March 22, 2023

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Wind interferes with F-1 cars more than you think: a 9 km/h gust takes 5% off downforce! And shoots down aerobatics

European summer 2022 will be remembered for high temperatures and low rainfall. Despite this, seven different race sessions were held in wet conditions before the summer break: Imola, Monaco, Montreal and Budapest. Experience can tell what will happen to the weather on a particular track at a certain time of the year, and the teams study the averages over 30 years to prepare, for example, the right version of the cooling system. But these are only averages, and forecasts do not always come true. Even in Bahrain it rains 10 days a year, and despite the fact that the races there are always held in dry weather, it often rains in March.

It is often said that the conditions are the same for everyone and that the weather helps to level the teams. But is it really so? Rain always causes visible changes in conditions, but the same can be said for wind, temperature, and even barometric pressure. If you can predict the weather and cope with different conditions, then this can lead to gain in time, and it’s worth it.

Let’s start with rain conditions. There was a time when different tire companies competed with each other, and the cars had different settings for dry and rainy weather, and you could change them at any time during the weekend. And then the wet conditions changed everything. These days, tuning changes are not possible after qualifying starts, Pirelli only has intermediate and rain tires in the set, and it seems that life has become easier. But she did not become simple.

It is important to understand, as always, what will happen to the rain at the next moment in time. If it intensifies, then the time must be set as soon as possible, if it weakens, then it is better to postpone the departure to the track. The main thing is to be on the track in the best conditions with optimal fuel load and optimal tire temperature. Sounds obvious, but it’s very difficult to achieve. Teams use sophisticated weather radars to better understand what is happening with the weather on the track. This was first introduced at Bennetton in the late 1990s, and now all teams have access to a single source from Meteo France, which is administered by the FIA.

When there is a threat of rain, we are often shown on television the image from that very radar. It allows the teams to determine quite accurately when the rain will reach the track, sometimes even in which turn. This is important for decision making, but knowing when it will rain is not enough – you need to know the exact air temperature, pressure, wind speed and direction. It is desirable that this information covers an area within a radius of several kilometers and for 90 minutes.

But not only the rain determines the conditions. Wind also has a big impact on cars that rely so heavily on aerodynamics. Physics tells us that for a given aerodynamic configuration, downforce is equal to the square of speed. Doubling the speed leads to a fourfold increase in downforce.

At Spa, during qualifying before the Le Combes corner, the wind was blowing in the back at 9 km/h, the fastest cars were approaching the braking point at 340 km/h, which means that they lost about 5% downforce compared to with the situation if there was no wind. Conversely, if there was a headwind, then even before reaching the same maximum speed, the riders would have a comparable increase in downforce. For all, the percentage of change in downforce with a headwind or tailwind will be the same, but everything changes if the wind is side. All cars lose downforce in crosswinds due to yaw. Each car will lose approximately 5% downforce in a 5 degree crosswind.

This is the yaw angle, and it can occur both when the car is offset in a turn, and when the car speed and crosswind speed are combined. For example, at a speed of 150 km/h, a side wind of 13 km/h will have the effect as if it were blowing at 5 degrees. Riders often complain that the car loses competitiveness in the wind. This is because the machine is more sensitive to yaw due to wind.

Another factor is temperature. There are two effects. Any additional cooling in hot weather results in a loss of downforce. The better the aerodynamics, the lower the losses and the faster the car. Tire temperature is also important. If a car is having trouble getting tire temperatures into the operating range, then a cold track will have a greater effect on it than on rival cars.

So the weather is not such a good equalizer. Depending on the external conditions, a team can have both a good day and a bad day. Between success and failure in the “Formula 1” is really one step.