Making gains when it rains

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Keith Howard

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The onset of bad weather radically alters the demands made both on engineers in the pits and on the man on the track

By Keith Howard

Many a motor race has been turned into a seat-edge spectacle by a sprinkling of the wet stuff. One sudden downpour can upset the form book and turn a race into a lottery, but we expect drivers to suffer outrageous fortune like the rest of us and rise above it. Some elevate themselves so far in wet conditions that it’s clear they have a special talent which slippery asphalt brings into the sharpest focus.

Luck aside, there’s plenty of skill involved in wet racing, and not just from the drivers. Teams have to learn how to extract the best performance from the car in wet conditions, and make the right strategic decisions to exploit changes in the weather to best advantage. Inevitably in modern racing, technology plays a part in this through the use of simulation software and hi-tech weather forecasting systems.

For an insight into wet racing from the engineer’s perspective, we spoke to Pat Symonds, Renault F1’s executive director of engineering, who only a few weeks earlier had been embroiled in the wet European GP at the Nürburgring. For the driver’s view we turned to Allan McNish, whose wide experience of racing many different breeds of racing car in variable conditions, including in grands prix, had been sharpened only a few hours before by round eight of the American Le Mans Series at Road America, in which he and Rinaldo Capello had lost an almost certain win in the Audi R10 as the result of a safety car interlude – caused by a deluge.

Interview: Allan McNish

Open or closed

“When you are driving a closed car, like a DTM touring car or GT1 sportscar, the obvious issue in the wet is the windscreen in front of you. The worst thing that can happen is that it fogs up. You’re strapped into the seat very tightly and there’s no way for you to reach that screen to clear it, even if you wanted to. Technically that’s quite an issue, and for the driver it certainly is. Vision can be tricky because you also have a wiper and when you get to speeds of 170 or 180mph at Le Mans it doesn’t stick to the windscreen that well. So you have inconsistent vision. The sheer curvature of the screen is a problem as well.

“Usually in a Le Mans car the first time you encounter torrential rain is in the race itself and by then it’s too late if you haven’t got the screen demisting right. Then you’re in serious trouble. There are many new, inexperienced designers and manufacturers who have arrived at Le Mans not taking that into account as they should.

“From a driver’s point of view there is very little difference between a sportscar that’s closed or open. Behind the safety car in an open cockpit you get wet whereas you don’t in a closed car but in terms of the real driving there’s minimal difference.

“Open-wheel racing cars are very susceptible to spray. Because of the aerodynamics you get big rooster tails of water and that makes it very difficult to see if you’re behind another car. The only way I can describe it is, imagine driving down the M1 on a horrible, wet Friday night and you overtake a truck with your wipers off. That’s the equivalent of being in traffic when you’re racing in the rain.”

What it takes

“There isn’t much that can be done about wet set-up in ALMS because of the length of the races. There’s a big chance it will be dry sometime in the race, so it’s difficult to go for a wet set-up. What’s important in the car is good turn-in and good traction. You want that in the dry but there you can drive around problems, whereas in the wet the car has to be inherently confidence inspiring.

“Controlled aggression and adaptability are what it takes to be a good wet racer. You have to be aggressive because you still have to brake late and you’ve still got to get through the fast corners fast, but you have to be on fingertips all the time. If you hit a puddle, you have to react instantaneously – you can’t catch it afterwards. And if you go into a corner too deep and lock up you have to be quick to regulate the braking so that you don’t slide wide. You also have to be working with the car and track all the time because a wet circuit is always changing, it’s never the same two laps on the trot. 

“Driving style depends on the car. Sometimes I’m very smooth and sometimes I’m quite aggressive. For example, if the front isn’t turning into corners very well then you have to throw the car into the corner. But after that your inputs have to be very smooth and fast to catch it.

“You lose less time in the wet with a car set up for the dry than you do in the dry with a car set up for the wet. The downforce that modern sportscars or F1 cars have overrides the suspension changes we used to make. A dry set-up car maybe has less grip in the wet, but at least it’s consistent, whereas a wet set-up car in the dry can be absolutely horrible.”

Interview: Pat Symonds

Times past

“Going for the ultimate wet set-up in the old days, you’d soften the suspension – springs, dampers and anti-roll bars. Aerodynamically the optimum downforce is always higher in the wet so you’d add more wing. You’d also alter the aerodynamic balance – not just put on more downforce but add more rear wing than front to increase understeer and build in stability. There was a time when we’d also raise the ride height because you have to be so careful of the plank aquaplaning. But two things stopped us doing that so much. First, the wet tyres became of slightly larger diameter so that they lifted the car anyway. Second, we found that when we were running that low we were having plank wear problems anyway. Your control systems have to know that the tyre diameter is different, so you need to alert them that there are wet tyres on the car. We do that via the rear light switch.

“You can also link this to the traction control map so you run your traction control differently. We have never changed engine mapping for wet conditions because we make the torque curve as friendly as we can anyway. You’d also alter both brake and engine cooling.”

Post-2004

“Today the regulations allow us to do very little. We still have the larger diameter extreme tyres, so in conditions where the car could easily aquaplane on the floor the ride height is increased a little. There’s not a lot you can do about the tyres aquaplaning since whatever you do to the car set-up you don’t affect its aquaplaning speed for a given tyre. All we’re left with in the way of set-up adjustments is that we can alter the cooling, and when we put wet tyres on we have to take off a whole raft of front wing. If you look at the video from the Nürburgring race this year you’ll see mechanics cranking away on the front wing as the different tyres go on and off. During a dry race you might adjust the front wing to fine-tune the balance – one turn on the adjuster, perhaps, which is about a quarter of a degree change in the angle of attack. Going from dry to wet it can be 10 times that. We can still change traction control mapping and the driver can change the differential map too, although we don’t have specific maps for the wet. We can’t do anything to the suspension set-up.

“I wouldn’t say that this restriction makes the cars much more difficult to drive, although they are off their ultimate performance. You can argue that a softer car is a little bit easier to feel and drive in the wet but I’m not sure it’s a big factor.

“In uncertain weather conditions, risk assessment is everything. If you have a car that’s set up for the dry and you run it in the wet, it’s a little way off its optimum performance. If you have a car that’s set up for the wet and run it in the dry, it will be a long way off. So your tendency is to stick with dry settings if you’re not sure of the weather. To go for a full wet setting would be very brave. You have to know 24 hours in advance that it is going to be wet in the race because your decisions on settings have to be made before qualifying. At 24 hours, notice comes from standard weather forecasting and we all know how accurate that is!

“Going racing is not like going for a picnic. Going for a picnic is about should I go or not, should I take an umbrella, is it going to rain in the general area I’m heading for? In racing we are dealing with just a few square kilometres of ground and about a 90-minute timeframe. We need to know whether it is going to rain over that small area in that period, and if so by how much. We use weather radar for detailed predictions [see panel right] but it is very short-term – depending on wind speed it can give us half an hour’s notice of rain, maybe a bit more.

“Having said all that, the optimum downforce for the dry is not super-critical. If you set it a little higher than optimum then the lap time may only be a few hundredths of a second slower. So if you know there is a chance of rain falling during the race you would probably choose the higher setting.”

Technical file: Weather radar

Technology helps F1 teams make precise rainfall predictions

“Use of weather radar in F1 started in the mid-1990s, when I was at Benetton,” says Pat Symonds. “I had been talking to David Moreton, a friend of mine who was a pilot with British Airways and about to retire, about the different radars on commercial aircraft. I said that what we wanted in F1 was a weather radar that’s located on the ground. Others had already done this, but we weren’t aware of it at the time. David put some equipment together and we used it that year at Silverstone. He then decided to make a business out of it, but we didn’t have the money to use him! So, initially, he worked for other teams. When we became Renault, we employed him exclusively in F1. He also works for Audi at Le Mans.

“The skill is in interpreting the radar data. David is normally a kilometre or so from the circuit but it depends on the geography. He wants to be up on a hill somewhere – at Monaco he has to be at the top of the mountain – with a view towards the prevailing winds. He gives us general forecasts to begin with and then on the Friday begins feeding us the detailed radar picture, which he sends direct to the pit wall. We have what is effectively a chat room so he can type messages to me directly, such as ‘Rain level 2 at Turn 10 from 14.13 to 14.19.’ At the Nürburgring this year, our radar was telling us what corner the rain would start at and how it would move around the track. 

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