Captain Avgas
Well Known Member
I've noticed in recent years that "high temperature" RTV gasket sealants have become almost the defacto standard for use on RV firewall transitions.
Typical products I now constantly see on RV firewall transitions include Permatex Red and Ultra Copper RTV gasket sealants as sold by auto stores.
However I would caution against using these products as firewall sealants because they are quite unsatisfactory in that application.
RV builders get confused because these products are marketed as "high temperature". However being temperature resistant and being flame proof are two quite different things.
The Red and Ultra Copper RTVs are actually formulated as gasket materials and are only good to temperatures of 700 degrees F (intermittent). They are certainly not designed to be exposed to naked flame.
In fact when exposed to any naked flame the Permatex Red and Ultra Copper sealants actually ignite almost instaneously. Once ignited they will continue to support combustion quite vigorously even once the initial source of ignition is removed (ie they become a combustion source themselves). And when they ignite they give off copious quantities of choking white smoke.
Needless to say you do not want either flames or choking smoke penetrating your firewall.
Builders contemplating using these products (or those who have already used them) might like to try burning a test sample for an enlightening (pun intended) demonstration.
For firewall sealing I recommend RV builders use a true "flame resistant" product. They could investigate Flamemaster CS 1900 sold by Vans or 3M FireBarrier 2000+ sold by ACS. Both of these products can cope with temperatures up to 2000 degree F (intermittent).
Typical products I now constantly see on RV firewall transitions include Permatex Red and Ultra Copper RTV gasket sealants as sold by auto stores.
However I would caution against using these products as firewall sealants because they are quite unsatisfactory in that application.
RV builders get confused because these products are marketed as "high temperature". However being temperature resistant and being flame proof are two quite different things.
The Red and Ultra Copper RTVs are actually formulated as gasket materials and are only good to temperatures of 700 degrees F (intermittent). They are certainly not designed to be exposed to naked flame.
In fact when exposed to any naked flame the Permatex Red and Ultra Copper sealants actually ignite almost instaneously. Once ignited they will continue to support combustion quite vigorously even once the initial source of ignition is removed (ie they become a combustion source themselves). And when they ignite they give off copious quantities of choking white smoke.
Needless to say you do not want either flames or choking smoke penetrating your firewall.
Builders contemplating using these products (or those who have already used them) might like to try burning a test sample for an enlightening (pun intended) demonstration.
For firewall sealing I recommend RV builders use a true "flame resistant" product. They could investigate Flamemaster CS 1900 sold by Vans or 3M FireBarrier 2000+ sold by ACS. Both of these products can cope with temperatures up to 2000 degree F (intermittent).
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