Ceramic Fiber Build Discussion

[matthewwalker]

Hey guys, new video up on using ceramic fiber. Hope you find some of it of value.

[briank]

Thanks Matt, this answers a lot of basic questions. When you say you were using ceramic fiber board unlined, was that with a J or batch box rocket?

[matthewwalker]

I've done both, that example was a batch riserless.

[DCish]

Very cool, thanks for posting! I particularly like the pizza stone idea for low-mass abrasion resistance. Another idea that comes to mind is that the light weight of the ceramic fiber board could allow for outdoor iteration on the core until a satisfactory version is achieved, then just carrying the core indoors and continuing the build.

[pinhead]

I've not used the ceramic-fiber board but have used ceramic-fiber blanket.

I won't build another heat riser any other way. Sliding the blanket inside a stove pipe is so easy and effective, it's scary. Pretty darn cheap, too. The only thing I might add is some rigidizer - mostly for peace of mind since this application is still fairly new.

I can see so many ways to use the ceramic-fiber board in my stoves but I'm kind of shy to the price. With the price of the blanket coming down, hopefully the boards will come down too!

[matthewwalker]

Thanks so much guys. Pin, I think you could do some good stuff, testing at least, with your same method. A shoddy non-flammable box of some sort, lined with your wool, then a thin abrasion layer like brick splits only in wear spots.

I love your riser tech. For anyone who missed it in the video, you can salvage enough superwool to make one like Pinhead does from a conventional glass top range/oven.

[craypappy]

Very cool. Thanks so much for great video.
Makes me ponder other uses, including the following.

Peter recommends putting insulation over the top of a slab of casted refractory concrete when capping the bell. I'm wondering if one could do better with having the insulation beneath the slab instead?

Questions:
1. Is ceramic fiber board strong enough to reliably support itself across a 2+ foot span?
2. If so, would the natural compressibility of the ceramic fiber board form a natural seal around the perimeter from the weight of the heavy slab?
3. Is the insulation from the ceramic fiber board sufficient to permit the use of regular reinforced concrete for the slab instead of refractory?

[matthewwalker]

I believe the answer is "yes" to all three. I'd most likely set the board in a bead of mortar, just because. But, yep, I think that would work. It comes in various thicknesses. I wouldn't go thinner than 1" for that span, the thicker the better.

[pinhead]

Sept 14, 2017 18:57:26 GMT -8 matthewwalker said:

I believe the answer is "yes" to all three. I'd most likely set the board in a bead of mortar, just because. But, yep, I think that would work. It comes in various thicknesses. I wouldn't go thinner than 1" for that span, the thicker the better.

Using CFB would make the roof of the firebox much easier to build, that's for sure - for me it would eliminate the requirement for metal supports when building with brick, as well as obviously increasing performance through better insulation.

I wonder out loud, though, if the reduction of mass in the roof could be a detriment to the efficiency during the "coaling" phase - as with a high(er) mass, hot roof would be radiating heat back down towards the coals. I suspect the "best" would be a highly reflective roof - though I don't know of anything that would last as the roof of a firebox while simultaneously having high reflectivity.

[matthewwalker]

Insulation in the firebox is always better than mass in my opinion. High mass anywhere near the burn robs heat from combustion, and if it gives any back in a useable way, it's far less than it stole from the early burn, IMO. Get the mass out of the fireboxes for peak performance, balance it with your durability goals.

[pinhead]

Sept 15, 2017 5:48:05 GMT -8 matthewwalker said:

Insulation in the firebox is always better than mass in my opinion. High mass anywhere near the burn robs heat from combustion, and if it gives any back in a useable way, it's far less than it stole from the early burn, IMO. Get the mass out of the fireboxes for peak performance, balance it with your durability goals.

Regarding a batch box - does your statement stand true even if the brick/mass is highly insulated? For instance, a brick firebox wrapped with 3-inches of Rockwool?

[matthewwalker]

Yes, I think so. Upon reload, that configuration leads to overfueling and difficulty controlling your burn. As for your thought on coaling, the more insulative, the more complete reduction of coals. That is a time when mass is very detrimental in my opinion, as it just leaches heat from the coals. Even mass with insulation around it. You might recall that my first Walker Stove, the one I took to DC, was a cast PvdB BB surrounded by CFB. I've burned many, many hours in that configuration. Worked very well, but not as good as straight CFB.

[ronyon]

Sept 13, 2017 10:05:58 GMT -8 matthewwalker said:

I love your riser tech. For anyone who missed it in the video, you can salvage enough superwool to make one like Pinhead does from a conventional glass top range/oven.

Can you share they video link?
Getting a riser, high tempature glass AND a ready made oven(with door!),sounds like a scrounger's dream come true.

[pinhead]

I don't have a link to his superwool salvage endeavors but here's a pic of my heat riser

[matthewwalker]

Sept 15, 2017 11:00:40 GMT -8 ronyon said:

Can you share they video link?
Getting a riser, high tempature glass AND a ready made oven(with door!),sounds like a scrounger's dream come true.

I just mentioned it in the video linked above Ronyon. There isn't any more info, nor do I show the unit. Any regular glass top range will have insulation. They also have ceramic fiber discs under the burner elements, could be salvaged for small firebox experiments or gap sealing or??