The Cabrio boom continues. Retractable hardtop from the automakers sparks demand. The trend for the Sport Utility Vehicle (SUV) is also unbroken. SUVs combine off-road capability with the driving properties of a limousine, the storage space of a small utility vehicle and the spaciousness of a van. With the Sport Utility Cabrio (SUC) Wilhelm Karmann GmbH and ZF Friedrichshafen AG present a road ready concept car, which unites the abilities of the booming lifestyle vehicles and creates a new vehicle niche with promising future. The cabrio specialists from Osnabrück attach a soft top with show roof to the roomy SUV and combine it with a separate glass rear window. ZF Friedrichshafen contributes an innovative chassis system. The SUC is a prototype with technical finesse. 'With the SUC we show what we can do. Of course, individual elements can also be transferred to other vehicle concepts', says Ronald Wellmann the SUC project manager at Karmann. However, in this case no OEM customers instructions had to be taken into consideration and designers and engineers have exploited this freedom.

Unique technical features: doors opening in the opposite direction with adaptive sealing system, the rear window that is integrated into the tailgate, the large opening angle of the side and rear doors as much as to 90 degrees and horizontally operable rear compartment door handles. The main attraction is the cover and soft top and storage area design because the soft top spans the SUV's occupant and luggage compartments. Because the rear window is not integrated into the soft top, it's comfortable to load luggage when the roof is open.

Up to 180,000 vehicles per annum

ZF Friedrichshafen has created a special chassis for effective transfer of power to the 22 inch wheels that also meets the requirements. Via the electronic CDC (Continuous Damping Control) with various parameters an optimal damping level will be reached. The system demonstrates its full efficiency by networking various control elements such as ESP, ABS or CDC. The results are more driving comfort, higher safety reserves and a clear reduction in vibration. For the Sport Utility Cabrio Karmann and ZF see the largest sales potential in Western Europe and the USA whereby the USA, due to the size of the total market and the wide spread of SUVs, offers the best prospects. According to one study sales could reach, all brands combined, up to 180,000 units annually between 2009 and 2015. The potential over the entire life cycle of the Sport Utility Cabrio amounts to about 900,000 untis.

Ideas and Development

Classic vehicle models, such as sedans and station wagons are increasingly threatened by new niche models. Vans, Mini-Vans, Convertibles, Coupés, Retractable Hardtop-Cabrios, Sport Utility Vehicles and many other varieties make the borders blurred. So, how do designers and engineers find new niches?

At the beginning of the Sport Utility Cabrio the idea was to combine the advantages of two strong-growth vehicles in a new, to-date vacant, vehicle concept. The concept cars builted by the Karmann design studio are all in the creative tradition of the VW Karmann Ghia. They take its striking lines and transport these into the present. The tripartition on the front area, the striking middle line and the air intakes is formative.

From the first rendering to the first model and to the concept car the best possible solution was sought between technicians and designers in order to present a vehicle feasible for production and economically viable.

As development service provider and full service vehicle supplier Karmann does not pursue the goal of developing its own car but giving car makers impulses for their new trends with concept studies. Moreover, the chassis specialists from ZF and the engineers from Karmann are the proof of this by successfully carrying out a very complex project in close cooperation.

Body solutions

In order to satisfy crash safety requirements the body of the Sport Utility Cabrio had to be additionally reinforced. The existing floor of the basic vehicle offered the possibility to be reinforeced with a second floor plate. The newly designed sandwich structure provided the necessary rigidity for the four-door Convertible. However, the locking systems were integrated into the shortened B-column to deflect the resulting forces in case of a side crash.

For comfortable access to all four seats an innovative door concept was created whereby driver and passengers can open the rear doors in the opposite direction independently from one another and completely collision-free. In addition, the engineers developed evacuable seals, which are inflated by two separate leak-proof lines when the doors are closed. When opening the doors the air is expelled from the gaskets so that the doors swing open without any problems. An additional bolt centers the closed doors with one another, prevents the opening of the doors by the air stream and reduces the vibrations.

The weight of the individual components also plays a decisive roll in the design of the doors. Instead of the conventional monocoque design the engineers use a spacious framework with hollow structures – the so-called space frame design. The resulting weight saving amounts to about 3.5 kilograms per door.

Comfort and Doors

Front and rear doors opening in opposite direction as well as ease-tomaintain are the two aspects are the basis for the door design of the Sport Utility Cabrio (SUC). An additional benefit of this design is the added comfort in getting in and out of the SUC, and the passengers can open the rear doors to an opening angle of 90 degrees. A rotating hinge, an encased cable duct and door tread lighting are the optical features of the design. The so-called 'dorstop' system provides additional comfort. It fixes the door in every position between zero and 90 degrees and prevents the doors swinging back even when the cars is parked on slope. The 'Dorstop' system enables to lock the door at 60 degrees.

In order to be able to use this feature comfortably and easily sliding door handles have been developed. The interior door handles of the rear doors adapt according to the ergonomic needs of passengers getting in and out of the car. Regulated by Bowden cables, the handles move in a manner that makes them easy to reach from any position. Moreover, a sophisticated sensor system controls all functions. The external door handles, flush with the exterior surface, further add to the elegance of the SUC. They protract when touched and control the following functions: unlocking the door as well as additional locks in the side panels and sills and bleeding the sealing system and the short-stroke control for the windows. The tailgate is on the contrary equipped with a conventional handle, but likewise has the 'Dorstop system'.

source: Karmann