Andy Scriven – Crawford Designer

British born Andy Scriven is the chief designer at the American company Crawford Race Cars, the Denver, North Carolina based maker of the Crawford DP03 Daytona Prototype chassis. Alan Lis spoke at length with Andy about the project. The images are all Alan's too.

How did you get involved in motorsport and how did you come to design the DP03?

dailysportscar.com“My first job in racing was at the UK constructor Tiga Race Cars in the 1980s working on Group C2 and Camel Lights chassis, then at end of 1985 I joined the TWR Jaguar organization, where I worked on the Group C programme for two and a half years. After that I moved to Brabham where I was involved in Alfa Romeo Pro-Car programme, one of Bernie’s pet projects, and then I went to Lola where I was chief designer for the Nissan Group C project.

“I first moved to the USA in the early 1990s when I joined the Penske Racing South NASCAR organization, where I ran the aerodynamic programme for the Winston Cup Pontiacs. Later I was transferred to Penske Cars in Poole, UK to work on the CART cars, and then back to the USA to do the wind tunnel programme for the first iteration of the Ford Taurus NASCAR racer. After that joined the PPI CART team where I ran the seven post shaker rig programme.

“By that time I’d known Max Crawford for four or five years, through the composite work his company had done for PRS and other Cup teams, and Max had always talked about wanting to build his own car. So in 1999 I moved back to North Carolina and started work on designing the SSC2K sports prototype. By the time it was finished, Grand-Am was already heading towards Daytona Prototypes rules and had come up with the concept of a steel tube frame chassis and not allowing composites to be used in the structural parts of the car. We then had to decide whether to stick with the SSC2K and try to covert it to run in the ALMS or effectively write off that project and commit to building a Daytona Prototype. It was a tough decision to make because we were primarily a composites company and that was our core business, but the unfortunate fact is that that the ALMS is an expensive proposition for a small manufacturer so we eventually decided against it. “

What was the timeline from the start of the DP03 design to the first car running on a track?

“Although we had been thinking about it for some time, and had done a lot of preliminary design work to get Grand Am approval, the financial go-ahead for the project came in May 2003. The first production drawings were made in June 2003 and the first car ran in November 2003. That’s a pretty short timeframe to build a car from nothing. Getting three cars to the Daytona test in January taxed us pretty heavily.

“Because we are a small team everything to do with the design of the DP03 started at my desk. A young designer called Chad Zimmer produced the body from the CAD data. That was a big job in itself: it’s not just a case of arriving at a shape, you have to define how it all fits together and how it will be manufactured. I think he did a fantastic job, the bodywork on this car is superb. Even a seemingly simple thing like making doors that open and close without interference is a hugely complicated process. They took several weeks alone.

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“We were also fortunate that Max’s daughter Kate has a lot of aerodynamics experience. She’s worked in Formula One with Jordan on their wind tunnel programme and she did all of the wind tunnel testing for the DP03. Having Kate and Chad taking care of their parts of the project freed me to concentrate on the chassis and structural areas of the DP03.“

Kate is shown with the CITGO car in the image below, at the Rolex 24.

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How has the Daytona Prototype programme affected Crawford Composites and Crawford Race Cars?

“Previously Crawford Composites’ core business was composites work for NASCAR teams, wings for sportscar and GT teams, historic parts and also repair work for historic cars. Now the two companies, Crawford Composites and Crawford Race Cars employ around 35 people: that’s gone up from 20 a year ago. For the car build we expanded into a new 12,000 square foot building. We have on site composite manufacturing and an extended fabrication shop. We have recently invested in a new five-axis CNC router for making the one-piece bodywork bucks.”

How did you approach the design of the DP03?

dailysportscar.com“The Daytona Prototype rules dictate some parts of the chassis design like the steel frame, but beyond that there is some freedom in how you can design the car. In our design there’s quite a lot of aluminium honeycomb, which is a material we are quite familiar with, so it was easy for us to make those panels. I was quite surprised at how hard I found the design. It had been about fifteen years since I worked on a metal chassis car. I had to re-learn how metal cars go together. Today building a composite chassis with materials like carbon fibre is pretty easy, I would venture to say that there’s more of a design challenge in making a metal car. The tubeframe part of the chassis is relatively simple, but how you join everything together, thinking about the structure in terms of how it will handle an impact and similar considerations, are the interesting and challenging aspects of designing a Daytona Prototype.“

How safe is a Daytona Prototype compared to a carbon fibre chassis car?

“The properties of metal and composites are different, so to make a metal car as safe as possible you have to consider how it will react in the event of a crash, how it will deform. As the designer of the car I feel a responsibility to anyone that gets in and drives it to make as safe a car as I can. Grand-Am has caught a lot of criticism for the rule requiring a large ‘greenhouse’ structure, but if you look at historic Group C and GTP cars that are racing here the driver is virtually sitting at the edge of the greenhouse because the cockpit canopy is so small. In a Daytona prototype the driver is well within the roof structure and from a safety point of view it’s hard to argue with that rule.

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"Although the Grand-Am rules don’t require cars to be crash tested, in my opinion the regulations do result in good safe cars. The driver is well within the chassis and there’s a lot of material around him. The cars may not be beautiful compared to some earlier designs like the Porsche 962 and the Jaguar XJR models, but that’s not the point. “

How do the Daytona Prototype rules address safety?

“There are minimum dimensions for the steel frame that you have to comply with and then you can use either steel or aluminium to build the rest of the main structure. There are a number of different ways of using metals, not just tubes and plates. We tried a few different approaches, but we’ve mainly stuck with aluminium honeycomb. In my view, size for size, you can build a stiffer lighter structure with honeycomb panels than you can with tubes and single skin panels.

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“One of the big issues in any racing car is the intrusion of the front suspension into the cockpit in an accident. We’ve addressed that by building a pedal box that is totally separate from the rest of the car, so that in the event of an accident will offer added protection. It also helps with maintenance as the box can be removed and worked on as a separate sub-assembly.

dailysportscar.com“The car also has a big carbon structure on the front that combines the front splitter, radiator housing and crash box. Most accidents tend to be frontal impacts so we’ve tried to incorporate a front crash structure similar to what we had on the old SRP cars. There’s a similar structure at the rear for safety, but also to satisfy performance requirements too.

“On the sides of the frame, there is a specified Grand-Am carbon box structure which must be fitted to the sides of the car. Crawford Composites makes them. They act like the sidepods on an Indycar. The more structure you can have between the driver and the wall the more energy can be absorbed.

“Performance and safety are key issues in the design process, but you also have to take into account the fact that the car also needs to be easy to work on. You never really have enough time, so I’ve tried to make the car as mechanic friendly as possible. All of the critical items that you need for tuning adjustments like springs, dampers, pushrods and such like are easy to get at.

“Most of the incidents you get in sportscar racing involve damage to the nose or splitter or the tail, so again those parts are easy to change quickly. We’ve also made the car like the SSC2K in that you can change the gearbox, bellhousing and complete rear suspension as a unit. That can be done in less than 10 minutes.“

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Some Daytona Prototype manufacturers have had driver-cooling problems, have you managed to avoid this?

“The front mounted radiator is mandated and is not to my personal taste but these are the rules for the class. You can have driver-cooling problems because of the front radiator, but there are a lot of things that you can do to alleviate that. We did a lot of wind tunnel testing for this project and as part of that programme we spent quite a lot of time deciding where we could place ducts to feed cool air into the cockpit. If you plan driver cooling in advance you shouldn’t have a problem. If it’s an afterthought you’re asking for trouble. We have a couple of NACA ducts in the nose that lead to some quite complex trunking into the cockpit, that blow through the dash and into the pedal box to keep the drivers feet cool. We’ve also paid quite a lot of attention to heat insulation in the car. At the end of the day it’s a metal car connected to a hot engine, so there’s only so much you can do. It’s all down to attention to detail, putting in as many heat barriers as you can to cut down the path for heat transfer. It’s easier if you think about all of this at the design stage rather than afterwards. “

How much of a challenge was the unstressed engine installation?

“Not as a big as you might think. The approved Daytona Prototype engines are all production based anyway, so they are not designed for use as a stressed member. We had quite a lot of help from GM with the installation of the engine and it’s development for this class. In my opinion it’s the best engine out there. It may not have the latest four cam, four valve technology, it’s a pushrod motor. But it’s a very small package with a low centre of gravity and it can comfortably and reliably produce the 500 bhp. For me it’s the engine of choice.”

Can you reduce the height of the engine?

“There are limits in what you can do. The size of the starter ring is specified which limits how small you can go. I’d say that with the GM LS6 engine and the Xtrac gearbox we have the optimum package.”

The consensus seems to be that with Daytona Prototypes it’s easy to make more front-end downforce than at the rear because of the spec rear wing?

“Yes that’s a serious problem with these cars, and that’s one of the reasons why we spent so much time in the wind tunnel. We were lucky in that where we are based in Denver, North Carolina we are just ten miles away from the ARC wind tunnel in Mooresville. It’s a very nice facility and we were able to book time there and test a model of our car. We spent a lot of time working on getting the balance of the car right. The small rear wing means that front downforce does predominate, so you have to find a good balance. Under the Daytona Prototype rules you only have one shot at it. Once the bodyshape of your car is approved that’s it. We wanted to make sure that we had it right aerodynamically and also from a styling point of view. We wanted to make a car that would appeal to the customer and the race fans. So far we’ve had a pretty positive response to the shape of the car. We wanted a car that looked like we’d paid attention to the shape and in particular the greenhouse. We tried to make a nice teardrop shape.

"One of the big criticisms of the Daytona Prototype class has been the look of the cars. We tried to tie styling in with the wind tunnel programme and come up with a car that was aerodynamically tuned to where we want it to be in terms of things like balance and pitch sensitivity, and also looked appealing and attractive. I think we’ve achieved that…“

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What aerodynamic areas of the car can you work on?

“Once your bodyshape is sent to Grand-Am for approval there are strict limits on the areas that you can develop. Ahead of and below the front axle centreline and rear of the rear axle and below the rear axle centreline - those areas are free to tune and try different devices if you wish. What you can’t do is design and build a completely different nose for every race: the shape of the nose is fixed until further notice, although the splitter is an area of freedom. You can add on dive planes, canards and that kind of stuff within the specified areas. What Grand-Am doesn’t want is a completely different noses and other panels for high downforce, low downforce and all points between. “

How much aerodynamic adjustment is built into the car?

“So far we have found very little need for adjustment. All we really play around with is the rear wing and the gurney flaps on the tail. That’s all we’ve found that we’ve needed to tune the car. So far we’ve not felt the need for extra front devices like dive planes. Of course that will probably change for some of the road course tracks, like Barber Motorsports Park, where you typically need to crank on as much downforce as you can possibly find. How you achieve that is limited by the areas in which you put those add-ons, and there are also limits on the front and rear overhangs too. “

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At the rear of the car, although venturi tunnels are specifically not allowed, the car seems to have been configured to for an approximation of tunnels albeit without the diffuser panels of a proper tunnel?

“The area behind the rear wheels is a place where you can put a bit of shape into the design and try things. Everyone has a different interpretation.”

With a flat floor ahead of the engine bay, air flowing under the car will pass through an expansion area. Is there potential to create downforce there?

“I’m sure we’re all trying to get something out of there. Getting as much rear downforce as you can to balance the front end is one of the key things with these cars, but there are limits. Early in the design phase we had a scheme for a rear crash box that also happened to help with rear downforce, but we were told that it was not within the spirit of the regulations so we had to get rid of it. The rules are strict, but there is some freedom such as the areas behind the rear tyres. I’ve seen what Multimatic has done in these areas on their car, but aerodynamics is a fickle art. We’ve tried several things that appear to work on other cars but they don’t work for us.”

How does the aerodynamic performance of a Daytona Prototype compare with other sports prototypes?

“I’m not prepared to quote precise figures but the downforce generated by a Daytona Prototype is nothing like an Audi R8 or even the SSCC2K, which was a flat bottom car. We have around 50-55% of the downforce that we had with the SSC2K. Daytona Prototypes are lower drag cars than open top prototypes. In qualifying for the Rolex 24 the better cars posted some decently quick times. They will get faster as the teams get used to running them and refine their set ups. Personally I think the cars are quick enough. Can a spectator really tell the difference between a car doing a 1m 40s lap or a 1m 46s lap?

“One of the benefits of the limited downforce is the reduction of the negative effects of running near to other cars, enabling the cars to run close to each other into and through the turns, increasing the opportunities for passing.”

How can you evolve the car for the future?

“Grand-Am doesn’t really want that to happen. There’s a fixed time frame for each car. After that time period we can introduce an update for the car, revised bodywork etc. The rules are looking for stability. Of course that makes it very important to get your car right first time. That’s why we spent a lot of time in the wind tunnel.

“The rules aren’t really going to change a lot – Grand-Am isn’t suddenly going to let carbon cars in. There will be evolution at intervals, but I don’t think there are going to be dramatic developments in the short term. At the end of the first time period I’m sure everyone will go away and have a rethink. I would hope that like the Riley & Scott MkIII these cars could have a service life of eight to ten years. From the point of view of the constructors and competitors, that would be a good thing. “

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The Daytona Prototype rules and cars have certainly come in for criticism over the past year and a half. What’s your view?

“There are accusations that this is NASCAR sportscar racing which is a fair comment, but at the end of the day, like or not, people are involved in motor racing to make a living. That’s the bottom line…

“Obviously the cars are not to everybody’s liking – and I’d have to be honest, and admit that I’d enjoy a bit more freedom in some aspects of design – but the economic situation we have now with these cars means that we can tool up to make a lot of cars. That’s better for business and in the long run it will pay off. It may not be as exciting as designing and building a state of the art Le Mans Prototype, but how many companies are making those cars and how many are they selling? The funding needed for a project like that is huge and the returns are unpredictable. As a company we simply can’t afford to take a risk with a project like that. With the DP03 we sold our first batch of four cars and we’ve started work on the second batch. There seems to be a degree of optimism in this series at the moment and there aren’t many racing series you can say that about right now.”

 

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