The term gull-wing door is used to describe automobile doors which are hinged at the roof. They are so named because, when opened, the doors evoke the image of a seagull's wings.

Conventional car doors are typically hinged at the front-facing edge of the door and allow the door to swing outward from the body of the car.

The most well-known examples of road-cars with gull-wing doors are the Mercedes-Benz 300SL from the 1950s, the Bricklin SV-1 from the 1970s and the De Lorean DMC-12 from the 1980s.

Practical Considerations

Despite the common misconception that the gull-wing doors are mere stylistic affectations, the design is a very practical one. The advantage is that when properly designed and counterbalanced (e.g. the Delorean), they require little side-clearance to open (about 35 cm, or 14" in the DeLorean) and allow much better entrance/egress than conventional doors. This is especially important for vehicles like the Delorean whose width would make conventional doors awkward to use when the car is in a conventional urban parking space.

Design Challenges

Gull-wing doors have a somewhat questionable reputation because of early examples like the Mercedes and the Bricklin. The SL300 used the door design to allow an unusual chassis design which required a very high door sill and forced the doors to be smaller than would otherwise have been optimal. The Bricklin was a more conventional sized door but the actuation system was problematic in day-to-day use and led to unreliable operation. In addition, there was some concern that in making the door as light as possible, it couldn't provide adequate protection in side-impact accidents. There was, however, no indication that this concern was justified.

The Delorean solved these problems by using a solid-steel torsion bar (supplied by Grumman Aircraft Engineering Corporation) to counterbalance a full-sized door and then used simple pneumatic struts similar to those found in hatchback cars to open the doors and dampen the movement of the doors.

Other disadvantages of the system were not so easy to address. For example, the gull-wing design makes creating a convertible version of the car virtually impossible since, for optimal efficiency the hinges must be placed as close to the center of the car as possible. This was never a concern for the Delorean since no convertible version was ever planned (though there were rumors of a four-door family car based on a front-engine chassis with room for four passengers).

It also makes sealing the car against water leaks more difficult because of the shape and movement path of the door itself. Many Delorean owners report leakage when taking their vehicles through automated car-washes because of the high-pressure water jets - though, in ordinary rainfall the seals were more than adequate.

Similar Designs

In addition to the traditional gull-wing doors, there are other unusual door mechanisms - particularly among exotic and expensive cars. Lamborghini uses a design which is a hybrid of the conventional and gull-wing design which is generally referred to as a "scissor", "jack-knife" or butterfly doors in which the door is still hinged at the front but swings upward from the car while staying parallel with the edge. This form of door was introduced in the Lamborghini Countach whose unusually wide chassis mandated the unusual door configuration. The design was carried forward to the Countach's successor, the Lamborghini Diablo. The only current Lamborghini in production which uses this design is the Murciélago.

This design combines some of the advantages of a conventional door and the traditional gullwing. The door can open upward rather than outward, which is important in wide cars. The hinge is in a similar location as a conventional door, so a convertible version of the car is not prevented by the door design.

The disadvantage is that the door still impedes access/egress much more than a gullwing and, in some cases, more than a conventional door.

The McLaren F1 roadcar and Mercedes-Benz SLR use a variant of this system which saw the door hinged at the a-pillar and caused the doors to swing both up and out. This increases the ability of the door to move out of the way of the car's occupants but does not prevent a convertible version. These doors are sometimes referred to as "butterfly" doors. The Toyota Sera was a limited-release car designed exclusively for the Japanese market which used this design. Due to its unusual design, some enthusiasts in Australia, New Zealand and England have privately imported the cars. It is only available in right-hand drive configuration.

Koenigsegg uses a "dihedral synchro-helix" system for their vehicles which seems combine the advantages of all the designs though with considerably more mechanical complexity.

The BMW Z1 used a novel design in which its doors were not hinged at all but rather retracted vertically into the chassis, leaving an empty (though unusually high) sill.

The kit car Nova/Sterling [1] [2] used a special type of door, actually a lifting canopy, on several of their models where the entire top section of the car was opened.

List of Automobiles

The following is a (partial) list of production and kit automobiles with gull-wing and similar style doors:

• AMT Piranha (kit car)
• BMW Z1
• Bradley GTII (kit car)
• Bricklin SV-1
• Bristol Fighter
• Dare DZ
• De Lorean DMC-12
• Eagle SS Mk1 (kit car)
• Fiberfab Aztec 7, a.k.a. Charger II (kit car)
• Foers Ibex
• GP Talon (kit car)
• Isdera Commendatore 112i
• Koenigsegg CC8S and CCR
• Lamborghini Countach, Diablo, and Murciélago
• Mazda AZ-1
• McLaren F1
• Mercedes-Benz 300SL, SLR McLaren
• Mirage K18/Scorpion K19
• Porsche 917 "Panzer" (racecar)
• Replicar Cursor
• Seta (kit car)
• Toyota Sera

References

• List of gullwing cars, with pictures
• The Quintessential DeLorean Website