Starting new 36" build

[Tscarborough]

Re: Starting new 36" build

One of the advantages of a barrel vault is that the expansion joints can be built in. The front and back are built with slip joints, and thus no cracking. I did get some cracking on the concrete cladding, but they are shrinkage not thermal.

[SCChris]

Re: Starting new 36" build

As long as you don’t have loose bricks, leave it alone, at least for now. If you’re concerned about the arch and you don’t have buttressing you might feel better by doing a bit of buttressing.

It’s my feeling that getting a bit of semi-permanent insulation over the dome will help to keep temperature differences to a minimum and so the thermal stresses might also be kept to a minimum. If you find that nothing loosens up in the final curing fires, button her up and cook. If you feel like doing a bit of patching, pull the insulation back, patch, insulate and button her up..

Enjoy the oven, you’re right there..

Chris

[Amac]

Re: Starting new 36" build

Dennis
I am impressed by the strength of that mortar mix - seems to have split one brick rather that follow the joints.
I got a lot of hairlines mostly following the horizontal courses higher up the dome around and once or twice following a zigzag downwards but alwasy along joints. One followed out to the entry arch. It was the only one I tried repairing (but only because I could see it and it was irritating) by angle grinding the mortar out and replacing it. I expected it to come back at the next firing but it never did.

I think it won't cause you any problems and will act as an expansion joint. I wonder should all the ovens be designed with deliberate straight line or not mortared joints rather like you would do with a large concrete slab. Then you could point it out as a "design feature"

[clg763]

Re: Starting new 36" build

Most people have cracks in their domes and arches, don't worry, they give an oven character .

[deejayoh]

Craaaaacks

Well, I got a little carried away with the curing tonight it seems. Friday, I lit a small fire and got it up around 450. Last night, a bigger fire and I had the oven up around 550 at the peak of the dome. My plan tonight was somewhere between 600 and 700. I had the fire going in there, and it was only about 450. So I threw a couple more pieces of wood on the fire and WHOOSH. Temperature at the dome spiked to over 800 in a couple of minutes.

Before I knew it, I had a crack running from the top of the dome to the entry arch. It started quite small but widened out within a few minutes to what you see in the picture. There are also some smaller horizontal cracks that showed up between the 3rd and 4th courses that are less concerning.

Biggest worry I have with this is that the crack goes straight through my arch. How concerned should I be?

[deejayoh]

Re: Starting new 36" build

Update on the curing -
I lit up 6 chafing fuel containers on Weds, and 9 last night. The oven temps were up around 270 at the peak and 170 at the floor with 9 containers going. Outside of the dome was up to about 115. Tonight I'll light up 12. I am hoping it will get up over 300 degrees. inside, and maybe 150 outside the dome. As of yet, I haven't really saturated the dome with too much heat so I can't assess how much cracks could be an issue. Saturday will be the first fire - but nothing too big. I will be trying to keep it under 500 degrees.

In retrospect, the chafing fuel approach has a couple issues. The fuel itself is pretty expensive, and it doesn't get as hot as I thought it might. I've kept a plywood form over the door to try to keep the heat in, without that the temps don't go up as high.

[jlopiccolo2]

Re: Starting new 36" build

thanks for the advice Tscarborough....much appreciated

[deejayoh]

Re: Getting started

After contemplating and planning for over a year, my build has begun, I have set the forms and laid the gravel. next step 6 mil plastic, rebar then lay the cement. I think pouring the cement this Sunday on fathers days is the best gift to myself....(the wife thinks I am nuts!!)

Looks good - but you'll probably want to start your own thread on your build

[Amac]

Re: Starting new 36" build

I added the buttress because my arch is free-standing from the dome in order to provide the heat break. I seemed pretty solid as a "unit", but the whole thing would rock slightly on the FB Board. The buttressing was intended to stabilize the arch, and it seems to have done the trick. No movement any more.

Ok of course - makes sense now! I did a roast in the WFO last Sunday which was perfect. Tried to make some Ciabatta bread afterwards. Tasted Ok but I think I could use the result as a weatherproof cladding - after a few days it is tougher than buffalo hide.

[Tscarborough]

Re: Starting new 36" build

Looks good, and I can think of nothing better for Father's day than hard labor. And Beer. Lay a 2' piece of rebar at 45 degree angles across those inside corners, if not 2, and/or cut a control joint across them.

[SCChris]

Re: Starting new 36" build

Slow and steady are your marching orders. It's Tuesday morning and depending on how you move forward, by the weekend you'll be able to roast a chicken. I don't quite remember how fast banhxeo76 cured with chafing fuel, but at 100F or so per day a chicken is doable for Saturday dinner for sure.

Slow heating and soak the dome with the heat!

Chris

[deejayoh]

Re: Starting new 36" build

Chris -
Still just the lamp. The temp was 250 at the dome peak only. The floor is around 120-130 degrees. Per the instructions in the FB guide, I think I am going to unplug the lamp this morning to let the oven cool down, and then start with the chafing fuel tonight.

[SCChris]

Re: Starting new 36" build

dejayoh, Are you still using a quartz lamp or did you go on to chafing fuel?

Chris

[deejayoh]

Re: Starting new 36" build

Wow! I wrapped the oven up in a tarp this morning because I thought it might rain before I got home. Came home late and checked the temps, and with just the lamp the interior is over 250 degrees. A little insulation goes a long way!

[deejayoh]

Re: Starting new 36" build

That looks fantastic Dennis - I know you said this isn't a race but I think someone just flashed past me on the finishing straight. I really hope that buttress is over engineering because it never even occurred to me that my entry arch would need buttressing. Hard to resist lighting a few fires in there I'd say, but take your time - the longer the mortar has to cure the better.

Thanks Aidan. I am pretty happy with where I am. I added the buttress because my arch is free-standing from the dome in order to provide the heat break. I seemed pretty solid as a "unit", but the whole thing would rock slightly on the FB Board. The buttressing was intended to stabilize the arch, and it seems to have done the trick. No movement any more.

As for the curing, I hear what you are saying! I wanted to throw a few wood scraps in there last night and fire it up - but I resisted. The mortar in the dome has been air-curing for 2 weeks, but the mortar in the arch is pretty fresh.

I've left the quartz lamp on in the dome 24 x 7 for a couple days. The temp inside ranges from ~90 - 170 degrees (bottom to top) and the dome is ~85-90 degrees on the outside. Tomorrow night I am going to try to get that up in the 250-300 degree range inside using the chafing fuel. Because of the heat break, I don't think that will get the arch much warmer than ambient temps.

I think I will be ready for first fire next sunday if I can stick to a schedule of +~100 degrees each night this week using the chafing fuel