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Old 02-15-2019, 03:37 PM   #1
Mini-Skoolie
 
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2-Part Polyurethane Foam by the Gallon

Okay, here's what:

I'm exploring insulation options, and I love the idea of closed cell expanding polyurethane, but I'm reeling from sticker shock. The kit Home depot sells says it covers 600 square feet at 1 inch thick, which equates to 50 cubic feet (unless my math is faulty), and costs $650. For enough to insulate the walls and ceiling of a 40' bus, that comes out to about an arm and a leg.

So I got to thinking...

I've had some pretty nice experiences with the 2-part foam you buy by the gallon; it's a heck of a lot easier to work with than Great Stuff, and it tends to be pretty competitively priced. It spreads, sculpts, and carves rather nicely, and can be applied in layers with a good mechanical and (I assume) chemical bond.

So, might it not be a good option to trowel the 2-part foam on (I expect I would use Bondo spreaders or homemade equivalents), repeat as necessary, and trim? As nearly as I can tell, it's the same stuff as the 2-part spray, just much cheaper and (granted, this is a hypothesis based in assumption and wishful thinking) less likely to waste excess material?

Here's a link to one manufaturer of this product that sells, among other things, a 40 cubic foot kit for $252 if you get 5 or more -

Urethane Foam , Expanding Marine Polyurethane Foam

- which brings up the question, does anybody want to go in on a big order if it turns out this stuff is a good answer?

Regardless, at their base price of $264 for that kit, it sounds like a much cheaper way to insulate with closed cell expanding foam.

One concern that has crossed my mind is adhesion. Will this product want to stick to the walls and ceiling? If not, would a coat of paint tack up the surfaces enough to make up for that?

Has anybody gone this route and/or can anybody tell me why not to?

Thanks in advance for your advice, comments, and insights.
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Old 02-15-2019, 03:52 PM   #2
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That stuff is usually poured into a space. I can't imagine the hassle trying to get it up on the ceiling and then staying there. I bet when you're done you'll be kicking yourself for not spending the extra for spray on.
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Old 02-15-2019, 03:56 PM   #3
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Interesting idea. Not sure how this differs from spray foam. I didn't see any r values listed for this product as it seems to be for flotation instead of insulation. It looks like it would work well to fill the void between the chair rail and outer skin. Not sure how well it would go on the ceiling.

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Old 02-15-2019, 04:02 PM   #4
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Quote:
Originally Posted by TJones View Post
Interesting idea. Not sure how this differs from spray foam. I didn't see any r values listed for this product as it seems to be for flotation instead of insulation. It looks like it would work well to fill the void between the chair rail and outer skin. Not sure how well it would go on the ceiling.

Ted
I believe the only difference is how it is applied. Which would explain why the pour stuff is not correct for this application. Expansion is hard to control.
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Old 02-15-2019, 04:23 PM   #5
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Hi Marc,

I seem to recall you being a fairly prolific poster/builder on DTT. Nice to see a familiar electronic face, even though the advent of parenthood has taken me away from bikes for the time being.

...I suspect I've got about a 1/2 gallon of that stuff hanging around (leftover from sculpting a bumstop seat and some other fiddly fiberglass bits for a bike), and I might just do a single panel with it as a test. You may well be right about the sheer PITA aspect of this idea. Still, even if it's just on the walls and I need to use the spray stuff for the ceiling...
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Old 02-15-2019, 04:34 PM   #6
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Make sure what ever you use is closed cell--open cell soaks up water.
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Old 02-15-2019, 04:44 PM   #7
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It's closed cell. My biggest concern about whether it would work is gravity; will it just run down into one big blob on the floor if I try to rowel it on?

...Or, could I pour it behind temporary forms (like pouring cement) and go up in courses?

I reckon if nobody talks some sense into me before the temepratures around here become appropriate for the attempt, I'll probably give it a whirl and let you know why it was (most likely) a bad idea.
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Old 02-15-2019, 04:52 PM   #8
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Quote:
Originally Posted by Buzz Nichols View Post
It's closed cell. My biggest concern about whether it would work is gravity; will it just run down into one big blob on the floor if I try to rowel it on?

...Or, could I pour it behind temporary forms (like pouring cement) and go up in courses?

I reckon if nobody talks some sense into me before the temepratures around here become appropriate for the attempt, I'll probably give it a whirl and let you know why it was (most likely) a bad idea.
How much more sense can I pound into you? It expands pretty well while curing. You would need hard forms to contain it. It's a liquid when mixed, so obviously it's not going to stick to a vertical wall by itself.
Tell me again what advantage you see with this product over spray foam , besides price? Price compared to rigid foam? I wouldn't even attempt a trial with this stuff for what you are trying to do.
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Old 02-15-2019, 05:06 PM   #9
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Besides price? Nothing.

I'm budgeting on a teacher's salary, so I'm an incurably cheap SOB. The spray stuff is prohibitively expensive, given the other things I want to achieve, so I'm exploring other options, and noticed that, while there was plenty of discussion here about Great Stuff and crap like that, no one seemed to have floated this idea (possibly because, as you appear to feel, it's offensively stupid.)

So - to be clear - you think the idea of pouring it in courses behind temporary forms and giving it time to expand and cure in between is untenable/unworkable/deplorable/dumb also?
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Old 02-15-2019, 05:41 PM   #10
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Quote:
Originally Posted by Buzz Nichols View Post
Besides price? Nothing.

I'm budgeting on a teacher's salary, so I'm an incurably cheap SOB. The spray stuff is prohibitively expensive, given the other things I want to achieve, so I'm exploring other options, and noticed that, while there was plenty of discussion here about Great Stuff and crap like that, no one seemed to have floated this idea (possibly because, as you appear to feel, it's offensively stupid.)

So - to be clear - you think the idea of pouring it in courses behind temporary forms and giving it time to expand and cure in between is untenable/unworkable/deplorable/dumb also?
Now you want to break it down to even more steps doing it increments.I think when you're done you will be kicking yourself saying " I should have sprayed or used rigid foam."
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