WFO CNR Build - Darwin

[UtahBeehiver]

Better, you can adjust the existing white brick width as well as the black outlined brick to split the difference so you do no end up with what is called a chip or that narrow triangle piece. These ovens are not exact science and lot of variables to deal with. So gradually transition from course 3 to 4 and move on. On the same token, make all you corrects in the front half of the dome and your best work on the back half, ie staggers, best faced bricks, tightest joints, etc, after the dome is closed only the back half will be seen and no one will be the wiser except you,

[terratree]

Been awhile since the last post, has been a trying year.

Some updates attached. Not far from keystone

Still deciding on outer arch details and really need the flue equipment before I start. Seems no one in Oz can supply an 8 inch collar/cowl to cover the vent. Any Aussies run into that issue ?










Middle block dropped in ok - IT gone

[terratree]

Keystone in. Yaaaafknhoooo

Made a meal of the 10 course, 11th was a bit better.

[terratree]

My current vent size plan is 14 inches wide x just over 3 inches deep. Is that sufficient for an 8 inch flue ?

[UtahBeehiver]

Ideally the vent opening should be the same or more area as the chimney so the vent is 14x3= 42 sq in and the 8" ID flue is pi x r2 = 50.3 sq in so you are short on the vent size. Also a circular opening is more effective than a rectangular opening so the 42 sq in vent is not as effective as a 42" circular opening. 14 x 4 is better.

However, DavidS has periodically talked about a venturi effect that is possible with a smaller vent area to a larger chimney. You may want to reach out to him for his take on this concept, out of my pay scale.

[terratree]

Thanks Russell, it's good to see your still on the forum.

I've changed it to allow 14 x 4. Will just extend with the halves.

So this is the plan below. Will tie in to the inner arch with 10mm ceramic fibre rope or 6.5 mm fibre glass rope. Not sure how much the stuff will compress yet. I do have a difference of about an inch between inner and outer arch, but don't see that as a huge issue. It appears I'll have room to adjust the adaptor bricks ok. I haven't seen this done on this forum...

On the dome, is it worth trying to use the IFB's in lieu of CF blanket and or vermicrete layer ? Not sure how I would get them to adhere to the dome. A high temp sealant ?

And a top vent ? ...I missed this during my research. Will have to check out the how to's on those too.

Appreciate the help.

J

[UtahBeehiver]

IFB are a lot of work,it is like building another dome and you still have to coat the IFB with something. Are you enclosing the oven or not? IMHO CaSi is the best insulation but also the most expensive. Ideally, CaSi on dome held on with tie wire, then a 8 or 10 one p or vcrete, then a stucco coat this is if you are not enclosing, if enclosing, CaSi on dome and if you really want to insulate more fill up enclosure with dry perlite or vermeculite over the CaSi.

[terratree]

Not planning on enclosing the dome Russell, as it's under some decent cover.

I have CaSi board beneath the floor, and originally purchased isolite Ceramic fibre blanket. (25 x 600 x 7200) or 1" x 24" x 283" and 2 x 13lb bags of vermiculite for the dome. What form does CaSi come in to cover the dome ?

In any case should I tidy the excess mortar up, before progressing?

Thanks.

J

[UtahBeehiver]

You already have the dome insulation with the Isolite Ceramic Fibre blanket. I sometimes interchange CaSi blanket with ceramic blanket. So based on what you have, ceramic blanket, 2" of 8-10 to 1 vcrete then render or stucco. 2-13 lb bags of vermiculite will not be enough though.I went through about 10 cubic feet.

[terratree]

Cheers Russell.

I decided to run with IFB's directly against the fire brick. B6 isolites are rated to 1400 Dec c I believe, so 3 inches of those, 1 inch of blanket (2 if I have any left), and then a render/stucco. Rendering directly on CF blanket will test me.

I didn't cut any bevel on these, just cut the bottoms so they aligned with the ones beneath. Just to allow for a small amount of adhesive placed at the back of each brick. These cut fast, and there's no weight to them.

Was concerned a little about the adhesive, but it's only there to hold the house of cards up, until the blanket goes on and there's no adhesive against the fire brick. It will obviously burn/melt.

I hope this works, and hope I've avoided the whole vermicrete drying time and water/steam issue during curing.

The blanket can be screwed directly to the IFB's.

J

[cobblerdave]

G’day
I had a go at the pearlite cement bit. It was a shit so I went a different path.
Had 2 inches mostly of ceramic blanket. Added 3 inch’s of rockwool. A layer of chicken wire tightened by twisting the wire where it was baggy to get it tight and the shape even. Another loose layer of chicken wire over that for the render to key too. Worked a charm and trust me the render will go on easier then trying to handle handfuls of perlcrete.
Good looking oven you’ve got there...
regsrds Dave

[terratree]

Hey Dave, Thanks for the info Mate. That's what I'm planning on.

Out of curiosity, how many days are you able to cook from a single fire ? Was trying to extend that time, with ample insulation.

Was going over your build the other night , nice work!!

Cheers

J

[cobblerdave]

G’day
mine not the highest insulation and no thermal break but it will give you a fair idea. But any oven the golden rule is you can’t get more heat out than you put in.
If you flash it up for 1 and 1/2, dry, it should get to usable pizza temps. Say this is Friday evening keep some small sticks burning in the corner keeps it on heat. Close it down. Insulated door. Next day you should still have 200C and be able to bake few bread and roast. A casserole in the afternoon maybe.
So again if on the Friday you flash it up and burn for 2 1/2 to 3 hours so that heats really saturated right through the brick. Cook pizza that night next day you can cook some bread and roast and still have heat for roasts or casseroles Sunday. But if you do say a full oven of bread you’ll probably find you will not get another full oven of bread without an hour of extra wood burning. All depends on what you take out.
You don’t have to get to pizza temps or fully saturate the oven every time either. A load of wood burns down in an hour. Scrape the coals to on side and cook “fire in oven” need some more heat a coupla thin sticks and the heat will be bouncing of those walls. Though in saying that you’ll probably find yourself shielding from the radiated heat more and aluminium foil is your friend.
hope this helps
Dave

[terratree]

Thanks Dave,

I'd be happy with that sort of retention.

Quick question - how does the attached pic look as far as the vent goes ? I see a lot of buttressing occurring and thought I wouldnt need it, if the 5 x outer arch bricks(on each side) overlapped onto the inner arch. Thought that would make it pretty strong, sharing the load.

I think I still have ample heat break with 10 mm ceramic packing.

Just havent located a build where the inner and outer arches were offset, like this. I dont see that as being an issue

Any advice welcome.

Thanks

Jay

[cobblerdave]

G’day
Brick in Oz has a link to all manner of brickwork and buttressing.
https://community.fornobravo.com/for...687#post212687
Steve’s build has quite a discussion on buttressing which influenced me to buttress mine as my entrance is quite deep.
https://community.fornobravo.com/for...i-at-bundaberg
regards dave