Early fibreglass – how long would it last?
Concerns about the longevity of plastic boats seem absurd now, when end of life disposal is a bigger worry. However, many boat owners are conservative by nature – or have out-dated knowledge – and in an era in which they were only too well aware that wooden boats had the potential to quickly decay, it’s perhaps not surprising that there were many concerns as to the longevity of fibreglass hulls and the extent to which they could be repaired.
The later discovery of osmotic blistering fuelled these worries, which were compounded by an industry that quickly sprouted to fix the problem – but often at an eye-watering price.
It’s certainly true that many of the early fibreglass hulls were poorly built. They may have had the benefit of many layers of chopped strand mat and lots of resin, but that’s just as well as the material was poorly understood and quality control was often lacking. Common problems, even among the top quality builders, included voids in the laminate, areas with too little resin (and therefore little strength), and areas with excess resin creating a brittle structure.
It has often been said that no boat has ever sunk as a result of osmosis. Strictly speaking that’s true of the Nicholson 32 Beduin (see page 21), but I know of no boat that has got closer. She has twice been treated for osmosis and the second time the layup was so badly compromised in one area that water was seeping underneath the old repair, through the decomposed remnants of the original laminate and into the bilge.
Fortunately fibreglass boats of this era are invariably made of extremely thick chopped strand mat. The outer layers of Beduin’s hull could therefore be ground away over the entire underwater area. Any areas with even more extensive damage were then ground even back further, before being locally repaired.
The entire underwater section – and a chunk of the topsides – was then relaminated with several layers of woven rovings and epoxy. It’s a repair that to date has lasted almost a decade and some 25,000 miles of sailing, including high latitude work in the South Atlantic and Pacific.
Fortunately, most boat owners don’t need to fear osmosis. As poor build quality is a key risk factor, most boats that succumbed to osmosis did so within 10 years of launch and locally treating blisters is usually the only treatment necessary. Most boats built from the 1990s onwards were laminated to much higher standards and from the end of that decade generally used isopthalic resins that are resistant to osmosis. In addition, much use is now made of woven rovings that, unlike chopped strand mat, don’t have enormous numbers of exposed fibre ends that wick moisture into the laminate. Next month: Part 3 – the 1970s