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Porsche 911 50 Years
EVOLUTION VERSION 1.0
Throughout the ascent of design Typ numbers from 695 to 754 to 901, Ferry remained committed to offering an open version of the new Porsche. F. A., his designers, modelers, and engineers had submitted three scale drawings and a model to Ferry, who followed up this review with a letter he wrote to Karmann in mid-October 1962. Karmann assembled the 356C and SC cabriolets and was the natural one to field this inquiry. Ferry asked the manufacturer to evaluate the concepts, which included a cabriolet system similar to the 356 configuration with a padded top, a clear plastic window removable by zipper, and a boot that hid the roof and stored it as low as possible in the car body. The second option was a collapsible top that required unsnapping the cloth material for stowage beneath the boot. The third version described a main top bow housed inside a rollover bar with removable top and rear panels. F. A. also had proposed a rigid but removable steel roof. Still other concepts followed, including one that described a collapsible and/or a removable rollover bar. Perspectives differed on the look of the roof and the profile of the car, top up or down. F. A. told Aichele that he preferred that “the open car should have a distinct feeling in the roof line, to underscore the Roadster feeling.” He offered a drawing in early December 1963 that showed this idea. It was not as severe as the “stepped roof” variations Erwin Komenda had made five years earlier, but it showed a definite, gentle break in the roofline behind the rear window. The roadster concept, however, brought up problems with the entire idea of an open car. As Eugen Kolb pointed out, “No one considered the cabriolet during design of the coupe. It was talked about but forgotten when the other discussions were going on.” Whether a rollover bar collapsed or a soft top folded into the rear of the car, there was no place to put it. One version completely sacrificed the rear seats for the top, its bows, and the rollover bar storage. There were other considerations. Although that recent evolution from an engine with two smaller cooling fans mounted over each cylinder bank to the Typ 901/1 with its single larger one certainly had improved engine performance, smoothness, and reliability, it had yielded one unanticipated consequence. Where Komenda’s 356B Hardtop Coupe had increased interior room for the 356, the B Roadster’s alternate bodyline reduced the space even when the top was raised. Lowered, it proved impossible to store any 911 top proposal because of the taller engine and the chassis parts. “Drawing the cabriolet, the system to open the roof, the kinematics, was not right,” Kolb explained. “The system for the 356 was completely developed, but nothing could be taken from it for the 901. If you had copied the 356 roof system, it would have been too high at the rear, like a Volkswagen, not like a Porsche.” Kinematics studies the mechanics of the motion of a body or bodies—in this case, the cloth top and support bows of a convertible roof—without considering its own mass or forces acting upon it. Most crucially, the estimated costs of designing, developing, and making stamping molds for new sheet metal for this 911 roadster body killed any chance. “ Drawing the cabriolet, the system to open the roof, the kinematics, was not right. The system for the 356 was completely developed, but nothing could be taken from it for the 901.” — Eugen Kolb After the September IAA debut, however, pressure increased. Sales boss Harald Wagner reported that many visitors asked about an open version. Over the next months, development continued on more concepts until early June 1964, when a prototype “open car” emerged from the shops. Gerhard Schröder remembered that Franz Ploch and engineer Werner Trenkler had gotten a car to work on. They also had done cabriolet development for the 356 models. By June 12, he and engineer Werner Trenkler had completed their first mockup, and Ferry had it photographed that day. Barely two weeks later, on the 24th, a group convened to review the car. Ferry Porsche, F. A., Hans Tomala, Hans Beierbach (now running Reutter for Porsche), Erwin Komenda (whom Ferry had put in charge of completing the 901/911 technical drawings), Fritz Plaschka, and Harald Wagner (Ferry’s sales chief) examined the car. Trenkler and Schröder were missing from the review. This was a case, Schröder explained, where those asking the questions asked the wrong people. Had he and Trenkler been present, he said, the story might have a different ending. Wagner argued vigorously for the fully open car, expecting it to sell at least as well as 356 cabriolets had done. Ferry listened as Beierbach and Komenda stressed the extensive work and the expenses Porsche might incur stiffening the chassis and revising the rear body panels to accommodate the soft top and its supporting bows. Ferry concluded that it was too costly, deciding instead to approve the roll-bar variation. However, it, too, needed some changes. “There were so many obstacles,” Kolb continued. “Of course, the car lost much of its stiffness. The cabriolet proved the 901 chassis was not strong enough.” One further consideration affected Ferry’s reluctant decision to let the cabriolet slip away: By this time, automobile safety advocate Ralph Nader in the United States had drawn a growing audience to his objections to vehicle design and engineering. Inside Porsche, engineers, designers, and marketing staff worried that legislators in its largest market might outlaw convertibles altogether. Called the Offener-Wagen, this drawing, completed May 23, 1964, showed Porsche’s thinking about its open 911. Barely two weeks later, Ploch and Trenkler had a full-size prototype to demonstrate. Porsche Archiv Soon after this, Ferry asked Karmann in Osnabrück, who did not respond to his first inquiry, to work further on an open 901. Porsche shipped them the Ploch/Trenkler prototype, 13 360. When that car returned to Zuffenhausen on September 10, 1964, it entered the system with a Cardex that showed the date, its number, and its specification as a Typ 011/KW, Cabriolet, a designation that modern-day engineers suggest may have been intended to disguise its real purpose. A few days later, Porsche started 901 production, on September 14, beginning with serial number 300 007 (oddly, Porsche did not assemble number 001 until the 17th). With production startup problems occupying his time and energy, it wasn’t until late in January that Helmuth Bott took a long evaluation test drive in 13 360. He paid particular attention to chassis stiffness (which, after Karmann’s work, he found no worse than the 356 cabriolets he had driven), and to the soft rear window flapping and fluttering. A few days later, testing the car with the removable roof panel in place, the wind noise was so great he could converse with a fellow engineer only by shouting. There was work to do. Chassis 13 360 appeared with a mockup rollover bar and removable roof panel on June 12, 1964. At this point concepts for the rollover bar remained in body color. Porsche Archiv The September 1965 issue of L’Automobile published this single photo with a caption that read, “With the end of the 356C models, Porsche had no cabriolets. Will we see at Frankfurt a Porsche 911–912 convertible? It’s unlikely but the demand, however, is strong.” Porsche Archiv “ There were so many obstacles. Of course, the car lost much of its stiffness. The cabriolet proved the 901 chassis was not strong enough.” —Eugen Kolb The August 7, 1965, issue of La Nouvelle Revue, from Lausanne, Switzerland, published this photo and brief story: "...In ceasing production of the 356C models, Porsche has no more cabriolets to satisfy the numerous demands of its clients. That is why one waits at Frankfurt for the debut of convertibles derived from the 911 and the 912.” Porsche Archiv
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