The 2021 season will be a transitional year for Formula 1 due to the technical freezes and the upcoming 2022 regulation changes, which are a radical departure from what we know now.
For the upcoming F1 season, despite the various freezes to most of the mechanical components, the FIA has also imposed aerodynamic limitations to limit the downforce, which it believed could reach dangerous levels without some form of intervention.
Aerodynamic limitations due to tyres
The main motivation of the technical changes for ’21 are to limit the mechanical stress to which Pirelli’s tyres will be subjected, with the development and increase in performance of the cars that naturally occur from year to year under stable technical regulations.
The debut of the 18-inch Pirelli tyres has been postponed to ’22, therefore the sport will stick with the current 13-inch tyres. This same compound and structure has been used for the previous two seasons and simply wouldn’t have been able to absorb the forces transmitted by the greater downforce.
To this it must be added that due to COVID, Pirelli has been unable to adequately work in the first six months of ’20 on a development program for ’21 tyres. In the final part of last year the Italian company took care to reinforce the structure of the tyre and make it suitable to withstand higher stresses.
The second Silverstone race last year was a clear example of just how much stress the tyres have to go through with the current modern car. Several cars, including race winner Lewis Hamilton, suffered tyre failures. Hamilton limped across the line to take the win with just three wheels intact. This was due to high tyre wear and blistering on a very tyre intensive circuit.
On November 1, the FIA approved the Pirelli tyres for the ’21 season, which will have a larger carcass than those previously homologated for the ’19 and ’20 seasons. It’s hoped they will be more efficient at coping with greater mechanical forces and suffer less blistering at lower pressures. Tests were carried out during the last races of the season, and Pirelli chief Mario Isola said he was satisfied that they had achieved their goal.
The FIA aimed to cut downforce by 10%
Despite the intervention on the tyres, the FIA’s Nikolas Tombazis intervened to modify the ’21 aerodynamic regulations, with the aim of reducing the overall downforce by about 10 per cent compared to ’20. All this obviously had the purpose of maintaining a safety margin on the tyres for the new season.
To limit the downforce, the FIA initially thought of intervening by limiting the downforce generated by the rear wing, which from ’19 has a greater area than in previous seasons. However, the FIA’s technicians decided to instead intervene on the flat floor area, reducing its aerodynamic impact with a diagonal cut towards the rear axle (RWCL).
The cut at the floor will start exactly from the C-C plane, orthogonal to the longitudinal axis of the car, which coincides with the rear part of the frame where the engine mounts are located (exactly 1800 mm from the front axle as per Article 3.7 of the Technical Regulations).
The floor will shrink by about a third compared to the ’20 configuration, and that should automatically make the various complicated slots and air channels disappear which were to reduce the impact of the air flow on the rear tyre (known as tyre squirt). The various ducts helped the aerodynamics of the cars to create a seal for the air flow, recreating a sort of “mini-skirt”, which increases the ground effect of the single-seaters, and the efficiency of the rear diffuser.
The reduction in the provision, however, created strong doubts during the various technical meetings, as it alone cannot be sufficient to reduce the overall downforce by the targeted 10 per cent. The same technical directors have expressed strong doubts on the fact that the teams can quickly recover the performance deficit.
The FIA has therefore added two other notes in the aerodynamic regulations, directly intervening with limitations to the diffuser and rear brake ducts.
For the diffuser, the regulations will impose a limitation on teams in the internal area of the extractor channel, at 250mm of lateral offset from the centreline of the car.
Compared to 2020, the fins (ie the internal drifts of the extractor channel) must be shorter than 50mm from the reference plane of the car, which substantially coincides with the central part of the “stepped” bottom. This, together with the diagonal cut of the floor, should help reduce the rear downforce of the ’21 cars, limiting the efficiency of the diffuser.
The modifications to the rear brake ducts, on the other hand, concern the cantilevered winglets, which make this area of the car very complex in the extreme search by the engineers to grasp the maximum aerodynamic effect even from the smallest element of the car.
For years now, the brake ducts, both front and rear, have no longer performed the single task of cooling the braking system, but are true aerodynamic elements. At the rear, a series of cantilevered fins attempt to transmit the maximum possible load to the rear axle for the best traction and maximum grip when cornering. In the diagram below, which represents a rear view of the hub carrier, it is possible to observe how the FIA has limited the cantilever extension of the winglets to 80mm, under a height of 50mm from the rear wheel axle. The winglets are highlighted in yellow, and protrude behind the brake grip from the brake bell.
How they aim to recover the losses
Already during the ’20 season, most of the teams have been working towards ’21, carrying out various aerodynamic tests in the free practice of various Grands Prix, with pre-configurations of the bottom, diffuser and brake ducts, whilst respecting the constraints of next season.
It is clear that the downforce handicap at the rear will upset the balance of the various single-seaters, and the engineers’ first task will be to stabilise the cars, with interventions on the front axle.
Teams such as McLaren, Ferrari, Red Bull, Renault and Williams worked hard during the 2020 season finale, bringing a cut bottom and simplified aerodynamics. The first interpretations of this have already been seen in Abu Dhabi, and among these, Red Bull and Ferrari stand out. On the other hand, the Mercedes is surprising, which among the top teams was the one that practically did not carry out any aerodynamic tests on the track in view of this year.
In the illustration below we can see the bottom introduced on the Red Bull RB16 in free practice at Yas Marina, where in front of the rear wheel, a vertical extension element has been added, which acts as a winglet (like the winglets of an airplane), to reduce the induced drag, and the eddies (vortex turbulence) that would impact the rear tyre.
On the other hand, the layout presented by Ferrari at Yas Marina is very interesting. It was a second version of a cut floor tested on the SF1000 (the first version was tested in Portugal).
It can be seen that the aerodynamic design is already more complex, in an attempt to recover the loss of performance due to the diagonal cut. Note the winglet in front of the rear wheel, to which three small 45-degree slots have been added. Three vertical fins have been inserted around about halfway through the diagonal cut, which act as a vortex generator to shield the rear wheel from flows.