Insulation for core for deck

Ray3

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Dec 8, 2018
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2
Hi all,

I have been going back and fourth with a couple people about using closed cell insulation as a core for a boat deck. Glassed both sides with epoxy. I don't think it would be sturdy enough but my father built a flybridge and top out of closed cell insulation which is pretty solid, but no one is walking on it either. For now I'm planning on using coosa or nida core unless I hear differently.

Thanks in advance for any opinions.
 

gm280

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Jun 26, 2011
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14,585
Interesting thought. I have no idea if it would hold up to foot traffic, but if you coated both sides with 1708 and polyester resin, I know it would be amazingly strong. But since I never experiments with such an idea, I really don't know. But I like the idea and may do some experimenting. And if the bulkheads were place underneath to support the laminated foam, it sounds possible. JMHO
 

kcassells

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Oct 16, 2012
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8,575
Only issue would be if you are going tp screw it down. You need to overdrill each hole and fill with resin.
So the srews don't go thru the faom and glass. With that substrate they will.
Alternatively you could make the wood under the boat stringers, bulkheads and such flush with the deck. Then screw direct into the wood. You would end up with a modular foam deck to fit between the raised stringers and bulkheads.
Sounds like too much work versus coosa or ply.
 

sphelps

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Nov 16, 2011
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11,429
I did something sort of like that but it wa a closed cell very rigid exspandable foam core .
I installed rigid foam cut into place in between the stringers stood vertically. Then made a flat bottom skin that I glued down to the stringers . Poured the foam over that then glassed over the foam .. Feels very solid but unfortunately I haven’t finished the boat yet to report back on how it’s holding up . :facepalm:
‘It’s just a turtle 🐢 in my yard at the moment ...
If I were to do something like it again I would use seacast instead ...
 

Ray3

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Dec 8, 2018
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I know I'd have to drill and fill the screw holes and I would be putting 3/4 ply where the seats would be bolted due to the lack of screw holding ability and even the crush factor of the foam. I don't want to raise the stringers and bulk heads flush with the deck...that could possibly get into ventilation issues and if I had to get underneath one side of the deck or the other I couldn't without a bunch of hatches.
The boat is a 32' Wasque downeast that will be used for day trip fishing. FWIW
I've heard that polyester resin can melt the foam if you get the mix too hot.
 

sphelps

Supreme Mariner
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Nov 16, 2011
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11,429
You can’t use poly on the foam .. It will melt it but epoxy won’t ...Take into consideration that gell coat ,if you plan to gell, does not stick to epoxy very well ...
 

Woodonglass

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Dec 29, 2009
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25,924
Several years back, I read about a guy in Australia that build an entire boat using HoneyComb fiberglass board and epoxy. Very structurally sound but...a Bit Pricey as I recall. Google Honeycomb Fiberglass Board and you'll find plenty of info.
 
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