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Old 30-11-2021, 17:41   #1
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Insulation over fiberglass mat

Hi there!

I'm working on a refit. While I have the panelling ripped out anyway (chainplate replacement), I was thinking of insulating.

The hull interior is woven fiberglass, which I fear I wouldn't be able to adhere aerocel to without some fairing. My thought had been to first paint or use a fairing compound in order to fill the recesses.

The boatyard we are working with says the only option is to tent the entire boat and grind the fiberglass.

Thoughts or ideas, personal experiences? If it's really going to be that much work, I'll just skip it. But we would like to go to the north sea some time in the future, and we have better access to insulate now than we ever will again.
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Old 30-11-2021, 18:10   #2
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Re: Insulation over fiberglass mat

Have you considered spray foam? It doesn't have as high an R value but it would stick well. I don't know where you are, but in the US you can get diy kits as large as 400 board feet. I have used them and they are easy to use, but you need to mask well.
Another option might be to spray a thin layer of foam then set the aerogel in the foam. It expands so would fill the weave of the fiberglass and then hardens into a suprisingly decent adhesive.
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Old 30-11-2021, 18:56   #3
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Re: Insulation over fiberglass mat

Fourlyons nailed it in one post.

Grinding away glass (which the designer specified to do its job) is the most absurd idea I’ve ever heard. I hope this boat yard isn’t making any of the decisions on this refit.
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Old 30-11-2021, 19:03   #4
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Re: Insulation over fiberglass mat

Fairing would be easier. Grinding may remove something you want to keep!


The adhesive is VERY sticky. You don't need perfection. I have installed this. Fairing will also work better around bulkhead tape and other transitions. Sanding may work other places, but I wouldn't go down one path.


And why on earth would you tent the whole boat? It's on the inside. I would run a few shop vacs to pull air and use a dust-free sander. But if that much dust in involved, fairing is easier.
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Old 30-11-2021, 19:16   #5
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Re: Insulation over fiberglass mat

You could also apply epoxy fairing compound and set the aerogel into the wet compound. Using the compound both to fill voids in the weave and as an adhesive.
There are so many reasons not to sand the weave flat.
I see now you're in Seattle; that explains the tent outside the boat, many of the yards there are now very restrictive.
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Old 30-11-2021, 19:48   #6
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Re: Insulation over fiberglass mat

My boat's hull is insulated with closed-cell polyurethane sheets. I removed some of it last winter when I was re-tabbing a bulkhead and doing glass work in the bildge to seal up my encapsulated ballast. It's almost 40 years old, has worked great and continues to do so.

I can't be sure what adhesive was used to hold the insulation in place against the hull, but it sure appeared to be contact cement. I found both the adhesive and the insulation in excellent condition with no problems other than four decades of grime on the outer surface of the insulation.

The adhesive was placed in strips about 2-inches wide and spaced maybe 1 to 1.5 feet apart. Most of the insulation just sat in place along the curvature of the hull some held in place by wood strip paneling while interior areas were uncovered. I think had the adhesive been placed over too large an area of the insulation, I would've had a difficult time removing it and likely would've needed to replace it. This might not be much of a consideration for you but I am certainly glad it came out easily and am happy to keep using it. My little boat is always warm and dry and it's been in areas with about 3 to 4x the annual precipitation that Seattle normally sees.

My hull's interior looks to be mat, but is pretty smooth.

I'm not sure what your interior looks like or how large of an area your insulation needs to span, but perhaps you could fashion a thin batten(s) to hold it in place in larger areas?

I haven't used spray foam other than to fill voids, but would that be hard to control and get a uniform surface? Just a thought, like I said, I've no experience with it in larger areas.

No recommendation here, just my experience for you to ponder.

Grinding the hull sounds crazy to me.
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Old 30-11-2021, 20:44   #7
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Re: Insulation over fiberglass mat

Nord Sal mentioned contact cement.

I used this to secure thin closed cell foam material, not so much for insulation but to replace open cell foam backed vinyl that was falling down.

Anyway, fumes from the solvent based contact cement were pretty bad...especially as it was obviously inside a rather closed area.

I found a 3M water based contact cement that was much better to use. IIRC, it cost back then (25 years maybe) more than double the solvent based, but its coverage was probably twice as much, so well worth it.
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Old 01-12-2021, 06:48   #8
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Re: Insulation over fiberglass mat

I’d hire an insulating crew to spray polyurethane foam-a good operator can do a most creditable job of laying on a consistent layer of foam. I wouldn’t spend five minutes fairing or grinding.
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Old 01-12-2021, 07:07   #9
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Re: Insulation over fiberglass mat

As long as there is no amine blush on the hull contact cement will work between the rough finish to hold the insulation just fine. Two coats of contact cement will help. Once the paneling or wood strips are back up they will also hold the insulation in place.

Aerogel is outrageously expensive for this kind of job. Closed cell foam is available in many thicknesses.
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Old 01-12-2021, 08:08   #10
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Re: Insulation over fiberglass mat

Quote:
Originally Posted by pillowfort View Post
Hi there!

I'm working on a refit. While I have the panelling ripped out anyway (chainplate replacement), I was thinking of insulating.

The hull interior is woven fiberglass, which I fear I wouldn't be able to adhere aerocel to without some fairing. My thought had been to first paint or use a fairing compound in order to fill the recesses.

The boatyard we are working with says the only option is to tent the entire boat and grind the fiberglass.

Thoughts or ideas, personal experiences? If it's really going to be that much work, I'll just skip it. But we would like to go to the north sea some time in the future, and we have better access to insulate now than we ever will again.
Hi
I used that pink styrofoam ( says pink panther) and glued it on with liquid nails polyurethane glue ( and no it does NOT desolve the foam) also used an adhesive non expanding foam in case there were some hollow-sounding spots 9 Drill small hole inject it and press it down
in new construction they use a top coat of "dryfit" has to be mixed with water till you geta paste like substance you apply thin coat 1. or 2 mm; a nylon mesh gets imbedded in this and covered with this paste, keep it smooth which is not that hard since your base is styro foam

In my V berth I did glue carpet over in the main cabin on the ceiling I used an acrylic decorative fine gritt stacco ( applied with trowel)
Any ways this looks great weighs only i pound per square foot looks great and absolute no more condensation
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Old 01-12-2021, 12:37   #11
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Re: Insulation over fiberglass mat

Quote:
Originally Posted by Chotu View Post
Fourlyons nailed it in one post.

Grinding away glass (which the designer specified to do its job) is the most absurd idea I’ve ever heard. I hope this boat yard isn’t making any of the decisions on this refit.
Amen! Painting also sounds like a bad idea, something to peel off. I would hazard a guess that the roving has enough surface area that it can be adhered to if clean.
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Old 01-12-2021, 18:22   #12
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Re: Insulation over fiberglass mat

Spray foam sounds interesting! Thanks all. I did think grinding seemed strange, I'm glad to hear y'all agree.
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Old 02-12-2021, 15:58   #13
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Re: Insulation over fiberglass mat

Just stay away from polystyrene, Styrofoam. Most solvents will turn it into a deadly gas.
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Old 02-12-2021, 17:00   #14
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Re: Insulation over fiberglass mat

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Just stay away from polystyrene, Styrofoam. Most solvents will turn it into a deadly gas.
Out of curiosity, what is that gas?

I’m not discrediting your comment in anyway. I am wondering what gas came out when I was machining poly styrene. That’s what precipitated my heart attack.

But, there are many adhesives to use that are not solvent-based and are specifically made to use on poly styrene.
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Old 03-12-2021, 12:58   #15
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Re: Insulation over fiberglass mat

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Originally Posted by Chotu View Post
Out of curiosity, what is that gas?

I’m not discrediting your comment in anyway. I am wondering what gas came out when I was machining poly styrene. That’s what precipitated my heart attack.

But, there are many adhesives to use that are not solvent-based and are specifically made to use on poly styrene.
I'll be damned if I could find it. Maybe I am wrong, it's 40 years since I order polyester, and acetone in 55 gal. drums and MEK peroxide by the gallon.
The dissolving of polystyrene sticks in my mind as something you don't want to inhale. You posed a good question and maybe proved me wrong.
And I thought I was perfect. :-)
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