John Simister: Fibreglass in cars

Plastic is for car manufacturers who can't afford to do it properly in steel. Plastic is kit cars, low-volume no-hopers. Plastic fits badly with terrible panel gaps. It is not to be taken seriously.

That's all tosh, of course. At least it is in the current century and was partly so before. But what do we mean here by plastic? We mean carbon fibre in the case of McLarens, many top-end racing cars and large pieces of aircraft. This particular plastic, or 'composite', is plenty strong enough to cope with massive stresses and it is usefully light. Better yet, it has been engineered by people we can trust.

So carbon fibre passes the OK-in-a-car test, even if the resin matrix part of the composite is technically plastic. Same goes for Kevlar, an aramid fibre. But below these in the composite canon sits glass-reinforced plastic, or GRP, known more widely as fibreglass or, indeed, glassfibre. Now, this material, too, can be industrialised into sharply-defined, ripple-free respectability, as every Chevrolet Corvette, the first three generations of Renault Espace and the first Ferrari 308 demonstrated. Later Lotuses do it pretty flawlessly, too. Modern techniques of injection moulding or heat stamping are the key here.

So it's in the old-fashioned technique of hand-laying sheets of prickly, polyester-resin-soaked glassfibre into a mould already coated in resin that notions of amateurishness linger. This was the mainstay of Britain's kit-car industry, and the conversions of Austin Sevens and Ford Populars into sporty-looking 'specials' before that. There was an element of a wing and a prayer here; could you trust a fibreglass car?

That trust was really put to the test when a car's entire monococque structure was of fibreglass. The original Lotus Elite, a beautiful jewel of a car, was one of the first to do this. The Imp-based Clan Crusader was another, surviving examples usually showing signs of repair where the rear suspension rather vitally attaches to the structure. 

But mostly a fibreglass car would have a separate steel chassis beneath (or glued plywood if an early Marcos; more trust issues for the cautious, although wartime Mosquito fighter-bombers, also part-plywood, generally held together). One of the most sophisticated British examples, in style and presentation, was the Gordon-Keeble. One of the most celebrated was the Lotus Elan. 

I used to have an Elan, a 1968 S3 Coupé. An Elan's fibreglass body sits over the central backbone chassis like a saddle, and contributes a worrying amount of stiffness to a structure which, even fully clothed, is still quite bendy. It's the main reason why Elans are softly sprung. Forget noble intentions of dynamic suppleness and flow; it's to stop the structure twisting.

I paid £12,000 for it in 2008. It was far from perfect but it was extremely fast, thanks to some well-judged engine tuning. When I was repairing some bodges in the bodywork – old fibreglass cars are very prone to such horrors because fibreglass is so easy to drill and chop – I simply mixed some Isopon P40, a resin filler full of glass strands, and healed the damage: Lotus Elan In A Tin.

So I had a plastic car. It was great fun to drive, but it was fundamentally an assemblage of proprietary bits, some simple folded sheet steel and welded tubes, and a plastic body. It wasn't a real car, somehow; it was a toy one, Lotus just-add-lightness magic or not. And I knew that if another car sideswiped it I'd be history, because an Elan has no side-impact resistance at all. (A monococque Clan Crusader does, incidentally.)

The classic car world has a habit of turning a blind eye to thoughts like that, falling back, if pressed, on the defence that a motorcycle is even more dangerous and they're still allowed. And many Elans have been retro-fitted with a roll cage which includes stout bars in the sills and across the base of the bulkhead, which improves things to a degree. I never got as far as that with mine, and sold it – two cylinder-head rebuilds, a gearbox rebuild, a replacement differential and much else later – for £14,000. My classics have had proper steel bodies ever since.

Meanwhile, a vigorous market has developed for un-bodged Elans, be they miraculously original or properly restored. Such an Elan hides its fibreglass-ness well, with modern specialist bodyshops skilled in smoothing ripples, sharpening edges and tightening panel gaps to a far higher standard than the factory ever managed. These Elans have been to finishing school and have been civilised, and they sell for prices which prove that, properly handled, fibreglass is no longer a stigma. A later owner put my old Elan through just this process. It emerged in BRM-look dark metallic green with orange bumpers, and sold at auction for twice what I got for it six years earlier. 

I had a quick look underneath it at the auction, though. And I reckon my Isopon P40 repairs were still there.