Aero Loopholes
If the Rulebook Didn’t Say You Couldn’t
Race-car builders had spent years fooling with spoilers, ducts, body shapes and every other place moving air could be persuaded to earn its keep. Jim Hall looked at all that and decided everybody was being unnecessarily patient.
In 1970 he brought the Chaparral 2J to Can-Am. It had a Chevrolet big-block, sliding skirts underneath and two enormous fans hanging off the rear like somebody had backed over an industrial air conditioner and decided the wreckage showed promise.
The fans weren’t there to cool anything.
Hall intended to suck the car onto the racetrack.
Why Wait for the Air?
Ordinary aerodynamic downforce comes with an irritating condition: the car has to be moving fast enough for the air to do useful work. Wings become more effective as speed rises, then surrender some of that help as the driver slows for the corner where extra grip might be particularly welcome.
Hall saw no reason to let the speedometer control the arrangement. The 2J carried a separate two-stroke snowmobile engine whose only responsibility was spinning two 17-inch fans at the rear. While the Chevrolet worried about moving the car forward, the little engine was busy trying to remove the air underneath it.
Sliding polycarbonate skirts followed the pavement and helped seal the underside. The fans pulled air from beneath the car, pressure dropped, and the atmosphere outside did the rest of the work.
Most racers were trying to make air push their cars down.
Jim Hall brought his own vacuum cleaner.
Better yet, the fans didn’t care whether the 2J was charging down a straight or crawling through a slow corner. The suction system could produce downforce without waiting for road speed to provide it.
That was clever.
It was also exactly the kind of clever that makes everybody else reach for the rulebook.
Define “Aerodynamic Device”
Can-Am allowed enormous technical freedom, but the rules already prohibited movable aerodynamic devices. That sounded perfectly clear until Hall parked the 2J in front of the officials and forced everybody to decide what those words actually meant.
The fans moved. Fine. But were they aerodynamic devices, or pumps removing air from beneath the car? The skirts moved too, but Hall could argue they were merely seals allowing the vacuum system to do its job.
Nothing was hidden. Nobody needed a flashlight, a secret panel or an informant from the next garage. Two giant fans were hanging off the back where anybody with functional eyesight could admire them, while the skirts slid along underneath.
The question wasn’t what the thing did.
Everybody could see what it did.
The question was whether the rulebook had actually prohibited doing it that way.
Competitors developed a sudden professional interest in the wording. Racing teams are remarkably tolerant of another fellow’s engineering experiment right up until the engineering experiment starts going faster than they are.
The Fellow Behind It Got a Demonstration Too
The 2J had another charming characteristic. Those enormous fans did not distinguish between useful air and whatever else happened to be lying on the racetrack.
Dirt, rubber and little pieces of debris could be sucked underneath and fired out the rear. Following Jim Hall was therefore an opportunity to be both outrun and sandblasted by a Chevrolet-powered vacuum cleaner with a snowmobile engine hanging off the back.
The fans weren’t thrilled with the arrangement either. Track debris could damage the blades badly enough that protection had to be added to their leading edges.
So the 2J was fast, disputed, mechanically complicated and occasionally tried to eat the racetrack.
Can-Am had seen stranger cars.
Not many of them came with their own cleanup crew.
The Ridiculous Thing Refused to Be Slow
If the 2J had been slow, the whole argument could have solved itself. Everybody could have admired Hall’s ingenuity, laughed about the auxiliary engine and waited for him to get tired of feeding two powerplants.
Unfortunately for the opposition, it worked.
At its first race at Watkins Glen, the Chaparral set the fastest lap. After that, it qualified on the pole every time it appeared. A strange white box circulating fifteenth is an engineering curiosity. The same box sitting on pole while two giant fans vacuum the pavement becomes a subject for committees.
The real enemy was reliability. Hall had created a collection of engines, belts, fans and sliding skirts that all had to cooperate for an entire race. When everything stayed together, the 2J was brutally fast.
Everything did not always stay together.
The rest of Can-Am probably appreciated that contribution.
Then the Rulebook Learned Some New Words
By the end of the 1970 season, the argument had run out of room. The sliding skirts were judged to violate the prohibition against movable aerodynamic devices, and the 2J’s Can-Am career was finished.
That is how a proper rulebook story usually ends. Officials write a rule for the thing they understand. A racer invents something they hadn’t considered, everybody spends several months arguing about whether the new contraption is actually covered, and then the contraption starts setting fast laps.
Suddenly the language becomes much easier to clarify.
Hall had not hidden an illegal wing or tried to sneak a suspicious part through inspection. He built a race car with sliding skirts, two giant fans and a separate engine to operate the whole business, then parked it where everybody could see it and asked the rulebook to explain why he couldn’t.
For a while, the rulebook didn’t have a very good answer.
Then the 2J got fast enough to help everybody find one.