Green: The build-up problem cannot be solved quickly

The advantage Ferrari and Red Bull have over Mercedes, and the championship team over everyone else, is largely due to the same phenomenon we’ve seen in Formula 1 since the very first tests in Barcelona.

New generation cars suffer from longitudinal build-up, which starts at speeds above 300 km/h, and a lot has been written and said about this. It is not so easy to understand the essence of this phenomenon, but it is even more difficult to get rid of it or at least reduce it to a certain relative minimum, ie Find a compromise where the speed does not suffer too much.

Andy Green, Aston Martin F1 Technical Director, believes that the extent to which the build-up manifests is directly related to the design features of the chassis. Because engineers and designers simply had nothing to rely on during the development process, because the teams simply had no experience operating machines that use ground effect, they had to make a decision dictated by the choice of one concept or another.

Andy Green: “It’s impossible to move in all directions at once. Instead, in the early stages of chassis development, we tested different concepts and tried to understand what we would get one way or another.

At the same time, we set ourselves certain goals, aimed at a certain estimated lap time. In terms of vertical chassis movement under downforce, we tried to anticipate where the ride height would be maximum and where the car would be most pressed against the track. This influenced the choice of geometry of the entire machine. If you initially opt for a certain aerodynamic concept, not the same as that of competitors, you eventually end up with two different cars.”

The underside of the new generation machines generates up to 40% of the total downforce – of course the engineers tried to make this part of the machine as efficient as possible.

“For this you choose a certain ground clearance where you think you can achieve the maximum return,” Green continues. “It also dictates the shape of the whole car and we started with a very low ground clearance. Gradually we came to a part of its meaning, which seemed correct to us. However, while working on the simulator, there was no indication that we might encounter the problem of destabilization of the machine.

This problem suddenly manifested itself only in tests. Some teams know how to handle it better, someone is in a more difficult situation. But the reason is precisely related to differences in aerodynamic concepts.

Championship cars can be divided into three groups: one includes those that are distinguished by high speed and relatively high ground clearance – the amplitude of their longitudinal oscillations is quite large, but that’s how they are designed. That is Ferrari, but also, albeit to a lesser extent, Alpine, Haas and Alfa Romeo.

The second group includes cars Mercedes, Aston Martin and Williams. To develop high speeds, they need low ground clearance and a hard-tuned suspension.

Cars Red Bull and McLaren – generally a special case. Red Bull Racing was able to drastically reduce the impact of the yaw on the final day of testing in Bahrain when they installed a new bottom and different side pontoons on the car. The team itself was surprised to see that this allowed them to regain three quarters of a second. After that, the rivals suggested that Adrian Newey had accidentally found a way to solve the problem.

When the RB18 car is stationary, the ground clearance is quite large, but on the track at high speeds, sparks fly from under the bottom with force and power, and this indicates that the car appears to be “crouching”, and accumulation does not prevent this .

It seemed that everything was more or less normal for McLaren during testing in Barcelona, ​​but the difficulties started later and were of a different kind, after which Lando Norris said: “Maybe we don’t have such a build-up because our car has too little pressure”.

Mercedes, as well as its customer teams, have their own problems: too much resistance.

Anyone who suffers from longitudinal build-up has taken certain measures in the order of fire, but this is clearly not enough to overtake the frontrunners.

“Some teams are less affected by car destabilization because their chassis is designed to handle increased ground clearance and the airflow around them flows in a certain way,” explains Greene. “Others who have followed the same path as us are facing serious problems. Our cars start to lose speed when the ground clearance is greater than the calculated one.’

On some machines, the clearance is increased by 40mm from the optimum value, leading to a loss of downforce and thus lap time. Losses can be more than a second and to make up for the lack of downforce, teams put bigger wings on the cars, inevitably affecting drag. This explains why the cars of Mercedes, Aston Martin and McLaren lose out to Ferrari and Red Bull in straight line speed.

“The problem cannot be solved quickly, this is a complex process, as we are forced to adapt plans to upgrade the chassis and choose a different direction for its improvement. That’s why it’s so important to fully understand the nature of the build-up problem,” Greene concludes. – But we are already at the stage where we are sure that a solution will be found.

This naturally entails high costs. But this is a priority issue that needs to be addressed. We know that the machine has great potential and we need to create the conditions to bring this potential to light.”