Tech analysis: Williams FW28

Williams entered 2005 with some optimism, but although their car appeared to have all the right features, a mismatch between their wind tunnel results and the car's true on-track performance wrecked their early season. It again fell to a long hard season of continued development to bring the team back to form.

Having worked out the issues between the team's two wind tunnels, the parting with BMW and Michelin has left the team with another tough development programme. The loss of Gavin Fisher, the team's long-standing chief designer, again broke up the continuity; with Fisher replaced by ex-BAR man Jorg Zander.

The parting with BMW in particular has returned the team to their independent "garagiste" roots, and the supply of Cosworth engines also echoes their past.

Last week, Frank Williams and Patrick rolled out their new car, the FW28. Designed under the new technical management and with a new engine and tyres, the car is a departure in many respects from the FW27. While certain details of the aerodynamics bear resemblance to the older car, the inevitable pre-Bahrain upgrade will see new bodywork and thereafter a new gearbox.

Over the winter, Williams prepared an interim car so as not only to assist their Bridgestone tyre development program, but also to allow the first on-track running of the Cosworth V8 engine. The Interim car was largely unchanged from the FW27 and had some troubled initial tests. However, running the interim car allowed Williams a long development period for the new car, which has seen them as the last of the major teams to run their new car.

In detail

Two major layout changes have affected the look of the new car. Firstly, the BMW-style lowered nose and keel-less suspension; and secondly, the higher sidepods.

Last year, Williams opted for a single keel and a very high nose tip in order to allow the front wing the most space to work in. However, most of the other teams used the interaction of the nose tip over the front wing for beneficial effect. Williams have hence gone the opposite direction to the FW27, with a large low nose curling over the front wing.

This effect is made more dramatic by the adoption of a lower front bulkhead to make the packaging of the front suspension easier. As with BMW-Sauber, Williams have mounted the front suspension directly to the chassis, resulting in a lighter monocoque with a cleaner flatter underside.

The sidepod design still follows the undercut fronts of the FW27, but now the low line design has gone with sidepods as high as the cockpit sides. According to Williams, this has been to the benefit of the flow passing under the nose around the sidepods - whereas last year the theory was that the lower sidepods improved flow to the rear by obstructing the rear wing less.

Along with these layout changes, Williams did not reveal how the weight distribution and wheelbase were altered. The other Bridgestone-shod teams have been able keep a slightly more rearwards weight bias, and lengthening the chassis was the route towards this - rather than the longer gearbox route, which most Michelin teams have followed.

Designed under Loic Bigois, the aerodynamic treatment on the car starts with a front wing similar to the late 2005 design, with three elements and a large plan area. In testing, the wing also had the endplate-mounted cascade fins refitted. Curiously, these cascades are now slotted, suggesting their angle of attack is quite aggressive.

Heading back past the keel-less nose, the team have retained a similar bargeboard set-up with tall forward mounted vanes and quite small boards ahead of the sidepods.

The sidepod fronts retain the unusually large floor level axe heads, and above these are a new take on the shoulder wing design. These are mounted about half way up the sidepod, featuring a small thick wing profile and a shaped endplate. They appear to interact with the long side-exiting chimneys and the FW27 style stack of winglets behind the chimney.

From the higher front, the sidepods sweep down, with extra cooling provided by slots around the exhaust fairings. The engine cover is now severely shrunken over the airbox. This has been possible because BMW used a very large airbox whereas Cosworth appear to be able to make use of a smaller one. The resulting spine maintains the regulated size, but is as thin as possible with a deep notch at the rear.

At the rear end of the car, the rear impact structure is shaped to facilitate the later addition of a winglet, while the diffuser shape is reminiscent of the FW27. All the aerodynamic bodywork will be likely to change ahead of the first race, though; such is the carry-over from of the old car.

Mechanically, the car has had to adapt, especially in the suspension geometry, to work with the Bridgestone tyres. With Bridgestone, different stiffness requires a different solution in order to make the most of the tyre mid-corner.

At the rear, the suspension has been reworked to make more of the aerodynamic benefits. This places wishbones above the winglet around the diffuser, and the toe link is unusually placed above the driveshaft. The effect is making the wishbones work as extension of the diffuser.

Currently the gearbox is a conventional seven-speed unit, no longer cast by BMW, as has been the case for the past years. But Williams have openly admitted they have a new shift system, dubbed "continuous torque", to reduce the amount of time the engine is not driving the car forwards during the shift sequence.

As admitted by Honda, and in use by at least two other teams, the potential of a more seamless gearshift is up to four tenths of a second per lap at certain circuits and allows the driver to shift mid-corner without unsettling the car. Williams have developed this system, with the aid of Cosworth in the final stages.

Cosworth have also worked hard to produce their new V8 engine, starting from the initial brief for a 2006 engine written by Alex Hitzinger. This brief was set out before the V8 rules were announced, so the initial work was to develop a very different concept of engine with a rev ceiling set at 20,000rpm.

When the FIA announced the rules and latterly firmed up the dimensions, Cosworth's target was altered - but only in respect to the power output. The rev limit stayed the same. As a result, Cosworth believe they had the highest-revving V8 engine in 2005 and will have the same again in 2006.

The resulting CA V8 did not run in a car until the test ban ended in November last year. How the technical competitiveness of these two fiercely independent companies will fair in 2006 will be interesting, as the antithesis of the single company under one roof approach favoured by the manufacturer backed teams.

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- The Autosport.com Team

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