Under the skin of the Williams FW35

Williams was the only one of the 11 Formula 1 teams to wait until the second test at Barcelona to unveil its 2013 car.

Described as '80 per cent new', the FW35's low-line rear end is carried over from the past two Williams, but several innovative features are already apparent, such as the nose treatment, the exhaust outlets and brake ducts.

After a terrible season in 2011, Williams bounced back in '12 with a new technical team and Renault engines. The 2012 FW34 was optimised around the unique rear of the FW33 and made best use of the superior packaging of the Renault engine.

Having better tyre management early in the year allowed the new package to show its strengths, leading to a win at the Spanish Grand Prix. The balance of the year was harder for Williams with some underlying aerodynamic issues, and the team never fully came to grips Coanda exhausts.

Moving into 2013, the team's technical director Mike Coughlan has been able to get into his stride and the level of innovation he explored at Arrows has seen a resurgence in the new car's details.

Thus the FW35 retains a lot of the layout of the older designs, but everything has been refined with the car now in its third year of evolution.

The extended front wing mounts act as bargeboards © XPB

Most startling is the new nose arrangement. Having already run the FW34 at the first 2013 test with a modesty panel, it was no surprise the 2013 car does not feature a stepped nose.

But the treatment of the front wing mounting pylons is all new. These pylons start at the tip of the nose and snake back to mount to the rear of the front wing. They act as a bargeboard and interact with the other vanes mounted under the nose.

Another departure for the new car is the front wing. Last year Williams created ever more intricate iterations of its wing, with the complex 'm' shape to its leading edge. This may have been one of the underlying issues with last year's car, so the FW35 returns to a simpler leading edge design.

The front push-rod suspension, key to last year's tyre management success, is largely carried over, but the aero treatment around the front wheel is new. The wheel gains a vane-like ring around the spokes, which helps the air passing out of the wheel from brakes.

Blowing air out of the wheel nut aids the aerodynamics behind the tyre © XPB

It was Williams that pioneered the scoop-less front brake duct last year. This year it has created an even more complex inner wheel cover. This now sports a creased leading edge to encourage more air into the brakes and features several vanes to aid the general aerodynamics passing inside the front wheel.

As well as feeding cooling air to the brakes, the brake duct also sends some airflow directly out of the front axle. This aids the airflow forming the wake behind the front tyre, although the idea isn't new as Red Bull tried this last year. However Red Bull's sharp pointed front axle vented its airflow outboard of the wheelnut.

n Monaco rival teams complained about Red Bull's design, as the duct extended too far, so it was banned and never returned. As Williams end its hollow axle at the wheelnut, it is perfectly legal.

Although the team tested Coanda sidepods as early as the Mugello test last year, the designs never made it to a race. This year's sidepods currently follow similar design to those tested last year, with a McLaren style semi-Coanda exit.

Having the benefit of the exhaust blowing effectively along the diffusers edge will be hugely beneficial for Williams this year. It will provide more downforce and more opportunity to raise the rear height for even more diffuser performance.

The siamesed exhaust opening will be contentious © XPB

Unusually for a car launched to the press, the exhaust outlets are a controversial design. The channel forming the exhaust outlet initially appears to be in two parts, but in fact is a single siamesed outlet.

The upper opening is for legality and sits directly in line with the tail pipe's exit. However the Coanda effect bends the exhaust flow and the actual plume passes out of the lower opening. With these two holes joined by a tiny slot, they are considered a single opening.

According to the published rules this design is legal, but as with Caterham's exhaust vane, the closed section of outlet is in contravention of a technical directive issued last year insisting that exhaust gasses cannot be re-ingested. Again we will have wait until Melbourne for FIA scrutineers to decide if this is allowed.

The rears of the recent line of Williams have all featured a unique low line gearbox, where the otherwise empty top half of the gearcase is removed to create more space for air to flow over the back of the car. This year's version is more refined and the way the gearcase mounts to the rear wing follows Sauber's swan neck mount. This is an arched mounting that holds the beam wing from above, to keep the wings harder working under the surface free from obstruction.

Williams has a uniquely low gearbox to improve airflow over the rear end © XPB

Above the beam wing, the rear wing endplates retain the slots in their leading edges. Like Ferrari's vanes behind the endplate, this is done to allow more flow from the sides to pass inside the rear wing for more downforce.

The rear suspension is again pull rod operated, but while the lower wishbone is mounted much higher, it does not enclose the driveshaft. Other teams have done this, but Williams appears to be happy with the wishbone and rear track rod to simply be aligned either side of the shaft for better aero.

The relationship with engine supplier Renault will be critical in getting the most out of the exhausts for aerodynamic effect. Already the Renault engine has provided Williams with lower fuel consumption, smaller radiators and better drivability. Unlike the other Renault customers, Williams produces its own KERS, with a Li-Ion Battery mounted below the fuel tank.

If the car retains the tyre management prowess of its predecessor and gains the lap time boost anticipated from the Coanda exhausts and other aero innovations, then last year's step forward in pace should be repeated this year.