Coachbuilder - Unibody Construction

Unibody Construction

The advent of unibody construction, where the car body is unified with, and structurally integral to the chassis, made custom coachbuilding (in the traditional sense of putting a bespoke body on a factory supplied separate chassis) practically impossible. Many coachbuilders closed down, were bought by manufacturers or changed their core business to other activities:

• transforming into dedicated design / styling houses, subcontracting to automotive brands (e.g. Zagato, Frua, Bertone, Pininfarina).
• and/or transforming into general coachwork series manufacturer, subcontracting to automotive brands (e.g. Karmann, Bertone, Vignale, Pininfarina).
• manufacturing of special coachworks for trucks, delivery vans, touringcars, ambulances, fire engines, public transport vehicles, etc. (e.g. Pennock, Van Hool, Plaxton, Heuliez).
• becoming technical partner for development of e.g. roof constructions (e.g. Karmann, Heuliez) or producer of various (aftermarket) automotive parts (e.g. Giannini).

Independent coachbuilders survived for a time after the mid-20th century for the chassis produced by low-production companies such as Rolls-Royce, Ferrari, Bentley. Producing body dies is extremely expensive (a single door can run to US$40,000)(period?), which is usually only considered practical when large numbers are involved - though that what was the path taken by Rolls-Royce and Bentley after 1945 for their own in-house production. In view of the high cost of dies for pressing metal panels from the mid 20th century many vehicles, most notably the Chevrolet Corvette, were clothed with large panels of glass-fibre reinforced resin requiring inexpensive moulds. Glass has since been replaced by more sophisticated materials but generally these replace, if necessary hand-formed, metal only where weight is of paramount importance.

Coachbuilders are: carrossiers in French, carrozzeria in Italian, karosseriebauer in German and carroceros in Spanish.

In reference to a recreational vehicle or motorhome, coach-built means a vehicle which has been purpose-built, using only a chassis as a base vehicle, as opposed to a conversion which is built inside an existing vehicle body.