NW Ohio Build - Opinions welcome

[perrysburg]

Re: NW Ohio Build - Opinions welcome

Started the arches yesterday....used a cement bag which is analogous to what a pastry chef would use for decorating a cake.

[GianniFocaccia]

Re: NW Ohio Build - Opinions welcome

I think you want to stagger the lengths of the dome bricks so you lay them on bond.

[NCMan]

Re: NW Ohio Build - Opinions welcome

I think you want to stagger the lengths of the dome bricks so you lay them on bond.

Ordinarily, that would be true and make it stronger. However, that's not how most of those ovens are built. It will be fine.

[david s]

Re: NW Ohio Build - Opinions welcome

Because your vault is not laid on bond, it's radius is quite large and your end wall is outside rather than under the vault, you should consider steel bracing right around the oven where the vault meets the walls.

[perrysburg]

Re: NW Ohio Build - Opinions welcome

I plan on framing out the oven with steel 2x4's and wrapping with cement board to stucco to match the bottom. I'm thinking if done right (and with a few cross beams where the top row/ 45 degree cut bricks support the arches) the framing will not only provide a structure for the cement board but also support the arches. The only unkown is the ceremic blankets--not sure how tight I can get the crossbeams with a layer of ceremic between the bricks and 2x4's.

I was planning on curing with small fires while the wooden 2x4's shown in the picture are in place and once that had completed removing and starting to build the steel framing. Should I (or can I) fire cure the oven before framing out with steel 2x4's or will the curing process weaken the bonds immediately and put the structure at risk?

ps., The refractory mortar recipe I used is 3 parts block glass mortar / 1 part fire clay.

[david s]

Re: NW Ohio Build - Opinions welcome

There are two schools of thought re curing with insulation on or off and pros and cons for each. I prefer to do it with the insulation in place. There are certainly more stresses on the structure when it is first fired because the temperature differences are greater when the lower parts of the oven are moister and therefore cooler. I would think this would also be the case if you fire it up without the steel bracing.

[Gulf]

Re: NW Ohio Build - Opinions welcome

I think that I would figure in using a rigid insulation for the flat side walls. No compression to worry about. No heat transfer to what ever buttressing is used.

[NCMan]

Re: NW Ohio Build - Opinions welcome

I think that I would figure in using a rigid insulation for the flat side walls. No compression to worry about. No heat transfer to what ever buttressing is used.

Are you saying that rigid insulation doesn't compress?

[Gulf]

Re: NW Ohio Build - Opinions welcome

Are you saying that rigid insulation doesn't compress?

In this application, not to the point that it would loose it's insulation value.

[gugahulk]

Re: NW Ohio Build - Opinions welcome

it is cement board. I saw it used in another thread. It made sense to me that it would more evenly disperse the weight of the firebricks on top of the foamglass. The foamglass is brittle and the cement board protects the foamglass from damage while lying the brick--hope that makes sense. -A

I was thinking on using the same thing when I started, However if you do a burn test on them they actually catch on fire. I did it and my got on fire in 10 sec. The little threads that are in side of the cement board will catch on fire if exposed to open flame. Try it you will see what I mean. I just got a small blow torch and put on it and it was instant. I guess once the threads are burned out you should be ok. Hope this helps you.

[NCMan]

Re: NW Ohio Build - Opinions welcome

In this application, not to the point that it would loose it's insulation value.

I get what you mean. One thing I would be concerned w/regarding rigid insulation is..... if it is touching or even close to steel (if steel buttress is used) is how it will take the heat? Some kinds of rigid insulation can be toxic when melted. Just throwing that out there. This is all just hypothetical, of course. Just askin'.

[Gulf]

Re: NW Ohio Build - Opinions welcome

I know that I did not specify them, but I was thinking of CalSil, CF board, V or Pcrete to separate the oven from the buttress. At least, that was what I was referring to as "rigid", as compared to the cf blanket. A WFO shouldn't see temperatures anywhere close to their melting points. Also, I envision the buttressing as being outside of the primary insulation layer. Far away from the extreme heat.

[NCMan]

Re: NW Ohio Build - Opinions welcome

I know that I did not specify them, but I was thinking of CalSil, CF board, V or Pcrete to separate the oven from the buttress. At least, that was what I was referring to as "rigid", as compared to the cf blanket. A WFO shouldn't see temperatures anywhere close to their melting points. Also, I envision the buttressing as being outside of the primary insulation layer. Far away from the extreme heat.

Oh, I thought you meant actual rigid insulation. I think you've totally lost me in your description, etc., anyway. I guess the part I don't get is....if there is any type of insulation that compresses, even a little, separating the oven from a buttress, how can the buttress do it's job effectively? Don't misunderstand me.....I'm not saying it can't, I just must be missing something. Obviously.

[Gulf]

Re: NW Ohio Build - Opinions welcome

Oh, I thought you meant actual rigid insulation. I think you've totally lost me in your description, etc., anyway. I guess the part I don't get is....if there is any type of insulation that compresses, even a little, separating the oven from a buttress, how can the buttress do it's job effectively? Don't misunderstand me.....I'm not saying it can't, I just must be missing something. Obviously.

Sorry for the confusion. I just did a search on the term "rigid insulation" and sure enough, the first hit was for Owens Corning Foam . Again, very sorry for the confusion .

I can't see a "firm" insulation layer "separating" from the buttress, if the buttress is on the outside of the insulation layer. I can see where the brick (expanding during the first few heat cycling) could compress the insulation a little. But, as the oven cools the pressure on the insulation would relieve. Unless something else takes up this area, the next time it is cycled, the expansion of the brick will only get back to the limits that were set by it's first full clearing.

If, any of the most commonly approved firm insulation (which are normally used for under the oven floor) are used between the oven and a well constructed buttress, there should be no catastrophic failures.

[Tscarborough]

Re: NW Ohio Build - Opinions welcome

Most product specifications will provide compression data, thermal expansion data, and some will have rebound data. For what we do here, a compression strength of a couple of hundred pounds is more than adequate for buttressing even the most extreme dome, provided that the thermal expansion is low (which it will be), and it has enough rebound to maintain congruity to both sides of the structure.