Tech analysis: Renault R26

Renault hit the jackpot in 2005. Their car dominated the opening races, and it was only by mid season that the pressure from McLaren really left the Anglo-French team behind on the pace. Renault brought the fight back to McLaren at the end of the season to secure both championships. However, largely reported as a reliability run to the championship, the more conservative solutions on the Renault car belied its speed.

Ahead of their formal 2006 launch, Renault began testing their all-new R26. The first tests were significant, as the V8 engine had not run in a car up until that point. Instead, Renault ran the engine solely on the dyno in France, and the 2005 chassis ran with a V10 engine tuned to mimic the V8 power delivery.

Despite the team's immense resources, the decision not to modify a car to run the new engine was a brave one. Yet the team reasoned that the careful testing of the V8 would not be hindered without the only true test of an engine, which is to run on track.

Still, the R26 appeared quite early in the new year for testing, and the initial runs have been reliable, so clearly the homework has paid off.

At first glimpse - and even in some detail - the car is a clear development of the successful R25. At the end of 2004, the team reflected on the edgy handling of the R24. Understanding the car's failings lead to the much more neutral handling of the R25. Were similar lessons carried onto the R26 program ?

"I think the key lesson we learned from the R25 to the R26 was not to screw up," says technical director Bob Bell. "We believe very strongly that it's important for the R26 to take all the good characteristics of the R25, which there were many of, and to embody them in the R26 to establish a baseline, where we could add performance during the season. We wanted a good, stable platform that was easy to drive and the drivers were comfortable with."

In layout, the team have retained the old wheelbase. Within the monocoque, the fuel capacity remains similar to last year. Bell admits that last year the actual rubber fuel bag in the rear of the car was not as large as possible; two tank sizes were raced to accommodate different strategies. The benefit of the smaller bag inside an oversized chassis is to keep the fuel weight contained under cornering loads. But Bell is coy on whether the undersized tank methodology is carried over this year, saying only that "it may or may not" be adopted.

At the front, the familiar narrow nose is altered for a shorter, fatter design. Currently the front wing appears similar to an R25 design and changes are planned before Bahrain.

Behind the nose is the same V-keel arrangement. This year, the concept has been revised in detail. The legs of the keel are a bit deeper, and the mounting of the rear of the wishbones has been altered.

Last year, the car sported a vertical splitter along the middle of the shadow plate. This part, called the "dolphin" by the team, was only half the height between the shadow plate and chassis. This year the device is taller and spans throughout the underside of the chassis, from the leading edge of the shadow plate.

The dolphin acts to split the flow left to right under the chassis and around the undercuts in the sidepods. To ease this more directed flow on either side of the car, the sidepod inlets are revised, with the lower parts now pinched to allow for the all-important flow to pass around and under the flip-ups.

Details around the sidepods are familiar, with the large chimney no longer aided by vast expanses of louvers. This is in keeping with the lower cooling demands of the V8 engine.

One area where the car has diverged from other 2005 designs is in the rear wing. Immediately noticeable, the wing is supported by a strut, in order to take the load off the endplates and the lower beam wing. But it is the actual wing shape that is so intriguing.

In recent years, rear wing profiles have become twisted in order to reduce the drag created by the vortices at the wing tip. This requires the wing to be less aggressive next to the endplate, thus the wing appears shallower at the outer ends.

What Renault has done is quite the reverse, where the wing is least aggressive in the middle with the steepest sections right next to the endplate. So why would Renault do this when all teams are seeking to reduce drag due to the lack of power from the V8 engine? The answer might not be in how the wing appears itself, but rather at the other aerodynamic influences around it.

Although the engine cover affects the flow that approaches the rear wing, the difference between the sides and centre is not that big to account for the different shape of the rear wing. Instead, if we look around the back of the wing, the flow out of the diffuser is perhaps the key.

Renault worked the middle tunnel of the diffuser very hard last year, with the lower side tunnels not as influential as the wake behind the car. This steeply rising flow drives the contra-rotating vortices formed behind the car. The larger this flow-field is, the more drag it induces. By being less aggressive in the middle of the wing, the rear wing does not add more drive to the flow and hence keeps the wake smaller and in turn creates less drag.

Allied to the new chassis, Rob White's team have developed an all-new engine. With Renault only having run a narrower angled (72-degree) engine for two years, the step towards a 90-degree format for the V8 is new territory. Although the V8 with its flat plane crank is prone to more secondary vibration, Renault's experience with the vibration prone wide angle V10s and the V8 GP2 engine was not directly related to the new unit.

White cites the recent V10 engines being more applicable to the new engine and in the end the vibrations were not the major issue most had expected. Like most teams, Renault adapted a V10 for initial V8 tests, but in Renault's case this necessitated a new cylinder block to set the bank angle at 90-degrees.

Dyno work started very early in 2005 on the mule engine, while the testing, design and development work fed into the definitive RS26 engine, built to the new regulations on size, weight and materials.

As the smaller capacity engine has less torque, its power delivery will be more peaky. As a result, the team has returned to a seven-speed gearbox, the extra ratio allows the driver to keep the engine in its power band for more of the time. This has made the gearbox a little longer, but with the shorter engine this hasn't been an issue.

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- The Autosport.com Team

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