Fire box insulation

[chsmoker]

Will using a ceramic insulation 2300 degrees fire rating. I would like to put a 1/2” layer on the inside to insulate the trailer underneath. Fire box pic attached. My concern is will this have impacts on the food being cooked? Anyone have any experience/thoughts? Thanks

 

[Starwise]

You don't want ceramic wool to spread into your cooking chamber, ever. Fibers of ceramic wool should be treated the same as asbestos, always wear respirator when handling, cutting, etc.
I would rather pour in a layer of refractory cement for thermal isolation. You can find many brands from the favorite online shopping site but my recommendation is the brand Girtech. It is non-toxic, doesn't contain harmful ingredients like many other do. It can be used as a mortar with regular firebricks and also as a pourable/castable refractory. 1/2" layer would give you 3100F heat isolating barrier. The only drawback of Girtech is that it is very gritty, but if you are pouring a layer that shouldn't be a big problem.

 

[bmudd14474]

We had a member use it where he had a sheet of steel on the inside and outside but put the ceramic in between the 2 sheets of steel. It works really well and since it was 100%sealed(welded) in between the sheets he didn't have to worry about the ceramic getting into the cooking chamber.

 

[tridiot]

I've used the ceramic fiber mat on a couple of pits. Works very well. This one I wrapped around 2 layers of 1" insulation.

 

[bill1]

I"d use 2 or 3 or 4 layers of steel (outside the firebox) spaced 1/4" apart as heat shields. If you can get stainless, great. Paint the down side (facing trailer) hi-temp black, keep the top side shiny.
That's how Detroit does it with catalytic converters.

 

[tridiot]

I"d use 2 or 3 or 4 layers of steel (outside the firebox) spaced 1/4" apart as heat shields. If you can get stainless, great. Paint the down side (facing trailer) hi-temp black, keep the top side shiny.
That's how Detroit does it with catalytic converters.

I don't know... that would get awfully heavy awfully quick - unless you're using just sheet metal, but even then, it would seriously add to the complexity of a build. Lots of guys just do an 'air gap' between the inner pipe of the firebox and the outer shell, usually like 2-3" or so. Some people have taken to calling this "semi-insulated" instead of "fully insulated" (i.e., with an insulating substance in the gap). It does work, though isn't as dramatic about keeping the outer skin cool. I know on my 2" ceramic fiber insulated firebox shown above, even running it full throttle in the hot summer sun, I can put my hand on the outside skin of the firebox and it's only mildly uncomfortable. Anything else, meaning not in direct sunlight in the summer, and it's just warm when I place my hand on it.