Science becomes art in aerodynamic stunt with Mercedes B-Class

Jeremy Hart is witness to how a bit of paint, black lights and a wildly powerful wind tunnel can highlight the aerodynamics of a little Mercedes-Benz.

The colourful effects of the novel paint job.

Just by looking at a car, it's sometimes difficult to tell what is aerodynamic and what isn't, and sometimes the shapes can be entirely misleading altogether.

A low, sleek Lamborghini Countach, for example, looks like a knife that would cut right through the wind. But compared with many normal cars today, its coefficient of drag can be more like that of a barn door. In fact, the Mercedes-Benz B-Class is far more slippery in the wind than the legendary supercar ever was, but you'd never tell that by looking at them.

Aerodynamics have long shaped our transport but now it's the latest tool in the quest for efficiency. Independent testing by the TÜV body in Germany proves the aerodynamics of the Mercedes-Benz B-Class can generate a Dh18,400 saving in fuel bills over 100,000 miles (161,000km) when compared to its predecessor.

The trouble is, aerodynamics isn't exciting. Top speed is glamorous, cutting-edge, built-in gadgets are cool, but aerodynamics? No matter how impressive, how useful, it's just that little bit too, well, nerdy.

But nerds get to have fun, too, particularly at Mira [Motor Industry Research Association], a top-secret, high security automotive research facility near Birmingham, England. It's here that cars of the future can be seen on the banked test track. Only they can't, not properly at least, as they wear spy photographer camera lens-confusing camouflage bodywork and paint to keep their multibillion pound development process as secret as possible.

Mira has a wind tunnel. It's one of only a few around where 130kph winds are possible. Generated by four massive propellers from an Avro Lincoln bomber (the successor to the fabled Lancaster), at the flick of a switch it gets pretty draughty, pretty quickly. This allows aerodynamicists to hone the flow of air over a car's body. As we all know, we might be able to feel the wind rushing by but we cannot see it. The boffins have thought about that, using either trails of smoke or fine fluorescent spray to judge the airflow around, over and under a car. And that gave Mercedes-Benz an idea. To show off the slippery properties of its new B-Class, Mercedes is taking the idea of the boffins fluorescent paint and turning up the volume.

Pollyanna Woodward, the British television presenter of Channel 5's Gadget Show, is going to spray intense fluoro-paint at the car under a bank of intense UV lights and allow the wind to do the rest. It's part Andy Warhol, part Top Gear and all high-tech.

Among the wind tunnel technicians is a small army of cameramen, riggers, stunt safety experts and crew. To a man they are all fully covered from head to toe - sporting gloves, balaclavas and goggles. For good reason. Strong enough to blister skin in minutes yet invisible to the naked eye, the UV lights are the reason for the crew's fully covered appearance. Everyone wants to get the shot, but no one wants to end up in the burns unit.

"When we were first called about this job it didn't seem too serious," says safety director Andy Harris, "but when we looked closer we realised it involved covering a car in flammable liquid [the paint is paraffin-based], next to a very powerful heat source [the UV lights run at 750 degrees], in a 60mph hurricane, in the dark."

"I'm not sure what to expect. But I'm in good hands," says Woodward as darkness falls. That darkness is important. The wind tunnel needs to be pitch black so the human eye will see only the fluorescent paint and how it shows off the lines of the car.

Film director Geoff Harrison explains: "This has never been done before. We're shooting a black car which we can't see until it's painted. The only thing the camera sees will be fluorescent."

"Action" comes the unseen call and the wind picks up, rising to a roaring, freezing howl that sends the temperature plunging to -10. And then it happens: "Cue paint."

Carrying a spray gun in each hand like a paint-toting gunslinger, Pollyanna opens with both barrels. The blackness is broken with fluorescence. Vivid yellow paint blasts from her guns like rocket plumes, exploding on the familiar Mercedes star on the nose of the B-Class.

The result is extraordinary, part art, all science and strangely alluring; aerodynamics is evidently not just for nerds, but those appreciating the aesthetic of economy, too.