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Old 14-07-2015, 12:24   #1
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Covering a wooden structure with epoxy/glassfibre

Hi guys,

So we got an old steel classic with a wooden "garage"; the sliding entrance hatch to the cabin. The boat was built in 1959, and when we first bought it, it seemed as if it hadn't seen any attention since then.

Long story short, I completely restored the whole thing and replaced the rotten aesthetical slats of wood with cork. It was at hand and I'd heard good things about cork. This was about a year and a half ago, and even despite the 4 coats of boat varnish, both the cork and the remaining slats are now rotting away too...

Instead of risking the same thing again by sanding the whole thing down again and replacing the cork by tropical hardwood, we're now considering covering the whole structure with epoxy/fibreglass. We could then paint this white to match the rest of the cabin roof and at least from an aesthetical viewpoint it would be a job well done.

Main question of course is wether there are any structural concerns regarding this approach... Will the fibreglass stick to the wooden structure? Will it remain so should the wood expand/contract due to temperature differences? Am I forgetting anything?


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Old 14-07-2015, 13:13   #2
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Re: Covering a wooden structure with epoxy/glassfibre

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Originally Posted by Orchidius View Post
Hi guys,

So we got an old steel classic with a wooden "garage"; the sliding entrance hatch to the cabin. The boat was built in 1959, and when we first bought it, it seemed as if it hadn't seen any attention since then.

Long story short, I completely restored the whole thing and replaced the rotten aesthetical slats of wood with cork. It was at hand and I'd heard good things about cork. This was about a year and a half ago, and even despite the 4 coats of boat varnish, both the cork and the remaining slats are now rotting away too...

Instead of risking the same thing again by sanding the whole thing down again and replacing the cork by tropical hardwood, we're now considering covering the whole structure with epoxy/fibreglass. We could then paint this white to match the rest of the cabin roof and at least from an aesthetical viewpoint it would be a job well done.

Main question of course is wether there are any structural concerns regarding this approach... Will the fibreglass stick to the wooden structure? Will it remain so should the wood expand/contract due to temperature differences? Am I forgetting anything?


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If the cork has already rotted, you will be wasting time/money to put glass/epoxy over it. It will fall apart again sokn as the cork continues to deteriorate under the glass.

Just use any old lumber, shape and attach as desired, then use epoxy only, over coated with varnish if you want a nice, clear, wood to shine through.

Or just paint over epoxy if not.

Edit: Epoxy seal all sides of the pieces before attaching them.
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Old 14-07-2015, 15:33   #3
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Re: Covering a wooden structure with epoxy/glassfibre

What construction is the hatch?? Is it a perimeter frame with slats filling in the interior or is it plywood covered. If the former, the wood will probably move way too much for the epoxy glass to make a permanent bond. May not be as fatal as the problems with the hull as long as water doesn't get underneath the glass. If it's plywood, probably not a problem though the frame/plywood interface could cause issues.
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Old 14-07-2015, 15:45   #4
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Re: Covering a wooden structure with epoxy/glassfibre

Friendly suggestion: post some photos, showing above, below, side views.
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Old 14-07-2015, 17:03   #5
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Re: Covering a wooden structure with epoxy/glassfibre

When younger I worked in several boat/shipyards and have done many fiberglass over wood projects. My current boat is fiberglass over wood decks and hatches. It has to be epoxy resin, Polyester resin doesn't stick. If you're trying to keep the cork look, epoxies have a special hardener that stays clear and doesn't turn yellow. However, any resin has to have a UV coating over it. Usually some clear varnish type coating with a high UV inhibitor value. Several coats and then sand and recoat at least every other year.
If you're painting the hatch and need to add strength, add cloth or RSM. All my decks and hatches have 2.0 RSM and properly done and cared for will last a very long time. Fully saturated cloth/rsm will look clear, so you can have the cork look with reinforcing cloth/rsm.
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Old 15-07-2015, 08:42   #6
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Re: Covering a wooden structure with epoxy/glassfibre

I have found that plywood checks if coated with just an epoxy resin. Accordingly, I always make it a point to put a layer of glass down and then apply epoxy resin.

As for what to do with the remaining wood, can't suggest anything until the scope of damage is known, and what kind of finish you want, i.e., natural or painted.
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Old 15-07-2015, 09:11   #7
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Re: Covering a wooden structure with epoxy/glassfibre

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Originally Posted by 2hullvenus View Post
If the cork has already rotted, you will be wasting time/money to put glass/epoxy over it. It will fall apart again sokn as the cork continues to deteriorate under the glass.

Just use any old lumber, shape and attach as desired, then use epoxy only, over coated with varnish if you want a nice, clear, wood to shine through.

Or just paint over epoxy if not.

Edit: Epoxy seal all sides of the pieces before attaching them.
Excellent advice.
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Old 15-07-2015, 09:17   #8
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Re: Covering a wooden structure with epoxy/glassfibre

I have a saltram saga 40 that has plywood decks and doghouse. The plywood is sheathed in epoxied glass cloth and then coated with a few coats of epoxy primer and topped with 2-pack polyurethane gloss white. The boat is 30 years old and most of it now has its third paint-job (the rest now needs doing!). At no point has the glass cloth delaminated from the plywood. I have also affected repairs using the same principle on teak but left it unpainted - with judicious sanding and re-painting with epoxy resin, it almost looks as though the wood has only been varnished (although this repair is in a shady area and is now only about 4 years old so I cannot vouch for longevity). Make sure the surface is sound, dry and scuffed-up to ensure good adhesion.
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Old 15-07-2015, 09:51   #9
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Re: Covering a wooden structure with epoxy/glassfibre

Have/Had exact same Steel boat --wood hatch.. Got pro to weld aluminum hatch, never looked back. DO NOT paint the aluminum. It will weather to a nice patina PS Stronger and lighter than wood and like your steel hull, it doesn't rot!

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Old 15-07-2015, 09:57   #10
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Re: Covering a wooden structure with epoxy/glassfibre

When applying epoxy to wood and especially all four side Make sure wood is dry before applying epoxy or it will rot from inside out .A moisture meter is the only tool for that job
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Old 17-07-2015, 01:07   #11
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Re: Covering a wooden structure with epoxy/glassfibre

Right guys, thanks for all your input and sorry for my late response, I was at the boat out of reach of civilisation .

Anyway, I was lucky enough to have a random visit from a professional boatbuilder that had helped me on a previous project yesterday and asked his two cents on the matter. He basically came up with the exact plan that's been mentioned above: replace the rotting wood/cork with any 'ol plywood scrap I have and cover with epoxy (I was told to delete the word polyester out of my vocabulary) and light glass-cloth. Sand and paint to match cabin roof.

This was my original plan (might not have been obvious from my initial post I now realize ), and I now have the reassurance the epoxy will stick to the wood just fine. As you see in the pictures, there's a white "flange" on both sides of the wood structure, and when covered in glass, the wood structure will form one smooth whole with the flange.

One thing I just realized is that there is caulking on the wood... I assume the epoxy won't stick to that, but is it an issue?
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