X-ray spec: Under the skin of Alan Jones' title-winning Williams FW07
Being first with the new idea is only part of the battle. Frank Dernie, Williams R&D chief at the time, tells Keith Howard how the team picked up the ground-effect ball from Lotus and produced a multiple winner with the FW07
Hegemony in Formula 1 — if you’re clever enough to achieve it in the first place — rarely lasts for long. Like breakaway riders in a cycle race, most teams who establish an advantage over the rest of the grid are quickly reabsorbed by the relentlessly pursuing group.
So it was for Lotus in the late 1970s when it pioneered ground-effect aerodynamics. In 1977, its type 78 wing car performed well enough to secure the Norfolk team second place in the constructors’ championship. But its points tally was well short of Ferrari’s, and few in F1 apparently appreciated that this car was only the warm-up act. When Lotus’s real star — the full ground-effect type 79 — appeared the following season, the world witnessed one of those rare occurrences in motor racing of any sort: dominance achieved through a single technical breakthrough.
With such a major research and development lead over its rivals, Lotus ought to have had the 1979 season sewn up too, even allowing for the fact that the 79 would be used as a template by other teams. But aware that its pursuers would be pedalling hard to close the gap, it over-reached itself. In attempting to realise the maximum possible downforce from the type 80, Lotus made the car a thoroughly alarming beast to drive. And so the pursuing group didn’t just catch Lotus; it rode straight over the top of it.
It was during that season that Williams introduced the car even Peter Wright — whom many regard as the true father of ground effect, and who played a key role in the Lotus breakthrough — has described as “the definitive ground-effect Formula 1 car”: the Williams FW07. In 1979, it demonstrated its potential by winning four of the last six races; in ’80, it would secure for Williams its first constructors’ title, and its first drivers’ title too, with Alan Jones. But this was no walkover in the style of the type 79. It was a hard-fought season which saw Williams secure its two titles over Ligier and Brabham only in the penultimate race at Montreal.
Frank Dernie, now back in the Williams fold, first joined the team in January 1979. His position was officially head of R&D, but, as he points out, “We didn’t really have job titles in those days. There were only three engineers at Williams then: Patrick [Head], Neil Oatley, who was just out of college, and myself. So I did lots of design, too. Some initial aerodynamics had been done by Neil at Imperial College, but I took that side of things over when I joined, and did all the aero work at Williams until I left in 1988.
“We had about six weeks a year development time at the Imperial College wind tunnel,” he recalls, “working at quarter-scale. I don’t believe there was another moving-ground tunnel in the world at that time. The revelatory moment there came when it became clear that if you did not have a working skirt you did not have a ground-effect car. Initially, for various reasons, the car had to be tested without it touching the belt, so there was a skirt gap. The car was massively sensitive to this. You could tell whether the upstairs lecture hall was full or empty because one of the balance supports went upwards; the movement of the floor as students shifted about had a significant impact on the downforce.”
Frank talks in depth about the FW07 below. The emphasis is firmly on the car’s aerodynamic development and performance, but no apology need be made for that. Ground effect was, after all, what Germans call the zeitgeist — the spirit of the age — in Formula 1 of the late 1970s and early 80s.
“Ground effect is not very sensitive to ride height as long as sliding skirts are permitted. FW07 had 75mm of spring travel and could be run soft. But once sliding skirts were banned and we went to flexiskirts, the necessity for a good seal did make the cars movement-sensitive as the skirts now only had a useful range of about 15mm, compared to 75mm with sliding skirts. Flat bottoms were still worse, even producing lift at quite tiny nose-up incidences. Whomever thought the flat bottom was a good idea, and would make better cars, was an idiot. I believe it was a French journalist’s idea, which Balestre read and believed. It got a touch better with the plank following Senna’s death, and better still now with the stepped plane rule.”
Sidepod / skirt box
Although the FW07 was closely modelled on the dominant Lotus 79 of 1978, it was designed with a better appreciation of the high loads imposed on the car’s body by the development of significant negative pressure beneath – a lesson that Dernie thinks Lotus failed to learn with the disastrous 80: “Our sidepod and skirt box were much stiffer than on the Lotus. Ours was aluminium honeycomb with considerable section: theirs was polyester glass with local blocks of foam laminated-in for stiffness – probably nowhere near enough. The skirts would probably jam at high loads, which I believe was the main cause of the 80’s porpoising. Peter Wright thinks that porpoising was an aerodynamic phenomenon caused by the airflow detaching and reattaching at different ride heights. But I did sufficient experimentation to conclude that it was caused by jamming skirts.”
“One of the most important aspects of FW07’s success was its skirt and skirt box design. The initial skirt system was a carbon/structural foam composite plank fitted with a polyethylene seal, ceramic rubbing strips and Tee slot guides: the later system used roller guides to reduce friction. I reasoned that the inward load on the skirt was highest on the inner skirt as the car rolled off it, so to keep it on the road more force was needed at long skirt extensions. The skirt suspension we had to develop to achieve this was more sophisticated than the suspension of the car itself! We could immediately tell if the skirts weren’t working properly because we got porpoising.”
“We used two different underbodies, depending on the circuit. The one with a more rearward centre of pressure had less downforce and the resultant car, together with its smaller rear wing, was quite a bit worse, so we did not use it often: Hockenheim and Monza spring to mind. I think they were the Mk4 and Mk27 – these are wind tunnel numbers, we did not make them all full-size. No standard wing profile is appropriate for ground effect, so we started from scratch. The underbody shape was carved in wood. We fitted a row of pressure tappings to it and used a manometer bank to monitor the underbody pressure. I then modified the shape following what I observed on the pressure profile. Later we had a hollow pod with a built-in scanivalve and pressure sensor, which was much neater.”
Most people’s diffusers stopped at the rear suspension. It was very difficult to keep the flow attached any further back, so all you got was more weight and less accessibility. I am told the Brabham BT49 never had attached flow rearward of the chassis because they never found a solution to keeping the flow attached after the sudden change of section. If so, it must have had a much better rear wing than ours! We sorted this just before Silverstone in 1979. The fairing that achieved it was discovered that week at Imperial. It was such a big gain that I came back from the tunnel, drew it full-size overnight and got It made and fitted in time for the race. It was worth 1.5 seconds a lap!”
“I don’t really remember how much the underside and rear wing contributed to the overall downforce – probably about 80/20 per cent. But since the rear wing was a significant part of defining the wake pressure which drove the underbody performance, it is impossible to separate them. The rear wing was not at the legal limit because overall performance was better with the underbody and wing coupled. The lift-to-drag ratio was between 6 and 7, I think. The thing I really remember was FW08 at 8.2 – which was the best we raced before flat-bottom cars.”
More grip gives the brakes a hard time – it was very difficult to get them to live in a 13-inch wheel. The toughest circuit was Montreal. We usually just fitted ducts to suit.” In fact the grip at high speed was such that, with no power assistance, drivers could no longer lock-up wheels everywhere within the car’s performance envelope; this meant its full braking potential could not be exploited. “The limiting factor was a driver’s leg strength! Maybe we couldn’t use all the grip potential of a ground-effect car back then, but the braking was still massively better simply because of that grip.”
The case for persecution:
“I don’t think any driver who experienced real ground effect did not like it: Alan Jones loved it. Sadly, the most famous and Influential drivers, Scheckter and Villeneuve, were at Ferrari, who never engineered a working skirt. Their car must have been horrible to drive. They assumed that all ground-effect cars were as bad as theirs, and their opinion was a big part of the journalists’ false view that ground effect was dangerous.”