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No Foam Insulation please !

Dustyone

Well Known Member
I have an RV in my workshop that had a landing incident that required all front and rear belly skins to be replaced.
This aircraft is only 3 years old and has only done 140hrs of flight time.

The builder elected to use Foam insulation throughout the aircraft including the firewall. He did a masterful job of sealing every nook and cranny of the lower skins.

The foam was a closed cell type that you can buy at any hardware store.

Problem 1
The foam was so well applied that it sealed in any moisture preventing the normal evaporation of condensation. Compounding this problem was that no skins or ribs were primed or treated with alodine. This was just bare alclad against alclad.
The accelerated corrosion was heartbreaking.
ACtC-3ca5X4ym5ZuUI1SlthcEDL2eBbHJUzfJ9nmma7Qak79anGbN-hKmM2jl5inmbbwwHCmTa3ZxIJuJcpo77I7AT37wSH2tN8AMKf-lBo8umhN2FTnzZAL4Y6MnTTHKIuZWQ4anj5RbZQx26R2GZe_nCQE4g=w659-h878


ACtC-3c6QQxV-CHd6mOI0Bg1GEp_d0oPSoChXvVXwpNSY_1az_wZHkXUsZAYKUEGM3q_MOZqbtKbSGgHUZtUk9GIkBgB6yo7moqNIO_NND_1fd5ofqc5rmZePyuiQ48PK8Gp1hRR9uBsbRWjPtel3GjjKawCaQ=w1170-h878


This aircraft is lucky that it had a landing incident that allowed us to replace all lower skins and ribs. In the Eastern side of Australia where I live it is hot and humid so alodine conversion treatment and priming parts is the norm.

Problem 2
This same insulation was all over the firewall !
A simple burn test showed that this stuff burns and smokes with only simple ignition. I'm not sure what was worse, the thick black smoke or the fire !!
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So please seriously consider where and when to use foam insulation in an aircraft. At the very least, do a simple burn test and if you are worried about noise, just use a good pair of noise cancelling headphones.
 
Great Post!

2 things here that are also my pet peeves.. Glued on foam (moisture and fire) and non primed inner skin surfaces. Seen this all too many times, and in the airliner maintenance business, even the OEMs recommended removing most all of the bilge insulation for that exact reason. Insulation where needed is best applied to the bottom of floor panels that are above the skins...I have seen carpet do the same thing as the insulation in the pictures.
 
Firewall and floor foam needs to be on everyone's pre-buy inspection list.

BTW, when subjected to an external heat source, all the foams seem to burn about the same. Remember, the popular claim of compliance with FAR 25.853 just means the material will eventually self-extinguish after the heat source is removed. It does not mean the material is anything close to fireproof. By the time a pilot can detect and shut down a firewall-forward fire, foam insulation is already roaring. I'm talking seconds.
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It is too broad of a statement to say "don't use foam insulation." There are quite a few neoprene products available that neither absorb moisture nor rapidly propagate fires. Simple enough to test both before using.
 
A material doesn't need to absorb moisture to cause a corrosion issue. And I guarantee no neoprene on Planet Earth is suitable for the cabin side of a firewall.
 
Bubble Insulation Removed

Our -6A was completed 25+ years ago and had much hardware store insulation installed. All removed. Fortunately no fires or corrosion. AZ it’s entire life. Thanks to VAF for giving me useful info.

I’m glad an ignition source never found this...
 

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It is too broad of a statement to say "don't use foam insulation." There are quite a few neoprene products available that neither absorb moisture nor rapidly propagate fires. Simple enough to test both before using.

When would you ever need to use spray foam insulation in an airplane and why would you ever use it? I've never seen it used in any airplane that was professionally built after 1903 - not even in Poland.
 
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When would you ever need to use spray foam insulation in an airplane and why would you ever use it? I've never seen it used in any airplane that was professionally built after 1903 - not even in Poland.

Nobody mentioned spray foam. lol
 
Expanding polyurethane foam was not mentioned here, but we have seen a few builders promoting the idea of using it under the front floor of an RV-10. A good prebuy will probably find similar in other models too.
 
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