Features - 2010 Grand Prix Review
FEBRUARY 19, 2011
McLaren: Original thinking
McLaren's MP4-25 will best remembered for its pioneering F-duct but it was an interesting car all around.
"The car philosophy was to get the absolute maximum out of the diffusers, to get the biggest, widest, longest diffuser and legalisation was quite a complex process," says engineering chief Tim Goss.
"The MP4-25 had a particularly long gearbox and rear wheelbase so, despite the fact that the fuel tank was longer for the additional capacity, we still stretched the gearbox. That was to push the engine as far forward and get the rear wishbone forward leg as far forward as possible.
"We had a wide, long ducted diffuser that linked into the rear main plane so the gearbox has to be quite long to control the expansion rate. The sidepods necked down very quickly and you got a good clean flow to the rear of the car, which drives the ducted diffuser. That's how it ended up being a long car.
"We think we stole a bit of an advantage in that if you looked down the back of our car into the duct you saw louvres, and that was a complex way of getting round the floor regulations. We did that and effectively opened up the diffuser -- instead of having a piece of floor there you end up with the louvres; it looks like floor from below but in fact it's open. To legalise that is complex and structurally quite difficult because the slots have to run forwards and back, so you end up with the louvres and the duct above it all cantilevered off the back end of the car.
McLaren launched its car with those features and, says Goss, "Renault shortly afterwards launched theirs without the louvres because, presumably, they hadn't sorted out the structural solution or wanted to they wanted hide it. They followed us before the start of the season and subsequently probably 50% of the teams copied some sort of solution along those lines. It allowed us to open up the main duct and get more mass flow through it."
The car's defining feature, the F-flap, "was actually developed from the end of '08," says technical director Paddy Lowe. "We considered running it in 09 but figured we had some more fundamental issues, let's put it like that! We had an F-flap advantage early on, obviously, improved it and so the original wing, RW80, was superseded by RW75 which was a more efficient version of F-flap, but the swing in performance up and down through the season was part due to F-flap sensitivity.
"Early on, circuits with high F-flap sensitivity, like Canada, played into our hands but subsequently there were other things. Around Turkey we felt we'd closed the gap but then we had a run of races where we appeared to lose ground, for a variety of reasons, including issues we had with front wings, particularly our third iteration, FW3.
The team candidly admits that it was a little slow off the mark on the blown diffuser. They obviously spotted it as soon as the Red Bull ran it at the pre-season Barcelona test but were working on large aerodynamic projects at the time. A little bit later they fully realised the value and dropped the other project, meaning that McLaren was a race after Ferrari and Renault in introducing it.
"The car's unhappiness on bumps was pretty much all down to the aerodynamic characteristics," explains Goss. "To get the most out of it aerodynamically we ran it at a given attitude and stiffness and even though we played around with different set-ups, we kept coming back to the same one. We put a lot of effort in, right since the first race in Bahrain where we were losing out significantly to the Red Bulls in the bumpy corners. And we put a lot of effort in after Silverstone where we weren't handling the bumps particularly well.
"We didn't need to change the stiffness for the blown floor but the reason we got more performance out of it is that we learned more about how to rebalance the car. At Silverstone it wasn't delivering to expectations although it wasn't actually any worse than the old floor."
Going back a number of years, all the designers used to put the exhaust out through the diffuser but changes to the regulations post-1994 made it more difficult and Ferrari bucked the trend and went to high exhausts.
"You got instability from the on-off blowing of the floor," Goss says, "but now we're all a bit more intelligent in how we deal with that. One of the problems early on was that you'd get on the throttle, pick up rear downforce and the car just understeered. It's great having a load of rear end downforce mid-corner but it doesn't necessarily make the car quicker if you're lacking front end. We learned more about the floor itself and the way to use it."
Prior to the season there was much speculation about whether McLaren could handle the managerial implications of having the last two world champions, both British, in the same team. In fact, they ended up being delighted by the Hamilton/Button partnership.
"There wasn't much divergence between the drivers and it was particularly good," says Lowe. "In previous years it's been quite problematic: Kimi (Raikkonen) and (Juan Pablo) Montoya was a nightmare! We ended up going different routes on wings and even front suspension, but these two liked surprisingly similar set-ups. Lewis uses the brakes differently -- he brakes very hard and prefers a different brake material. They have different driving styles but not so wildly different that we have to go in different directions. The biggest difference we saw was at Monza, where we had two packages developed in parallel, and it's a shame Lewis had his accident and we didn't really see which was the right choice!
"They have actually been good for each other. Lewis thought he was going to have an easy ride of it early on, then he was out-qualified several times, Jenson picked up the wins where Lewis didn't and it made him raise his game. Some wonder if it's the right approach to have two top line guys but it has always been ours. Every driver has a bad day and if the guy on the other side of the garage is a good reference, then your performance is underwritten somehow. If only one is strong and he's having a bad day, then you're in a bit of trouble."
Goss got a bit frustrated by claims from elsewhere that the Mercedes engine had a significant advantage. "The Ferrari is not a weak engine and the Renault can't be that bad," he says, "you can't get pole at nearly every race without having a decent engine! I think it was a bit unreasonable to complain that they've been hard done by with the engine freeze. Even now there are plenty of parts of the engine inlet, let's say, that are free. Exxon Mobil put in a massive effort every year to develop our fuels and somehow it's lumped in the pool and not recognised. Apparently that should be neutralised and I don't agree with that. Having said that, Mercedes does do a fantastic job with the engine - it's certainly among the best and very reliable."
The great unknown for 2011 are the Pirelli tyres. McLaren has always been strong with its tyre modelling whenever there has been a change of regulations and Button was convinced after initial testing that the need to look after the soft tyre will play to his strengths.