#11  
Old 03-24-2010, 03:33 AM
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Default Re: Chimney Size and Design

Placing the flue at the back and the bottom sounds rather like a downdraft kiln set up. I think that this would work extremely well once you got the thing up to about 350 C, but below that I think you would have trouble with smoke deciding that it would prefer to exit out the front door. I am certain someone would have tried this and found it didn't work well. You have to get a really god draft happening to draw a flame downwards. Wood as a fuel also easily provides an excess of fuel leading to unburnt fuel (smoke) The idea of having a flue somewhere other than at the front is attractive because of the flue creating xtra problems of reaching into the oven.
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  #12  
Old 03-24-2010, 05:33 AM
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Default Re: Chimney Size and Design

Thanks. This is the kind of information I needed. Will crunch a calculation today and see how it looks. May have to rebuild the chimney exit and use larger pipe. Will let you know. Best, Lloyd
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Old 03-24-2010, 10:40 AM
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Default Re: Chimney Size and Design

I checked the numbers. The opening is 204.25 sq inches which means I need 20.43 sq inches of flu (10%). The 5 inch pipe is 19.63 sq inches. It will be close, but should work. The pipe is enroute in the Atlantic on a ship and should be here within a couple of weeks. I will install and give you a report. Thanks again to all that responded to my questions. Lloyd
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  #14  
Old 05-21-2010, 08:47 AM
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Default Re: Chimney Size and Design

Wanted to let you know that I finished repairing the chimney. It now goes through the patio ceiling and roof and is about 12 feet long. It draws well and smoke goes where it should! It was quite a job cleaning off all the soot and smoke from the patio walls and ceiling and then repainting it. The 5 inch pipe is working so will not have to change to 6 inch. Thanks for all your input. Here is link to photos of the repair:

Wood Fired Oven Project - Chimney Repair

Lloyd
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Old 05-24-2010, 06:39 AM
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Default Re: Chimney Size and Design

Beautiful pictures, love the dome and arch combination.
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Old 05-24-2010, 11:41 AM
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Default Re: Chimney Size and Design

Thanks for your kind comment. We like the arches and how the oven fits into the design. Best, Lloyd
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Old 06-08-2010, 09:55 AM
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Default Re: Chimney Size and Design

I'm about to cast a vent similar to Lloyd's pictured above and I have a couple of questions:

Can I place a rebar across the length of the lip of the vent for reinforcement as my vent will only be supported at the two ends and will span across with no other support underneath? Will the rebar expand at the same rate as the castable refractory?

The roof of the vent will be cast around a 7" diameter 22 gauge stove pipe. Will the pipe expand enough in diameter to crack the vent? Should I leave a little wiggle room?

Thanks...George
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Old 06-08-2010, 10:17 AM
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Default Re: Chimney Size and Design

I don't think rebar is used in refractory castable. Stainless needles are the reinforcement of choice.
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Old 06-08-2010, 10:23 AM
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Default Re: Chimney Size and Design

Quote:
Originally Posted by dmun View Post
I don't think rebar is used in refractory castable. Stainless needles are the reinforcement of choice.
I kinda figured that as I have not seen rebars used in any of the cast oven builds.
Are stainless needles commonly available? I've seen them on Ebay before.

George
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  #20  
Old 06-08-2010, 12:51 PM
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Default Re: Chimney Size and Design

George,
If you cast directly against the flue pipe it will get hot first and expand and perhaps cause the castable to crack. This happened to the second oven I built. You can wrap some cardboard around the pipe when you cast it, remove the cardboard and pipe, then reinsert the pipe and fill around it with vermicrete. It is better for the flue to bea slightly loose fit to reduce stress on your casting.
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