GRP Boats

Rule out GRP and you rule out a lot of boats

 I can't imagine many amature builders choosing to construct a vessel in this material without access to specialist environments and equipment. But as a secondhand purchase? Could it be a better buy than wood or steel?

 I was thinking about the ideal boat when I received Michael’s comments yesterday (See Sailing Contradictions 28'4/12) about the boats he had sailed. Like me, he ruled out wood (unless you have serious skills in that area) and he mentioned a couple of other craft which were produced in GRP. In earlier posts I considered the pros and cons of wood, steel and plywood. All have their advantages but the truth is, Michael has raised a really serious point here. If I want a low cost cruiser, I may have to consider GRP.

In some ways, that would be no bad thing, my woodworking skills are not good and I know nothing about working in steel, welding and that sort of thing. So would GRP be the sensible option?

When it first came onto the scene it was advertised as an inert ‘no-maintenance’ option. Owners used to boast of having to dust their bilges rather than having to pump them out and the general feeling was that GRP eclipsed all the other materials in all respects except perhaps cost.

Later, came the panic, the material seemed prone to a disease or virus – the dreaded ‘O’ word – Osmosis, AKA ‘Boat Pox’.

There were horror stories about the time and expense of repair even though reports of boats actually sinking due to the condition were rare indeed.

So, should GRP be on my list or not?

I guess the answer is ‘Yes it should’, because, quite frankly, my shortlist would be very short if I discounted any boat built of this material. ‘Yes’, also because I may have a better chance of maintaining GRP than other materials, and ‘Yes’ because my reading around the subject suggests that the older GRP boats seem to have suffered from Osmosis less than the more recent examples and, let’s face it, with my resources I’m hardly likely to be offered a recently built boat.

The reason given for the apparent superiority of old GRP seems to be that in the early days (1960’s) it was a less well understood material than today. As a result, designers and builders over-built and over-engineered their vessels. A 1960’s GRP boat that has not suffered Osmosis yet is unlikely to do so. Another factor to take into consideration is that our views and our treatments of Osmosis have changed over the years. It is no longer considered to be life-threatening and if you can find a boat which is currently free of the disease, there are steps you can take to reduce the risk of ever getting it. Those steps seem to involve ‘painting on an additional barrier coat such as International Paint’s Gelshield. Well, scraping, filling, sanding and painting are within my skills set, so there should be no need to be afraid.

Putting Osmosis to one side for the moment, does GRP have any other qualities which need to be taken into account – are these other qualities in its favour or against it? Well, the notion of dusting rather than pumping bilges is attractive. To a large extent, the claim that it is an inert material are true, the marine environment in itself does not damage or degrade GRP as it would a raw steel hull, and as a moulded shape, it does not rely on frames and fixings to be held together.

Downsides?  Well. It is not maintenance free. It needs looking after as any material does. It can get Osmosis, and it becomes more brittle with age so it may be less able to absorb the knocks and shocks than wood or steel. Major repairs may need to be carried out in expensive temperature and humidity controlled environments – so if you buy a bad one, it can prove to be an expensive investment.

The trick, as with all materials, is to gain as much understanding of the material as you can. If there are blisters, you need to understand the cause, if there are cracks or patches of crazing, are they due to impact or internal stresses introduced during the building process? As with all renovation and repair, it is the underlying cause which has to be addressed rather than the cosmetic symptom.

Given a fair wind, I think I could deal with the cosmetics and the minor problems caused through heavy usage. It may be that an old GRP boat will need painting, but this only makes her as needy as a wood or steel vessel – no worse. But if there were inherent faults in the material introduced at the building stage I would struggle. 

If I’m going to get a sound low cost cruiser, I’m going to have to be a pretty good surveyor and I’m going to have to see beyond the cosmetics. It won’t matter how bad she looks now – in fact poor looks may help me achieve a reasonable price. What really matters is how much work and expertise, will I have to buy in.   Am I right here? Or have I missed a really important ( and potentially expensive) point?

Seaward