New Williams lightest ever.

The car that BMW Williams hope will take on Ferrari this season has taken to the track in front of the world's press in Valencia today, and it represents the lightest-ever F1 contender the team has ever built.

A painstaking approach to every element of the chassis means that the team has achieved its lightest-ever chassis, meaning that maximum use can be made of the ballast required to bring the car up to the minimum weight for the regulations.

Fundamental changes in the rules mean that the BMW Williams team, just like everyone else in the pitlane, faces a big challenge. Engines now have to last two race weekends, and one set of tyres must last not only the entire race distance, but also be the same set which was used for qualifying. This is allied to the new rules regarding wing placement meaning the FW27 has somewhere in the region of 25% less downforce than its predecessor.

This left the squad with plenty to occupy the 250,000 man hours spent developing the new FW27 chassis, but there was something else playing on the mind of the team boss, and everyone working for the team. "We want to move back to the winning lane," explains team boss Frank Williams. "The mistakes of 2004 must not happen again."

2004 did see the team off to a poor start and much of the blame has subsequently been attributed to the twin keel 'walrus' design with which the FW26 started the season.

The Williams BMW squad is now firmly back in the single-keel way. "One of the things we weren't happy about was the twin-keel on the FW26," explains technical director Sam Michaels. "It has small amount of downforce gains but ultimately the weight penalty to ensure you had good enough stiffness wasn't sufficient for us. We decided at an early stage to return to a single-keel."

There is interest around the front-wing of this year's car, albeit not to the same degree as there was last year. Whilst the wing endplates now must be some 50mm higher than before, there's scope for some variation and the Williams approach tries to maximise a low centre section in a similar way to BAR with the 007's front wing.

"We've taken the front wing main plane down as far as we can, to work closer to the ground," explains Sam Michael. "The more you can work the centre part of the wing, the more you can downforce you can generate on the front axle to get the aero balance you require."

Elsewhere on the sleek new chassis, the radiator sidepods are of note, housing very small radiators, with the leading edge reckoned by Michael to be around two inches lower than the competition "We managed to get it as low as possible, helped by the heat rejection of the engine," he says. "We have a tight leading edge of the sidepod and a tight coke and low top deck. It is the smallest sidepod we have done."

Small radiators can't keep the engine men happy, especially with the prospect of motors having to last two race weekend. This BMW Motorsport director, Dr. Mario Theissen, confirms. "It's a trade-off between engine and chassis targets. We'd love to run the engine a lot colder with bigger radiators. But then you sacrifice aero,"

Williams will soon be running their new challenger in the company of some of its rivals, we will soon have some idea of just how good the car could be.