Longmont, CO new WFO build - casted over sand

[cnegrelli]

Question: Is there any reason that I cannot fill the CMUs (all 8 with rebar) at the same time that I pour the slab? I'm doing a monolithic slab form. Seems like its more efficient, but I don't recall anyone doing it in one step.

[RandyJ]

The only issue I can see would be trying to keep the rebar centered in the core. make sure that you fully support the slab with a frame work as that will be what is holding the wet concrete up. Just remember it takes a fair amount to fill the cores. Make sure you have enough to do the whole job.

Randy

[Toomulla]

from memory you need 1 cubic meter to fill 120 blocks, if you use a 10 mm concrete mix you should not have any problem soak the blocks prior to filling

[david s]

Standard (8") blocks take 3 litres per core. If you use 6" blocks it's 2 litres per core.

[cnegrelli]

I went ahead and filled them this morning. I had planned on 10 bags of 60lb concrete and it took 9.5! Decided I wanted to be sure that the corners of the dry stack was anchored solid before I started loading it down with the hearth.

[cnegrelli]

Ready to pour if the thundershowers pass on.

[agrasyuk]

Weather is indeed quite a bit of a factor in this. Good luck on the pour, make sure your concrete is not to watery (thats a lesson to myself).

[cnegrelli]

Concrete top of stand is now curing. Moving on to next phase and I plan to have the dome rest on either the insulation layers or firebrick, so as not to have the dome in contact with the concrete (heat sink).
Planning to use the same FoamGlas, CalSil sandwich as UtahBeehiver but I will be casting my dome on sand, not building from firebrick.

Build on firebrick or on CalSil board? Firebricks would then be on inside of dome walls, so they could be replaced/removed? Opinions?

[david s]

It is far easier to build the dome on top of the firebrick floor. Any floor brick that cracks orneeds replacing will be in the middle not at the perimeter. You can then easily trim any floorbricks that extend past the dome after you've finished the dome casting.

[cnegrelli]

Glad I asked!

[asudavew]

Sounds like a fun oven to build. More pics!

[david s]

You have a huge base for a 28-30" oven, given that most cast ovens of that size only have a 2" thick inner shell..Will all the area outside the oven be for prep?

[cnegrelli]

It's up to a 32" oven now. So 36" diameter outer shell.

Yes, the tradeoff given the slab existed, was make a bigger oven which I have resisted the urge, mostly because of things I've read from you! I don't see the need functionally to go much bigger. I do now plan to build an enclosure, but it's minimalist, leaving room for 2 par stools on the right side and room to work on both sides.

Here's a picture of the octagon shape (in 3D that I plan to build mostly because my wife likes it and she has design say, while I retain engineering say-so!

I'm on vacation at the moment and starting to plan the casting of the flue gallery. Really struggling with how best to do that with simple molds. I plan to use a sand form for the dome, but it would seem inadequate for the flue gallery - so any suggestions welcome. Looking ot maximize function here, as it will be enclosed ultimately.

Also plan is currently for a thermal break just outside dome area (Inner arch). This will be the transition from the dome to the gallery, if I'm getting my terms correct. Comments?

[david s]

Once you've cast the dome over the sand mould, and it has set after a few days, remove the mould door plate and build another sand mould in front of the door. Make it slightly wider and taller to create the door rebate. If you want to make the expansion joint there, place some cardboard there that can be removed after it sets. You will also need to make another front mould plate for the flue gallery mould.

[cnegrelli]

You will also need to make another front mould plate for the flue gallery mould.

I am envisioning this above as three mould plates. One when doing the dome. Then 2 for the flue gallery (back and front)?

I plan to use an anchor plate to attach a SS chimney. Are you saying I could use sand to shape the flue? Having some 3D visualization issues here!