32 Igloo Build, Lakeway TX

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

I am (I think) within dome-closing distance -- one more chain then a plug ought to do it.

I started having problems with bricks sliding inwards about 3 chains ago. The solution for me, which I hadn't seen elsewhere was to use a 'lock stone'. Think of it as the opposite of a key stone:
- A key stone locks the whole chain by being the last brick in place -- once it's in place, the whole chain can't slip inwards because they push against each other.
- A lock stone means after completing one chain, I immediately place the first brick (or 2) of the next chain. The IT supports this brick while it sets, so that the next day I can set the rest of the bricks in the chain and have something immovable to lock against until I complete the whole chain and place the key stone.

This has worked well for me so far -- no slippage, no need for extra support mechanisms.



I need to get a bit more fireclay and sand for mortar mix before I continue, but going well. I'm getting better at this as I go along of course -- now that I'm getting close to completion . At least I'll be reasonably good with the mortaring for my exposed exterior arch.

Looking into getting blanket and chimney soon. Blanket is pretty straight forward, but not sure on exactly what kind of duravent to get yet. Consensus seemes to be 8" duravent is best, but would 6" be just as good if my chimney is particularly tall? I.e. does taller == draws better? My Chimney is likely to be about 7' tall to make sure i'm 2' higher than any nearby rooflines.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

Been making slow progress -- one chain per weekend usually (though I got two this weekend. Things I've learned:

- Homebrew mortar mix was a good idea so far (3:1:1;1 sand:cement:lime:fireclay).
- I get better with each chain (as you can see from the photo, ).
- A simple Tilt and Turn jig on the wet saw works really well, but I wasn't able to use the spreadsheet well -- I always ended up just eyeballing the first couple bricks and cutting a few times till they held in place properly, then cutting the rest of the bricks for the chain the same way. Easier to just prop with different thicknesses of scrap than to actually measure angles.
- Angling the inside face of the arch bricks worked out very well -- no really odd cuts to make so far. The next chain might prove problematic though as the arch is I think slightly higher than chain #5. Shaving the bricks might be hard. It's the opposite problem to the dreaded droop others have I think.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

Miltcook, if you check the posts from June 1 in this thread, you'll see that I wanted to avoid the floor firebricks directly touching the concrete countertops, so I made a form that leaves about 3.5" between the counters and the oven proper -- they're both on top of the vermiculite layer but not touching each other. Once the dome is complete this gap will be filled by ceramic blanket and more vermicrete over the oven.

Edit: if you were talking about the contact between the oven landing bricks and the concrete counters, yes they do touch and there will be some thermal leakage there. There is a small (~1/8") break between the 'real' oven floor bricks and the bricks under the entry arch to mitigate this. When the door is pressed against the oven, it will be right on top of this gap, which will fill with ash. I wouldn't go putting my hand on the bricks in the entryway, but hopefully this will be enough to make the counters themselves safe. There have been some other threads around designing thermal breaks at the oven opening, but common consensus seems to be that they are overkill. You can cook for days even without them.


Work has kept me away from the oven for the last month, but yesterday I finally went vertical: i has arch!
17" wide by 11" tall, ~63" of the final ~17" dome interior height.
Backs of the arch tapered to approximately match the dome angle at the point of intersection.
This is the 'interior' arch, which won't be seen from the outside (it will be completely covered with blanket and vermicrete and stucco). For the outside arch I will be more careful with the cutting of the corner pieces

[miltcook]

Re: 32 Igloo Build, Lakeway TX

Counters are in and feeling indestructible. 2.5" of reinforced concrete just feels more secure than 2.5" of solid granite would have been. I wont' worry about jumping all over this thing to build the dome.

Newby question here, because I'm just in the planning stages, but since the floor firebricks directly touch the concrete countertop, won't that be one big heat sink? I don't see an insulation there. I like the look, but would be worried about the heat on the countertop.

Milt

[FrankT]

Re: 32 Igloo Build, Lakeway TX

Keep up the hard work, your oven will reward you.


Great build!

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

Counters are in and feeling indestructible. 2.5" of reinforced concrete just feels more secure than 2.5" of solid granite would have been. I wont' worry about jumping all over this thing to build the dome.

[mrchipster]

Re: 32 Igloo Build, Lakeway TX

That's not bad it looks a lot further in the picture for some reason.

Chip

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

I think it's just forced perspective from the camera angle or something. From memory, it's like 10" of counter and 11" of oven landing bricks then the circle -- tanding in front of it I don't think there will be a problem. But yes, I will be using a long-handled peel.

[mrchipster]

Re: 32 Igloo Build, Lakeway TX

Poured the oven-level counter today, will protect the vermiculite layer so I can climb all over the oven while building the dome. Also will let me return the cement mixer I'm borrowing -- all mortar etc from here on out should be smaller batches only.

I'm doing this a bit backwards from most builds by doing the counters first, but I think it makes sense. Main difficulty is making sure the counters are about level with the top of the floor firebricks and making sure the poured concrete countertops don't but up against the oven itself (would suck all the heat out of the oven). So I built a circular form out of scraps of 2x4 and melamine boards, topping with a flexible strip of synthetic lattice to get the exact right height to match the sides of the form. A bit of effort, seems to have worked perfectly and will give me 3.5 inches between the soldiers and the concrete counters, plenty for ceramic insulation.

That is quite a bit of counter in front of the oven, I hope you have some long tools.

Chip

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

Poured the oven-level counter today, will protect the vermiculite layer so I can climb all over the oven while building the dome. Also will let me return the cement mixer I'm borrowing -- all mortar etc from here on out should be smaller batches only.

I'm doing this a bit backwards from most builds by doing the counters first, but I think it makes sense. Main difficulty is making sure the counters are about level with the top of the floor firebricks and making sure the poured concrete countertops don't but up against the oven itself (would suck all the heat out of the oven). So I built a circular form out of scraps of 2x4 and melamine boards, topping with a flexible strip of synthetic lattice to get the exact right height to match the sides of the form. A bit of effort, seems to have worked perfectly and will give me 3.5 inches between the soldiers and the concrete counters, plenty for ceramic insulation.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

The chunks of 2x4 will allow a 3.5" gap between the soldiers and the concrete countertops, when I get the materials and pour those in place. Don't want all my heat leaking directly into the countertops! The gap will be filled with insulating blanket and/or vermiculite that covers the dome.

The concrete countertops will but up directly against the entry bricks on the other hand. These bricks are "outside" the oven, and heat loss there is less of a worry.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX



Will be 33" interior diameter after finding center, making sure soldiers won't go off edge of the level area, etc.

I will put a strip of cardboard around the floor bricks once they're levelled, then mortar the soldiers (half brick high) in place. The cardboard will turn to ash and fill the space between soldier and floor.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

As seen in the picture above, the opening/arch area seems rather wide. My dimensions:

35" Inner Diameter dome

+ 4.5 brick thickness + 4.5 brick thickness means 44" outer diameter

18.4" Arch opening width

+ 2" reveal + 4.5 brick thickness + 4.5 brick thickness means that my outer dimension of the entry tunnel is 29.4"

11.6" Arch opening height (approx -- can adjust this part later)

My entry tunnel will be 9" (one firebrick) long after getting past the arch. The flue will be about half that and as wide as I can make it reasonably.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

Due to the texture of my vermicrete layer (rough and loose bits), it would have been pretty hard to level my oven floor. So I decided I needed to do a levelling layer:
1) cut out cardboard showing total outer dimensions, including the opening, and find desired position
2) use old spray paint (green) to outline area
3) make a form from flexible lattice (circle) and scrap 1x2 (opening)
4) mix up some very wet mortar and spread it on



It's probably not perfectly level -- I will probably still need some leveling sand & fireclay under the oven floor bricks. But it should make that step much much easier I think.

I used a somewhat random mortar mix -- about 1/2 quickrete mortar mix, 1/4 fireclay, 1/4 sand -- and mixed it pretty wet so I could spread it. It won't be structural, so probably won't matter. The instructions say to level the floor with just water sand and fireclay after all.


Unfortunately my order of new countertop-mix (need a couple more bags) isn't in yet at Lowes, so not quite ready to pour the oven-level countertops. I want to do this soon to protect the vermicrete layer while I'm jumping all over it making the dome.

[pfennigthecat]

Re: 32 Igloo Build, Lakeway TX

This is what approximately 1400 lbs of firebrick looks like. About equivalent to having eight full adults over the rear wheels of my minivan. I probably shouldn't have.