Red Bull Racing and Ferrari have asked the FIA to provide a rules clarification with respect to the rear wing design of the McLaren MP4-25. One of the most noticeable aspects of the overall profile of the car is the contour of the rear dorsal fin, which extends from the airbox to the rear wing, where it attaches to the surface of the second wing element. The airbox, fin and wing form a unified aerodynamic device.
It now appears that the dorsal fin is hollow, and its function is to channel air from a secondary duct in the airbox to a duct inside the wing element, and then through a slot in the rear of the wing, where the air is released.
The net effect of this design is to decrease drag in straight line runs. It’s estimated that the McLarens are able to increase straight line speeds by 6 mph. The reduced drag also allows them to increase the camber on the second rear wing element, which adds to downforce.
As reported in The Guardian, Red Bull team principal Christian Horner said at Barcelona last week, “There’s a bit of a fuss over McLaren’s rear wing. They have a slot on it [that affects the air flow] and they can pick up a lot of straight-line speed. I think it will get resolved before the first race. We’ve asked the FIA for clarification although I think Ferrari are probably more excited than we are to be honest.”
It’s not an entirely new idea, and apparently BMW experimented with a similar design last year. With this concept, however, McLaren have taken an aggressive approach in their interpretation of the rules (no doubt still smarting from last year’s experience of being overly conservation in their rear diffuser design), and both Red Bull and Ferrari are now trying to get some clarity in yet another gray area in the FIA’s technical regulations.
“It’s something that’s been done quite a lot over the years,” Horner said, “but with the wing separators you’re not supposed to do that. Our question ultimately will be: ‘Is it clever design or is it in breach of the regulations?'”
Horner also went on to say, “[McLaren] must be very confident that it’s legal. I would think it will be legal.”
Not to be caught napping, Horner also said that his team had already begun developing a similar upgrade, which they might deploy, depending on the final ruling of the FIA. No doubt both Ferrari and Mercedes are exploring a similar option.