DUCKTAIL SPOILER

The first aerodynamic aid on a road-based sports car, Total 911 reveals how the Bürzel aids stability

Much of the technology you read about in this column is hidden from view. We may have to point out the difference between Varioram and Variocam, but not so this month. Here, we look at something very much in every 911 enthusiast’s lexicon: the Ducktail spoiler, which was first used on the 1973 Carrera 2.7 RS.

911s and rear spoilers are almost synonymous, but that wasn’t always the way. The svelte 911 body was always intended to slice through the air as neatly as possible, and the original, clean-bodied 911 did this superbly well. A little too well, it turned out. The same iconic curves and low back-end that reduced aerodynamic drag – giving a drag coefficient of 0.38 on the 1963 model – also meant there was little to press it down on to the road at high speed. It wasn’t exactly taking off, but there was a noticeable lack of stability at speed. Porsche’s head of vehicle design, Helmuth Bott, was tasked with reducing lift, both front and rear. Whatever the solution, it was decreed that existing production 911s needed to take advantage of it, too.

Inspiration appeared after a design team member, Tilman Brodbeck, noticed his new Fiat 850 felt quicker than a 5bhp increase should, and pondered the small flick on the car’s engine cover. Using basic materials, Tilman fashioned three similar spoilers for a 911 and tested them in the wind tunnel. Test mules drew comedic responses from colleagues, but not when the test drivers reported higher speeds and greater stability compared to a standard 911 around Weissach.

Increasing the spoiler height and measuring drag and top speed identified the ideal spoiler height… and a problem. Authorities raised concerns about rear crash safety, meaning the final design was a balance of safety and effectiveness, before being patented (no. 2238704) and nicknamed the Entenbürzel, or ducktail. Fitting it alongside the recently designed fibreglass front air dam reduced lift, but engine cooling improved and drag was lower, too. At 150mph, rear end lift dropped from 145 to just 45kg, while at the same time improving rear wheel grip by 20 per cent.

The Carrera RS was the first sports car to feature a rear spoiler in the ducktail. But the real-world verification and lessons learnt led the way for later aerodynamic solutions of equal iconic status and effectiveness, such as the whaletail and teatray. As iconic as the ducktail is, it didn’t appear on another production 911 after the 1973 RS until 2010’s 997 Sport Classic.