Joanna Moss On The Aerodynamic Development of the 1998-99 Toyota GT-ONE Racecars

Alan Lis follows up John Brooks’ feature on the previous incarnation of a potential Toyota race winner with this fascinating item.

Jo Moss studied at Hatfield Polytechnic sponsored by British Aerospace. After graduation with a degree in aeronautical engineering, Moss joined Jaguar Cars in Coventry where she worked in the prototype development shop for three years before joining Lola Cars as an aerodynamicist.  At Lola Moss worked on various projects including Formula 3000, Indy Lights, CART and sportscars and was also part of Lola’s trackside engineering effort in the USA in 1996. At the end of that season she was brought back to Huntingdon to work on the Formula One project that eventually led to the company going into administration in 1997.

She recalls, “After the Lola F1 cars failed to qualify in Australia and then went to Brazil where it was impounded, I thought to myself Lola is probably not the place to be right now. So I started looking for something else and it was back to the jobs pages in Autosport.

“Toyota Team Europe was looking for an aerodynamics liaison person between Dallara and TTE. I thought ‘I could do that,’ so I spent most of a day trying to construct a letter in my school level German. I’m not sure that the letter made much sense but it must have made some impression. I think I was the only English applicant who had at least attempted to write a letter in German. It all happened pretty quickly after that. Within a couple of days of posting the letter I had a message on my answering machine from the agency that was dealing with the vacancy saying that my CV had been passed on to TTE and that in 2-3 weeks I might hear something. Within another day there was another message on the answering machine asking me to come out to Cologne on the Saturday and this was Thursday.”

Were you aware that the job was working on a Le Mans car?
“Yes, but I didn’t know if it was just a Celica with a big wing on the back or a proper project. I didn’t really know what to expect. They phoned me on the Friday with flight details and to arrange to pick me up from the airport. The Tuesday of that week was the first time I’d had any contact with TTE and by the Saturday I was on the plane to Cologne to be interviewed.”

“When I met Andre de Cortanze he was so impassioned about Le Mans that it was quite infectious. It was exciting just hearing what the plan was for the project. Jean-Claude Martens was already there too and Jorg Zander was also there because he came from the TTE rally team. In all there were 5-6 people already working on the project. Andre had already sketched some ideas of what he wanted the car to look like and I was shown them when I went out to Cologne and thought ‘Wow!’ Perhaps not particularly aerodynamically sound but ‘Wow!’

How close were those conceptual sketches to the final car?
“The concept of having a front wing rather than a splitter was there from the beginning even though the original car looked quite different. Andre’s concept for the last Group C Peugeot 905 essentially had a front wing but the ACO banned the concept used on that car by introducing a rule that saying that the front wing could not have a trailing edge. The front wing on the Toyota GT-ONE had no trailing edge so therefore was legal under the ACO rules. That was Andre’s way of getting around that rule and I suspect that finding a loophole was as important to Andre if not more so than it actually being any good.

“On that first visit to Cologne Andre showed me a wooden mock-up of the car which was not anything like it eventually turned out but it did give me some idea of the scale of the thing he was attempting to do. This five metre long, two metre wide monster machine was far from the Celica with a big wing that I thought it might be. The real appeal for me was not only that it would be good for my career and an interesting project, I also felt that I could have some impact on it too. From the way Andre was talking it was clear that he wanted input.

“Andre offered me the job there and then on the Saturday, called in someone to come and write my contract while I sat there, he signed it and then stood over me while I signed it. I went away at the end of the day with a new job in a different country.”

“TTE wanted me to start as soon as possible and Le Mans was only a couple of weeks after I signed the contract. I went back to Lola but because they were in administration they were keen to cut costs. I didn’t want to work out my one month notice period because I wanted to go to Le Mans so I did a deal where I worked one week for free in exchange for leaving three weeks early. I trained up one of the other Lola aero guys on CAD for that week, got him up to speed with what I had been working on, and left. I was sorry to leave because Lola had been the only company to offer me a job when I had no experience but it did go a bit off the rails over the Formula One project which all but bankrupted the company.

“I wasn’t officially working for Toyota at Le Mans in 1997 but they arranged for me to be there with Andre to look at the cars. He was pointing at every little shape, the brake dust and oil, trying to determine what was causing it to swirl in this way or that and asking What’s causing this? What’s doing that? Where did that come from? What do you think of this?

“While we were at Le Mans Andre’s first sketches had been turned into a model and had been run in the wind tunnel for the first time. When I saw the results I remember thinking that we had some work to do. The concept was there but the actual shape was diabolical.

“I started work at TTE on a Monday in July 1997 and the next day I went to Dallara to start working on the aero in their wind tunnel. The wind tunnel model was kept there which made things a little difficult sometimes. I had a meeting with Gian Paulo and his engineering boss before I left at the end of each visit. I would go through everything I wanted designed and made for the next test. So by the time I’d finished a two day test I not only had to understand exactly what had happened during the test but I also had to allow enough time to experiment at the end in order to know what you wanted designed and made for the next test. There was a two day test every fortnight.

“Between the two day tests I was working at the factory in Cologne. Anything that I was getting directions on was being drawn full size on the CAD system. I was also sketching what I wanted and e-mailing my ideas to Dallara and talking through the results of the tests with Andre to get his opinion.

“I was doing the aero programme all by myself and couldn’t do everything so I stuck with the wind tunnel. Nowadays there would be an aerodynamics group but then I was operating as a one man band although obviously the guys at Dallara helped as well. They would be sitting in at the wind tunnel tests and we would discuss things. It was my responsibility to decide what to do next but they would throw in any ideas that they had. If I thought they were good ideas I would put them on the list of things to try.

“I was finding that when I got back to Cologne I had to try to remember exactly how something was on the model to consider if a new idea would work with what we already had. Trying to do that with photographs rather than the real thing was difficult so for the second year I managed to convince Andre to let me bring the wind tunnel model back to Cologne and to employ a model maker so that we could make changes to the model at TTE. Of course the downside of that was that I would have to drive the model down to the wind tunnel every two weeks which was a 2,500 km round trip every fortnight.

“At the time we were using it the Dallara tunnel would not accept a model larger than 33.33% scale. It was an open jet tunnel in which the wind speed wasn’t as fast as some other tunnels and the model size was quite small. That meant that you had to be really careful with the model because you could tape something onto in a slightly different way and get wildly different results. The parts for the model had to be very well made. I remember that we found that if we had slight wobble in the front wing section it would translate into an enormous wobble at full scale.

“Over the two years of the GT-ONE project the model changed quite a lot. The initial concept was for a car with shrouded top front wishbones like the Peugeot 908 had later but I didn’t get enough downforce from that configuration so it was binned. The front wing section and the profile of the front wheel arches took a long time to get right in order to make sure that there was enough cooling. Initially Andre didn’t want the side entries for the intercoolers which had intakes ahead of the rear wheels. Originally I was only allowed small openings at the front of the side pods to feed all of the cooling requirements but there wasn’t enough flow to keep the car cool and we would have ended up with reliability problems as a result. So I talked Andre into allowing me to open up the sides of the car and that was the only way to make it work even though it went against his philosophy of having no openings at all. I needed a good exit from the front wing because there was so much flow coming through there and the only way to get that was to have big opening at the front of the sides. Then I needed rear brake cooling and intercooler inlets so I had to take away even more of the side pod. In the end the whole side of the car got pushed in to make one smooth shape, essentially to appease the aesthetic requirements for the car.

“If you look at the 1992 Peugeot 905 Evo 2 you can see that the Toyota GT-ONE is an evolution of it. I suppose the GT-ONE seemed like a big step on from the other GT Prototypes that were around at the time. I’d imagine that if I hadn’t had Andre as my boss I would probably have given up on the front wing concept because it took a very, very long time to get it to work properly. The shape had to be exactly right. When I started working on the bodywork and aerodynamics for the GT-ONE it was June 1997 and the car had to be designed and built to be ready to roll out before Christmas that year. I think a lot of people would have given up the front wing idea as a bad job and stuck a splitter on the front of the car like everyone else did at that time. But Andre being Andre there was no way that was going to be allowed to happen. It was a case of ‘You will make this work’, regardless of the laws of physics…”

How did the front wing work?
“The flow over the top goes into the radiator ducts and the flow underneath goes out of the sides but you have to try to speed up the flow underneath as much as possible. A lot of time was spent designing turning vanes and other assorted pieces attached to the floor to assist the air to exit from underneath the car.
Arriving at the right size for the side openings to get the air out smoothly without creating a huge amount of drag on its way out took a long time. To do that I had to try and get the outward flow turned so that it ran along the side of the car as far as possible.”

How important was flowing air over the upper surface of the floor?
“It created downforce but it was more important to get the air out of there. I particularly didn’t want the flow going under the floor because obviously I was trying to create suction with the flat floor so I didn’t want a whole load of additional air heading under there. The idea was to get as much air out at the front as possible.

“Andre had designed the tub for the 1998 car before I had started on the bodywork and aerodynamics so there were odd bits and pieces that linked the flat floor and the rest of the body which caused a few headaches. One of these was a point where there was a convergence of surfaces that was not in the right place for my requirements and in fact shed a nasty vortex. After a bit of experimenting I found that I could actually use this vortex to my advantage if I directed it under the car. So I had a slot cut in the floor and flowed it out there. Under the rules for 1998 you were allowed to make holes in the floor of the car as long as they were outside of the track width measurement of the roadcar that your car was based on. In the case of the Toyota GT-ONE that gave us about 4-5 inches at the edges of the floor that we could do something with. So we cut slots there to take these vortices off the corners of the chassis. That cause quite a bit of finger pointing at scrutineering for the 1998 race and in 1999 holes in the floor were banned, the surface had to be continuous.

“The slots in the floor weren’t a do or die for the car. It was marginally of benefit but I think Andre loved it because it was controversial. We had something similar at the back of the car that we called elephant’s feet. Just ahead of the rear wheels there was basically a link between the floor and the top of the rear wheel arch. What I tried to do was position the elephant’s feet in areas of low pressure on the rear wheel arch so they sucked air out from under the floor. I got them to work on the 1998 car but they were banned for 1999 too. There were quite a few things that we did just because we could. They were an improvement but not crucial. Andre was happy if he could find something that was a little bit close to the edge of the rule and was a benefit.”

How did the 1999 car differ from the 1998 car?
“The chassis of the 1999 car was quite similar to the 1998 but pretty much all of the bodywork was changed. I did a lot of work on the underside of the front wing. In 1998 it was essentially a constant profile across the full width. For 1999 I was able to do what I would like to have done for 1998 but didn’t have the time. I did a lot of pressure tapping of the wing to understand what was happening and then to try to get more effect from the outer edges of the wing I twisted the surface so there was a lot more angle outboard than I had inboard. That created more front downforce and then to match that I had to do something with the back of the car. The rear wing was very limited, if you put more angle on it, it really only increased drag so the engine cover was completely changed.

“The work for 1999 was mainly about increasing downforce and a bit of work on reducing drag. The 1998 car had been designed around a lot of unknowns like the size of wheels and tyres. Nothing was really finalised until the design and build was already underway so the design had to be done on that basis. For 1999 there was a much better and more fixed mechanical spec for the car so the bodywork could be brought much closer. Everything was a bit more sleek in areas like the wheel arches.”

Was the increase in downforce the result of changing the engine cover to improve flow onto the rear wing?
“No we actually changed the whole profile of the engine cover to give it a flick shape. It worked the diffuser harder because it made a lower pressure area at the back, it worked the rear wing harder but it also created downforce in its own right.

“The twisted rear wing endplates were better than flat ones but they were actually born from a styling perspective and I managed to tweak them to make them work. In a lot of cases Andre would have an idea of how he wanted something to look and even though it might not work in the wind tunnel in essence that was how he wanted it to look so it had to be modified until it did. The endplates were a case in point. Andre had a desire for twisted end plates so that’s what we had on the car. By the time I got them to work they did help drag a little.

“When you stood on the grid at Le Mans and looked at the car it was a beautiful piece of machinery and something to be proud of. It helped that I also ended up engineering one of the cars so I was there for all the tests and races which gave me a better feel for the GT-ONE. With some aero projects your only involvement is the wind tunnel testing and you end up quite isolated from the actual car. With the GT-ONE I got to hear the driver’s comments first hand. That’s how I prefer to work.

“With regard to the aerodynamic performance of the GT-ONE over a ride height map of where the car would be during a full lap of Le Mans the efficiency of the car averaged out to about 3.6:1 l/d. Between 1998 and 1999 the work I did on the body brought a 16% improvement in efficiency. At a speed of 320 km/h on the fastest parts of the Le Mans circuit the car generated about 1600kgs of downforce and about 480kgs of drag.

“With a roofed car you are always going to struggle because the roof creates so much lift but on the GT-ONE we had the front wing system and the extraction system from the sides of the car which meant that you required the engine cover and the rear of the car to balance that. The car did have a lot of downforce. That was something that the drivers always commented on. There was a good level of downforce on the 1998 car but they still noticed an improvement on the 1999 car. The car was also more aerodynamically stable in 1999 because of the twisted front wing. On the first version of the front wing I had to put strakes in to compartmentalise areas of the wing so the flows wouldn’t mix, create cross flows and stall the wing because I didn’t have the time needed to investigate different angles for each section of the underside. For 1999 I was able to get rid of all of the strakes and do all of the flow control with the shape of the wing.

“When the Mercedes cars flew at Le Mans in 1999 AMG’s solution was to add dive planes to the side of the nose of the CLKs which they said added 30% more downforce, that made me think that if that was the case then they really had almost none to begin with. The car I was engineering, with Thierry Boutsen driving, was behind Peter Dumbreck’s Mercedes when it took off on the Saturday evening. Initially AMG tried to blame us for what had happened, I suppose they must have thought we had a way of projecting air flow forwards but I don’t believe any car can affect the flow of air 20 metres ahead of it!

“The ACO changed its rules regarding the height of the front splitter after the 1999 race at Le Mans because they wanted to make sure that no one could build a car like the CLK again but really you can’t regulate against bad design. The changes to the aero rules were the only way that the ACO could find to stop people making cars with rock hard suspension and splitters that hit the track on a bump and lost all downforce.

“Our car would have been legal if we had gone back to Le Mans in 2000 because it didn’t run low anyway. We actually needed flow under the nose of the car to make the front wing work. With a splitter you don’t really want flow going under the nose because you’re not going to use it and you have nowhere to put it. On the GT-ONE the nose was low enough to get ground effect but we needed the flow underneath.”