Venturi capitalists

Colin Chapman was renowned for discovering the next big F1 thing --- and the Lotus boss was a sucker for this particular idea, explains Gordon Cruickshank

Downforce without drag --- the holy grail of Formula One aero experts. By the 1970s designers knew how effective a wing was in loading the tyres and boosting cornering speeds, but on the straights the effect was like towing a caravan. Driver-adjustable aerofoils could slash drag, but had been banned. This was the conflict which Peter Wright set out to resolve for Lotus in 1974.

Chapman's team were floundering with its 76, and so he initiated a clean-sheet think-tank, with Wright at its centre doing after-hours sessions in the Imperial College wind tunnel — and if it hadn't been a rolling-road unit he might have missed the signs. Under the panniers of the mock-up 78, the rolling rubber belt began to lift. Negative pressure was building. A breakthrough.

Tentative experiments with brush skirts fitted to the 77 had hinted at underbody effects, so with cardboard and tank tape Wright deepened the pannier sides, and the downforce soared. The figures were so profound that at first they didn't believe them.

What came out of that was the Lotus 78 'wing car', which opened everyone's eyes. But Chapman knew ground effect had been lost translating the 78 into reality, and was determined to win it back. He was more closely involved with 79 than its predecessor, partly because the 78's designers had both left, partly because he was excited by the new field. "Colin went on holiday to Ibiza," remembers Wright," pencilled out the whole thing and handed it to Martin [Ogilvie]."

Ogilvie and Geoff Aldridge were charged with turning Chapman's scheme into metal.

"Colin took overall charge, for better or worse," Martin says. "He would get his teeth into one thing, what he called the 'unfair advantage', and ignore the other factors." The result was a conventional but narrow steel monocoque. Airflow through the suspension was crucial to the venturi, so the springs, dampers and rollbar links vanished inboard at both ends, and the exhausts were tucked up high and tight. Fuel tankage, in the sidepods on the 78, was moved behind the driver, pushing him forward, and oil and water radiators went in the sidepod noses. This left most of the sidepod free to form the venturi, the narrow-waisted tunnel which speeds up the air, producing low pressure and sucking the car to the road. Of course, if you allow air to rush under the sides the effect is lost: hence the skirts.

"Colin compromised the structure to leave the sidepods free," says Wright, "but then nobody knew what the loads would be. We were creeping up on the skirt problem because we didn't know what was allowed. It was only when Harvey Postlethwaite fitted sliding skirts to his Wolf and they weren't banned that we realised we could go that route."

It was these 'board in a box' skirts which closed the gap between theory and practice. With full-length sliding skirts instead of the 78's short flexible ones, the 79 started to generate real suction. Chapman had his 'unfair advantage'; true ground effect was born.

Testing showed snags — lack of stiffness and inadequate cooling air over the twin exhausts — which would dog the 79, especially in its second season. Nevertheless, Mario Andretti, more technically minded than team-mate Ronnie Peterson, was sure Chapman had scored another jump on the opposition.

With its elegant shape and JPS colour scheme, the 79 was dubbed 'Black Beauty' when it was revealed to public gaze. And its first race, the non-championship International Trophy at Silverstone, seemed to confirm the team's hopes: Andretti put the new car on pole. Those hopes were washed away in a raceday downpour, when Andretti aquaplaned off while leading. But the American loved the planted feel of the car, and when Zolder came around, he sliced a whole second off the field to take pole. And the only guy tailing him was Peterson in a 78 — who despite stopping to change tyres, hoovered up the field for a Lotus 1-2.

It was the same in Spain, by which time Peterson also had the new car. Yet Chapman's rivals had worked out what the underneath of a 79 looked like and were designing their own versions. Gordon Murray was the first to look like puncturing Chapman's balloon; his BT46B 'fan car' out-vacuumed the 79 and won in Sweden. Immediately, Lotus R&D went into overdrive, working on a twin-fan car, one for each venturi; Chapman said later that if fans hadn't been banned, he'd have had a fanassisted 79 ready by the British GP

But they were banned, which meant Hethel had a clear year with a car way above the rest. Yes, they also had two of the finest drivers, but the 79 showed how clean its heels were when, after Peterson's death at Monza, Jean-Pierre Jarier, with no experience of the car, turned in the fastest race lap at Watkins Glen, then took pole and led at Montreal. With six wins and four seconds, Lotus stomped on Ferrari for the constructors' tide.

But the response wasn't long in coming — and from an unexpected quarter: Ligier. As 1979 opened, Gerard Ducarouge's take on the venturi-car hit all the right notes before everyone else, and highlighted the 79's basic flaw — that flexibility. 'The 79 was never stiff," says Ogilvie, "and the torsional strength almost halved after a couple of races as its rivets loosened. We had our doubts, but you just didn't argue when Colin was on one of his charges."

The French machine stood up to the high loadings far better than the Lotus, and Chapman's 'next big thing', the 80, wasn't ready (see page 136). Ligier's candle burned out quickly enough, but by then Patrick Head's Williams FW07 ("a stiff 79", Wright calls it) had the baton. And last year's cream-of-the-crop Lotus couldn't grab it back. Worse, nor would next year's Lotus.