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-   -   Thoughts on a Centered Chimney (http://www.fornobravo.com/forum/f9/thoughts-centered-chimney-5809.html)

leemc 12-19-2008 10:13 AM

Thoughts on a Centered Chimney
 
I have started my WFO and my plan is to do a chimney centered on the dome similar to the oven used by Jamie Oliver on his cooking show. You can see the progress pictures of my oven and a discussion of the centered chimney on the forum under Brick Oven Photos the Florida Igloo project.

Anyway I found some pictures of the Jamie Oliver build on the internet here:

Jamie Olivers Project

When you look at the pictures it looks like they have built some sort of flat structure over the inner dome to support the chimney - at least that's my guess. It started me thinking - should I do some type of reinforcement of the dome to support the weight of the chimney? My plan for the insulation is to do 2" of ceramic batt and 2'-3" of vermiculite concrete over that. I could do a solid layer of vermiculite concrete just over the crown of the dome - with no batts underneath -to spread the load of the chimney. Anybody have any thoughts? How much weight will that inner dome support?

Lee

dmun 12-19-2008 03:39 PM

Re: Thoughts on a Centered Chimney
 
I would think a layer of vermiculite concrete would be enough to support a light-weight chimney, one of the pre-fab stainless numbers. Your Avatar shows something that looks like a centered brick chimney, which I would think would need more support.

I built a cast reinforced concrete bridge over my dome to support the weight of my chimney, but that was a two-story two flue extravaganza.

Why not use the bottle kiln idea, where the exterior brick structure tapers upward to a centered chimney, if you want to use brick?

http://www.plu.edu/~vanwyhga/gladsto...tle%20oven.jpg
http://www.thepotteries.org/photos/b...igh/bottle.jpg

james 12-19-2008 03:53 PM

Re: Thoughts on a Centered Chimney
 
I really like the look of the centered chimney as well -- heck, I have one (though it's a walled stucco enclosure, not a brick igloo). Your oven dome will easily carry any weight from the chimney. I can picture that this is going to look very nice.
James

sarah h 12-19-2008 04:24 PM

Re: Thoughts on a Centered Chimney
 
Just want to be sure you are aware that Jamie Oliver's vent is still at the mouth of the oven (evident in photo jo_12). The ductwork curves up and back to route the chimney around to the centre of the dome, and then up - I wouldn't want to see you vent it from the centre by mistake! :eek:

leemc 12-20-2008 07:49 AM

Re: Thoughts on a Centered Chimney
 
Sarah

Yes I would still vent at the arch and run the chimney back at an angle to the center of the dome.

Dmun

I think the bottle might get the oven too big. I am already getting heat from my better half that it's going to be too big.

I think what I might end up doing is try to reinforce the dome on the outside some how before insulating. I have some thoughts on what to do but can't think of a good way to describe it. Build like a arched cross or X shaped band of reinforced concrete over the top of the inner dome and then a solid layer of vermiculite concrete just under where the chimney will be. I think James is right that the dome will hold the weight of the chimney without any reinforcing but what a disaster it would be if it didn't.

Lee

Riva-t 02-20-2009 12:55 PM

Re: Thoughts on a Centered Chimney
 
Hi
Just a thought. The inside dome is self suporting because of it's shape, the exterior is the same(metal, stucco etc). If the insulation between, surrounding the flu is loose and the flu is standard ss ducts and bends and is suported at the arch and at the exterior dome, then the suport on the interior dome, as long as it's not fixed to the flu is basically just a sliding suport and not taking a lot of stress.???

Cheers

arevalo53anos 02-20-2009 03:29 PM

Re: Thoughts on a Centered Chimney
 
Lee:
The spherical structure of the dome is the strongest one, hence, I am sure that the chimney will be supported without any problems.
The gases flux along the chimney will be better if it is cylindrical and installed directly straight up.
If the chimney has another shape than cylindrical, there will be turbulence points or sectors that lean to disturbance and poor gases flux.
If the installation is not straight, the angles in the chimney will be at least of 120 degrees.
The gases exhaustion will be stronger when the chimney will be hot.
If the chimney is running over the dome, it will be convenient to run directly over it, to better utilization of the heat that came from the flares down the bricks. No isolation in between.
Good work.
Luis


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