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Old 06-06-2016, 04:13 PM   #1
Mini-Skoolie
 
Join Date: Jun 2012
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Year: 1986
Coachwork: Blue Bird
Chassis: P30
Engine: Chev 350 gas-replacement
Great stuff in walls?

I'm putting up a Murphy-like bed in my shorty. I removed the steel inner wall under the 3 windows where the bed will be, and pulled out the original (nasty) fiberglass insulation.

The steel wall will be replaced with cardecking bolted to the ribs. The brackets for the Murphy bed will then be bolted to the cardecking.

I bought a piece of 1.5" Styrofoam-like insulation, but planned to use Great Stuff around the edges to get a good seal.

Many moons ago I read someone's post about the roof of his bus having a few small rusted areas. As he got into pulling the ceiling down, the damage was more obvious, and the roof was damaged beyond repair. Appeared that the damage was caused by spray foam. I don't recall whose post that was (can't find it) or what the final outcome was, but I sure don't want to destroy the side of my bus.

Another question--should the shiny foil side of the insulation face toward the outside of the bus, or the interior?

Any thoughts or input would be greatly appreciated!

Thanks,
TA
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Old 06-06-2016, 05:17 PM   #2
Bus Crazy
 
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Yeah, I remember that bus too. I do recall we've concluded that single-part spray foam, aka Great Stuff, is corrosive in its liquid form. Once cured it should be ok though. A problem that can arise is "will the stuff be able to cure if I spray it in that spot?" A wall rib filled from a hole at the top looks an awful lot like the can the Great Stuff is shipped in so we might expect it not to cure very well applied in there. My guess is that if you filled the gaps around a rigid foam panel in several thin passes with plenty of curing time between each application it'll probably turn out fine.
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Old 06-06-2016, 05:43 PM   #3
Site Team
 
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I only use great stuff where the crevice I'm spraying into has significant exposure to atmosphere.

Aaron's Great Stuff Rules:
  • Spray with can upside down at all times.
  • Spray a small bead along the gap you are filling, don't go full fill on the first pass.
  • Let the crap expand a while and see how far it goes, then lay another bead in.
  • Try to never spray into crevice you can't see into (like poke the straw into a hole)
  • Plan ahead and use the whole can.
  • Great stuff doesn't really have a great R value, and it's not a replacement for doing a real insulation job. It's main purpose is to prevent air exchange between cavities.


I placed the foil side in and out. (double thickness insulation)

Quote:
Originally Posted by Tool Amour View Post
I'm putting up a Murphy-like bed in my shorty. I removed the steel inner wall under the 3 windows where the bed will be, and pulled out the original (nasty) fiberglass insulation.

The steel wall will be replaced with cardecking bolted to the ribs. The brackets for the Murphy bed will then be bolted to the cardecking.

I bought a piece of 1.5" Styrofoam-like insulation, but planned to use Great Stuff around the edges to get a good seal.

Many moons ago I read someone's post about the roof of his bus having a few small rusted areas. As he got into pulling the ceiling down, the damage was more obvious, and the roof was damaged beyond repair. Appeared that the damage was caused by spray foam. I don't recall whose post that was (can't find it) or what the final outcome was, but I sure don't want to destroy the side of my bus.

Another question--should the shiny foil side of the insulation face toward the outside of the bus, or the interior?

Any thoughts or input would be greatly appreciated!

Thanks,
TA
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Old 06-06-2016, 06:49 PM   #4
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
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I used great stuff to seal my HVAC lines to my house back in 2009... that stuff hasall detiorated. even the stuff that wasnt out in the daytlight.. it got hard and is crumbling.. some of it got wet and the little bubbles hold water.. and ive noticed the junk I pulled out of the crevices in the walls is greenish instead of the bright tan / yellow it was new.. which means it likely mildews if any water does hit it...

I dont think its all its cracked up to be.. now granted maybe there are newer products or perhaps great stuff has been revised since 2009 when I put it in...

one product i wonder about is that spray material that is rubberized and supposedly seals anything... (ie the stuff the guy takes and makes a boat out of a screen door with).. i havent tried that yet.. I may spray my firewall with it to seal up all the air-holes that let engine heat into the bus..

-Christopher
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Old 06-06-2016, 10:05 PM   #5
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Join Date: Mar 2011
Location: Houston, Texas
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Ya...Great Stuff ain't so great for much of anything. And as noted above...it will attack steel like a metal munching piranha. Also...if injected into a closed area...it will remain fluid and never set except around the outer edges. Crapolla in my book.
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