| [GMCnet] removing foam insulation [message #241432] |
Tue, 25 February 2014 22:30  |
larry erd
Messages: 132
Registered: August 2010
Karma: 0
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When I gutted my coach I looked at a lot of options
and found where the factory foam was very thick
the roof was every rigid and oil canned where it was
thin. I resprayed the entire ceiling with fire proof foam
and now I can walk any where on the roof with my 155#
weight with out a problem. I have 1 15000 BTU AC/Heat pump
here in FL and it is nice and cool, Leak and squeak free.
IMHO I would never remove all the foam, it adds a lot of
rigidity.
Larry Erd
ex Kingsley w/ Murphy bed
Lake Wales .
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| Re: [GMCnet] removing foam insulation [message #241452 is a reply to message #241438] |
Wed, 26 February 2014 07:04  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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| USAussie wrote on Tue, 25 February 2014 23:40 |
...
1) Remove all the old foam (from the ceiling at least)
2) Pop rivet aluminum sheeting on the inside of the ceiling from side to side out to the extrusion that runs the full length of the
coach.
3) Fill the gap with insulating foam....
Comments / criticism welcomed!
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Rob, before you inject foam into a closed structure, you need to think about the pressure that the foam will create as it expands. IMO, you are asking for bowed panels big time. Once mixed, that stuff is GOING to expand unless it is REALLY, REALLY constrained and the aluminum roof of a GMC isn't enough. Plus it won't fully cure until it does.
I had a void that had a small hole access. I carefully and slowly filled it with foam, letting it expand before I added more. The next morning,it was still oozing out of the access hole. A day later it had stopped but a screwdriver stuck in the foam came out sticky.
Instead, I'd suggest spraying new foam OVER the existing stuff, trimming it off flush with the stringers and ribs after it cures with a handsaw, and then putting on your inner sheet metal if you want two layers of aluminum (won't add that much strength over that distance). If you leave the original foam in place and only add new foam to fill the voids, you're not changing any of the structural aspects of original construction...only adding insulation.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] removing foam insulation [message #241479 is a reply to message #241438] |
Wed, 26 February 2014 11:19 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Senior Member |
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Rob, I can't see that working too well. A better approach would be to fill the cavities with spray foam, trim flush, and than bond the aluminum with adhesive to the foam.
And I also question the aluminum inner skin. You're going to be covering the aluminum with something I assume, and there are better substrates.
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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