Longmont, CO new WFO build - casted over sand

[cnegrelli]

Removed all of the sand this morning. On first inspection, I don't see a single void. Because I didn't use newspaper, it's a bit rough, but fully functional.

I am extremely happy with the sand mold process. The gallery flue area also came out as expected. There is a small void/blemish if you will near the top of the flue on the front that would be visible so I may try to doctor that up today. But I will probably practice on something else that won't be seen to evaluate how that goes.

[cnegrelli]

I've dry mounted the Duratech Anchor Plate to my casting. Bought this product here at Forno Bravo. https://www.fornobravo.com/store/6-d...-anchor-plate/

In my casting, I tried to form the flue opening a bit wider in diameter to accommodate the approximately 1" deep metal circular piece (6" diameter) that goes down into flue area, with some added space for potential expansion. However, I'm finding the fit to be a bit tight.

How big a concern? I don't want cracking because of expansion of metal and had hoped to have made it bigger than it actually came out.

[cnegrelli]

I did not cut my 4" of hearth insulation (FoamGlas and CaSi board) to exactly fit the dome, since I plan to do an enclosure. Thus the CaSi is exposed to the elements at this point, although no rain in sight for a bit.

I plan to use a cement board product for the enclosure, over steel framing. I've done this before with my indoor fireplace remodel.
I also plan to pour concrete counter tops (polished) to raise up the level surrounding my build.

Dumb question #1: Which one comes first?
Dumb question #2: Assuming countertops first, how do you pour up to the exposed CaSi board? Is a render first applied to cover it? I think I saw UtahBeehiver do this before pouring his countertops?

Any tips, suggestions, appreciated here.

[david s]

I've dry mounted the Duratech Anchor Plate to my casting. Bought this product here at Forno Bravo. https://www.fornobravo.com/store/6-d...-anchor-plate/

In my casting, I tried to form the flue opening a bit wider in diameter to accommodate the approximately 1" deep metal circular piece (6" diameter) that goes down into flue area, with some added space for potential expansion. However, I'm finding the fit to be a bit tight.

How big a concern? I don't want cracking because of expansion of metal and had hoped to have made it bigger than it actually came out.

Having cracked the casting on both the second and third ovens that I built, I was sure that the expanding ss flue pipe was the culprit. I had cast directly around the pipe, so it was super tight. If I were in your position I'd be getting some really rough sandpaper and try reaming out the inside of the casting a bit. It shouldn't take too much.

[david s]

Removed all of the sand this morning. On first inspection, I don't see a single void. Because I didn't use newspaper, it's a bit rough, but fully functional.

I am extremely happy with the sand mold process. The gallery flue area also came out as expected. There is a small void/blemish if you will near the top of the flue on the front that would be visible so I may try to doctor that up today. But I will probably practice on something else that won't be seen to evaluate how that goes.

Scrub the inside surface with a stiff scrubbing brush. You don't want to have sand falling on your food.

[cnegrelli]

Sand paper as opposed to my grinder? Do I need be that gentle?

[david s]

See how you go, but I think a grinder is a bit too savage.

[cnegrelli]

You may have some voids to fill on the inside so keep the casting damp until you remove the sand. I sieve out the larger aggregate and make up some mix to a peanut butter consistency for doing this operation.

Brushed out the sand this morning and I do have a void in the top of the dome that is about a 1/4" depression, perhaps 2" in a circular shape. Is this worth opening a new bag of the castable and filling the void?
There is a 2nd void near the entry where the sand mold up against the door had shifted (previously shown). But that area is 3" thick and is cosmetic only so I will only address that if I'm addressing the other.

Opinion from david s ?

[david s]

If it were mine I'd be filling them. Keep the unused castable in sealed plastic buckets. I like to do this operation straight after de-moulding the casting so it's still moist. That way the patching material doesn't dry out too fast. As yours has been a week you may have to try and dampen the whole casting first, fill the voids, then keep it covered for a day or two.

Great going for a first build. You laid the floor a week ago and you've now finished the dome and gallery. It takes most brick builders months to get that far. The hard part is now done,

[cnegrelli]

Was able to ream out the area for the chimney a bit, but went from sandpaper to grinder quickly..

Mounted anchor plate with high temp caulk. Put my 48" chimney on top and everyone thinks it's too tall. Hmm.
That's the engineer in my. 48" is more draw than 36". Plus I got it on Craigslist for $40. Back to the drawing board I suppose.

[cnegrelli]

Here's the build I'm going to copy, likely with a dark stucco

. Not sure if I can figure out how to slope the roof. May need my buddy to throw this into a cad program. Building it with metal framing is also hurting my brain...

[david s]

I hope you are not planning on copying that stand. If it's on wheels that stand is dangerous.

[deejayoh]

I hope you are not planning on copying that stand. If it's on wheels that stand is dangerous.

I saw that and agree with you. Had to do a little research to see where it came from, and it sounds like the OP hasn't had problems - but I personally would opt for a little wider base! I was expecting pictures of a Humpty Dumpty oven.

https://community.fornobravo.com/for...229#post225229

[SableSprings]

Mounted anchor plate with high temp caulk. Put my 48" chimney on top and everyone thinks it's too tall. Hmm.
That's the engineer in my. 48" is more draw than 36". Plus I got it on Craigslist for $40. Back to the drawing board I suppose.

I just helped a friend add another 48" of 6" diameter chimney pipe to his existing 48" on a Casa2G90. We added the extra height so the smoke doesn't blow into an upper deck area. Funny to me that when I put the extra sections in place I thought "Wow, that looks really tall!" and after a week I didn't even notice it (other that no smoke in my face during martini time on the deck ). The oven does draw very well and for its height, the extended chimney has proven very stable in pretty strong winds. I think your setup looks great...and when eating pizza from the WFO nobody is looking at the chimney!

If you are planning on covering the oven with a tarp during the winter, think about making it easy to remove the chimney. We leave only the base 24" section, cap it with a bucket and then wrap the oven with a double tarp when we close up the place for the winter. Lots of snow and high winds in their "off the grid" cabin by Hihium Lake, B.C. Canada

[cnegrelli]

We really don't get much precipitation here in Denver area (unless it's Monday night football). I am doing an enclosure, but it won't be waterproof, and in fact will behave more like a stucco dome than most enclosures. I will probably cover it up for the bigger storms with a tarp. We mostly get sunny and dry.

In fact "sunny and dry (and hot)" is making me wonder about doing the patches above discussed with David.

We've been hovering this week around 95 degrees (35 C) with 15% humidity this week. That humidity is not unusual for us, counter to popular opinion. I'm not sure I can pump moisture in it under these conditions.