If you’ve been following paddock gossip over the past few weeks, you will know that Aston Martin are threatening the FIA with legal action over allegations that this year's regulations unfairly disadvantage low rake cars. Regulation disputes are nothing new in Formula 1 but, what exactly does all this mean? Guest writer, Ingrid has jumped in to explain.
Rake? What’s that?
Rake is defined by the angle of the slope created between the rear ride height of a car in relation to the front ride height, effectively meaning the car is set up with an upward slope front-to-rear. So as we see, Formula 1 cars can be categorized as high or low rake.
The rake concept across competitors:
When examining the main competitors, the Mercedes AMG cars are characterised by their low rake concept. Since Aston Martin have heavily based their car on the 2019 Mercedes concept, they also classify as low rake.
On the other hand, Red Bull are notorious for their high rake concept. Alongside them, Ferrari are another great example of a truly high rake car. Meanwhile, McLaren are somewhere in the middle ground between the middle to lower side of this concept.
The 2021 regulations & Aston Martin striving for rule equitability
Since Mercedes have had one of the quickest cars for the past 7 seasons, the new regulation changes have obviously been implemented in order to cut back their advantage and bring the grid closer together. This involves putting the low rake angle cars at a slight disadvantage.
Besides some gearbox and ERS (energy recovery system) issues, in the pre-season tests and first races of the season, it has been apparent the low rake Aston Martin’s is clearly affected by the new regulations, and so is Mercedes to a lesser extent.
Aston Martin are questioning the intent of the technical regulations and are now engaging in discussions with the FIA for clarifications. This has caused somewhat of a confusion amongst the other teams in the paddock because in the prior seasons, when the 2021 regulations were discussed, the intent to minimise the production of downforce was clear, hence the unanimous vote in favour of the rules.
Is this a disadvantage?
Aston Martin are not content with their performance in 2021, so far only scoring 5 points in 3 races. Bahrain was a disappointment, especially due to the possible advantage of Mercedes powered cars from the superiority of their power unit.
Imola was a downforce track, meaning downforce is more important than the power unit. Red Bull usually tend to do better at these track styles, suggesting that Mercedes and Aston Martin would be at a disadvantage. However, they were much faster than Red Bull when you compare qualifying lap times from 2021 with the previous year. The lap time difference is the most significant for Mercedes, being 0.8s slower than 2020. This is only natural since they were the ‘main target’ of the technical regulations. Mission Accomplished!
However, rake is not the only technical element which has been impacted by the new rules. Thus, this cannot be considered entirely responsible for performance loss. The cars are an assembly of parts, concepts and set-ups.
For Mercedes, it is quite difficult to analyse their performance during race weekends, because in Bahrain, the cars were already at a disadvantage due to ERS issues; In Imola, Hamilton’s quick recovery through the field indicated that the car can perform well at twisty tracks, displaying big advantages when overtaking Ferrari and McLaren, both teams being high rake rivals. The snappy rear that the Mercedes cars displayed in pre-season testing was a matter of finding the right set-up for the specific track.
The physics of rake angles:
The rake functions are closely related with another aerodynamically sensitive part – the diffuser. Rear of the F1 car is the point where most downforce is created which explains why the rake has such a substantial effect on the performance of the car.
F1 cars aim to get as close to the ground as possible, in order to reduce drag and generate other benefits. Although rake is a little different: the centre of gravity (CoG)is raised due to the increase of the rear ride height representing a slight disadvantage overall. However, in theory, the larger the rake angle, the bigger the diffuser angle, results in an increase of downforce.
But why? The bargeboards constrain and redirect the air to the underside of the car (another important factor where a lot of suction is produced) and a bigger rake angle, indicates there is a greater void existing between the underfloor of the car and the ground. As air tends to fill the void, in order to fill it quickly, it increases its velocity. Increase of velocity, therefore signifying more air travelling along the underside of the floor and through the diffuser, generating more downforce.
Why was Mercedes’ low rake better and how exactly do the new regulations affect it?
To better understand the greater loss in rear downforce, also acknowledged by Mercedes Team Principal, Toto Wolff, we need to take a closer look at how the low rake concept influences the structure of the car and the 2021 regulations.
The response of the low rake to the produced downforce of the high rake is a larger floor area. Not only in width, but also in length. This implies the Mercedes and Aston Martin cars require a longer wheelbase (a longer distance between the front and rear axel). Consequently, the disadvantages of high rake cars are avoided by low rake cars: smaller rear height reduces drag and lowers the CoG. Nonetheless, the harvested aero-efficiency is slightly offset by the added weight of the extra floor area, which can affect acceleration and tyre degradation. This is a reminder that when designing a car, there is no right or wrong way to do it, because it is a matter of discovering the most effective compromise for each team’s car development and set-up.
In terms of the regulations, it was enforced that engineers need to reduce rear downforce by 10% and that each team can decide on their own how to meet this goal. The only common decision by the competitors was to cut the floor, which clearly displays how Mercedes’ and Aston Martin’s aero performance has been cut back.
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