Flying on the ground
Racing cars normally progress by evolution. But Jim Hall took the 'blue sky' approach for his new car. Preston Lerner explains how composites and aero expertise created the Chaparral 2
Some cars belong in the motorsport Hall of Fame because they were technological marvels. Others are enshrined because they won so many races. Only a handful score top marks in both categories. Chaparral 2 was one of the few.
Jim Hall's flightless fibreglass bird broke new gound with its monocoque chassis, composite construction, clutchless transmission and, most importantly of all, cutting-edge aerodynamics. Chaparral 2 also destroyed the competition, winning well over half of its races, including a memorably rainy Sebring 12 Hours. Oh, and the tubs were the foundation — literally — of the Chaparrals that went on to win two world sportscar championship races.
But the most remarkable thing about the car was that it was the first to be designed and built by Hall himself. Or maybe, ironically enough, that is exactly why it was so successful. As Hall himself explains: "I was young enough that I was willing to go ahead and do what I thought was best. It's only when you get older and you make a few mistakes that you become afraid to take those sort of chances."
Chaparral 2 was a counterpoint to the not-quite-fast-enough Chaparral 1. For his new car, Hall decided on the mid-engine configuration already proven by Cooper and Lotus. But for the chassis he sought inspiration not in the race-shops of Great Britain but in the American aerospace industry.
Hall and fellow West Texas oil man and hotshoe Hap Sharp found just what — and who — they were looking for at the General Dynamics plant in Fort Worth, where the world's first all-bonded aeroplane had been built. GD's composite materials group on the B-58 programme was headed by an enterprising structural engineer named Andy Green, who moonlighted building reinforced fibreglass yachts. Green had never designed a car before. Hall considered this a plus rather than a minus. "We don't want anybody with any preconceived notions," Hall told him.
Green went ahead and unleashed a revolution. Not only did he fashion a monocoque — standard aviation practice — but he built it out of fibreglass-reinforced plastic and established the general layout that's still used to this day. Suspension, by contrast, was standard fare, and the engine was the ubiquitous small-block Chevy, rated at 415bhp when the car made its debut, and more like 475 by the time it retired.
Hall drove the bare chassis on the test track — Rattlsnake Raceway — he'd built in Midland. This private facility was often used by General Motors' R&D engineers to test high-performance gear. And so it came to pass that a GM concept car provided the general shape of Chaparral 2's original body. This turned out to be a blessing in disguise.
"There was so much front-end lift that the car went straight at 130mph no matter how much you turned the wheel," Hall recalls. "But the car had been good before we put the body on it. So we realised that the problem was aerodynamic."
Hall, a graduate of the prestigious California Institute of Technology, created his own test rig to develop the aerodynamics. When Chaparral 2 arrived at the big pro race at the end of the 1963 season, it sported a front end resembling a snowplough. It qualified on pole.
But Hall wasn't satisfied. During the off-season he went after the Holy Grail of aerodynamics — eliminating front-end lift. He reverted to a beak-like nose and cleverly channelled airflow through the radiator. "But the car didn't handle like I expected," he says. "It was nice at low speed, but as you went faster, it developed more and more oversteer. I scratched my head over that for a while before the light bulb finally came on. When I started putting downforce onto the back of the car, the lap times dropped dramatically."
Hall wasn't the first person to recognise the advantages of downforce, but he understood its potential better than his rivals and he exploited it more ruthlessly than anyone for years to come. He started with a small tail spoiler, known as a fixed flap in Chaparral parlance, that got progressively bigger. "By the middle of '65," he recalls, "we were putting so much downforce on the car that it was slow down the straightaways. We were still turning the fastest laps, but a car like the Lola T70 could blow past us on the straights and then hold us up in the corners."
Enter the adjustable flap — a spoiler that could be moved by the driver, using a pedal, from a high-drag to a low-drag setting for different parts of a circuit. This worked so spectacularly that Hall decided that bigger must be better. The 2E Can-Am car opened the 1966 season with a giant wing, and racing would never be the same again.
Another unique aspect of Chaparral 2 was its clutchless drivetrain. "That was Hap's idea," Hall says. "He said, 'We can spin the tyres in any gear. So why do we need a transmission?'" With GM's help, Hall modified a Corvair gearbox for racing. Although the system was usually described as an automatic, it was actually a torque-converter that permitted clutchless shifting between gears.
Because there was no clutch pedal, Chaparral drivers braked with their left foot. "I always thought this was an advantage," Hall says. The brakes, though, got a real workout. To keep them cool, Hall came up with another innovation — cast-aluminium alloy spoked wheels that still look contemporary.
In 1964, driven by Hall, Sharp and Roger Penske, Chaparral 2 won seven of the 16 races it contested, dominated the US Road Racing Championship and swept the year-end professional races at Laguna Seca and Nassau.
The 1965 season was even better: the car won no fewer than 15 of 21 races, humbling the competition in both USRRC and international competition. The high point was Sebring, where race promoter Alec Ulmann allowed the lightweight Chaparrals to compete even though they didn't meet with FIA specifications. They were so fast that Hall parked his car for several minutes during a torrential downpour that left spare tyres floating through the pits. Even so, Hall and Sharp crushed the factory Fords.
By the end of 1965, Hall had built a new car, the 2C, with a smaller aluminium monocoque and more sophisticated bodywork. But the thermoplastic bathtubs underpinning Chaparral 2 lived on. One became the 2D, which won at the Nurburgring in '66. Another was transformed into the 2F, which won the BOAC 500 at Brands Hatch in '67. Still more exotic Chaparrals would follow — Hall says the 2E was his personal fave — but Chaparral 2 was the first of his fantastic flock and the best of the breed.