#11  
Old 09-04-2008, 10:17 AM
jengineer's Avatar
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Default Re: Hello from Oklahoma

I shot a note off to CanuckJim as he is our resident bread baker. What I would like is some of our other builders to chime in on this discussion. This thread may get better reception over on the Pompeii Oven Construction section...

As for the splitting the floor I don't think anyone has done that. You would be forcing heat quicker into your insulating layer and if the insulating layer is not up to the challenge then you are heating up base and sand. Since the dome is resting on the floor you will have a dickens of a time getting the edge floor pieces out - it would require a bit of contorsion to get a cutting wheel in there to cut out the perimeter. So how about adding insulating where you can?

Hre is where I need others to chime in!

I am assuming you did not cement in your floor and you have more firebriack available. Pull up the full floor bricks where possible. Trim out the partials where it is not too tough. Add in the cement-pearlite insulation up to the level of a full brick. Relay the floor. This poses one slight problem and theat is the entrance way. If you use a full brick then your entrance has just gotten lower in height. At the section of the dome that makes up the entrance slice your bricks at an angle so that you maintain the full original height but it ramps up once you are inside the dome cavity. Since you are not too far up in your courses you can agjust the rest of the dome to maintain the original interior height.

OK forum member what do you think?

Modify the dome to get more insultiion under hte floor or bag it and build it as originally planned - after all sourcing wood for the oven is not a problem.

je
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  #12  
Old 09-04-2008, 10:18 AM
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Default Re: Hello from Oklahoma

I'd really have to second what je says about base insulation. Although it might seem like a massive amount of (re)work and mess, you simply won't get proper retained heat performance from your oven without under floor insulation, and lots of it. The trick is to isolate the hearth from surrounding masonry materials with some sort of insulation band. As well, if possible, you could retrofit high heat unsulation board UNDERNEATH whatever layers you've already done, but only once the oven is definitely dry and cured and fired (several months).

You may have forty acres of forest, but my guess is you'll be cutting down the shrubs around the house when that runs out.

The trick with retained heat baking is just that--retention. Without sufficient underhearth insulation your heat drop off curve will be very steep, and you won't be able to get multiple bakes out of one firing. Just maybe, depending, you'll find the temp drops to fast during just one bake, with the resultant loss of volume and good crumb.

This remains true even if you plan for tons of insulation on the dome. After all, it is the hearth on which the baking is done. Insulating one part and not another will not work.

Really, I know it's a pain, but do the insulation now. You won't regret it.

Jim
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Last edited by CanuckJim; 09-04-2008 at 10:20 AM. Reason: Incomplete
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  #13  
Old 09-04-2008, 10:42 AM
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Default Re: Hello from Oklahoma

Here's a suggestion that might save you alot of work and get you cooking with less fuss than tearing up the whole floor.

It looks like you used clean sand for your slab support. And from the detailed photos you should be able to locate the positions of the rebar in the slab.

Bore several 2 " diameter holes thru your floor in locations where you will miss the rebar. Use carbide hole saws and a heavy duty right angle drill like they use to bore holes in studs for wiring a home. These drills usually can be rented the hole saws themselves will be junk when finished with this and you may go thru several.

Now comes the fun part: Break up the sand using rods and vaccum out the sand using a shop vac. You might try building a nozzle much like a suction dredge, wherein you would take a piece of 1 1/2 inch PVC pipe and bore a hole in the side to accommodate a piece of copper tubing. Bend the copper so it is centered in the PVC and extends slightly below the bottom end of the pipe. Then flare and attach an air line to the copper tube outside the side the PVC pipe. Attach the 1 1/2 inch pvc pipe to a suction line of a shop vac and suck the sand out. The air breaks up the sand and the vaccum sucks it out. You might have to get creative with bent rods to break up the sand. Once you get two holes connected the job should go quicker as you could force air in one hole (using bent copper tubing for the angled end) and suck sand out the other.

Sounds a bit harebrained perhaps but I would try it before ripping up the whole floor as that would be hard to do without tearing up the oven.

I would suggest starting with a empty vaccum and keep track of how much sand you remove. But when you get the sand out refill the space with loose vermiculite or perlite. You do have the column in the center that still will act a a heat sink but that would be a lot less than what you have at present. If you get most of the sand out you will have quite a bit of insulation beneath the hearth. Plug holes and cook.
Wiley
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  #14  
Old 09-04-2008, 10:49 AM
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Default Re: Hello from Oklahoma

Second thought and easier: Cut a hole in the outside (six by six inches or better) and get the sand out. Patch hole, you are using river rock knock so out a large one in the back where it won't be seen or a noticeable and close hole with a similar sized rock. Bore single hole in top and fill with vermiculite or perlite.
Wiley
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  #15  
Old 09-04-2008, 10:57 AM
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Default Re: Hello from Oklahoma

Hey Wiley - I like that idea. His base has lots of rebar and should hold up nicely. He also put in a centre column so there is little chance of any movement. Since this oven is for retained heat it woulde be fine to have that mass of the base heat up. There will be heat loss around it if it is not insulated but at least you now have a solution to getting the floor insulated properly.

Pat - CanuckJim made an Alan Scott bake oven which has insulation under the concrete floor for a mssive heat. The set up there is insulation stuctural concrete which is a heat sink and then firebrick. After he got the oven up and running Jim found out that he was losing heat from his insulation layer and he had to engineer more insulation under the oven. Wiley is doing that with his suggestion. You will still have areas of the oven that may not be insulated but the majorbad actor has been mitigated.

je

Last edited by jengineer; 09-04-2008 at 04:24 PM.
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  #16  
Old 10-20-2008, 04:23 PM
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Join Date: Aug 2008
Location: NSB Florida
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Default Re: Hello from Oklahoma

LOVE the rubber ball you used to form your ceiling - A+ creative patngayle.
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  #17  
Old 10-20-2008, 07:53 PM
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Default Re: Hello from Oklahoma

Welcome .
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