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Old 06-13-2011, 11:36 PM   #1
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Thermal break

I am planning on adding a thermal break between the ribs and the interior skin when I replace the interior skins.

What I am planning on using is a self adhesive silica fabric strip that is 1" wide and .03" thick - about 1$ per foot

McMaster-Carr

It has a very low thermal conductivity. I used this material when I built my last powdercoat oven and it does an amazing job of stopping heat transfer.

Has anyone done this?
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Old 06-14-2011, 12:50 AM   #2
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You might have found something there, whatever this means in their specs: "Temperature range is -40° to +482° F. Heat flow rate (K-factor) is 0.76 Btu/hr. x in./sq. ft. @ 75° F. Density is 61 lbs./cu. ft. Color is off-white. For indoor use. Cut with a utility knife or shears and install with pins and washers. Meets UL-94 5VA flammability requirements..."
Can anybody translate this to an R-value we could understand?
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Old 06-14-2011, 12:54 AM   #3
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With any luck your Airstream skin will never reach temperatures necessitating such high tech material... why not use fiberglass tape?

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Old 06-14-2011, 01:02 AM   #4
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Bart, did you ever put a temp gun on the outside skin on a hot day on playa? Especially the blue. I did, OUCH! 120+ on the inside, forget the outside number. He might have a good idea there...
But I think he's talking about using it as insulation.
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Old 06-14-2011, 01:11 AM   #5
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Quote:
Originally Posted by NevadaGeo View Post
You might have found something there, whatever this means in their specs: "Temperature range is -40° to +482° F. Heat flow rate (K-factor) is 0.76 Btu/hr. x in./sq. ft. @ 75° F. Density is 61 lbs./cu. ft. Color is off-white. For indoor use. Cut with a utility knife or shears and install with pins and washers. Meets UL-94 5VA flammability requirements..."
Can anybody translate this to an R-value we could understand?
R-Value





So, .76 BTU*inches/sq. ft.*hour*F /.030 = 25.3 or an R value of .04.

From
R-Value Table

we can see that 1/4" plywood has nearly 10x this R value....

I'd guess ripping some 1/8" Luan ply into strips might work better...
It's clear what matters here is thickness.

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Old 06-14-2011, 01:41 AM   #6
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There is a foam back glazing tape that is
adhesive
used in storefront glazing in fact I believe Airstream has it under the window flanges. Its not going to do as much good as you think with all the rivets breaking your thermal break 98418X12BL - CRL Black 1/8" x 1/2" Double Sided Foam Glazing Tape ENERGY STARŪ– CRL is an ENERGY STARŪ partner, and our fenestration foam glazing tapes carry the ENERGY STARŪ seal. ENERGY STARŪ is a government backed program helping businesses and individuals protect the environment through superior energy efficiency.
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Old 06-14-2011, 07:54 AM   #7
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Silica tape K factor is 000.78
Aluminum K factor is 250.00

For a limited thickness I have the feeling the Silica will provide a noticeable result.

I will still have heat leaks where the aluminum rivets link the ribs to the interior skin.

I have a lab pyrometer, it may be worth a little experiment.
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Old 06-14-2011, 08:01 AM   #8
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Quote:
Originally Posted by barts
With any luck your Airstream skin will never reach temperatures necessitating such high tech material... why not use fiberglass tape?

- Bart
Fiberglass can be used as well. I have found from using both on an oven, the silica transmits less heat in the 0-275f range. It is a little more in cost but I feel it may be worth it.
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Old 06-14-2011, 06:56 PM   #9
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jeepers.

My '73 27' has at least nine ribs at 18 feet each, and ten Sixteen-foot shell cross-rib rails riveted in, plus around 80 foot of horizontal rib on each end, then eight or more feet per window frame and door.

That is $450~ before knowing if that adhesive will forever cement tape to ancient aluminum - plus all the heave and shrink from thermal expansion and the pinch of riveting / road vibration may well grind the refractory type insulation to dust.

Fireproof or excellent fire resistance and nearly inert to 300°F - automotive gasket paper? This is not a place that really needs R-Value, just to arrest the torrent of heat aluminum can transmit.

How about Tyvek housewrap paper, it melts at 275°F and ignites at 750°F, the printed side has been treated to accept inks so glues may adhere better long term.

There are many sorts of synthetic roofing underlayment paper that is good to 300°F - glued to the shell ribs with an automotive caulk like a fast-setting Sikaflex or Vulkem equivalent...
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Old 06-14-2011, 08:38 PM   #10
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Tyvek sounds good.
How about spray stuff. Is there any spray stuff to spray a coat in the inside of the aluminum to arrest the heat transfer there? Thanks in advance.
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Old 06-14-2011, 10:10 PM   #11
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My plan is 1.5" closed cell fire rated spray foam in the cavity plus a thermal break strip on the ribs.
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Old 06-14-2011, 10:12 PM   #12
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That would be in addition to a white roof, polished sides, and a high quality solar film on the windows.
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Old 06-15-2011, 12:26 AM   #13
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I can't wait to hear how this turns out. All I hear is that spray foam want work, but I saw a picture of a 69 avion c10 with foam that looked great. Its been 40 years and I'm sure the foam is a little better now. Keep us posted
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Old 06-15-2011, 12:55 AM   #14
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I will be the guinea pig.

There is two ways to do foam.
1. Scuff the surface and spray foam
2. Spray a latex paint and then spray foam

The second choice will keep the foam from binding to the aluminum so if you ever had to replace an exterior skin it would be less work . The first choice makes for a more solid leakproof structure. I am going for no 1.

The E-84 foam will give R11 @ 1.5"
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