The rush

An eerie atmosphere lingers over Thurleigh airfield. This Second World War relic, six miles north of Bedford, was once the location of the Ministry of Defence’s most important research centre. Abandoned concrete buildings litter the site, which has recently become home to the infamous Yarl’s Wood detention centre for asylum seekers, a motor racing driving school and the UK’s first sky diving simulator. Now another element is about to be added to the site’s strange mix of uses: a state-of-the art Formula 1 testing facility made from a vast concrete wind tunnel used by the military to test missiles and aircraft for nearly 50 years.

The daunting task of turning the 114 m long wind tunnel into a testing facility for Formula 1 cars fell to multidisciplinary firm Ridge. The reinforced concrete structure had to be overhauled and a new structural frame for a £6m rolling road – the F1 version of a gym treadmill – had to be shoehorned into the building (see diagram). In total, the project will have taken Ridge nearly two years. This is the story of how post-war engineering has been harnessed to develop some of the fastest cars in the world.

The 53-year-old wind tunnel first came to the attention of a man called Dietrich Mateschiz, the Austrian owner of the soft drinks brand Red Bull, when he bought Formula 1 team Jaguar Racing last year. Jaguar had acquired the wind tunnel two years previously from rival Arrow Racing, which had snapped it up after the MoD left the site. In the close-knit world of Formula 1, this facility, which also tested scale models of Concorde, is regarded as one of the best wind tunnels in Europe. After the takeover of Jaguar and the launch of Red Bull Racing, Mateschiz was eager to complete the project.

That completion of the wind tunnel really could give the Red Bull Racing wings, to borrow the brand’s advertising slogan. Guy Austin, a partner at Ridge, believes that wind tunnels are the key to success for F1 teams. He says a large part of Ferrari’s success is due to its early use of two wind tunnels to test the aerodynamics of body parts 24 hours a day, and the other F1 teams are now in catch-up mode. “With today’s strict engine and tyre regulations, the wind tunnel has now become the most important tool for F1 teams,” he says.

Other teams have decided to build their wind tunnels from scratch, but Austin feels that Jaguar Racing and Red Bull made the right decision in opting to convert the Thurleigh wind tunnel. “If it’s good enough for Concorde it’s good enough for F1. The tunnel is recognised as being the best in Europe due to its quality of air flow,” he says.

Airflow quality is determined by the amount of turbulence in the wind tunnel’s testing area: the lower the turbulence, the more accurate the test readings. The 114 m length of Thurleigh’s wind tunnel means that the fan can rotate at a slower speed than other facilities, generating a slower initial wind-speed that minimises turbulence. But as the air approaches the actual test area, the tunnel narrows, accelerating the air to a speed of around 180 m per second.

The fan itself is a feat of post-war engineering. The one tonne blades were fabricated by a boatbuilder from strips of laminated mahagony. Such was the quality of the workmanship that moisture did not damage the blades and Ridge has not had to repair them during the renovation, and a spare blade lies untouched in a side room.

On the other hand, the disadvantages of adapting an existing facility were considerable. Unlike modern testing facilities, Thurleigh’s wind tunnel was not in an environmentally controlled building. The concrete structure had to be made absolutely airtight, with no room for error.

Ridge’s first task was to renovate the concrete tunnel. Over the years, the tunnel walls had suffered severe carbonation, causing concrete shrinkage and the subsequent exposure and rusting of the reinforcement bars. For six months, subcontractor Gunite blasted away the affected concrete using 10,000 psi pressure hoses. “Felt and bitumen had been gobbed on to the walls. Sometimes the water from the pressure hoses blasted through the 30 mm concrete walls into the wind tunnel,” says Austin.

Ridge also faced troublesome concrete when it was digging out the foundations for the testing frame, which had to be structurally isolated from the rest of the building. “The concrete specification [of the original building] was unbelievable. The jackhammer bounced off the concrete so we had to core drill out the foundations, which took two months,” says Austin.

The balance frame from which the F1 test models would be suspended also needed to be altered. Despite being 1 m thick, the columns did not provide enough mass to insure against vibration during testing. As a result, Ridge had to baulk up the columns using more concrete.

As well as isolating the main building structure, the balance frame and the testing frame with movement joints, Ridge also had to separate the testing centre acoustically from the viewing and control rooms (see diagram, page ??). This meant providing acoustic protection for the jumble of service ducts that thread their way through the three frames. No mean feat when you consider that the 97 decibels produced in the test room had to be reduced to 45 decibels in the adjacent rooms.

Mateschiz has told the press that the first year of Red Bull Racing would be a transitional one. Perhaps he has noted that the first cars to benefit from the aerodynamic testing at Thurleigh will not be ready until the start of the 2006 season. But when the facility does come on line in May, it could be just the stimulant that the fledgling Red Bull Racing needs.