Why F1 teams still deem windtunnel investment necessary

With the stated intent of the F1 Commission to work towards a ban on the use of windtunnels over the next 10 years it might seem perverse that two teams, McLaren and Aston Martin, are investing in new windtunnels right now.

Current aerodynamic testing restrictions, while variable from team to team, are framed in such a way that it is reasonably easy for teams to share windtunnels, so what is it about this particular testing technique that makes such a huge investment still worthwhile?

PLUS: Why the end is nigh for F1's most dependable design tool

To answer this perhaps we should first explain what a windtunnel is and how it works. It is an indisputable fact that most of a Formula 1 car’s performance comes from aerodynamics and, while the costs involved are huge, aerodynamic research provides a better bang per buck than any other performance area.

That research falls into three categories: computational fluid dynamics (CFD), windtunnel testing and ‘on-car’ measurements. I often refer to this as the ‘infernal triangle’ because none of the techniques give a precise answer.

CFD, while extremely good at understanding and developing aerodynamics, still struggles to anticipate the effects of highly turbulent flows without enormous computational power.

Windtunnel testing is limited in many ways including the fact that, like most CFD, it gives a time-averaged solution but in addition suffers from not being able to truly represent the curved flow that a car experiences when cornering. Add to this inevitable modelling inaccuracies, such as the difficulty of having a correct deflected tyre shape, and one can see that in spite of the sophistication there are gaps in true realism.

Windtunnel testing is limited, but still the favoured method of aerodynamic proving

Photo by: Juergen Tap / Porsche

Even on-car measurements are difficult. A racing car is just that – it is not a scientific instrument – and as such, even with the sophisticated instrumentation available now, it is difficult to make precise measurements. Indeed, any load that is fed direct to the wheel – such as that from the brake duct winglets – cannot actually be measured. Add to that the ever-changing conditions of wind and tyre wear and one can see that accurate measurements are not possible.

That said, the windtunnel is still the instrument of choice for development – so what does an F1 windtunnel look like? Perhaps the first thing to understand is that on the track a car moves through stationary or near stationary air as it is driven by its rotating wheels along the ground. In a windtunnel, we reverse that procedure and blow air past a stationary model. Under the model is what is called a moving ground plane. This is like a huge conveyor belt that simulates the difference in speed between the road and the car and that drives the wheels on the model.

When I worked for teams, I would often show visitors round the windtunnel and shock them when they saw the model and I explained it was the second most expensive car they were likely to see

The model, which by regulation can be no bigger than 60% scale, is suspended on a strut via a measuring device called a balance which can measure loads in all directions. The balance sits inside the chassis or spine of the model and to this is attached the suspension, wings and the bodywork.

In general, the wings are machined from aluminium and have their own load measuring devices while the bodywork is largely made of 3D printed materials – although carbon fibre and aluminium may be used for some parts.

The suspension is generally capable of imposing significant loads on the tyres via an active system which will simulate the tyre squash seen on the real car. The tyres are a science in themselves. They are pneumatic and the construction is such that the loads applied deform the sidewalls to exactly replicate the behaviour of the real tyre.

When I worked for teams, I would often show visitors round the windtunnel and shock them when they saw the model and I explained it was the second most expensive car they were likely to see. A current 60% model, which incidentally weighs around 230kg, built from scratch but without instrumentation, will cost around £750,000. The balance adds a further £60,000. In addition to this, a number of pressure scanners will be fitted, each capable of measuring 64 separate pressure points around the model and costing over £10,000 each. You can see that building a model from scratch can easily head toward £1m.

Ferrari has recently installed a new windtunnel

Photo by: Ferrari

The tunnel itself doesn’t come cheap. The duct work housing the model, fan and turning vanes would set you back around £30m. The fan, with a huge 3.5MW (4,700BHP) motor, a further £11m, the moving ground system £12m, the motion system that positions the model around £7.5m, and you can add a similar amount for the control and cooling systems for the tunnel.

By the time you have added a building to house it in, there will be little change from £75m. When we built the windtunnel at Enstone, for what is now the Alpine factory, it cost £800,000 in today’s money just to get enough power on the site.

Once built, the tunnel is a hungry animal. Even with the current restrictions on running, the electricity bill will be around £1m; materials and maintenance over £1m. The staff to design and manufacture the model and run and support the tunnel might add a further £3m, and all this before you have actually employed the aerodynamicists whose job is to exploit all this expensive kit to try to add performance to the car.

So why would anyone spend such a vast sum to build a new windtunnel when a ban on their use is looming just 10 years away? The simple answer is that there is no more cost-effective way to make a car competitive than aerodynamic testing and, with current technologies, the windtunnel is the backbone of that. Aston Martin and McLaren, both of whom understand the wisdom of this, have no hesitation in committing this sort of money. Even the FIA, custodians of the budget cap, are allowing one-off capital expenditure exemptions to allow this to happen.

The days of windtunnels are numbered, but for now they are here to stay.

Aston owner Lawrence Stroll has broken ground on a new campus that will include an on-site windtunnel

Photo by: Glenn Dunbar / Motorsport Images