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-   -   Cast chimney cap? (http://www.fornobravo.com/forum/f9/cast-chimney-cap-18156.html)

couchpotatoe 07-31-2012 01:52 PM

Cast chimney cap?
 
I've got a question for the experienced masons out there. I want to cast a chimney cap for a 9" x 12" oval, clay flue chimney. I'm thinking it should be about 1.5 to 2 inches thick with sides that drop down a couple of inches all the way around to keep rain from blowing into the chimney. The sides would be spaced out about 1.5 inches from chimney itself and be about 1 inch thick. The bottom surface of the cap would sit about 1.5 inches above the flue pipe on crosspieces that extend into the sides that drop down. Hopefully, that will keep the rain out.

Anyway, what should this thing be cast out of to resist the heat from the oven? Would regular cement be OK, or would the temperature be too high? Would addition of fireclay or lime help? I was originally thinking of a 2:1 or 2.5:1 mixture of coarse sand to cement, with some colorant added to get close to the color of the flue/chimney.

Any advice on making a mold - one use only (hopefully)?

Thanks for your help.

david s 07-31-2012 08:34 PM

Re: Cast chimney cap?
 
Unless it is subjected to sustained flame impingement (you have way overloaded the chamber if you have flames out the top), you should be fine with normal concrete. However if it were mine I'd be throwing in some lime to help out.

couchpotatoe 08-01-2012 11:55 AM

Re: Cast chimney cap?
 
Thanks for your input David. Does anyone know how to proportion lime to cement to get the most heat resistant mix? And does anyone know if fireclay would do any good?

ATK406 11-08-2012 07:47 PM

Re: Cast chimney cap?
 
I'm also interested in casting my own chimney pot or cap. I've settled on a stainless steel cap for now. I would be interested to read anybody elses experience/recommendations on this subject...I still don't understand why "commercial" clay chimney pots are so expensive...seems like a simple design could be marketed for under $200 but everything I have seen runs $400 and up. Does FB offer anything (given their module WFO designs - maybe they could market a simple clay pot)?

david s 11-08-2012 11:13 PM

Re: Cast chimney cap?
 
3 Attachment(s)
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Two years ago we spent a week on the Greek island of Paros and among other things I noticed how varied their chimney caps were. Hardly any two were the same. Here are some pics of just one of them.I liked the simplicity and cleverness of this one.

ATK406 11-09-2012 06:07 PM

Re: Cast chimney cap?
 
Thanks for the pics. I'm surprised the cap isn't all sooted up - especially given its color. Anybody have any idea if a clay flower pot would work? Granted it would take alot of "customizing" to make it look like anything but a flower pot. I guess if you shopped around you might find something different...but I'm not sure it would hold up to the heat cycles. I sure wouldn't want to be standing underneath when it cracks and comes tumbling down from the top of the chimney. :eek: After building the oven, casting my own chimney pot can't be too hard right!

Les 11-09-2012 06:21 PM

Re: Cast chimney cap?
 
Quote:

Originally Posted by ATK406 (Post 141691)
I'm surprised the cap isn't all sooted up - especially given its color.

I agree. The lack of soot is impossible for any design. David - do you know if this was ever fired?

ATK406 11-10-2012 12:12 AM

Re: Cast chimney cap?
 
Hey I just found this on another web site :eek:...don't worry, this one is so much better! But it looks like somebody has already beaten me to the "cheaper" chimney pot....I think I'm cured....actually I think it's kind of cool....I'm such a scavenger!

david s 11-10-2012 12:32 AM

Re: Cast chimney cap?
 
3 Attachment(s)
Quote:

Originally Posted by Les (Post 141692)
I agree. The lack of soot is impossible for any design. David - do you know if this was ever fired?


I agree, It looks like its never been fired, you can see a steel inner flue pipe and it's also really clean. I was pretty busy enjoying the food and scenery at the time so didn't bother to investigate. Transport on the island is a bit slow.


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