioned behind the driver, intended to be used in competition at Formula One racing events. The regulations governing the cars are unique to the championship and specify that cars must be constructed by the racing teams themselves, though the design and manufacture can be outsourced.
context_section_description: F1 regulations heavily limit the use of ground effect aerodynamics which are a highly efficient means of creating downforce with a small drag penalty. The underside of the vehicle, the undertray, must be flat between the axles. A 10 mm thick wooden plank or skid block runs down the middle of the car to prevent the cars from running low enough to contact the track surface; this skid block is measured before and after a race. Should the plank be less than 9 mm thick after the race, the car is disqualified.
  A substantial amount of downforce is provided by using a rear diffuser which rises from the undertray at the rear axle to the actual rear of the bodywork. The limitations on ground effects, limited size of the wings (requiring use at high angles of attack to create sufficient downforce), and vortices created by open wheels lead to a high aerodynamic drag coefficient (about 1 according to Minardi's technical director Gabriele Tredozi; compare with the average modern saloon car, which has a Cd value between 0.25 and 0.35), so that, despite the enormous power output of the engines, the top speed of these cars is less than that of World War II vintage Mercedes-Benz and Auto Union Silver Arrows racers. However, this drag is more than compensated for by the ability to corner at extremely high speed. The aerodynamics are adjusted for each track; with a low drag configuration for tracks where high speed is more important like Autodromo Nazionale Monza, and a high traction configuration for tracks where cornering is more important, like the Circuit de Monaco.
caption: A rear diffuser on a 2009 Renault R29. Rear diffusers have been an important aerodynamic aid since the late 1980s
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