Why F1's 2021 rules hurt low rake Mercedes more

Mercedes' confirmation that it believes its low rake car concept has been hit hardest by Formula 1's 2021 aero rule change has added an interesting dynamic to the title battle.

Why F1's 2021 rules hurt low rake Mercedes more
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With Mercedes and Red Bull at the two extremes of the low rake/high rake solution, how the reigning champion team bounces back from this situation will be fascinating to see.

While Mercedes hopes it will eventually be able to claw back the extra downforce it has lost, here we take a look at just why the low rake cars may have come off worst.

What is rake?

Ferrari SF1000 rake

Ferrari SF1000 rake

Photo by: Giorgio Piola

The term rake is used to describe the nose down attitude of the car and is perhaps most widely associated with Red Bull and its lineage of cars since 2009.

It's also a design trait that has been almost universally adopted by the entire grid too, as it's widely accepted that, if the conditions are right, a car designed with a higher rake angle will be able to generate more downforce from the floor and diffuser than one at a lower angle.

This is down to the additional volume that's created between the underside of the floor/diffuser and the ground.

In simple terms, Red Bull's high rake potentially increases the volume of its diffuser due to the increased ground clearance.

On the other hand, Mercedes has preferred to go for a low-line rake philosophy, tied to its longer wheelbase. This gives it more floor space to create that volume in the area ahead of the diffuser.

However, if you cannot effectively seal the edge of this floor volume, you will lose any potential downforce that can be generated and you will start to have some unwanted side effects instead.

When F1's new floor rules for 2021 were announced, with a section ahead of the rear tyre cut out, the initial suspicion was that it would actually hurt the high rake cars like Red Bull more.

But as the teams have worked and adapted to the floor changes, it has become clear that a change of emphasis has come more from a further clampdown on the use of holes and slots in the floor – which appears to have hindered Mercedes' ability to seal the floor edges.

All teams have regularly been using fully enclosed holes that stretch almost the entire length of the floor, rather than in the section just ahead of the rear tyre, to generate this seal.

These helped the floor become an extension of the diffuser and it appears that, losing this performance boost, is what is hurting Mercedes the most.

And while some may suggest Mercedes could simply solve the problem by raising the rear of its car to increase the diffuser area, F1 designs are not that simple.

The whole aero concept of the Mercedes, and indeed the shape and design of its suspension, are all based on running at a low rake angle. Raising the rear of the current W12 would simply cause more problems.

Tyre impact

Lewis Hamilton, Mercedes W12

Lewis Hamilton, Mercedes W12

Photo by: Charles Coates / Motorsport Images

But it is not just the rake that is hurting Mercedes, for its situation is further complicated by the change of tyres for 2021.

Pirelli is supplying a revised tyre for 2021 that will not only handle the demands placed on the tyres more effectively, but also allow the Italian tyre manufacturer to prescribe lower minimum starting pressures for the coming season.

This is crucial, as it means that the teams not only have new rules to focus on, they also have to deal with a revised tyre construction. This ramps up the aerodynamic challenge significantly, as they now have a relatively unknown variable in the middle of all the other technical changes.

This is a battle that aerodynamicists have been tackling for decades but one which has certainly seemed to take centre stage as the team's find gains with infinitesimal tweaks.

But, whilst it's easy to think about how the rear tyre behaves in the centre of this storm, there's also the front tyre to consider. A different deformation characteristic here means any flow structure created to deal with the turbulence it generates will also have to be tuned to recover that performance.

This means that teams will not only have to make alterations to the parts directly affected by the regulation changes, but pretty much every aerodynamic surface on the car as they relink the aerodynamic connections that have been severed by the regulation changes and new tyres.

So for Mercedes it has meant a perfect storm of dealing with aero headaches at both the front end, the middle section and rear of the car.

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