What we know about the 2021 regulations

Ahead of the Bahrain GP the heads of F1 got together at Liberty Media’s St James’s Square office to discuss the future of the 2021 regulations. None of the details from that meeting have been made public, but with the 18 month deadline for the 2021 regulations fast approaching we discuss what is known ahead of the next rule cycle.

Aerodynamics

Since Ross Brawn accidently let slip one of the artist concepts for the 2021 regulations in a presentation ahead of the Singapore GP last year, speculation has been rife as to what the cars will actually look like and a number of rather vague artist renders did nothing to sate that interest. Until, that is, FOM released three CFD images to Racecar-engineering of their working model, codenamed “India” i.e. the NATO phonetic alphabet designation for the 9th iteration of the design. This model has been distributed among teams to run in their CFD packages to speed up the development process, as only a handful of engineers are employed by FOM on this project. The teams are allowed unlimited CFD time to test this car, provided that data is shared in full.

2.5 The FIA may permit, at its absolute discretion, non-RCFDs to be made for the sole purpose of contributing toward the development of the 2021 regulations, subject to the following conditions :
a) Such opportunities will be offered to all the teams on an equitable and transparent basis.
b) Such work will be optional for each team.
c) The full list of simulations (geometries, options, flow conditions, etc.) must be approved by the FIA in advance of any work being carried out.
d) Full reports of the results, and any CAD geometries must be made available to the FIA and to the other teams, provided no team-specific Intellectual Property is shared.

To the untrained eye this car may look like any other F1 car, but it features a number of interesting, if not exactly groundbreaking, aerodynamic concepts underneath some attractive but probably unenforceable styling.

Underbody

The most striking feature of the India concept is the two large tunnels at the front edge of the floor, a similar concept to the underbody tunnels used in CART (e.g. the Lola B03/00, Reynard l01 or Panoz DP01) or Japanese SuperFormula (Swift 017.n) from the 90’s to mid-2000’s, this area of the car is currently only allowed to curve up from the flat stepped floor with a radius of 100mm. These tunnels work like a diffuser, in reverse, smoothing the path of air under the car. The tunnels are augmented with a pair of large vortex generators which have two purposes, (1) is to push unwanted air such as the front tyre wake outboard of the floor, (2) to produce vortical flow to enhance downforce - the low pressure core of the vortex infers a low pressure on the surface which increases suction under the car. At the front of the floor the “silly plate” or “tea tray splitter” is no longer a feature at the front of the floor, instead the keel under the driver goes directly to the reference plane. The silly plate and bargeboards are some of the key areas of development since 2017 and their loss will certainly limit some of the variation between the teams that we nerds love to pontificate over.

The floor retains the step in the centre, but the vortex generators and outer edge of the floor bridge that gap, effectively making a pair of tunnels under the car - albeit the floor in the middle of the tunnels is flat between the inlet tunnels and rear diffuser. The rear diffuser itself is longer and taller than in 2019, but also narrower at the exit, the intention being to take that underbody flow and thrust it upwards in a narrow jet - to better allow the wake to “mushroom”, i.e. the “dirty” air affected by the car is pushed up, with “cleaner” air filling the void behind the car. The diffuser itself shows 2 distinct low pressure zones with a double expansion shape, an initial kick followed by a near horizontal region allowing the boundary layer to recover and the diffuser to pass uninterrupted under the rear suspension, with a second aggressive kick near the exit. Another feature of the diffuser is a lack of vanes splitting the two tunnels. These vanes are used on a modern car to split the diffuser into multiple channels also inducing vortices both of which reduce the likelihood of flow separation, but also make the diffuser exit flow very low energy, which adversely affects a following car. To assist the extraction of flow from the diffuser, the lower beam wing returns. This helps create a low (static) pressure bubble behind the car, which helps to suck flow through from the front of the floor, while also working with the upper rear wing to pull the wake upwards.

These changes do not necessarily mean that the underbody downforce is increased from the current spec. Currently as much as 65% of the car’s downforce is produced through the floor and the loss of the diffuser vanes will take away a lot of downforce at the rear. The inlet tunnels and beam wing will counteract this somewhat, but it’s likely the distribution of downforce will be similar to 2019, i.e. 15-20% front wing, 20-25% rear wing and 60-65% floor.

Front Wing

The front wing is a further simplification to the 2019 regulations, reducing the number of elements from five to three. The wing also drops the FIA section which has been a feature of the cars since 2009 and was implemented by the original overtaking working group - who found that the centreline of the front wing was most significantly affected in a wake. The FIA section had an unintended side effect, which was the Y250 vortex. This vortex runs along the side chassis, rotating with centreline downwash which in turn pulls air from above the car, which hasn’t been affected by the front wing or suspension, down into the sidepod undercut. The direction of rotation also creates downwash at the front edge of the floor, effectively increasing the incidence at the front of the floor, and has been a key part in the ever increasing rake over the past decade of development. Instead of the neutral centre section, the front wing sweeps upwards to join the nose box of the car, effectively doing the same job of reducing centreline downforce, but without creating the vortex. The endplates themselves look to be in the same location as now, at 75mm above the reference plane, while the bottom of the nose cone also looks to be in the same location as 2019, 135mm above the reference plane. The car does not fully do away with the Y250 effect though, as a large lifting wing is placed behind the front suspension, pushing air down into the underbody tunnels, but also creating an outwashing vortex.

Rear Wing

The rear wing is an incredibly interesting bit of kit, gone are the traditional flat (not that current endplates are really flat) endplates and instead the upper and beam wings blend into the endplate surfaces. The main reason for the size of endplates these days is not aerodynamic but for sponsor exposure, and a reduction in side projected area may be a sticking point with team bosses seeking to maximize income. The rear wing is has a vital role in the “mushrooming” of the wake discussed earlier, with the tip vortices rotating with ground level inwash and centreline up-wash. The low pressure core of the tip vortex can be seen on the outside of the endplates as the flow rolls from the high pressure zone above the wing to the relatively low pressure zone outside the endplate. The wing itself appears to be even higher than in 2019, sitting around 900mm above the reference plane (rather than 870mm).

Other interesting features

There are a number of other interesting features on the India car. The front brake ducts have been tidied in the 2019 rules, removing various vanes which were used to prevent the front tyre squirt encroaching on the underbody, one such vane can be seen under the front suspension in this model. A second vane is also present around the front tyre, sitting above the front wheel so try and reduce the size of the separated region behind the wheel - much of the effort in 2019 is spent controlling this tyre wake to reduce its impact on downstream components. The wheels themselves feature covers, like those last used in 2009, it is again unclear if these are a geometric simplification as there appears to be no brake ducts or hub through flow, or if these will return in 2021. Their outlawing in 2009 was due to a negative effect they had on the wake, so it’s unclear

In the middle of the car the halo is slightly different to the 2018/19 spec, looking more like the original Mercedes concept. It has not been announced that any progress has been made reducing the bar size of the halo, so this may remain in the current form beyond 2021. The wing mirrors do not follow the regulations for 2019, where the centre of the mirror face has to sit in a prescribed volume between 500mm and 550mm from the car centreline to help rear visibility.

At the rear of the car, the rear “brake ducts” are very interesting. The stacked winglets which help to create upwash around the inner face of the tyre are retained, but a large vane is added. This works like the exhaust blowing of 2010-13, sealing the tyre contact patch squirt off from the diffuser flow. As they are attached to the wheel hub, their location in reference to the ground is fixed (the tyre sidewall flex will affect this slightly) meaning the diffuser will be protected regardless of the ride height of the car - which in this version of the model appears to remain ~100mm higher at the rear than the front, which can sit lower to the ground with the loss of the silly plate.

Wheels & Tyres

The tyre tender process is slightly out of sync with the technical regulations cycle, meaning the newest tyre tender will run from 2020 to 2023. Rather than extending the existing supply by one season and starting a new tender from 2021, the tender required supply of tyres for 13” wheels in 2020 with 18” wheels from 2021. With no other major manufacturer willing to produce such vastly different tyres for just one season Pirelli retained the right to supply tyres to F1 until 2023.

Low profile Pirelli tyres with 18” wheel rims will be a part of the 2021 regulations (from Pirelli motorsport).

The tyres themselves will get a fairly substantial increase in the inflated diameter from 670mm to 720mm to accommodate the larger wheel rim, shrinking the sidewall height from 169.9mm to 131.4mm. It is not yet known whether the brake discs and wheel hub will increase in size to fill the new wheels, but it is likely the discs will increase from their current diameter of 278mm closer to the 381mm (15”) specified in the WEC rules, where 18” wheels are also used.

The front tyre tread width will also shrink by 35mm compared to the current tyres. This points to a potential change in the centre of gravity rule which currently specifies that the minimum weight distributions on the front and rear axle may be 45.0% and 53.5% respectively. As the centre of gravity and aerodynamic centre (the centre of pressure or “aero-balance”) are so inexorably linked, moving the “mechanical grip” rearwards would also suggest a rearwards shift in the COG and COP. This could in turn be linked to a limit of the wheelbase from 2021 of 3400mm, around 325mm shorter than this years Mercedes W10, which would move heavier components like the powertrain closer to the rear axle. It would also reduce reliance on the front wing for total downforce, where it currently produces 25-30% of the cars downforce, which in turn should make the front wing less sensitive to the effect of another vehicle’s wake.

The tyres will retain the “improvement to the show” brief which has made Pirelli much maligned by media and drivers alike, retaining the three compounds at each Grand Prix and a desire for multiple stop races. 2021 will also see the tyre warm up blankets dropped, a move which has been discussed for some time.

Standardisation

It has been well publicized that the FIA are seeking a single gearbox supplier for the 2021 thru 2024 seasons, for the supply of gear cassette and ratios for all teams at a fixed cost. The official decision on who will win the tender will be made between the 15th and 30th of this month, but so far only Xtrac has officially made public their intention to fulfill this supply. Xtrac were the initial favourites and have a history of supplying gears to F1 teams, last officially supplying gearboxes to the now defunct Manor and Caterham teams, though it is a well known secret that they cut gears for a number of current entrants. They also supply gearboxes to the Indycar series, as well as a number of WEC entrants.

Other standard parts which have been rumoured in other media sites including (but not limited to) the brakes (disc, pads & calipers), steering columns, wheel rims, rear and side impact structures and drive shafts, though no official tender process has yet been started for these parts. Given the deadline for the 2021 regulations is fast approaching it currently seems unlikely these will be ready in time for 2021.