2007 British GP Technical Review

Just a week after the French GP Formula One arrived in the UK, at the high-speed Silverstone circuit.

Similar in demands to France, the back-to-back races have given teams no time to test or introduce new parts, so most teams sported similar packages to what was used in France.

However, Silverstone places slightly different demands on the cars. The track is one of the few circuits still featuring very high speed corners, and these are offset by fewer slow complexes and long straights.

Thus, the teams choose to run a lot of downforce to keep the cars stuck to the track through the fast direction changes.

These high loadings prompted Bridgestone to choose the medium and hard compounds from their range. With moderate temperatures and mostly dry conditions, both compounds fared well during the race.

In fact this race saw more variation in tyre strategy than we have seen all year, with drivers opting for the softer compound in any one of the three stints. Such was the durability of the softer tyre that Honda opted for a one-stop strategy.

The race also demonstrated the increasingly common strategy of front-row qualifiers being compromised on race strategy. So closely matched are the front four cars that the drivers running less fuel in Q3 may get pole position, but have to stop earlier in the race.

If the heavier-fuelled pair of drivers can keep up with the pace in the opening stint, they are able to stop later and make up the gap when the leader pits.

This creates a quandary for driver and team alike; the driver that can qualify well with the most fuel has the greatest chance of winning the race.

Ferrari

At Silverstone, Ferrari finally presented their front wheel fairing for a race weekend. As has been mentioned previously, these covers are fitted to the front wheels and remain static while the wheel rotates.

Last year Ferrari had been the first team to exploit the revised front brake duct regulations that allowed any bodywork within the wheel to be regarded as a brake duct, regardless of whether the part actually provided any brake cooling function at all.

At first, rear wheel covers bolted to the rim were used. These grew increasingly larger, to the point where Ferrari's rear fairings enclose the wheel completely, aside from the access to the wheel nut.

Despite some unofficial protests, these parts were considered legal and Ferrari have taken the next step.

The flow around the front wheels creates a large proportion of the car's drag, and the irregular flow from the rotating wheel can upset the flow along the rest of the car, costing aerodynamic efficiency.

As CFD has developed as a tool to analyse complex air flows, so the focus on the behaviour of the air around the wheel has grown. Many teams' senior aerodynamicists have cited wheel flow as a major area for development.

Both the fairing and retention mechanism are attached to the wheel nut. Strakes aid the flows exit © Scarborough (Click to enlarge)

A Formula One wheel and tyre rotating against the ground creates a complex structure of vortices. The main flows are where the air passes under the front of the tyre and curls up and around the rear face of the tyre.

This sends a powerful spiral of air trailing behind the wheel (blue) and also a bubble of reversed flow right behind the wheel (blue arrow).

The same sort of structure is created above the wheel (yellow), but the flow over that also passes over the top of the tread makes the reversed flow even more complex (yellow arrow).

The result of these flows is an area just below the axle line where the two vortices can pull air in behind the wheel. It is this area that Ferrari choose to vent the brake duct (red).

This could make the small exit as effective a larger open duct, which has little control over where the flow is sent. The fact that the duct is static allows the exit and the flow over it to remain in the ideal position.

Usually. we see brake dust being ejected several feet from the wheel under braking. This actually visibly demonstrates the interference the heated brake flow has with the rest of the car, effectively making the car wider than it actually is and increasing drag.

As with these fairings, the flow is sent right behind the tyre, reducing drag as the wake around the front wheels is narrower.

To make the fairing work, Ferrari have redesigned the entire hub and wheelnut assemblies. The new set-up moves the nut retention mechanism to the wheel nut, and then attaches the fairing to the wheel nut via a bearing.

Inside this assembly is a central shaft which houses the securing mechanism for the wheel nut, and also locks the fairing into the correct position.

Honda have a revised rear end, the diffuser is simpler and the beam wing (yellow) is taller © Scarborough (Click to enlarge)

The drive lugs on the wheel nut are accessed through matching slots in the fairing mount. The pegs on the wheel gun have to be longer to pass through the fairing mount and into the wheel nut.

When the mechanic fits the wheel nut with the specially adapted wheel gun, he has to engage the retention mechanism. A pin extends from the central shaft inside the wheel nut to lock it against the hub.

The mechanic then spins the fairing to lock the tip of this central shaft to upright. Thus, the fairing is unable to spin freely and the wheel nut is secure.

Honda

As part of the changes introduced for the French GP after testing at Jerez, Honda have a new diffuser and rear wing arrangement.

As mentioned in the French GP analysis, the diffuser has simpler outer channels, no longer creating a supplementary channel between them and the central tunnel.

However, the large gurney flaps are still a feature; an attempt to gain as much exit area as possible. To aid the diffuser, the rear beam wing has been modified and now features a lip running along its full upper edge. This helps pull the flow up from the diffuser to join the upwash through the rear wing.

A simpler carbon fibre ring was added to the Williams front wheels © XPB/LAT (Click to enlarge)

Williams

While Ferrari stole the headlines with their front wheel fairings, Williams introduced a much simpler solution, mimicking Ferrari's early rear wheel fairings.

A simple ring of carbon fibre was bonded to the front wheel to reduce drag, Curiously, the team did not fit rear wheel fairings to match the fronts.

Red Bull and Toro Rosso

By virtue of the joint design company Red Bull Technologies, both Red Bull teams have seen detailed development around the front end in the past few races.

Both Red Bull teams raced these brake duct fins and bargeboard fences (yellow) © Scarborough (Click to enlarge)

First, a fence was fitted under the main bargeboard to run parallel to the front splitter (yellow). As this fence lies within the width of the step under the car, it is allowed to be lower.

This makes the fence more efficient, as the rest of the bargeboard must be in line with the raised part of the floor, five centimetres above it.

In France, Red Bull introduced a large lip to the front duct. This extends to the maximum allowable width inboard of the wheel, and runs from the front of the duct to the rear.

While the fin probably makes its own downforce, the main aim is direct the flow off the front wing endplate.

A distinctive delta rear wing has been a new development for Super Aguri © Scarborough (Click to enlarge)

Super Aguri

Having already raced it in France, Super Aguri also ran their new rear wing in Britain.

This new wing owes nothing to their previous designs, nor Honda's. The main plane has a slight twist in its profile, while the flap has a distinctive delta profile, reach a point at the middle of its leading edge.

This resembles Ferrari's early season rear wing. Additionally, new endplates are more cutaway around the wheels and join the gearbox via revised beam wings.