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wotavidone 12-08-2013 04:10 PM

New Build in South Oz
 
Well, I went around my mate's place last night and there was the beginning of an oven stand.
Looks like we are going to build an oven.

Like me, he isn't exactly flush with funds for fire brick and refractory cement. It's another pavers and homebrew job. Since mine has endured at least 75 cycles from dead cold to white and back again with no spalling or major cracks, I'm OK with that.
He wants an oven "same size as yours, but with a bigger door so I can fit a turkey in"

There are going to be challenges along the way.
He's keen to use the 5 inch thick real (industrial smelting type) firebricks he has for the cooking floor, while building the dome from the ordinary 3 inch thick fired clay pavers he also has, and he wants to put the pavers on edge like I did so the thin wall dome heats up quickly.
I see potential for a mismatch, in terms of heat transfer characteristics and thermal mass, between dome and floor. I also reckon if he wants to do roasting and baking more than pizzas, then the dome should be a bit thicker than three inches.

I have explained that my door is sized to give the "right" ratio of door to dome height, etc, and that making the door significantly higher while keeping the same diameter (my oven is 750mm/29.5 inches diameter) would mess up the ratio.

I reckon the way to deal with the door is to make the oven diameter a little bigger than mine, say 850mm/33.5 inches, and the door a little less than he really thinks he needs. I'm thinking 11 inch high door with a 16.75 inch high dome for a ratio of 0.66 keeps everything reasonable, if not spot on. Not quite the 12 inch door he would like to see, but pretty good, I think.

Of course this works out to be a "high dome" oven, not a dedicated low dome Neapolitan fast pizza oven, but it'll certainly do a nice pizza and better suit his other cooking ambitions. Imagine a roast turkey in a low dome oven? Some potential for burning the top of the bird, I suspect.

So, soon we will be away. Last night was spent discussing the structural slab and the insulation that go under the oven.
I suggested three options. Structural slab of reinforced concrete topped by either vermicrete or hebel panels, or do what I did and make the structural slab with scoria to give it some insulating properties. He's gone off to price Hebel AAC panels, which I think would be a good choice.

He has made his stand 5 feet wide, big enough for a 850mm dome with 100walls and 100 mm of insulation and 15 mm render. That would leave about 4 inches either side. Should look just about right, I think.

One area I invite comment on.
The simplest way to match an arched opening to a hemispherical dome is to use a simple semicircle. To get the semicircle to be 11 inches high, then at the bottom it will be 22 inches wide.
I'm thinking we'd get away without too much heat loss, because a semicircle with a width of 22 inches and a height of 11 inches has an area of 190 square inches. If the opening was 22 by 11 rectangular, it'd have an area of 242 square inches.
Still, it's a wide opening for a 33.5 inch oven. Is it too wide? It also occurs to me that the wider your arch is, the further back into the oven dome you have to set it.

cobblerdave 12-08-2013 08:07 PM

Re: New Build in South Oz
 
Gudday
I'm pretty sure that Russel, Utahbeehiver has used those super firebrick, he would be able to offer some Insite into them.
I don't think the door width will make much difference with only marginal heat lost when the fire is going for pizza. I think ever oven is different and there owners are always the best operators anyway. With a insulated door on it will not make difference at aull .
The wider door will have to be set into the dome further to fit however, that could be interesting. You might have to consider less than a symmetrical dome shape to make it fit. I would however consider making the dome deeper than wide because that's what I read thats recomendedwith other types for heat retention. Perhaps an advocardo shape like a lot of cob ovens are made.
Just a wild thought. A two door affair. One set with a smaller width opening and height at the 63 per cent that was removiable then giving you a larger opening for the turkey and of course a larger insulated door to fit that
Regards dave

wotavidone 12-08-2013 09:42 PM

Re: New Build in South Oz
 
Ta Dave.
If the arch is semi circular, it should marry into the dome quite nicely. The difficulty will be in how much of the dome I have to slice off. The wider the door the further back into the dome we have to go.
I've been mulling an oval design a bit like this:
Artigiano120 Brick Oven Specifications
I reckon it would not be hard to do, just have two centres for the indispensable tool to pivot on. The further apart the centres, the longer the oven.
It would take back the length sacrificed for the arch.

wotavidone 12-11-2013 06:09 AM

Re: New Build in South Oz
 
Dave, How did you bed your hebel that went under your floor for insulation?
I've done a little research that indicates that the first layer of hebel blocks in a wall is not done with the proprietary hebel thin-bed adhesive, but rather done with 6:1:1 sand, cement and lime. It was in a New Zealand spec-sheet for hebel block wall construction.
I can only get the hebel adhesive in 20 kg bags, and I reckon we'd be throwing away at least 3/4 of a bag.
I'm thinking a layer of 6:1:1 mortar put on with a 10mm notched trowel, and bed the blocks like tiles.

cobblerdave 12-11-2013 01:07 PM

Re: New Build in South Oz
 
Gudday Mick
I just bedded them with Portland sand lime / notched trowel. I then locked them on the sides with concrete contained in a layer of pavers on the outer of rim of the stand. I have since drilled holes in the slab to let any water out as this method gives you the swimming pool effect. I would alway recommend if you use hebel its a secondary insulation use a layer of say pearlite-Crete to temper the higher temps.
I know I've had 3 good years use out of 2 ins of hebel and full thickness firebrick but it could come down to the way I use the oven. I would call myself a moderate user I have never pushed out more than 20 pizza at one firing. Heat holding ability seems to be the same as most ovens and I have brought it back up to pizza temp on the Sunday with an hour burn after a Friday pizza night on more than 1 occasion.
Regards dave

wotavidone 12-20-2013 05:25 AM

Re: New Build in South Oz
 
Dropped in to see the mate tonight, and there is a pallet of Hebel blocks. 600mm by 200mm by 150mm thick. Imperial would be just under 24 by 8 by 6 inches.
70 blocks. This stuff really is the ducks nuts I reckon. Looking at a chipped corner, it is just thousands of tiny bubbles.
It's kinda fun being able to take a block that big and lift it with ease.
Well, the decision has been made. The oven will sit on 6 inches of aerated concrete.
I'm confident they'll take the heat under a layer of 3 inch bricks. I know they are made with portland cement, but so is vermicrete.
Dave, do you take your oven to fully white, 90 second pizza territory?

UtahBeehiver 12-20-2013 06:38 AM

Re: New Build in South Oz
 
Just saw this post about super duty, my floor thickness is 3" with 2.5" of Foamglas and 1.5" of CaSi board underneath. I don't have a comparison on performance of heating of regular duty vs superduty but I can comment on the super duty are much harder to cut. But in the case of a floor, the number of cuts will be a lot less than the dome. That said, base on what I observe from other WFO builders wood usage to fire is similar. Once the brick is saturated it get at least 3-4 days of cooking (pizza, then bread,then roasts, etc, much more than I have time to do.

wotavidone 12-20-2013 01:40 PM

Re: New Build in South Oz
 
Found the template I used to make the outer arch of my oven, I'm looking at 18.5 inches wide, 11 inches high.
I'm thinking that would be a pretty good inner arch/entry size for a general purpose oven? i.e. a high dome Pompeii whose owner will probably do more roasts than pizza evenings.
We are having much discussion about whether the floor should be inside the dome bricks or underneath.
I reckon we can do whatever he likes best, but it does depend a little on how easy his bricks are to cut. I've brought one home to see how easy it is to cut.
Also, my mate likes the trapezoidal bricks on edge like I did, making a thinner dome and much smaller mortar gaps. It would still be at least three inches thick since that's how thick his bricks are.
However, my mate hardly mentions pizza. It's definitely a roasting and baking oven. Maybe a little more thermal mass is in order?
It would certainly mean a lot less cuts if we just went with half bricks. We can get two trapezoids out of one brick using 3 cuts. But half bricks are only one cut:)
What to do, what to do.:confused:

wotavidone 01-01-2014 04:01 AM

Re: New Build in South Oz
 
Progress, even with blistering heat and New Year interfering.
My mate built the stand and laid the 6 inch/150mm thick Hebel insulating layer.
Since Sunday arvo, we've built an arch and a rough IT, laid two courses of brick and installed a floor cut to fit inside the dome. The floor took a while, as he had his heart set on a herringbone pattern. The bricks are not bedded at all, since he has his eye on some other floor material and wants it to be easy to replace the floor with the other stuff.
I'm reasonably happy with the rate of progress. We could be going a little faster, but there are several guys mixed up with this build who've never built an oven or even thought about how to, and courtesy demands explanations as we go along.
For instance, my preference is to use the IT as I really like the accurate placement of bricks. With being able to fully load the joints with mortar that squeezes out in all directions, ensuring the joint has no gaps, and then having ease of access for cleaning the inside face of the brick as we go, I reckon it's the best way to go.
So I have to explain why I like it better than laying the bricks on a sand dome or an inflated exercise ball, etc.
It's all part of the fun, and many a Southwark has lubricated the conversations. His wife is a truly tolerant woman.
(Southwark is a beer than only a South Aussie raised on the stuff, or a maybe a Broken Hill boy of a certain generation, could enjoy. Hint: its nickname back in the day was "Green Death".)
Once I demonstrated the IT today, I believe I have made a couple of converts.
My poor mate did comment today that he hadn't realised that "I'll give you a hand to build an oven" really meant "Stay out of the bloody way and don't touch anything." :D
Really I sorta had to do it, because there was so many opinions flying around on how to do certain things that we were in danger of doing bugger all. So I decided to be "project leader".
I promised him he could lay a brick tomorrow.:D

wotavidone 01-01-2014 04:24 AM

Re: New Build in South Oz
 
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