The aero uncertainty facing F1 teams ahead of testing

The FIA's package of aerodynamic rule changes provided Formula 1 teams with a major challenge over the winter as they honed their 2021 cars.

The aero uncertainty facing F1 teams ahead of testing

And despite the hours spent in their windtunnels and on sophisticated CFD modelling, the aerodynamicists won't be completely confident that they've got their sums right until their new machines have completed a decent amount of testing in Bahrain later this week.

Teams are always keen to pursue correlation between their real cars and the tunnel, which is why they often focus on gathering aero data at the first test.

However, on this occasion there are specific concerns because one of the key areas of bodywork change – ahead of the rear tyres – is notoriously difficult to model with the desired level of accuracy.

Teams that have completed a filming day or shakedown already have some data, but 100kms was not sufficient to obtain all the answers, especially for those who only ran in the wet.

For Mercedes and Haas, who haven't conducted a filming day and whose new cars won't hit the track until Friday, the Bahrain test is potentially even more important. Ferrari is in a similar situation, as the SF21 will have a late shakedown in a filming day at Sakhir on Thursday.

The huge influence of the rule changes also explains why teams have been very selective in the images that they have released. At the Mercedes launch the W12's floor was heavily disguised, as technical director James Allison noted.

"The bit we're not showing you is down along the edge of the floor," he explained.

"That area is the area that was most affected by the new regulations, where they tried to pull performance away from the car by changing the floor regs. Down there, there's a bunch of aerodynamic detail that we are not quite ready to release to the world.

Mercedes AMG F1 W12

Mercedes AMG F1 W12

Photo by: Mercedes-Benz

"Not because it's not there, but because we don't want our competitors to see it. We don't want them starting to try and put similar things in their windtunnels. It just buys us a couple of weeks extra.

"I think we all look very closely at what our competitors do, so we know our competitors will be looking. And we don't have to show it yet, so we're not."

The aero changes came in two stages late last year as the FIA sought ways to trim downforce in 2021 in order to help Pirelli's 2019 tyres survive into a third season.

At the time, it was anticipated that the tyres would be unchanged. In the end, Pirelli did manage to squeeze in a test programme in a Friday practice session and learn enough to develop a more robust tyre in 2021, but by then the aero modifications were already in the system.

The FIA's aim was to trim downforce by around 10%, and the teams have spent the last few months trying to claw that back.

"The combination of the floor area that people are trying to hide, the change in the brake duct shape and the change in the diffuser fences is certainly a pretty substantial reduction in downforce," says Alpine technical director Pat Fry.

"I think that will be one of the main areas of development. So we haven't just got one solution, we've got a myriad of things to test just to get on top of it. It's certainly been a significant loss. We haven't recovered all of it yet, but it's still a work in progress.

"It'll be when we get to the first test where I think it'll become really interesting, when we actually see how well things are correlating to windtunnel and CFD, as well as the actual absolute numbers that we get out of the car."

Alpine A521

Alpine A521

Photo by: Alpine

Fry's admission that Alpine will try various solutions on track is intriguing, as it shows how much effort has been required, and how there is still some uncertainty regarding what will actually work.

Teams won't just have to test their own bits in Bahrain – they will be looking at what everyone else has done and assessing if there's something they've missed.

As Allison admitted, the huge impact of the aero changes has led to teams being more cautious than ever about showing their hands before they really have to.

"I think it is just a point of principle, more than anything," says Fry. "You never give anything away. I've been taught that for 30 years, so I find it hard to change now.

"I think that the secrecy that people are showing at the moment, the areas that we touched on earlier, the area around the side of the floor, in front of the tyre, the brake ducts, how people reacted to all that area, I think is the thing where people will be trying to keep their powder dry.

"We all think we're clever and we all try and hide what we're doing, and then you find out how quick you are come the Bahrain race."

Aston Martin technical director Andrew Green cautioned last year that the aero reg changes would be significant, and that has proved to be the case.

"It was a big challenge, mainly due to the lateness of the change," says Green. "There were two changes. I think the first one took the car a step back, and then the second one, again, even further.

"And it's been our challenge over the winter to recover. I don't think we're where we would like to be.

Sebastian Vettel, Aston Martin Racing

Sebastian Vettel, Aston Martin Racing

Photo by: Aston Martin Racing

"But everything's relative, so we'll wait and see. We're happy with what we've done so far. There's still more to go. But I think we've given ourselves a solid foundation to work from."

There's an extra dimension to 2021's aerodynamic focus. This year revised testing regulations have introduced a sliding scale of windtunnel hours and CFD usage based on last year's championship standings, with Mercedes getting the least, and Williams the most.

In tandem with that comes the obvious urge to focus aero resources on the 2022 package. Haas has already decided to concentrate entirely on the new car, and others will make a full transition as soon as they dare.

The last thing any team needs now is to discover in Bahrain that it has missed a trick and that it now has to divert extra effort into re-evaluating the 2021 rule changes, thus taking focus off next year's project.

"I think the biggest challenge that we see at the moment is the 2022 car, which is on the horizon," says Green.

"And which is such a step change in concept from anything we've done before. It is eating a significant amount of development resource that would normally be put into the current season car.

"So I think there is a lot of performance left in the '21 car. I think our biggest challenge is to try and extract it in the time that we have available, which is quite limited."

Lance Stroll, Aston Martin Racing

Lance Stroll, Aston Martin Racing

Photo by: Aston Martin Racing

Ferrari boss Mattia Binotto has already made it clear where the Maranello team's priorities lie.

"Our focus during 2021 will be developing the 2022 car," says the Italian. "That will be the main target, so we will not spend much time on the 2021 during the season."

Binotto stresses that aero correlation will be key.

"Obviously we know how much we progressed with windtunnel power. But more than that, what will be important is to see the track delivery. How really the car will be on track compared to expectations.

"We have experience in the past and we are not the only ones that sometimes you may have mismatch from the windtunnel to the race track.

"And I think that will be a key point for all the competitors, because again having changed the regulations on the rear of the car I think there is somehow a work of correlation which is needed, and I think that will be a key factor for the season."

Teams have only a single three-day test, and so there is no second chance to try updates on the track before the Bahrain GP race weekend – although Mercedes does have a filming day scheduled at Sakhir on 16 March, and it may keep a few parts hidden until then.

Thus there's not much of a safety net for anyone who discovers at this week's test that there's some extra aero work to be done, and don't forget that Friday race weekend running has been reduced this year, so once the season starts it will be harder to catch up.

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