Christo's Cucina

[Hendo]

Re: Christo's Cucina

Chris,

Fantastic effort. I'm with RT - that first pic looks superb! You've certainly achieved a lot since that beer we had two weeks ago ...

Congratulations,
Paul.

[christo]

one more cracked flue tile

Looks like I can join Fio in the cracked flue tile department.

Was working on the roof of the oven and found the tile had a crack in it lengthwise down the backside.

It was sitting on top of my transistion piece - no stress at all - except thermal.

I have not had a big roaring fire in the oven yet. The two times I've made pizza have been slow gradual fires over the course of 3 or more hours.

I think now I may change plans to a 8x8 transistion to double wall stainless pipe. It doesn' thave the look I want but cracking is not a good thing, either.

Bummed -

[wlively]

Re: Christo's Cucina

Chris

Your experience is easing my mind. I went with the KS-4 and duravent and I was thinking I may have been too extravagant. The pipe is performing flawlessly though, after an hour of roaring fire you can easily touch the outside of the pipe. It also made me allot more comfortable with closing it in and forgetting it.

I also agree with you on firing with insulation. All the discussion got me thinking that insulated would be much less stress on the bricks and mortar. So I did not fire till I at least had the blankets in place. I took a good long look today before the first cooking fire and no cracks to be seen.

[christo]

Re: Christo's Cucina

Well, the flue is not all that has cracked.

I noticed during the last firing that I could see some hairline cracks around the hexes and pentagons. I was disapointed and attributed it to lighting drying fires without insulation. Upon cool down I could not see the cracks. Knowing that everything was a tapered fit, I was tempted to just leave the insulation on and proceed.

I didn't. I removed the ceramic blanket and put it in the garage. What I fouind underneath was that each hex and pentagon had cracked around the periphery.

When the oven heats up the brick face expands - I figure the inner was much hotter than the outer (with no insulation) and perhaps that's how I tweaked it.

Instead of slathering more refrax over the dome, I decided to make a series of interlocking tabs (foil on one side of the joint to create a slip plane). I'm also mixing some perlite and mortar to apply around the bottom ring to keep it in place.

I was tempted to keep my problem to myself - but you have all been such a great help. It would not be right to keep my failure to myself... I see it as a setback - We will get over it!!!

Christo

[maver]

Re: Christo's Cucina

Chris, your description suggests that the bricks are contracting with heat, which if I recall correctly is the expected performance of firebrick when heated. I'm not sure an outer buttress helps this (perlite mortar). Any evidence the cracks are allowing smoke to escape (smoke staining the thermal blanket)?

[james]

Re: Christo's Cucina

Hey Chris,

Thanks for posting that. I think it will be very helpful -- particularly to other folks considering doing your design.

To Maver's point, if you simply coated the outside of the oven with a layer of RefMix (or whatever), that would hold the structure together and seal the oven, so that even if the individual brick pieces continue to expand and contract, that no heat or smoke could escape.

What do you think?
James

[dmun]

Re: Christo's Cucina

Chris, your description suggests that the bricks are contracting with heat, which if I recall correctly is the expected performance of firebrick when heated.

I really don't think bricks shrink with heat. About the only thing that shrinks when it gets warmer is ice, and that's a special case. There are a few materials that have a very low expansion rate, like fused quartz and Invar, but they too, are special cases. Materials have different rates of thermal expansion, but the C/E of firebricks and refractory mortar should be closely matched. I wonder if it has something to do with the two kinds of refractory mortar used?

I'm really confused about what's going on here, and concerned because I have a dog in this race, so to speak. Is the thin oven inherently unstable? It's the same thickness or more as the pre-fab ovens...

I'm also a little embarrassed because I was the cheerleader for the geodesic oven. Hmmm.

[maver]

Re: Christo's Cucina

OK, I'm sure I saw the contraction idea here about six months ago, but it makes no sense now that I consider it. I suppose someone might have been trying to convey that firebrick may expand less than other materials. Allow me to retract that idea.

[christo]

Re: Christo's Cucina

Yes the cracks go all the way through and there was some smoke stain on the blanket.

I believe the oven expands when heated - each brick according to the heat applied.

This means that the oven expands slightly during and then contracts after each heating cycle. As I kept the outer side of the oven un-insulated during most of my drying fires - that means the differnece in heat expansion was quite different on the insde skin vs outside skin. Full insulation would have almost made that heat difference negligble during the slow heat ups that I used. No insulation means that inside was expanding while the outside tried to stay reasonably the same - result cracks..... AKA my fault vs. design concept.

That is the mechanisim that I see - If this is the mechanism that caused my oven to break - then coating the outside joints with heat resistant mortar should be a reasonable patch to keep the pieces in place once I put all the insulation back in place!!!

Any other ideas out there??? Thanks!!!

Christo

[jwnorris]

Re: Christo's Cucina

<snip> If this is the mechanism that caused my oven to break - then coating the outside joints with heat resistant mortar should be a reasonable patch to keep the pieces in place once I put all the insulation back in place!!! <snip>

Have very little scientific background but, being brave enough to throw an idea out, what if you coated the oven while still hot? Or at least warm. This would put the oven in the expansive state.

J W

[DrakeRemoray]

Re: Christo's Cucina

First I say, Do not despair!

My flue tiles did not crack (that was Fio), but I did have several cracks in my dome that were leaking smoke.

I heated up the oven and applied furnace cement in the cracks. It seemed to do the trick.

Ace - Rutland Fireplace Mortar

Hope that helps!

Drake

[christo]

Re: Christo's Cucina

Moving ahead. Thanks for all the suggestions and moral support. I think I will do a combination of the refmix layer and furnace cement. I wil use the refmix layer with foil to create a slip plane and use the furnace cement to cover all joints after the slip plane is created. I think it will all be good!!!

Time for the entry arch - A few questions come to mind.

I believe I will assemble on the ground vs. making forms and assmebling in place. Based on the picture attached - I think I may assemble the left and right sides and then put together later along with the keystone.

I figure I should wait 4 days before attempting to pick up the arch and assemble in place. Is this being over conservative?

I had the black granite shelf made at the local countertop place from scrap. they charged me their standard price for machining and polish the bull nose only. They also gave me a matching sink cutout that will be the mateiral for the keystone. (The keystone in the picture is a piece of paper spray painted black).

When installing the decorative arch, I understand it should be separate from the dome - how do people stablilze the arch when there is no surrounding brickwork? Would be acceptable to put brick ties in the joints of the arch while prebuilding and during installaion bend these and cement to the firebrick opening with refrax after installation of the arch?



Thanks!!

Christo

[wlively]

Re: Christo's Cucina

Christo

I fully enclosed my entry, so I used a layer of cladding and screwed the durock to it so the arch isn't going anywhwere. But, early on I had considered leaving the first half of the entry exposed. My idea was to keep the arch as clean as possible, so my plan was to secure the base of the arch with "pins". I was going to drill small hole in floor and matching hole in base of first arch brick. Then cut a nail in half and mortar it and the brick in.

[maver]

Re: Christo's Cucina

Time for the entry arch - A few questions come to mind.



When installing the decorative arch, I understand it should be separate from the dome - how do people stablilze the arch when there is no surrounding brickwork? Would be acceptable to put brick ties in the joints of the arch while prebuilding and during installaion bend these and cement to the firebrick opening with refrax after installation of the arch?



Thanks!!

Christo

I used brick ties attached to my oven (I used a rotary hammer and masonry anchors) and then built the arch with the brick ties in the joints, but I built it standing with a form and I also mortared the front arch to the vent - there is not a lot of heat in the vent area so I don't think a thermal break is needed. Maybe if you want to preassemble you could do the vertical sides and two top segments all separate, then attach the sides with brick ties at the corners and on either side of the keystone.

I'm glad you are moving forward with a patch plan for the dome. I wonder how many ovens leak a little smoke once they are fully cured and insulated? Most of us have not done the dissection to find out.

Marc

[Hendo]

Re: Dinner!!!!!

The picture shows the door with the temperature probe unit outside the the door (it sends temp readings about 50 ft to a unit inside the house!)

Hey Chris,

This setup looks great! Would you be able to post details of the unit, supplier and prices etc? There are some people here (and me) that would be interested.

Cheers, Paul.