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post #1 of 21 Old 05-06-2019 Thread Starter
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Polyurethane foam insulation

Hi,

I have come across a beautiful sailboat that has been insulated with sprayed on Polyurethane foam. Some reviews call it solid gasoline for its fire risk, releases cyanide gas on ignition and soaks up water like a sponge.

Is the one used in boats a special non flammable type?

Does this sound like a good idea or just a way to cover problems?

Last edited by Pasadena; 05-06-2019 at 12:11 PM.
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post #2 of 21 Old 05-07-2019
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Re: Polyurethane foam insulation

Look up the difference between polyisocyanurate and polyurethane foams and make sure what was actually used in this case. Is it a steel boat? They often have foam sprayed inside to try to prevent rust. If the hull is prepared properly and the spraying done properly, this means that the hull will rust elsewhere first, before rusting inside. Foam is even better than paint for covering up problems, but it doesn't necessarily mean that there are problems being covered up. That is what makes boat buying so exciting.
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post #3 of 21 Old 05-07-2019 Thread Starter
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Re: Polyurethane foam insulation

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Originally Posted by paulk View Post
Look up the difference between polyisocyanurate and polyurethane foams and make sure what was actually used in this case. Is it a steel boat? They often have foam sprayed inside to try to prevent rust. If the hull is prepared properly and the spraying done properly, this means that the hull will rust elsewhere first, before rusting inside. Foam is even better than paint for covering up problems, but it doesn't necessarily mean that there are problems being covered up. That is what makes boat buying so exciting.
Thanks Paulk, It is a rollercoaster, thank you for the hope. It's a fiberglass, lived in boat, so this was a way for the owner to deal with condensation. Maybe cabin and deck fiberglass are fine. Another red flag is that the boat bottom has been sanded down to the fiberglass to get rid of some blistering that was starting to happen with the plan, to prime it again and paint to the waterline. I saw it on the dock and it looks strong but...

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post #4 of 21 Old 05-07-2019
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Re: Polyurethane foam insulation

The fact that the bottom has been sanded down to the glass should not be considered a "red flag". Blisters happen, and need to be fixed. The important thing is that the bottom is properly barrier coated again after the repair.

I don't know about the spray on insulation, but I am thinking that if you have a fire on board there are a whole lot of things that will produce toxic smoke. If you are still on board while the boat burns, you've got big problems regardless of the insulation. I doubt it will make a fire any more likely to start than if it wasn't there.

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post #5 of 21 Old 05-07-2019 Thread Starter
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Re: Polyurethane foam insulation

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The fact that the bottom has been sanded down to the glass should not be considered a "red flag". Blisters happen, and need to be fixed. The important thing is that the bottom is properly barrier coated again after the repair.

I don't know about the spray on insulation, but I am thinking that if you have a fire on board there are a whole lot of things that will produce toxic smoke. If you are still on board while the boat burns, you've got big problems regardless of the insulation. I doubt it will make a fire any more likely to start than if it wasn't there.

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Ok, that sounds promising. It is a gorgeous boat, best one we've seen by far. The bottom paint is left for me to do after the gel coat was sandblasted. I've seen the hull and keel, I need to prime it and paint it, but at least I know what is there instead of just guessing. And most boats need a coat of antifouling anyway.

Do you think is any problem that the bottom has been left in the yard without the gelcoat since July last year? It looks dry from the outside.

Last edited by Pasadena; 05-07-2019 at 02:02 PM.
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post #6 of 21 Old 05-07-2019
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Re: Polyurethane foam insulation

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Originally Posted by SchockT View Post
The fact that the bottom has been sanded down to the glass should not be considered a "red flag". Blisters happen, and need to be fixed. The important thing is that the bottom is properly barrier coated again after the repair.

I don't know about the spray on insulation, but I am thinking that if you have a fire on board there are a whole lot of things that will produce toxic smoke. If you are still on board while the boat burns, you've got big problems regardless of the insulation. I doubt it will make a fire any more likely to start than if it wasn't there.
Based on what? The ignition and flame spread properties of light-weight polyurethane foam are vastly different to wood or fiberglass that would be normal inside a boat. Look up the video from the station nightclub fire.. Yes it's basically gasoline, with some air mixed in. FWIW exposed PU would not be allowed in buildings..

And it's not about whether you'd survive being onboard during the fire, it's about the fire growth rate and how much time is available for egress.
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post #7 of 21 Old 05-07-2019
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Re: Polyurethane foam insulation

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The bottom paint is left for me to do after the gel coat was sandblasted. I've seen the hull and keel, I need to prime it and paint it, but at least I know what is there instead of just guessing. And most boats need a coat of antifouling anyway.

Do you think is any problem that the bottom has been left in the yard without the gelcoat since July last year? It looks dry from the outside.
The paint that needs to get onto the bottom first is an epoxy Barrier Coat. Then you can think about antifouling.
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post #8 of 21 Old 05-07-2019 Thread Starter
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Re: Polyurethane foam insulation

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The paint that needs to get onto the bottom first is an epoxy Barrier Coat. Then you can think about antifouling.
Yes, I plan to smooth the surface with epoxy, then 5 coats of interprotect 2000E then 3 coats of interlux antifouling.

That part I can do, it doesn't worry me too much. But I think, I would want to try to get as much cabin foam out as I can, to at least minimize the hazard.

I am asking the owner about the exact type of foam used to do further research. It is Polyurethane, but maybe there is a version with retardant that I don't know.
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Re: Polyurethane foam insulation

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Yes, I plan to smooth the surface with epoxy, then 5 coats of interprotect 2000E then 3 coats of interlux antifouling.
I did a job like this a long time ago after getting advice from a boatbuilder. After getting down to the bare fiberglass, I used a couple coats of clear epoxy—Interlux 1000 (at the time)—before using an epoxy fairing coat. I then followed with more than 5 coats of Interlux 2000, which does not built up that fast, requiring lots of coats. I then used 3 coats of Interlux ablative antifouling. I didn’t have to apply maintenance antifouling for 5 years after that.

FWIW, the Interlux products have improved since then, but you can save yourself a lot of work by observing the maximum time between coats without having to sand. Following the Interlux directions in this regard is well worth the effort to schedule your coating applications.

Good luck with your project. It is definitely within the capability of a do-it-yourselver if you follow the directions provided by Interlux, assuming the underlying fiberglass is sound.
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post #10 of 21 Old 05-08-2019 Thread Starter
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Re: Polyurethane foam insulation

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Originally Posted by fallard View Post
I did a job like this a long time ago after getting advice from a boatbuilder. After getting down to the bare fiberglass, I used a couple coats of clear epoxy—Interlux 1000 (at the time)—before using an epoxy fairing coat. I then followed with more than 5 coats of Interlux 2000, which does not built up that fast, requiring lots of coats. I then used 3 coats of Interlux ablative antifouling. I didn’t have to apply maintenance antifouling for 5 years after that.

FWIW, the Interlux products have improved since then, but you can save yourself a lot of work by observing the maximum time between coats without having to sand. Following the Interlux directions in this regard is well worth the effort to schedule your coating applications.

Good luck with your project. It is definitely within the capability of a do-it-yourselver if you follow the directions provided by Interlux, assuming the underlying fiberglass is sound.
The fiberglass looks solid, I found a few pin holes to treat. It's good to see the bear bones of the boat. I found out more about the foam and is class 1 fire rating, so no worries there either.

Something that I have been thinking is if sanding away the Gelcoal could weaken the structure of the Hull?

Last edited by Pasadena; 05-08-2019 at 12:06 PM.
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