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The Aerodynamics of the Porsche 917

WE RETURN, once again, to the 917 racecar to discuss its aerodynamics.

There is an excellent Porsche personalities interview series on YouTube called Fresh Brewed & Air Cooled. One of the recent guests was Peter Stevens, who was one of McLaren’s F1 designers. He also worked on various Porsche projects including the Canon 924, 956 and 962C team cars. While talking about the 917, some of Peter’s aerodynamic drawings flashed by during that interview. Illustrated in the accompanying photos, using scale models, are some of Peter Steven’s and additional aerodynamic points.

Interestingly the models are both from French companies, Profil 24 and Heller respectively. There are some inaccuracies, but they do not affect the points regarding aerodynamics. The illustrations show clearly the changes made to cure the early instability problems (see Provinz, May 2020). The long-tail image is as the 917 appeared at the 1969 Le Mans race where it was only four hours from a convincing victory.

In 1969 Porsche arrived at Le Mans with the long-tail with movable rear wing flaps. Unfortunately, the movable aerodynamic devices had been outlawed earlier that year due to some serious accidents caused by Formula 1 wing failures. Porsche successfully argued that the 917 would be too dangerous without that wing movement. Porsche sent Rolf Stommelen out to demonstrate how dangerous the 917 was with a fixed wing. It was easy for him to drive as if the car was unstable. The 908, however, was required to run with a fixed wing while the 917 was allowed to run with a movable wing.

This version of the 917 clearly shows the raised tail discovered in testing which cured the high-speed and braking instability. This is the configuration with which Porsche won its first overall Le Mans 50 years ago.

Current Porsches have movable aerodynamic pieces that work extremely well. Technology marches on. </>

Illustrations by Dave Walker | Photo courtesy of Porsche AG

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