#11  
Old 01-18-2010, 01:11 PM
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Default Re: Perlite Concrete on free form igloo

Marty,
A mixture of vermiculite and cement, 10:1 will work well as insulation around the flue tiles, then you have something to stucco against. It is slightly flexible and works well as a thermal expansion layer.
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  #12  
Old 01-18-2010, 02:00 PM
Peasant
 
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Default Re: Perlite Concrete on free form igloo

Hey Marty, cool looking flue work, I was wondering how big the oven is and if is was build partially into the brickwall behind it ? As far as the fluejoints go you could wrap the pipe in regular metal hardware screen, like the type for windows, and skim coat the flues with a portland, fireclay and sand mix. a little extra protection and even insulate after that. And then your adobe brick, did you make those?
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Old 01-18-2010, 06:51 PM
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Default Re: Perlite Concrete on free form igloo

I'm thinking you may want to mound up some vermiculite concrete under that chimney to give it better support, instead of the occasional brick. I don't see any reason you couldn't use the fiberglass mesh that's used to bind sheets of cement board on your joints, with refractory mortar, of course. That's not normally done, but it's normally laid close to vertical.
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  #14  
Old 01-18-2010, 07:27 PM
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Default Re: Perlite Concrete on free form igloo

That looks to be a little over the maximum recommended 30 degree offset. If nothing else, you should add a good vertical stack at the other end to help with draw. As well, you should keep it very clean to prevent a flue fire.
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  #15  
Old 01-18-2010, 09:43 PM
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Default Re: Perlite Concrete on free form igloo

1. The flue angle is under the recommended angle of 30 deg--closer to 45. I was constrained by the location of the existing chimney and a concrete bond beam that goes around it. As we've made a bigger fire today there was some smoke escaping out the front. Not much, but more than is acceptable. The vertical stack currently is about 7'. I am going to add to that and see if it takes care of it. If not I may try opening the throat a little wider. Its about 2 inches narrower side to side that the flue liner on top of it. I am also thinking the unsealed joints in the chimney may be impacting the draft.

2. I plan do plan on supporting the chimney as suggested with perlite cement after I get the kinks worked out. I am a little concerned about resting all the weigh on the oven because of anticipated movement of both the oven and the flue.

3. I put a match to some fiberglass tape used for cement board and it burned readily. I don't know that the chimney would ever get as hot as an open flame, but I would rather find something that could take the heat better. Hardware cloth may be the ticket as you suggested, John.

3. The oven is 36" dia and it does recess into the adobe wall. I insulated between the adobe and the fire brick with about 3 inches of mineral wool filling the gaps with loose perlite. The adobe bricks were site made by my wife and I and anyone else we could persuade to help. 10,000 in all over 2 summers.

We are hoping to get it hot enough to cook in by the weekend. Thanks to all of you for your interest and suggestions.
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Old 01-19-2010, 01:43 PM
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Default Re: Perlite Concrete on free form igloo

Please do keep us updated on this! I know your chimney R&D will be helpful to more than a few members, and the subject of indoor WFO's seems to be getting a ton of action lately on several threads.
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  #17  
Old 01-19-2010, 08:40 PM
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Default Chimney throat adjustment

After last nights smoke leaking I was a little disappointed. I finally decided to open up the throat a little as shown in the pictures. It seemed that most of the smoke was leaking past the throat on the sides. I cut the throat to curve from the edge of the oven opening up to match the width of the flue liner. A little dusty for an inside job and unfortunately I nicked a few bricks with the grinder wheel, but I did manage to get a nice curve. I loosely put the chimney back together, temporarily taped the joints with aluminum tape and built fire number 4. Not a lick of smoke leaked this time. I plan to keep the chimney in its temporary unmortared state until the curing process is done and I have seen enough fire conditions to be sure the chimney is working up to expectations.
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  #18  
Old 01-20-2010, 01:02 AM
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Thumbs up Re: Perlite Concrete on free form igloo

Marty,
another possible solution if you continue to get smoke out of your front archway is to make a door or even a blind to fill the top half of the opening thus making it harder for the smoke to escape with the rush of air into the oven. A top half door will also force the smoke up your generous flue.


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Old 01-20-2010, 05:43 AM
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Default Re: Perlite Concrete on free form igloo

You might also consider a draft door to channel air and smoke on startup. Your oven is unlikely to leak smoke once the fire's going.
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Old 01-20-2010, 05:54 AM
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Default Re: Perlite Concrete on free form igloo

I plan on making the front arch 2" lower than the inner arch to help with the smoke leaking. It appears yours are the same height?
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