MPH: F1 grey area that's hobbled McLaren's flexible rear wing

September 20th 2024

McLaren has been pushed into modifying its flexible rear wing after footage of its 'mini-DRS' effect in Baku. It's just part of the cat-and-mouse game that teams play, writes Mark Hughes

Baku spec rear wing will be modified after rival teams complained

DPPI

Author

Mark Hughes

McLaren has been informed by the FIA that the ‘mini DRS’ rear wing it has been running recently will not in future be considered acceptable. Yet the governing body accepts that the wing met the technical regulations as written.

The apparent disconnect between those two positions is all about the process teams go through in discussing with the FIA the legality or otherwise of any innovation. It’s a tentative game of cat-and-mouse where only one side knows what the end intention is.

You may have seen the footage from the rearward-facing camera of the McLaren in Baku. It shows how the gap between the rear wing’s main plane trailing edge and the flap’s leading edge expands as the underside of the flap bends upwards at the outboard ends. As the gap between the flap and mainplane increases with speed, so the drag will be reduced. It’s been described as a ‘mini DRS’, but working when the DRS is not deployed. It only acts upon the outer tips of the flap – which is always the draggiest part of a wing. The feature – which has been on the car since Spa – may have played a critical part in Oscar Piastri being able to keep Charles Leclerc’s Ferrari behind him to win last weekend’s Azerbaijan Grand Prix. It will also have been particularly valuable on the long straights of Spa and Monza.

McLaren flexible wing at the 2024 Azerbaijan Grand Prix — Piastri’s wing flex was quickly spotted by some viewers

F1

The regulations deal with rear wing assemblies which rotate back (which this is not doing). They also specify how much deflection is permissible in the wing flap itself (7mm with a 500N load). But that’s about the flap flexing downwards. What the McLaren’s is doing is flexing its underside upwards. There is no specific regulation about the flexibility of the flap’s underside. There is a coverall, “All aerodynamic components or bodywork influencing the car’s aerodynamic performance must be rigidly secured and immobile”. But flex is not the same as mobility.

The slot gap has to measure between 10-15mm when not in DRS mode. Did the gap ever exceed that? Difficult to tell from the footage… and that’s where the grey area resides.

So now the flex has to be reduced. But in the meantime, McLaren has enjoyed the benefits of it on three circuits – Spa, Monza and Baku – where low drag is especially valuable.

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That’s part of the game. Red Bull has in the past had its flexing outlawed either by regulation change (rear wing flex in mid-’21, for example) or by a similar ‘we don’t wish to see that again’ approach to that which has just been applied to McLaren.

The team itself emphasised the informal resolution — and suggested that others should be paid a visit by the governing body. “Whilst our Baku rear wing complies with the regulations and pass all FIA deflection tests, McLaren have proactively offered to make some minor adjustments to the wing following our conversations with the FIA,” it said in a statement. “We would also expect the FIA to have similar conversations with other teams in relation to the compliance of their rear wings.”

Rob Marshall, 17 years at Red Bull but for the last year McLaren’s Chief Designer, is renowned for his ingenuity with structures. At Singapore, he explained the process of dialogue which happens before such a feature is introduced. This is where the game starts.

“You wouldn’t discuss it in terms of aero elasticity,” he says. “You discuss the requirements of the regulations, and whether you’re compliant with regulations. You don’t talk about aeroelastics and characteristics. It’s not what the FIA are interested in. They want to ensure that the cars that are delivered to the circuit are compliant with the regulations and any directives and any opinion they may have. And you work with them to ensure that.

“Obviously, the nearer the front you are, the more scrutiny you come under. But all teams scrutinise their own cars, as well as other people’s. We scrutinise our car. Work with the FIA to understand the grey areas of whatever element of the car it is. And move forward accordingly.

“Other teams have all got their own opinions. We work with FIA to establish the legality of our cars. As long as the FIA is happy that’s the only opinion we need to worry about.”

Significantly, the latest action by the FIA comes in the wake of anger from rival teams. It’s all part of the total competition of F1.