Some people have said “fibreglass is crap”. I too have known such exasperation, but to be more accurate, fibreglass only shrinks. If it seems to be useless, its not – it only shrinks. This is an article about why I know these things…
First, one must understand the mother tongue, the language of the fiberglass world. Long ago, before the Meyers Manx and fiberglass dune buggies I created the tooling, among other things, from which large sail¬boats were produced. This meant that I had to work from the Naval Architect’s drawings to loft and build full-size, the mock-ups or plugs from which fiberglass production moulds were made. These moulds would ultimately spawn the fiberglass parts that largely comprised the completed sailboats. So there you have it – the plugs from which moulds are made, and the moulds that produce the parts. I soon discovered that no matter how exacting my efforts to hold fast certain dimensions in the construction of these plugs, the part that was produced from the mould, from said plug, was dimensionally different than its intended shape. So why was this?
The inherent shrinkage of the polyester resin was the culprit. I discovered that this was not much of a problem in long unbroken surfaces, like the length of a hull, but more noticeable where there were lots of corners such as around the cockpit and foot well or around any collection of corners. To illustrate, if one were to build a plug with two or three 90 degree intersecting surfaces (like the corner of a box), make a fiberglass mould of this and a resultant part from that mold, one would find that the surfaces wouldn’t intersect at 90 degrees anymore. They would be something less – maybe 88 or 89 degrees. One reason for this is that the corners collect more resin which cause more shrinkage, closing the included angle of the corner, and all the while the mould is doing this too – so old moulds are even worse!
When I built the plug for ‘Old Red’, the very first Manx, I was aware of this problem, but I didn’t make enough allowances for it. Old Red, like all the first 12 monocoques, had no metal VW floorpan, was like a large tub, and even had a built-in petrol tank. The result was that I had so many resin-catching corners, the whole thing became a giant accordion that squeezed in against itself. I had given the carburettor over an inch of clearance from the body, but later when installing Old Red’s first engine, the body had shrunken inwards, over two inches! This is why the earliest Manx’s had a narrower horizontal top rail than the later ones that I widened, plus the license plate surround became fatter.
All this shrunken corner business is why a Manx body, and any other new buggy body for that matter, so often won’t settle down to a perfect fit on ones floorpan. All four vertical corners have closed a small amount causing the lower vertical edge of the body to sit on top of the seat tracks. No problem – just flex the body outwards, tapping a small wooden wedge in the space between – both sides, and then check the fit front and rear. The fibreglass bulkhead near the pedals often sits on top of the intended surface of the front metal bulkhead, just behind the pedals. Again, just push it rearwards with a piece of 4×2 wood jammed against the front axle beam until it pops back and down over the outrigger by the pedals. At the rear, where the Manx body crosses the tunnel, there may be a frightening amount of space between the chassis and Manx body. The access cover should be removed over the gearshift coupling. Here, a short piece of wood can be placed, bridging the inspection hole side to side. Two clamps reaching into and under the lips of the hole can be tightened, pulling the fibreglass downwards to a good fit. Now is the time to bolt down the perimeter of the floorpan including a couple of bolts on the rear slope below the two clamps still holding the body down. This rear area, above the two clamps, has several corners that have shrunken up, lifting the Manx body away from a perfect fit. But not to worry! If fibreglass can shrink so much, it can also flex back to where it was designed to be. My nephew, Peter Smiley, works with me tooling new Manx’s. He had lived for many years in Santa Cruz California where he had worked with his son Kurt in fiberglass tooling and boat building. They are both experts. Son Kurt, still lives in Santa Cruz California. A year or more ago, Peter said that he was going up to see his son and would deliver one of our new Classic Manx kits to a customer near Santa Cruz. He picked up Kurt and they together delivered the kit. The customer was waiting with prepared chassis. With few words Peter and Kurt carried it in, placed it on the chassis, noted some bumps on the underside of the body, grabbed a sander, re¬moved them, sat the body in place, pushed it this way and that, jammed lit¬tle wedges alongside of the seat tracks, stuffed a stick of wood against the front bulkhead & clamped a block down over the rear inspection hole. All this left the customer speechless when finally he said “I wouldn’t have known to do all that… And you did it in minutes!”. Peter and Kurt had shown him how accommodating the ever flexible fiberglass can be, without which I wonder if we would have ever known fiberglass fishing poles, tent poles, snow boards, ski’s, ski poles, CB antenna’s, bows and arrows and all the other necessarily flexible products we have taken for granted. I am reminded once again of the collection of stories about fiberglass buggies involved in fender bender accidents on city streets and highways. The sheet metal of the other car crunches up absorbing energy and stays that way – a mess costing thousands. The fiberglass buggy (if it didn’t lose a chunk of fiberglass) absorbs energy by bending inwards and pops back with little more than a small white ding to show the point of impact. Another example of fiberglass’ incredible modulus of boingocity and twangability!
By Bruce Meyers
