Allison: Quest for lost downforce with 2021 rules an 'entertaining ride'

Mercedes technical director James Allison says the efforts to recover part of the downforce lost in the wake of this year's regulations changes has taken his aero department on an "entertaining ride".

In a bid to limit costs, teams must carry into 2021 their current chassis. However, with last year's increase in downforce putting Pirelli's tyres on the limit of their resistance, the FIA has mandated a series of aero tweaks.

While there will be changes to the diffuser and brake ducts, the most significant modification will involve a reduction of the rear outer floor area of a car, the trimming of which will impact downforce levels.

For Mercedes, and Allison in particular, reacting to the challenge posed by this season's changes has been "most intense and difficult".

"Four quite significant aerodynamic changes were made last year in anticipation of this new season," the always articulate Allison explained in a Mrercedes video.

"First and foremost, there has been a triangular cut-out to the edges of the floor in front of the rear wheels [illustrated below by Haas’s 2021 floor test in Abu Dhabi last year] which when you see it, you’ll think, ‘that doesn’t look that big’.

"But on its own, in its rawest form, if you just chop that area off your car it’ll take about a second a lap away from the car.

"The little fins and flicks that were on the rear brake duct were reduced in their span just by a few millimetres but again, they were very powerful devices and that change lost a lot of performance from the car.

"At the back of the car, underneath in the diffuser area, the fences that you can see if you peer up the back end of the car were reduced in height so that they can’t go as near to the ground.

"They can’t create as good of an aerodynamic seal to the ground as they did previously. And they shed a bunch of downforce when they are trimmed upwards.

"Finally, the front end of the floor, as you approach where the bargeboards are, if you looked at the 2020 versions of those floors you see that they look a bit like a venetian blind, with lots and lots of slots, an aerodynamic feature there that generates downforce.

"All of those slots have been removed for 2021," added the Mercedes engineer.

"It’s been our challenge over the weeks and months since those rules were set in stone to try to recover as much of the performance as possible.

"That has been quite an entertaining ride in the windtunnel and in CFD to try and make sure that we get that performance as far as possible back onto the car."

Dealing with Pirelli's revised 2021 tyres is another change that teams have been required to factor into their work.

F1's exclusive tyre supplier is offering a more robust product this season to help mitigate durability concerns that emerged last year.

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However, with limited data derived from testing the new tyres in the back half of last year, "optimizing" its 2021 car has also been a challenge for Mercedes.

"We got a first glimpse of these new tyres back in Portimao in 2020," said Allison.

"We've had two other occasions where we could test them, and they were in Bahrain and then in Abu Dhabi the last race of last year.

"That's not really very much opportunity to take on board a new tyre and get ready for a new season with it because these tyres will affect the way that the car performs, and they affect the way that you have to design the aerodynamic platform, and the way that you have to set up the car.

"So it's been a big challenge for us to try and stretch out that testing data that we had at the tracks last year and to try and make as much as we can out of the tyre data supplied to us by Pirelli, so that we would be ready to really optimise the car around the characteristics of these new tyres."

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