Scuderia Ferrari Indianapolis dilemma
Alex Cinelli explains Ferrari’s aero thinking
The F2005s are rebuilt ahead of Friday practice. With the cars being air-freighted directly from Montreal to Indianapolis, Ferrari will be lining up the same two F2005 for Michael Schumacher and Rubens Barrichello in the US Grand Prix that they used in the Canadian event.The cars will be completely rebuilt in the spacious garages at ‘The Brickyard’ as the Indianapolis circuit is known and settings of all the key elements of the car – engine-gearbox-suspension etc., will be modified to suit the needs of this track. With most teams introducing new aero packages for Montreal, aerodynamics is once again a key item on the agenda this weekend.
But before looking into the specific demands of this famous track, Ferrari’s race aerodynamicist, Alex Cinelli gives us an insight into the challenges presented by the new rules concerning aerodynamics, brought into force since the start of this year.
Cinelli trained in aeronautical engineering at London’s Imperial College and after doing a Masters degree with Fiat at Turin, went straight into a Formula One job with Tyrrell, before spending four years with Williams, prior to joining Ferrari three years ago. In all his time as an aerodynamicist, the 2005 rules presented him and all his counterparts in other teams, with one of the biggest challenges of the past few years.
“When the new rules were introduced, we got a big shock because we lost a lot of car performance, so it has been an interesting technical challenge trying to get back as much performance as possible,” he says. “The loss of performance varied from team to team and I think we were hit quite hard, because our 2004 package had been so effective. We have now recovered nearly all the lost downforce. We are happy with the way we have been developing the car, but there is still a way to go to reach the levels we had at the end of 2004. It has opened up a lot of new ideas and paths to follow.”
But there is no perfect aerodynamic solution, therefore work in the wind tunnel is a never ending process. “At the moment, there are still a lot of gains to be had,” continues Cinelli. “The work is never finite and there is always more to be had. It is question of looking at all the areas in the car and quantifying the loss, seeing how the balance of the car has shifted and looking at the trade-off between downforce and drag and how much efficiency one has lost.”
In simple terms, downforce is good aerodynamics in that it helps glue the car to the road, while drag is bad downforce, as its effect is to slow the car.
“With new rules, you have to start afresh and look at different concepts, trying very different things,” reveals Cinelli. “For example, before the changes, the front wing was optimised for the rest of the car, working with the turning vanes and the diffuser and it was a nicely integrated package. Now the rear wing is in a different position, the diffuser was affected, the front wing was altered, so we had to come up with different ideas, designing new parts and testing them. We made pretty big steps initially and now we are fine tuning our current package. All the teams look at one another’s cars and everyone tries ideas they see on other cars, especially this year with the new rules. But in the end you have to do what is best for your car.”
Time to look at the specific aerodynamic dilemma that is the Indianapolis circuit. Why a dilemma? Because the straight, which is part of the famous banked oval, run in the opposite direction to that used for the Indianapolis 500 Miles race, provides at around 22 seconds, the longest flat-out section of the season, while the rest of the track – the infield – has some of the slowest turns of the year.
“Ideally in Indy, you want a very small rear wing to give you the top speed on the straight and a lot of wing on the infield, where you need more downforce and are not so worried about drag, but of course, you can only have one wing level,” theorises Cinelli. Simulation programmes show that, in terms of actual lap times, there is hardly any difference between running the sort of wing level required to go quickly down the straight and selecting a wing that provides more grip in the infield. However, as Cinelli explains the realities of getting ahead and staying ahead of other cars in the race is the determining factor.
“Our simulations and our past experience go hand in hand when we decide what wing levels to run. In terms of lap times the speed on the straight is very important because it is so long. Plus, a driver who is quick down the straights can maintain position or even pass other cars and then, if his car has less downforce through the infield and is therefore slow, he can still keep the other cars behind him as it is very hard to pass in this section of the track. Too much wing on the straight and you might get overtaken.”
Downforce levels are not decided in isolation. Everything from tyre choice to engine configuration to suspension and strategy can affect the aero package for any particular race.
“We know what our top speeds will be at Indy and when we decide on downforce level for any race, we have simulations from our Vehicle Dynamics department and our experience from previous years at the track to rely on,” says Cinelli. “We factor in the tyre situation when fine tuning the aero set up and also consider brake and engine cooling. As aerodynamicists, we want to run everything as closed as possible to maintain aerodynamic efficiency, but we have to balance this against the cooling requirements of the components.”
22 seconds of straight has its own demands
The length of the pit straight means that Indianapolis provides the perfect example of the slipstreaming phenomenon. In simple terms, if one car follows another closely at high speed, the front car punches a hole in the air, allowing the second car to travel at the same speed while using less engine power and it is thus able to pull out of the slipstream, apply more power and overtake. However, the complex aerodynamics on an F1 car means that the following car’s balance is upset by this and either cannot get close enough to pass, or loses downforce which can lead to loss of grip and a crash. Indeed, in conjunction with the FIA, Ferrari carried out tests at Monza a couple of years ago to see the effect of one car following another closely and how the downforce loss and drag reduction changes the nearer a driver gets to the car in front.
“We found that the average air flow over the car is reduced,” says Cinelli. “Air on the car creates dynamic pressure and if there is a car in front of you, it has two effects. The air on the car is reduced and so the car generates less downforce and the air coming towards you is not “clean” it is turbulent. Cars do not like that. As a car closes to the one in front, the following car loses more downforce because of the turbulence of the air and there is an upwash from the car in front so air hits the car from an angle it is not designed to deal with.”
Of course, none of this theory matters to Ferrari drivers Michael Schumacher and Rubens Barrichello in the heat of battle in the race. They are simply concerned with controlling their F2005, trying to anticipate any changes in grip levels, as they battle with their rivals at some of the highest speeds seen all season on the most famous race track in the world.