2021 bodywork rules analysed - Part 1

The culmination of two years of research concluded on October 31st when FOM and the FIA jointly presented the rules for 2021 in Austin. The car presented was the FOM wind tunnel model which is highly stylized, but what do the regulations say and how will teams go about designing cars for 2021?

In this first part we take a look at the general wording of the bodywork and aerodynamic rules, before going into details about the front and rear wing design and the new underbody geometry in later articles.

As discussed in our article on the evolution of regulation volumes the bodywork is forced into ever more restrictive boxes (shown below). Parts are more tightly regulated than before with more boxes to split components into sections. There has been a massive departure in how the rules are written, where previously article 3 (the bodywork regulations) described volumes where bodywork was allowed, that job is now done in the technical appendix with article 3 dedicated to describing the bodywork which may fit in each volume. For example the front wing volume is split into four, namely the "profile volume" with up to four wing elements allowed, the "endplate volume" with only one section allowed, the "tip volume" which has to blend the profiles to the endplate, and dive plane volume - but more on that in a later dedicated article.

The cars will be slightly taller and slightly shorter than in 2019/2020 with a long overdue wheelbase limit coming into enforcement. The limit will knock some 100-200mm off the wheelbase of some of the longer cars but the main visual impact to the proportion will come from the the bigger wheels and tyres and a reduction of the rear overhang, owing to the removal of the massive sloping rear wing endplates. To overcome the larger diameter tyres (up to 725mm from 670mm in 2019) for the new 18" wheel rims the cockpit entry and head rests are moved up 20mm. Alos, to accommodate slightly taller drivers the minimum monocoque length is increased from 1800mm to 1850mm. All this means that despite the wheelbase being comparable in length to the 2017-20 cars the 2021 cars will look slightly better proportioned.

Because of the higher cockpit and the fact the front wing joins it the nose tip looks lower, infact the nose tip height remains 135mm from the ground with the front wing volume sloping up to meet it. The lowest point on the front wing is increased from 75mm to 100mm at the tip, this means the front wings should be slightly less pitch sensitive and teams may well elect to use three element front wings like the show car, rather than the maximum allocation as they do now.

At the rear the diffuser exit can be slightly taller than in 2017-20 and the rear wing is moved upward to 900mm at it's highest point. Unlike previous rules, the floor volume specifies a minimum Venturi tunnel height, so the diffuser exit could be as low as 200mm or as high as 310mm. The minimum diffuser volume means the fence thickness at the exit can only be up to 10mm across, this stops the teams from expanding the diffuser laterally - which in turn helps to drive the wake upwards where it affects a following car less.

Spec parts

Much was made ahead of the announcement of these 2021 regulations of a spec series, or GP1, and teams fought back against standard gear cassettes, braking systems, and fuel systems, but many standard components remain. So called PDC's or "Prescribed Design Components" include but are not limited to, the underbody legality plank, front and rear wheel drums and the front wheel arch, wheels, wheel hubs, and rear impact structure. The secondary roll structure, or halo, is a PDC but unlike the swoopy halo presented on the show car is currently conforming to the current FIA halo (FIA Standard 8869-2018), this may change as and if the FIA can crash test a new thinner halo to the current standard but teams will need that part signed off by the middle of 2020.

To assuage teams fears about a spec series, yet also allow for cost cutting for parts FOM and the FIA believe fans are disinterested a group for open source parts is being created. The OSC's are "components whose Design Specification and intellectual property is made available to all Competitors" and must be uploaded to an FIA server for access by all teams and any team using an OSC must declare it to the FIA. Open source parts include, the rear wing DRS actuator, drive shafts, steering wheel and column, brakes, and pedal box.

CAD based scrutineering

One of the most interesting changes in the 2021 rules is the CAD based checking of legality. Previously the FIA have a series of guides and templates which they put up to the car to check for legality during the Thursday scrutineering session. Teams will instead have to provide the FIA with the CAD models of their aerodynamic surfaces for digital checking. This means teams can only nominate one aerodynamic platform per race as they cannot deviate from the digital model. Physical tests at the track will be performed using a 3D scan of the car - which is then checked against the CAD model to a prescribed tolerance.