I have “core samples” that were left in the nav station drawer by the prior owner. I have one that looks like the cutout for the speed transducer. I would estimate the thickness of the fiberglass to be about 7mm while the gelcoat thickness is about 9mm. I have another sample from my transom and it looks like the fiberglass is 2mm and the gelcoat is 2 mm. Finally I have a sample from my deck and it looks like the fiberglass is maybe 0.5mm and the gelcoat is 3 mm.
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| Hull sample, white gelcoat on top fiberglass on bottom |
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| Transom sample, white gelcoat on the bottom, fiberglass on top |
Is this excess gelcoat? Was this a quality control problem? Does it matter; after all it is a 35 year old boat? I ask because on old boats many people grind off the underwater portion of gelcoat and apply an epoxy barrier coat to prevent blisters. The gelcoat is ground off because epoxy does not stick well to it. When I did my bottom paint in 2010 Something Else had a few blisters. I ponder if I should just treat any new blisters locally or something else.
Hi Greg,
ReplyDeleteThis was a mystery to me when cutting in cockpit lockers and hatches on my Centaur as just like your core samples my boat seemed to have a gelcoat layer as thick if not thicker than the structural laminate. Turns out after picking the brains of far more learn-ed people than i it was something alot of yards did back in the seventies and that was to add pigment/gelcoat to the laminating resin.
The coachroof on my centaur is solid white all the way through and about 13mm thick.
When my hull was planed 5-6mm most of the exposed area was still white and after a year trying to dry it was told by two different surveyors it won't as the laminating resin is a mix of gelcoat and resin. My first question to one of them was, wont this create a weak hull? To which i was told; not really as the total laminate thickness is so overbuilt, although on close examination of these solid white panels i removed for the coachroof hatches there was generally less fibre found in them than the green/vanilla colour laminate.
cheers rog
www.agentlemansyacht.com
Sound like you went thru a ton of work stripping 5-6mm. The thick non-structural layer was not what I expected. I asked this same question about thick gel coat on the fix it forum of Sailing Anarchy. Before the post broke down to… total anarchy it seemed the best advice was that it served the boat well for 35 years, sail it for another 35 years. I guess I over analyze this stuff.
ReplyDeleteDo you think I should apply epoxy barrier coat the next haul out? Would that trap the moisture and cause the barrier coat to blister? My anti fouling is 3 year old so next year I need to do something.
Hey Greg,
DeleteI wouldn't sweat it too much mate, if your gel coat is in good nick i'd be inclined to leave it unless there's any obvious visible problems with your hull. I did what i did as i started to over-think the problem a bit too. In hindsight i only ever needed one layer of cloth not two and that would be considered over-the-top by most yards.
Seeing as this was my first time tackling such a problem i knew no better so much like Westerly themselves added way more than was needed. I echo the sentiments of the SA respondents, if it ain't broke..........
A book i would heartily recommend is called 'Fibreglass Boats' by Hugo De Plessis which sets out in a very matter-of-fact way what osmosis is and why some boats get it and some don't but most importantly the plethora of new problems you can create trying to cure the original one.
I should point out i got his book after i did the work and i was gutted to find out i didn't need to undertake anything like the work i have on my boats hull, its great for setting your mind at rest about such issues.
cheers