Mark Hughes: No more teardrops at Mercedes as F1 aero innovation is effectively banned
Mercedes' Formula 1 cars will run without clever aerodynamic devices in Austria after being told to remove them. What did these innovative blisters do? And how much time did they bring?
Mercedes has been told to remove the teardrop blisters on its diffuser ahead of the Austrian GP
Cristobal Herrera-Ulashkevich/AFP via Getty
Last week’s hot technical topic was Ferrari’s rear wheel rims. This week, on the eve of the Austrian Grand Prix, it’s the Mercedes diffuser, specifically how the team has been obliged to remove the extra teardrop-shaped blisters atop its diffuser which were introduced in Montreal. This follows the feature being questioned by Ferrari to the FIA.
It’s a very interesting topic which really shows the ingenuity of these two teams in particular. But to properly understand what’s going on here, you need a bit of background.
The bodywork of the car – ie all the non-mechanical surfaces – is tightly defined in the regulations by a series of dimensional boxes. So for example the diffuser can only be within a notional box, defining its positioning within the car and its height, width etc. There is a separate box for how far back any lower bodywork can extend – 6cm behind the inboard end of the driveshaft (ie where the driveshaft goes into the differential). Conventionally the differential would sit on the rear axle line – but not necessarily. Because the placement of the mechanical masses also has dimension regulations to meet. In the case of the differential it can be within 6cm either side of the rear axle – so behind or in front but only by a maximum of 6cm. So hold that bit of regulation in your mind.
Next, consider how far the lower bodywork can extend back in relation to where the diffuser’s dimensional box is. If you’ve mounted your differential on the rear axle line, your lower bodywork (‘lower’ as defined by another dimensional box) can stretch back only to the same place as the diffuser. So you cannot add any more. But if you have mounted your differential as far back as permitted (ie 6cm behind the axle line), then 6cm behind the differential takes you to beyond the end of the diffuser – opening out a useful little area into which you can put additional bodywork. That is what Ferrari has done with its SF26.
Ferrari introduced its diffuser ‘extensions’ in F1 testing (highlighted, inset, in green), then added a redirection vane
Giuseppe Cacace/AFP via Getty
What Ferrari was then able to do in that space was add a ramped piece of bodywork following the same ramp angle as the diffuser. The two were not joined physically, so the ‘diffuser’ was still of the legal dimension. But the airflow doesn’t see dimensional boxes or legal definitions; all it sees is a great big diffuser. Ferrari took further advantage of that extra bit of bodywork by adding its exhaust-redirecting vane, increasing the flow to the rear wing underside.
So it was a really clever bit of design and lateral thinking, though it has involved some very careful layouts of the angled driveshafts and associated CV joints.
Mercedes – and everyone else – missed this loophole (though the Haas and Cadillac teams inherited it by dint of using Ferrari rear ends) and has mounted its differential on the axle line. But it sought to replicate the effect by way of teardrop-shaped blisters atop the diffuser roof. These create vortices which increase the speed of the airflow behind the diffuser exit, manipulating the air pressure there in a way which encourages the airflow to ‘see’ a bigger diffuser. This feature was introduced to the car in the Canadian Grand Prix weekend.
So, how do these blisters – which extend beyond the diffuser’s dimensional box – comply with the legal requirement? Because they are not physically connected to the diffuser, even though they initially appear to be. Close inspection reveals they are mounted on a thin metal strip which is attached further forward. These legality strips serve the same function as those used on the initial front wing flap of last year’s Mercedes.
Mercedes provided drawings to the FIA before introducing the feature but following Ferrari’s questions the FIA has rethought its interpretation and instructed Mercedes (and Red Bull) to make suitable changes to their diffusers for this weekend.
How much lap time difference are we talking? Probably hundredths of a second. But hey, this is F1.
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