Porsche has unveiled the convertible version of its all-new 911 sports car.

Essentially a soft-top version of the new-generation (codename: 991) 911, the new 911 cabrio features an innovative fabric and composite plastic folding hood to provide a cleaner appearance, improved aerodynamic efficiency and more refinement.

Eschewing the traditional multi-layered fabric structure of the 997-series 911 cabriolet, the new model adopts a specially developed lightweight hood that uses a fabric-skinned composite panel for the upper and rear part of the structure, providing it with a more uniform shape together with a tauter fit that is claimed to make it more resistant to buffeting at high speeds.

The new hood, which is supported on a magnesium frame, also receives a glass rear window glued directly to the outer fabric skin. The cabrio’s development boss, Michael Schaetzle, says this process involves a newly patented process, developed by Porsche, and will also feature on the upcoming third-generation Boxster, due in 2012.

While the upper and rear parts of the hood receive composite panelling, the sides retain a similar multi-layered fabric design as used previously, which allows it to fold and stow behind the cabin underneath the tonneau cover – now larger than the outgoing model’s. All up, the new structure takes just 11 seconds to raise or stow, and can be operated at speeds up to 60kph. Along with the new roof, Porsche has also provided the new cabrio with an automatic wind deflector.

The soft-top will initially come with the same horizontally-opposed six-cylinder engine choices as the 911 coupé. Buyers will be able to choose between a standard seven-speed manual or an optional seven-speed double-clutch gearbox. The 911 cabriolet will be officially showcased at next year’s Detroit Motor show.