Fibreglass body

Fibreglass body /fy-ber-glass bod-ee/ noun (countable)

A fibreglass body is a form of vehicle coachwork constructed from glass-reinforced plastic (GRP), a composite material made from fine glass fibres embedded in a resin matrix. This was the wonder material that launched a thousand British sports car companies, and sent most of them into bankruptcy shortly after. For the shed-based innovator of the 1950s and 60s, fibreglass was a godsend: cheap, light, rust-proof, and capable of being moulded into swooping shapes without the need for hugely expensive metal presses. Of course, it could also be wavy, brittle, crack if you looked at it too hard, and smelled of chemicals, but these were considered minor quirks in the noble pursuit of lightweight performance.

The Full Story of the Fibreglass Body

The story of the fibreglass car body is a story of necessity. In post-war Britain, steel was rationed and expensive. For a small company dreaming of building a sports car, the cost of the tooling required to press steel panels was an impossible hurdle. Glass-reinforced plastic, a material developed during the war, offered a miraculous solution. The process was simple enough to be done in a shed: create a mould, lay in sheets of glass fibre matting, slather them with polyester resin, and wait for it to cure. The tooling was cheap, the material was light, and it didn't rust.

Colin Chapman of Lotus was the material's high priest. His 1957 Lotus Elite was a revolutionary masterpiece and a cautionary tale: the world's first fibreglass monocoque production car. Its body was not just a shell; it was the chassis, providing all the structural strength. The result was a car of incredible lightness and sublime handling. It was also fragile, noisy, and a nightmare to repair, as suspension components were bolted directly to a material with all the load-bearing integrity of a flatpack bookcase. Chapman wisely returned to using a separate steel chassis for his next car, the legendary Elan, clothing it in a stunningly pretty, non-stressed fibreglass body.

Fibreglass democratised car production. Suddenly, anyone with a bit of pluck could become a manufacturer. Companies like TVR, Gilbern, and Ginetta were born, creating muscular and distinctive sports cars. The material was also the lifeblood of the booming kit car industry, where enthusiasts could buy a swoopy fibreglass shell to bolt onto the rusty chassis of a written-off Triumph Herald.

Life with a fibreglass car was, however, a unique experience. The quality of the finish was often dreadful, with ripples and waves that no amount of paint could hide. The smell of curing resin could linger for years. While the body would never rust, the steel chassis underneath it often would, silently rotting away out of sight. Repairing a crack was a messy, dusty, and intensely itchy process involving more resin and matting.

In the mainstream, fibreglass was largely shunned, with a few notable exceptions like the Reliant Scimitar GTE. Today, it has been superseded by more advanced composites like carbon fibre in the high-end market, but it remains the material of choice for Britain's low-volume specialist car industry, a direct and enduring legacy of those ambitious, resin-fumed pioneers of the 1950s.

For The Record

Is fibreglass the same as carbon fibre?

No. They are both composite materials, but the reinforcing fibres are different. Fibreglass uses glass fibres, which are cheap and versatile. Carbon fibre uses carbon fibres, which are vastly stronger, lighter, and eye-wateringly more expensive. Carbon fibre is fibreglass's incredibly successful, over-achieving cousin from the world of aerospace.

Does fibreglass rust?

No, which was one of its greatest advantages over the notoriously rust-prone steel used on British cars of the era. This, however, created its own special problem, as the steel chassis or components underneath the pristine fibreglass body could be merrily rotting away completely unnoticed.

Was the Lotus Elite's monocoque a good idea?

It was a brilliantly innovative idea from an engineering perspective, creating a car of phenomenal lightness and stiffness. From a practical, real-world perspective, it was a disaster. Bolting the engine and suspension directly to the fibreglass caused stress cracks to appear, making the cars fragile and fiendishly difficult to repair properly.

How can you tell if a car is fibreglass?

The easiest way is the "tap test." A fibreglass panel will make a dull, solid "thud" sound, whereas a steel or aluminium panel will make a more metallic "ting" or "thunk." The underside of a panel, inside a wheel arch for example, will often show the raw, woven texture of the glass matting.

Are any modern cars still made of fibreglass?

Yes, many low-volume specialist sports cars still use it because its low tooling costs make it ideal for small production runs. Brands like Noble, and many kit car manufacturers, still rely on it. The Chevrolet Corvette in America has also famously used glass-reinforced plastic body panels for decades.