2016 FIA WEC - Porsche 919 Hybrid vs Audi Sport R18 vs Toyota TS050

[mav1178]

Good luck differentiating the cars on the track!

[Captain Snooze]

Could someone tell me what is it about the design of these cars that make dorsal fins a necessity?

[hey_mikey]

Originally Posted by Captain Snooze

Could someone tell me what is it about the design of these cars that make dorsal fins a necessity?

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It's mandated by the FIA. The fin disrupts airflow over the car when it gets sideways, reducing lift and the chance of a rollover in the event of a spin.


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[hey_mikey]

Another interesting tidbit - the low pressure side of an airfoil is more sensitive to airflow disturbances than the high pressure side, so the dorsal fin stops short of the rear wing and goes up and over to support the wing from the top. This allows the underside of the wing to be uniform across the entire wing, maximizing the pressure differential and lift.


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[mav1178]

Originally Posted by hey_mikey

It's mandated by the FIA. The fin disrupts airflow over the car when it gets sideways, reducing lift and the chance of a rollover in the event of a spin.

To add to this point, they want to avoid the epic crashes of Le Mans past... the worst ones are often after the car gets sideways and airborne fast.

once in a while, a bad wreck still happens.

[ame="https://www.youtube.com/watch?v=bfTVJ9sJAD4"]24h Le Mans 2012 Toyota crash - YouTube[/ame]

[hey_mikey]

It's always a Ferrari causing the big LMP1 crashes... :hiding:

really though, once the Toyota's wheels left the ground after the initial contact, the freestream flow under the car picked it up and probably caused a loss of all ground effect from the underbody aero. If you watch closely, the right side wheels never regained contact with the ground after the initial impact. as the car got more and more sideways with the right wheels in the air, the freestream flow under the car combined with the angle of the underbody to produce an upward force component that increases with the roll angle and eventually launched the car into the air.

The dorsal fin only works if the car keeps all four wheels mostly planted on the ground. Once you get a large, flat underbody away from the pavement and facing a high velocity flow, there isn't much you can do to keep from going airborne.


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[Talus1]

Does anybody else find it mildly entertaining that Audi is still running a diesel in the WEC, in view of the VAG emissions scandal? Clearly they were/are committed but it must be a bit of a marketing nightmare.