How the 1972 Porsche 911 Carrera RS 2.7 and Its Ducktail Made History

Ever wonder how the iconic Porsche ducktail spoiler came to be? We’ve got answers.

byRonan GlonJun 24, 2022 11:30 AM
How the 1972 Porsche 911 Carrera RS 2.7 and Its Ducktail Made History
Porsche
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From ducks to whales, Porsche’s spoilers have taken on many forms in the past five decades. But all of the aerodynamic devices that the company has put on its road cars can trace their roots to the 1972 Porsche 911 Carrera RS 2.7, which was released as a homologation special and built in limited numbers. This race car in street clothes spawned the successful line of RS-branded models (that’s Rennsport, or “race sport” in German) that continues today, half a century later, in 2022.

Adding a spoiler to just about any car has become idiot-proof, regardless of whether or not it’s genuinely needed. Your local auto parts store likely carries a wing that you can rivet onto a 2012 Nissan Versa. But the playing field was completely different 50 years ago, and the 911 Carrera RS 2.7’s distinctive ducktail was the result of a long trial-and-error process. 

On a recent trip to Stuttgart, I sat down with two of the Porsche employees who designed the car to get the full story.

The Ducktail Origin Story

Soft-spoken engineer Hermann Burst started his career in 1967 at the Research Institute of Automotive Engineering and Vehicle Engines in Stuttgart, where he worked on anything from the Wankel-powered NSU Ro80 to a vertical take-off and landing aircraft. Porsche recruited him in 1969 to develop race cars. He didn’t miss his cue: he played an important role in creating the 917, which was one of the fastest and most successful racers of its era. Armed with this unique experience, he set his sights on righting one of the 911’s biggest perceived wrongs: a lack of stability that manifested itself at highway speeds, especially with side winds blowing.

“On the 917, we learned a lot about aerodynamics and understood how the front end and the rear end interact with each other,” he explained through an interpreter. “We were then asked to what extent these findings could be transferred to the 911. [In 1971], the 911 was in its seventh year of production and it sold very well, but some of the customers were not happy about handling. The major complaint we got was that the car was simply not stable enough. While working on the 917 project, I took a 911 to the wind tunnel to try to find out what could be improved to overcome these problems.”

He switched to English and summed up his findings in one sentence: “From the side, it looked like a wing.”

Burst and his team received permission to develop a more stable 911 on one condition: they couldn’t alter the car’s basic silhouette. They started by experimenting with different spoilers for the front end because they initially believed that the lack of stability came from the gap between the center of gravity (which, as is the case with every car powered by a rear-mounted engine, was towards the back end) and the aerodynamic center. Fitting a front spoiler to a 911 S in 1971 made Burst realize there were a lot more hurdles ahead. The rear end also needed work. Giving it a Kamm tail would have solved many problems but it was out of the question.

Still working in a wind tunnel, Burst and his engineers played a game of “tweak, test, and repeat” until they created the now-emblematic ducktail. It was an excellent compromise: it added downforce to the rear end without increasing drag and it didn’t significantly change the 911’s profile. This last point, a requirement that was absolutely set in stone, partially explains the unusual shape that was chosen. “We removed the mass below the edge of the spoiler because we did not want the eye to perceive it as an extra element,” Burst recalled.

Burst added that giving the 911 a duck’s ass brought several unexpected benefits. The spoiler sent additional cooling air to the engine, which in turn improved combustion, and making it relatively narrow allowed the air flowing over the roof to keep the rear lights clean. This was a bigger problem than it might sound: “In the 1970s, there was a lot of construction in Germany so there was a lot of dirt on the roads which would stick to the rear lights,” Burst noted.

The 2.7

But as one team honed the 911’s aerodynamic profile, another group worked on the drivetrain. It’s important to clarify that the aforementioned aerodynamic changes weren’t initially part of the Carrera RS 2.7 project. The original idea was simply to take a 911 2.4S and transform it into a 911 2.7S of sorts to bump it up into the 2.5-liter-and-above category in racing in a bid to give BMW a run for its Deutsche Marks. Porsche settled on 2.7 liters because this displacement pelted the 911 in the next class up while leaving enough metal to grind to go even bigger.

The FIA’s Group 4 specifications shaped the rest of the RS 2.7, including its weight and the width of its tires. Finally, Porsche had to sell at least 500 street-legal units to homologate the model. Its sales department didn’t believe in the car but fans welcomed it like a well-stocked Christmas basket: 1,580 units were made—more than three times the number required to put it on a starting grid. Porsche historians joke that over 1,700 are left because a tremendous number of replicas have been built, much to the chagrin of unsuspecting collectors who have been duped.

‘It Was the Beginning of Something Very Special’

“It was the beginning of something very special. When we look back, [the Carrera RS 2.7] represented the first time that a competition-oriented model line was produced next to the normal production car. This is still a successful concept today; look at the GT3,” Harm Lagaaij, who joined Porsche in 1971 and designed the 2.7’s “Carrera” decals, said. He left Porsche in 1977 and returned in 1989 as chief designer, a position he held until he retired in 2004.

On a secondary but equally significant level, the ducktail marked the beginning of spoiler development at Porsche. It’s part of the reason why the 992-generation model still looks like a 911 rather than like an eighth-generation Chevrolet Corvette or like a Jaguar F-Type.

“We have retained the car’s beautiful shape with movable spoilers and with very clever aerodynamics. We have been able to keep the 911’s appearance,” Lagaaij said.

It would have been far easier for Porsche to scrap the 911’s design and start from scratch—the 928 was an attempt to do just that. Evolutionary styling updates are much more difficult to pull off than they might seem: Heritage is often at odds with modern safety standards, crash test norms, and environmental regulations, and the 911’s designers have been constrained by both sides of this tug-of-war for many decades. 

And yet, they’ve managed to keep the 911 looking like a 911 thanks in part to the lessons learned 50 years ago with the Carrera RS 2.7.

An American automotive journalist and historian, Ronan Glon is based in France. His work has appeared in Autoblog and Digital Trends.

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