Nathan's 36" SoCal WFO build

[n8huntsman]

Rebar is in, ready for concrete

Those rebar pieces sticking out the front are really going to get in the way wile I build the oven! I gotta pick up the little orange rebar caps so I don’t impale myself. I’m shooting to have a mix on site truck come on Saturday to mix up a 1/2 yard of 2,500 psi concrete for the 5 1/2″ thick hearth. I’ll be trying out my concrete skills for the first time. If it comes out well, I think I will pour the countertops in the bar myself which will save a lot of money.

[Greenman]

Re: Nathan's 36" SoCal WFO build

It would be best if they tie into each other. Whether you do that by bending the bar to make it continuous or leave a section of bar exposed above the first pour to tie the bar to for the second pour to.

Your planning is impressive. If you apply the same attention to detail with the build it will be a beauty. Look forward to following your progress.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

I assume that even though I'm doing two separate pours I should make the rebar continuous as shown, correct?

[deejayoh]

Re: Nathan's 36" SoCal WFO build

Have you checked with your local council about building so close to a boundary fence? In our country most councils require anything to be at least 1.5 m away from a boundary fence.

That's a good point. I know here it's 5 feet for a permanent structure. There have been builders here that have not been able to use their ovens or forced to move them. Better to know now.

[david s]

Re: Nathan's 36" SoCal WFO build

Have you checked with your local council about building so close to a boundary fence? In our country most councils require anything to be at least 1.5 m away from a boundary fence. In addition, because the fence is timber there are usually rules about how far any fire or flue can be away from anything combustible. In practice I don't think you'd have a problem, but a complaining neighbour may be able to use regulations or lack of compliance to mount a legal argument to prevent you using your oven.

Some aluminium checker plate screwed into the deck just in front of the oven is a good way to prevent coals burning your deck. No matter how careful you are you will drop some around the oven mouth sooner or later.

[n8huntsman]

Hearth forms are complete!

I ran out of daylight and didn’t get a final picture of the back curved area, but it is done and ready for concrete. I found a local company, Short Pour Concrete. They have a volumetric truck and mix on site. $185 for a half yard. No minimums, no standby time. This time next week, I may have a hearth poured.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

Why do you use bricks without trimming. The figure is one of the bricks for Pompeii oven which
I designed for my friend. Joint thickness of not more than 3mm.

Short answer, because I was convinced in previous posts in this thread that it would be a waste of time. I do like the look of it though...

[valentin]

Re: Nathan's 36" SoCal WFO build

Why do you use bricks without trimming. The figure is one of the bricks for Pompeii oven which I designed for my friend. Joint thickness of not more than 3mm.

[david s]

Re: Nathan's 36" SoCal WFO build

I see what you mean about a thermal gradient across the material inducing stresses but I'm a little confused about something still. I thought some people used vermicrete under their cooking floors as insulation? How would my vermicrete thermal break between the arch and dome be any different? Hot on one side, cool on the other.

The vermicrete, having lots of air in it is able to absorb minute cracks spreading. An example of this is IFB's being more resistant to cracking than dense firebricks, both bricks containing the same materials except the IFB's contain lots more air.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

I see what you mean about a thermal gradient across the material inducing stresses but I'm a little confused about something still. I thought some people used vermicrete under their cooking floors as insulation? How would my vermicrete thermal break between the arch and dome be any different? Hot on one side, cool on the other.

[david s]

Re: Nathan's 36" SoCal WFO build

Any large cast concrete (either calcium silicate or calcium aluminate) section that is subjected to heat, particularly if that heat is uneven, is subject to thermal expansion stress. It is the primary reason most oven floors have unmortared bricks of relatively small units. The entry area is particularly vulnerable as the outside is in ambient air, also having cool air being sucked over its surface, while the part closer to the oven receives much more heat via radiation and conduction. If you have a thermal break then the conducted heat should be greatly reduced. My first oven (no thermal break) had a large fire brick (310 x230 x 80 mm) at the entry and developed a crack right down the centre. The brick was a heavy duty one rated at over 1400 C. I believe it was the uneven heat that it was subjected to that caused the crack. Not that cracking makes any difference to its function or performance.
PhotoPlog - Finished Ovens

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

I have 3 options for the concrete hearth. I think option 1 is the strongest but most difficult, and three is the easiest and least strong. Do you think strength will be an issue with any of these options? If not, I think I'll make it easy and go with #3.
Option 1 - Single Pour
Option 2 - Pour a single flat hearth, then come back later and pour a second L shaped floor.
Option 3- Pour a single flat hearth up to the edge of the block stand, then later, pour another flat floor, partially on top of the existing floor.

For two and three I could drill into the hearth and insert rebar to anchor it to the entry floor.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

Got some time over Christmas to work on the design, so here is where I'm at.
There is 3 inches of cal-sil between the floor and the concrete entrance. It is capped with a .012" thk piece of Inconel. For the rest of the thermal break I plan to use vermicrete. It will be exposed inside the entry arch and vent area. Is this okay? The vent partially sits on the vermicrete.
Any other issues that anyone sees or anything else that I may have overlooked? I'm probably far enough along in the design to start forming for concrete unless someone spots an issue.

[n8huntsman]

Re: Nathan's 36" SoCal WFO build

I see most people make the cal-sil board the same radius as the dome. Are there any reasons I shouldn't extend it out another 3" So that it will be about flush with the insulating blanket that goes around the dome as in the attached image?
Thanks

[deejayoh]

Re: Nathan's 36" SoCal WFO build

I agree - the process of cutting all four sides of each brick did take a little extra time, but no extra materials, really. I mixed up minimal amounts of mortar and since I got a pallet (377 bricks) of firebricks (irregulars that weren't perfectly rectangular) for $50, I didn't care.

John

Don't you end up with a shorter brick face on the vertical? I haven't done the math, but seems to me if you trim 5 degrees off the top and bottom of each brick, you're using 10% more bricks to get the same face area. If bricks are free/fixed cost, I take your point. Most of us have to pay for each!