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Old 05-08-2018, 07:52 AM   #1
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Adding layers of fiberglass to deck

I have soft decks on my flybridge and it got me thinking that on my particular boat the fiberglass on the decks is too thin(imo) and wanted to sand off the gelcoat/paint and add some layers of fiberglass..

I know the correct way would be to remove the coring(there's little to no coring left)and replace but obviously adding layers would save me from having to cut the deck and the boat is in the slip with haulout very far away(making debris removal a problem).

It's boating season and I want to get on with it..

in the end if I need to recore I can inject the deck or cut out like I would but salvage the top layer.

I honestly think that adding 2-3 layers of fiberglass would essentially solve the problem but add some weight(not concerned much there).

I'm just trying to talk myself into it and at this point
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Old 05-08-2018, 08:05 AM   #2
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It's the "sandwich construction" that gives the deck strength. You really need to replace the wet,rotted core then re-glass to get the strength back.
You can do that in smaller sections and knit it back together with the layers of fiberglass.
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Old 05-08-2018, 08:20 AM   #3
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Adding layers of fiberglass will not solve the problem. It will only make it that much more difficult to actually solve the problem when it finally has to be done. Fix the core problems now, or wait until the day when your foot goes right through the flybridge floor, and THEN fix it.
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Old 05-08-2018, 10:23 AM   #4
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The hassle is GRP is strong but not stiff.

You could consider rebuilding a new deck on top of the older deck, with a fresh new core. Just ignore the old rotten crap, and use the deck surface it as your form.

Would add about 1 inch to the deck height and about 3 lbs per sq foot of deck.
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Old 05-08-2018, 11:43 AM   #5
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+1 on all the responses. You really need to address the coring issue. It is similar to an I beam in the strength versus a layer of plywood without the I in the beam, the plywood will sag and so will the deck without the core. Sorry, not the news you want to hear, but just adding a couple of layers of glass probably won’t do the job. If you were to add enough glass to make it say a half inch thick then it would work, but that is why the coring is there to add strength without the weight of all the glass.
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Old 05-08-2018, 01:05 PM   #6
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Been there, done that on a Mainship mk1. Your bridge deck is full of water and balsa mush. For details use the search function on here or go to the Yahoo Mainship site. Sorry Mrwesson. There is no short cut.
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Old 05-08-2018, 01:11 PM   #7
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I agree with all of the above. While I'm not against half-measures, in this case adding a few layers of glass mat won't gain you much and isn't all that much more work than cutting the deck, taking out the balsa and replacing with a synthetic core. Not saying that isn't a lot of work, but not a lot less than doing what you are suggesting.
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Old 05-10-2018, 01:46 PM   #8
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I agree with all of the above. While I'm not against half-measures, in this case adding a few layers of glass mat won't gain you much and isn't all that much more work than cutting the deck, taking out the balsa and replacing with a synthetic core. Not saying that isn't a lot of work, but not a lot less than doing what you are suggesting.
What about solid fiberglass hulls? They seem pretty strong.
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Old 05-10-2018, 01:54 PM   #9
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What about solid fiberglass hulls? They seem pretty strong.
They are, but they are also a lot thicker.
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Old 05-10-2018, 02:16 PM   #10
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I totally agree with all that has been said above.

There are lots of ways to do this job, but one way to approach the repair is to completely cut away the top layer of glass at the edges. Pull up the top layer in one piece or at worst a couple of pieces cut on the smooth surface lines. Then you can scoop out the balsa mush, replace it with new balsa core and epoxy it to the bottom glass layer. Then epoxy the top layer back down to the new core.

This way you reuse the non skid pattern and the only patching required is along the edges.

With heavy, thickened epoxy troweled over/under the new core top and bottom, the deck will be stronger than new.

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Old 05-10-2018, 04:54 PM   #11
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David, would you replace with balsa or use one of the synthetic core materials?
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Old 05-10-2018, 04:59 PM   #12
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They are, but they are also a lot thicker.
Never drilled more than 1" through a hull and even solid fiberglass sailboats are under 1.5"...
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Old 05-10-2018, 05:13 PM   #13
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Never drilled more than 1" through a hull and even solid fiberglass sailboats are under 1.5"...
If you want to add fiberglass to your decks, you certainly can. If you decide to do it, let us know how it works out.
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Old 05-10-2018, 06:15 PM   #14
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You need to do both. Maybe put in a foam core rather than more wood to rot out.
My understanding is that if you remove the teak planking, you have to restore "stiffness", I suppose strength too, and to get a good waterproof seal. On my boat when I had the teak removed, we put 2 layers of fiberglass mat where I opted for a painted finish fwd, and one layer where we put fresh glued not screwed teak sides and aft.
I only had to repair my core in 2 small squares where teak had been used in the sandwich,it was replaced with foam,as was used everywhere else.
But, if you opt to just lay more glass without touching the core, that`s probably still an improvement.
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Old 05-10-2018, 06:54 PM   #15
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David, would you replace with balsa or use one of the synthetic core materials?
Balsa has superior structural properties to anything else typically used for coring: it has higher sheer strength at the core to laminate bond and it has higher compression strength. Anything else you might use will be weaker.

And if balsa is installed properly, and any penetrations are sealed properly, it will last forever.

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Old 05-10-2018, 07:22 PM   #16
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Balsa has superior structural properties to anything else typically used for coring: it has higher sheer strength at the core to laminate bond and it has higher compression strength. Anything else you might use will be weaker.

And if balsa is installed properly, and any penetrations are sealed properly, it will last forever.

David
Good to know, thanks. The key of course is making sure that any penetrations are sealed properly.
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Old 05-10-2018, 08:58 PM   #17
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If you want to add fiberglass to your decks, you certainly can. If you decide to do it, let us know how it works out.
Don't favor one way or the other but just can't wrap my head around the logic of it all rather than just saying because.


"You shouldn't because it'll add weight up top" or "you'll use more resin than you need to" I can see but fiberglass is pretty strong on its own unless you use 1 or 2 layers for waterproofing the core material in which it gets it's overall strength.
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Old 05-10-2018, 10:35 PM   #18
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Never drilled more than 1" through a hull and even solid fiberglass sailboats are under 1.5"...
Then lay on 1” of glass and let us know how that works out.

Or, cut open the deck, dig the core out and lay the glass in there.
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Old 05-11-2018, 02:52 AM   #19
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Because its a waste of your time and your money. Covering a water-soaked rotten deck with more fiberglass isnt a fix or even a patch.
If you were to cover the decks like you mentioned, you would still need to remove the hardware & flybridge. Thats a big chunk of your labor right there.
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Old 05-11-2018, 03:01 AM   #20
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I think we have pretty well explained the reasons why it is a bad idea to not fix it properly. However, his boat, his choice.
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