Technical (Almost) Everything you ever wanted to know about Ground Effect.


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It occurred to me the other day that it was 30 years ago in November 2012 that FISA outlawed side skirts and ruled that all cars must have a flat bottom between the front and rear axle line. This effectively brought to an end the generation of cars known as “The Wing Car” or “The ground effect era”. It is a subject that has come up on a number of occasions on the site but I thought an article bringing everything together in one place would be useful for those who are less familiar with the terms, concepts and history. So here then is (almost) everything you ever wanted to know about the “Ground Effect Era”.

In the Beginning

Wings first sprouted from formula one cars in the 1968 season giving rise to a whole new generation of aerodynamic concepts. Initially simple in design the wings grew taller and more complicated as the year went on. By mid 1969 it was clear that things were getting out of hand with movable wings on struts well over a metre high delivering their loads directly to the suspension uprights. More often than not these simple devices could not take the loads being applied to them and would part company with the car at high speeds. This was the cause of many a crash and injury and so by the Monaco GP of 1969 the then F1 sporting commission had seen enough and rules banning high wings and later movable aero and applying loads to the un-sprung parts of the car were introduced. Designers such as Colin Chapman at Lotus and Tony Rudd at BRM looked to find different ways of clawing back this lost down force and it was Rudd who first looked at the concept that would become known as the “wing car”. Rudd’s design featured a wide flat inverted wing shape body that channelled air below the car and through what would today be recognised as the rear diffuser area. Designed to speed up the airflow below the car and thus produce an area of negative pressure allowing the car to be forced down onto the track, the car showed some initial promise in the wind tunnel at Imperial College London. Sadly, due to internal politics at BRM the car design was pulled before full scale testing began. Rudd left the team in disgust and took his design work to Lotus.

Developments in the USA

In 1970, Jim Hall’s Chapparal 2J became the first recognised car to exploit negative pressure and under body aerodynamics however the Formula one world would pay little attention. The ungainly looking car used two snow mobile engines to suck the air out of a skirted region below the car. The sides were sealed using sliding skirts (a term that would not find its way into F1 for another 7 years) while the front and rear were sealed using sprung plates that maintained contact with the track. The snow mobile engines were run separately to the cars main engine and were renowned on start up for sucking up anything below the car in the pits area and blowing it at speed down the pit lane. Since the fans ran all the time the cars actual aerodynamic shape was fairly redundant and therefore the 2J cannot be considered a true ground effect car but its design would be seen again. Jackie Stewart actually drove the 2J in a Can-Am race in that 1970 season however no one in F1 took much interest and by the end of 1970 Can-Am banned the novel concept.

The ground effect baton was next picked up by an American Indy Car designer called Bob Reilly who produced a 1973 Ford based car with a true venturi shaped underbody design. Again, Reilly’s design lacked side skirts but it was successful enough for him to continue his work, which lead to a refined design being produced to run in the 1976 Indy 500. Reilly’s cars finished a strong 3rd and 4th, however he did not pursue the work any further. The biggest problem with the design of his cars, which was something that Reilly later recognised was the lack of the large diffuser area at the rear to enable the air flow to be slowed before rejoining the airstream behind the car.

F1 starts to catch on

Independently of the work going on in America the designers at the newly formed March team produced side pods on their 1970 March 701 design that were shaped as inverted wings. This design can be considered as the first “wing car” in F1 however the shape of the side pods was more accidental than by design. The March car required additional fuel tank capacity for longer races and these were in the form of the bolt on side pod tanks. Since they were adding to the cars profile it was decided to try and reduce the drag they would cause as much as possible, hence the inverted wing shape. There was some debate at the time whether the side pods added anything to the cars overall down force generation, however in a later interview Mario Andretti, who tested the car in South Africa, stated that while the March 701 had a poor top speed, he suggested that the side pods could be causing additional drag and that he tested the car without them. After several laps without the wing shaped pods, Andretti claimed that he had to add 2 ½ degrees of additional wing to the front of the car showing that although small, the wing shaped pods were having some effect on the performance of the car.

The next ground effect development in F1 came from Gordan Murray/ who added fibre glass strips to the underside of his Brabham BT44 design to channel the air flow under the car. It was reckoned that these strips produced an additional 150lbs of downforce, however the fibre glass strips were not fully in contact with the track, only touching the ground while the car was braking. The strips themselves were easily damaged and were only used at a handful of races that year. The main thing that came about as a result of Murray's work was that a precedent had now been set for underbody strips or “skirts” as they would become known.

Lotus makes the breakthrough

Having joined Lotus, Tony Rudd was pitched into the development work of the Lotus 72 whose distinctive wedge shape and sidepod mounted radiators would change the face of F1 car design in the early 70’s. The car, being a victim of its own success, raced on until 1975 by which time it was a dinosaur among far greater cars such as the McLaren M23. Lotus had lost their way and needed a breakthrough after the Lotus 76 proved a total failure, Rudd produced some of his early ground effect designs and showed them to Chapman. Chapman immediately saw the potential and produced a list of requirements that a new design team at Hethel would have to satisfy in order to produce the new car. The team of Rudd, Ralph Bellamy and Peter Wright among others, were locked away in Hethel to produce the outline designs. When work transferred to the wind tunnel at Imperial College London (scene of Rudds earlier work) it soon became clear that Lotus were on the right track. A suitable design for the wings was stumbled on when Chapman who had spent several years in the RAF, recalled the design of the World War 2 fighter bomber the De Havilland Mosquito which had its radiators embedded in its wings close to the fuselage. A couple of Lotus men were sent to a Norfolk air base where a Mosquito remained on display at the main gate to take some measurements. As Peter Wright recalled in an interview, the major breakthrough in ground effect design came about like so many major breakthroughs, by total accident. While the Lotus test model was being constantly modified with wood and plasticine over the course of a week in the wind tunnel, by the end of the week the side pods would be sagging and hanging from the car. As the side pods sagged so that they were almost touching the rolling road at the edges, the design team noticed that the downforce results would increase. Thinking this was a false result, Wright initially braced the side pods by sticking strips along the side of each sidepod that almost made contact with the road. The reading showed a huge increase in downforce for almost no increase in drag. Not believing their initial results it took several more tests to confirm that with inverted wings leading into a rear venturi area and sealed by skirts between the car and ground, the car gained a huge amount of downforce and the ground effect could be predictable and managed. The next problem was finding substances that could tip the end of the skirts without them breaking and the Lotus 77 was used as a test bed for this. After trialling brushes which were the hardest wearing but least able to form an effective seal, a layer of rubber on aluminium, tipped with a ceramic rubbing strip was settled upon to provide the skirt seal. The Lotus 78 was ready to run by late 1976 however Chapman vetoed any running until the start of the 77 season as he did not want to give his rivals any chance of copying his new breakthrough.

Ground effect takes off

Perhaps because the Lotus 78 was so unreliable through much of the 1977 season, F1’s designers failed to catch on to the new idea that Chapman and his team had given the sport. Indeed, so slowly was the take up of competing ground effect ideas that the Type 78 was still able to win in the first few races of 1978. It was at this point that Lotus unleashed the Type 79 which sought to regain a lot of the downforce that had been seen in the wind tunnel models of the 78 but lost in actual practice on the track. The 79, known by many F1 fans as the black beauty, was a massively tidied version of the 78 featuring cleaner lines, more effective sliding skirts and a better venturi effect rear. In Mario Andretti and Ronnie Peterson’s hands it was unbeatable. Gordan Murray at Brabham knew what Lotus were doing but was unable to modify the Brabham BT46 to include the type of side pod needed to produce a wing car. It was then that the Chapparal 2J design gained a lease of life in F1 as Murray introduced the Brabham Fan Car at the 1978 Swedish GP. The car was immediately successful in the hands of Niki Lauda however the rest of F1 were not going to allow the car to run claiming that, as was the case with the 2J, the fan sucked up stones from the track and fired them through the fan, at cars behind. There was also the sticky issue of the movable aero device rule however Murray claimed the fan was primarily for engine cooling rather than sucking the car to the track (it was actually true that Brabham did have serious issues with engine cooling at the time). Ecclestone, in the process of building his fledgling FOCA empire quickly gave ground on the issue and agreed that the car would only run in the next two races after Sweden claiming that time would be needed to develop an alternative. Eventually however, the car only appeared at that single race before being consigned to F1 history.

By 1979, teams such as Williams had finally managed to unlock the full potential of their own ground effect designs however, Patrick Head among others realised there was an Achilles heel that required development to make their own cars successful which for some reason Chapman remained blind too. That was the stiffness of the chassis. Andretti had long complained to Chapman that the 79 had the stiffness of a wet lettuce and the follow up to the 79, the type 80 proved to be even worse. Lotus failed to win a single GP in 79 while Williams and Ligier picked up the baton. At this point there began to appear grumblings from those teams that were using turbo engines. Because of the design and rear ends of these cars, they were not particularly suited to exploiting ground effect designs and all though Ferrari had taken the 1979 title, had Williams introduced their car a few races earlier into the season it may not have headed to Italy but instead to Britain. By 1980, Ferrari were experiencing one of their worst ever seasons while Williams went from strength to strength. Also, the forces now being experienced by the driver were becoming ever more dangerous. One of the key features in managing ground effects was maintaining a constant centre of pressure under the car, i.e. the downforce being applied happened consistently by spreading from a single theoretical point on the car. If this centre of pressure moved then the effect on the handling of the car could be anywhere from disruptive to disastrous. Such was the reliance on ground effect that any dramatic change would almost certainly see the car pitched off the track. The term 'porpoising' entered F1 lingo to describe the effect on the car of dramatic changes in the centre of pressure that would literally see the car pitch up and down from front to back until the effect became so bad that the car was bounced off the track. In order to reduce the effects of these pressure changes, suspension springs became ever stiffer in order to reduce the amount of bounce the car could make and to try and keep the skirts at a constant ground clearance. To howls of outrage from the teams who saw it as a move to help Ferrari, Renault and Alfa Romeo, FISA initially tried to ban skirts all together for the 1981 season however they finally settled on a rule that would ban sliding skirts. allowing fixed skirts only and insisting that all cars had to maintain a 6cm ground clearance.

The end of an era

The teams quickly realised that there was no way that the 6cm rule could be measured while the cars were underway so starting with Brabham, introduced hydraulic rams that lowered the car on the track while raising it to the required height in the pits. The effect of the no sliding skirts rule was far more serious and this caused a further stiffening of car springs in order to produce almost no suspension movement at all. The stress on the car itself was now huge and McLaren and Lotus produced the first all Carbon Fibre chassis in F1 in order to produce a car stiff enough to take the loads generated by these new breed of cars. Lotus as always, produced a unique and controversial solution to the no sliding skirts rule in the form of the Lotus type 88. Designed before the change of rules and tested using a revised type 80 model (called the type 86) Lotus produced a car that they claimed had two chassis. The primary chassis contained the side skirts, radiators and trimming wings at the rear, this was attached via rubber bump stops, directly on to the wheel uprights while the secondary chassis contained the driver, engine and wheels which also had a normal suspension. The theory was to transfer the ground effect load directly to the wheel uprights while the remainder of the car responded to normal suspension inputs and the driver wasn't given the horrific ride he had come to expect from a ground effect car. Frank Williams among many other team managers told the world at the first GP of the 1981 season (Long Beach), if that car runs then I will withdraw mine. The legal wrangling surounding the type 88 ran on through much of the season resulting in Lotus eventually dropping the idea and running with the conventional type 87. The truth was though, that in actual fact, the type 88 was a flawed idea and in reality it didn’t work.

For 1982 the fixed side skirts remained however it was becoming clear that besides aerodynamics, if your team didn’t have a turbo engine then you were not going to get very far. The venerable Cosworth DFV was finally reaching the end of its racing life. The cars were finally deemed to be un-drivable and in a season that saw the deaths of Ricardo Paletti and Gilles Villeneuve plus the serious injury to several other drivers including championship leader Didier Pironi, enough was deemed to be enough and by November 1982 side skirts were out and flat bottoms were introduced for all cars between the front and rear axles. This effectively ended the ground effect era.

The Ground Effect Legacy

Ground effect could claim to be the final piece in aerodynamic car design that saw the growing development of overbody aero packages linked to the underside of the car to produce a single aerodynamic concept. It’s lasting legacy however will have been to produce an increasingly dangerous series of cars that saw the drivers exposed to ever increasing loads. One major effect was that in order to produce the largest possible area for under body air flow management and to balance the rearward bias of the ground effect, drivers were pushed further and further forwards. So much so that by 1981, the drivers legs were almost completely beyond the front axle line of the car. This would have a major effect in the serious injury to Pironi and the death of Paletti. The banning of sliding skirts created an even bigger problem that would have the same effect on car handling as the total ban on driver aids in the run up to the 1994 season. Any damage experienced by the side skirts would have huge consequences on the handling of the car.

The flip side of the coin though is that it produced some very important advances in F1 design. Without ground effects would carbon fibre have appeared as early as it did and less well known is that Lotus produced F1’s first active suspension in 1982 (it finally appeared on 1983's Type 92 and with more success in 1987 on the type 100T) to try and produce a system that would manage the cars ride height in order to maintain a constant ground clearance to get the maximum from the non sliding skirt era.

Modern F1 cars still exploit partial ground effects by using the rear diffuser and by blowing streams of air beneath the car to form a boundry layer and act as a type of skirt. These areas of development have often caused controversy in recent years with Brawns double diffuser, Red Bulls high rake angle and flexible front wing and many teams using blown exhausts all being a legacy of ground effect design work.

In recent years there has also been a suggestion that a limited return to ground effects would be allowed in the sport in order to try and return to less over body aerodynamic reliance that causes cars to be unable to overtake due to their handling in the wake of other cars. So will we see a return to long side pods with skirts? I doubt it but anything is possible in F1.
Terrific summary.

I'm intrigued by the fact that JYS drove the 2J at around the same time Derek Gardner was designing Tyrrell's first car. They had neither the resources nor, I suspect, the inclination at that stage to get involved in windtunnels, but maybe there was an opportunity missed there. How different things might have been then...
Great read! Regarding the Lotus 88, didn't they ban it before it could have been tested? I was under the impression that Chapman was adamant on running the car but the FIA (or FISA) wouldn't let him do it. Could it have been competitive? From the article you suggest it wouldn't have been ... Thanks!
Olivier, the concept was originally tested as an un-raced test model dubbed the type 86, this was basically a massively revised Lotus type 80 tub including the problematic curved sliding skirts. This proved reasonably promising so they went on to develop the Type 88 from that. The type 88 was ran at Long Beach but was black flagged, then in Argentina but was black flagged again. Lotus withdraw the car and then re-entered it as the 88B for the British GP. The race scrutineers passed the car to run but FISA threatened to withdraw the race's championship status if the car wasn't banned. At that meeting the car did run in one full practice on the Friday and would have qualified provisionally in I think 22nd and 23rd places (can't quite remember now). The Lotus team ran the more conventional Type 87 chassis on the Saturday with Mansell running faster than he did in his 88 and De Angelis running slower but both type 87s eventually qualified. As far as I can tell those runs on the Friday were the only officially published times for the Type 88. I haven't been able to find any for Long Beach or Argentina.
In practice 1 (Friday) at Long Beach de Angelis set a time of 1m 22.380 compared to Mansell's 1m 22.461. Alan Jones was fastest on Friday with a 1m 20.911. All the Saturday times were faster (apart from Stohr's Arrows) so it's difficult to make a comparison of the 88 vs the 81. I presume de Angelis' time was set in the 88 as, according to that year's Autocourse, he ran the 88 in the Friday session and it wasn't banned until the Friday evening.
Very comprehensive article cider_and_toast .

One of the criticisms aimed at full ground-effect cars from what I remember reading was that a lot of people thought that if disproportionately favoured the part taken by bravery over that taken by sheer skill when it came to drivers' performance.

Impossible to know whether it was true or not but there certainly were a lot of different GP winners within the 1978/82 period. Maybe some drivers who weren't among the most naturally-talented had a few more opportunities to grab results through sheer bravery over their more gifted colleagues?
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