Controversy was again sparked around the Red Bulls legality at Monaco. Several teams were unhappy with the detail of the RB8's floor and sought clarification from the FIA, although no formal protest was lodged.
The entire issue revolves around small vents the team have fitted to the floor ahead of the rear tyres. According to the technical regulations, these must not be enclosed holes.
Other teams have also adopted these vents and they join them to the edge of the floor, whereas Red Bull does not appear to have done so.
These vents were common back in 2010 and are used as a way to gain better diffuser performance. When the airflow around the car hits the rear tyres, it is split and the flow passing inboard of the tyre blows laterally into the diffuser. This slows the flow through the diffuser and costs downforce. This lateral flow is known as "tyre squirt".
To offset this unwanted tyre squirt teams use these vents as a way to redirect the flow and keep the diffuser working efficiently.
They work by bleeding air from above the floor to the area just ahead of the tyre, under the floor. This adds energy to the flow splitting around the tyre and prevents it passing into the diffuser. In 2010 these vents were legal, but the rules were subsequently reworded to ban the double diffuser, which also effectively banned these vents.
Sauber's solution to the vents in front of the rear wheels
Article 3.12.5* in the Technical Regulations says that "All parts lying on the reference and step planes, in addition to the transition between the two planes, must produce uniform, solid, hard, continuous, rigid (no degree of freedom in relation to the body/chassis unit), impervious surfaces under all circumstances."
Thus the rules called for no enclosed holes in the floor, this was to counteract the extra entrance under the floor to feed the double diffuser.
In 2011 exhaust blown diffusers offset tyre squirt by blowing the gap between tyre and diffuser, replicating the slots effect. With the rules again reworded for 2012 to ban the exhaust blown diffuser, these solutions have become attractive again.
Sauber was the first team to reintroduce these solutions, by creating a slot in-between the floor and an aerofoil section just ahead of the rear tyre. This was legal as the slot extended to the edge of the floor, thus it was not a hole, but a continuation of the periphery of the floor.
Ferrari soon followed Sauber with a simpler trio of vents, each joined to the floor's edge by a thin slot to maintain legality. As the slot creates a continuation of the floor's periphery, the vent is not an enclosed hole. Some small amount of the vent's performance is lost by having a slot, but the overall effect of the vent on the car is far greater than this loss.
Ferrari followed Sauber's lead but uses a trio of vents
These legality slots to join the vent to the edge of the floor are akin to the slots to create the "fishbone"-effect cooling louvers around the exhaust outlet. The rules do not stipulate how wide any gap must be, simply that there must be a gap
Red Bull had tested solutions similar to both Ferrari and Sauber, but it was observed in Monaco that their vent may not join the floors edge at any point. This therefore could be seen to contradict the regulation regarding enclosed holes. This is why the other teams raised the issue with the FIA.
In reality the performance gained by Red Bull in not having a slot joining the vent to the edge of the floor is tiny, if not immeasurable. But if this rule is not upheld and teams are allowed to create enclosed holes in the floor, it reopens the avenue to create double diffusers and other aerodynamic tricks with the floor, which were supposedly closed off in 2010.
So it is the principle rather than the actual benefit of the Red Bull vent that's being argued.
*Article 3.12.5: "All parts lying on the reference and step planes, in addition to the transition between the two planes, must produce uniform, solid, hard, continuous, rigid (no degree of freedom in relation to the body/chassis unit), impervious surfaces under all circumstances.
"Forward of a line 450mm forward of the rear face of the cockpit entry template, fully enclosed holes are permitted in the surfaces lying on the reference and step planes provided no part of the car is visible through them when viewed from directly below. This does not apply to any parts of rear view mirrors which are visible, provided each of these areas does not exceed 12000mm² when projected to a horizontal plane above the car, or to any parts of the panels referred to in Article 15.4.7."