Tech Analysis: Renault R28

On the face of it, finishing third in the championship last year should be viewed a good result. But the figure belies the season that team boss Flavio Briatore called "a disaster".

Not only was the result was poor for a team that had won the two previous championships, but the car's pace was well behind BMW Sauber, never mind Ferrari or McLaren.

At the launch of the new Renault last week, technical director Bob Bell spoke candidly about the reasons behind the slump, and highlighted the progress made on the new car.

The problems in 2007

If we look back at the second half of 2006, Renault were fighting a tight championship with Ferrari. In the second half of the year Ferrari was clearly faster, and Renault faced a challenge to maintain its pace to secure the titles.

In maintaining its lead, Renault pressed ahead with development of the R26. It was too late to bring major updates to the car from Turkey onwards, but the team added a host of detailed aero upgrades, and this is where the problems first started.

The problems were both complex and numerous. Firstly, the pressure to develop the 2006 car diverted resources from the 2007 car, but more importantly, it affected the way that the team evaluated the new parts.

As has been the case for many teams, the results found in the wind tunnel were not being realised on the track. It wasn't the wind tunnel itself that was at fault, but nevertheless the results weren't being replicated on the track and the team wasn't picking up this problem.

I asked Bell whether this led the team down aerodynamic dead-ends, and his response was surprising.

"In fact, we were putting parts on the car that were taking performance off, not putting it on!" he said. "You would think, why the hell would anyone want to do that?

Renault have tidied the mid section of the car, with the mirrors no longer connected to the pod wing © Scarborough (Click to enlarge)

"Well, we put an awful lot of very small improvements on the car; some of them were so small it was very difficult to do a track test to see if it is better or not. The measurable benefit is in the scatter between two identical runs, so you have to take it on trust what the wind tunnel is telling you.

"If you just look at any individual test, you can't tell if it is an improvement or not. It's only when you look at it over time, and unfortunately that's where we lost performance in the car."

So by the end of the season Renault had lost the correlation between tunnel and track. This was leading the team to make false assumptions about the benefits of new developments. At this point the problem had not been discovered. and the pressure to prepare a new car for 2007 to suit the new Bridgestone tyres was a priority.

This is the second twist that lead to the difficulties of 2007. Not only were the aerodynamics a problem, but Renault's extended period on Michelins had led the team to settle upon different balance on the car.

It's well known that Renault adopted a more rear-ward distribution of weight and downforce as its solution to make the Michelins work. In describing preparations for 2007, Bell recounted the period when they first realised that they were going to lose ground against the opposition.

"At the end of 2006 we all went to a winter test. In the same cars we put on Bridgestones, they (McLaren) put on Bridgestones. They went 0.5s quicker than us."

Bell believes the difference was down to the balance of the car.

"It's to do with Michelin, because they (McLaren) believed what you needed to do with Michelins is move the aero forward. We didn't, we thought you wanted it back with Michelins. So when we went with Bridgestones they (McLaren) were already down that route."

Thus, the team 2007 started with a need to move weight and downforce forwards and an aerodynamic testing process that was flawed. The problems quickly became apparent at the season began, and while the team worked to understand the shortfalls in the testing, it was clear that the season was lost and focus needed to be brought onto 2008.

The 2008 car

With aero testing now bringing more accurate results the team started early on their 2008 car, the R28. One of the key demands was the need to move weight, and thus aerodynamic load, forwards to suit the Bridgestone tyres.

The underside of the nose is arched to create a channel leading from the front wing (yellow) © Scarborough (Click to enlarge)

Secondary to that are the rule changes on electronics and gearboxes, particularly the ban on driver aids.

To move weight forwards the car needed a change in layout; not specifically a change in wheelbase, but an alteration of the locations of the major masses (engine, gearbox and fuel) and wheel positions.

There are various ways this could be achieved, but Bell confirmed that it was the engine moving forwards that shifted the mass, with the gearbox being lengthened and the fuel cell being shortened to maintain the old wheelbase.

Allied to this, the need to put more aerodynamic on the front was a challenge for Renault. Clearly, the new car has a very different nose and keel arrangement to the outgoing car. Firstly, the V-keel has gone. Retaining the V-keel for 2006 was correct for Renault, despite other teams adopting a zero-keel format.

"It is absolutely the case that with Michelin tyres, we did not need as much front downforce," Bell explained. "Under those set of circumstances the best aero solution we found was the V-keel. Now, with the Bridgestones, you need every bit of front-end you can get."

Thus the team have adopted a zero-keel solution, but the change could not be made in isolation as the keel area needs to work with the front wing and the suspension geometry. Thus a much larger front wing was designed, and the flow under the nose was considered.

Equally the loss of the V-keel suspension brought unfavourable changes in suspension geometry, with the way the camber of the wheel changes through the suspension movement.

Renault resolved the problem the same way that Ferrari did when it moved from single-keel to zero-keel - by spacing the upper wishbone away from the tub to create unequal-length wishbones.

Also, to maintain reasonable wishbone angles, Renault dropped the height of the front bulkhead. This is the point where the monocoque meets the nose cone.

This change has not brought the bottom edge of the monocoque in line with the lower wishbone mounts though, as Renault has metal extensions jutting from the bottom edge of the tub to mount the wishbones. This is almost a twin-keel set-up, although Renault itself have termed it zero-keel.

In creating this keel arrangement the team has created an opportunity to try a novel aerodynamic treatment with the front wing and nose.

A vent at the rear of the engine cover is aimed at simply venting hot air from the sidepods © XPB/LAT (Click to enlarge)

By having the keels dropped slightly from the bottom of the tub, a channel is formed. Renault has made use of this by sending the flow off the middle of the front wing through this channel. From the front, the front wing appears to touch the low nose tip, but in fact the nose cone has an arched underside to match that created by the keels.

This flow only exits the channel after the rear leg of the lower wishbone, then passes around the undercuts in the sidepods.

Potentially, this set-up will prevent the upwash from the front wing passing up around the tub, keeping flow to the rear wing clear.

But the arrangement is complicated and is tied into the structure of the car. If the team find it is too sensitive or that limits front end development, it will be hard to completely remove it.

Allied to the all-but-hidden undernose arrangement, the front wing itself is a departure for many conventions adopted for recent front wings.

Firstly, the wing discards the vertical pylons used to mount the wing to the nose. Instead, the pylons are rotated sideways to a near-horizontal position - this makes use of the pylon to shape the flow over the front of the car, rather than being benefiting the aero around the nose.

"We tried to do something useful with them" said Bell, who added "It's a heavier solution," but the weight is at the front which was one of Renault's aims for the car anyway.

The wing also sports an unusual profile, particularly in respect to the centre portion which droops suddenly from side sections of the wing.

Intuitively, this could make the wing sensitive to attitude changes, as many solutions like this in the past have been short-lived. The new set-up appears to be making the centre of the wing work harder, obviously working in unison with the arch under the nose.

A new addition for 2008 is a bridge wing. Renault had been the first team to adopt cascades and then bi-plane elements over their front wing - the team sees this solution as a evolution of the same concepts.

However unlike other teams, the bridge flap has a small support steadying it, whereas other teams have left their wing unsupported, which leads to come deflection at high speed. But the FIA have not felt that the flex is advantageous, and have not asked other teams to reinforce this part.

Elsewhere, the car is far more conventional. The conjoined pod wing, mirrors and flip-ups of last year have been split up once more. The mirrors, with a more pointy shape, have been moved back to the cockpit. Bell suggests this was purely for aerodynamics, but admits that last year "they did vibrate, although we fixed that."

Meanwhile, the pod wings are much smaller and the flip-up starts farther back along the sidepod. Although initially appearing similar, the sidepods are an exaggeration of the shape developed last year. The front shoulders of the pods are hunched forwards and the general shape of their widest point is very rounded, leading back to a slim coke-bottle waist.

Renault has retained louvers on the top face of the sidepods. The upper shape is retained even if the car's cooling outlet area is blanked with panels underneath to restrict flow.

According to Bell, "the louver doesn't cause you any harm. It's an easier solution than to blank them from underneath."

More cooling is provided by an outlet at the tail of the engine cover. Some teams have a cooler mounted inside this outlet, but Bell explained they are used for "a general evacuation of warm air from the sidepods."

Beneath the skin of the car, a lot of weight has been shed and the packaging has been tightened up. The new, longer gearbox case has had a revised quick-shift gear cluster developed to last four races and to be controlled from the new singe ECU (SECU).

Equally, the engine has been developed as far as the rules allow. This year the engine freeze rules are expanded to encompass the ancillaries, thus elements of the airbox, injection system and pumps are included.

As with most engine department chiefs, Rob White feels that little could be gained with the engines performance this year. He also said that the SECU has not limited the engine peak power output, but that it has limited the engines transient behaviour.

Thus, the engine will not be as drivable as the team would like, but work on the control systems should recover more of the engine potential as the season progresses. Indeed, this is one of the few areas that can be worked on through the season, leaving only fuel and oil development to improve engine response.