If there's too much weight on the arch the sideways thrust on could make it fail. The remedy is to support it with buttressing. The question is how much weight is too much? At a guess I'd say you'd probably be quite safe with two rows of bricks on top of the arch.
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42" Pompeii construction in Adelaide
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Thanks David S and thanks for the earlier comments Russell. David, I agree that two rows seems like it would be ok but who really knows. I’ve confirmed the weight of 50 kg or around 110 lbs. the question is would the extra weight help keep it all stable or exacerbate any cracks/ movement, hard to tell.
Russell, the cuts have been fairly straight forward after seeing what others have done. I’ve actually enjoyed forming the arch, the dome was also good to do but took quite a while.
Additionally can anyone advise, for a fairly standard 42 inch oven, is there any advantage in going for a 10 inch flue over an 8 inch, and being fully outside, is double skin recommended?
many thanks.Adelaide, Australia.
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Since you have a full arch, the outward pressure will be more vertical than horizontal. I have a set up similar to what you are talking about with no buttressing. 8" ID double wall is just fine for a 42" Double wall reduces the outer temp considerably and more for safety issues than performance issues.
Russell
Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]
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I can’t entirely agree with you Russell re the double flue. As the stainless is expensive a double flue raises the cost considerably. Of course if it penetrates a roof and is anywhere near timber you need to go double or even triple, but if it’s outdoors then it’s not necessary. The location of the flue is well out of the way to be a danger for little kids to touch. The flue’s only purpose is to keep the smoke out of your face. In fact the oven would work just as well if it had no flue as some cob ovens operate this way.Kindled with zeal and fired with passion.
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David brings up good points so it depends on your situation. I do recall that it is more difficult to get double wall SS in Australia and many builders have had to import in from the US.Russell
Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]
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No it’s easy enough to get double wall here. I’ve done a couple of ovens with double wall but used standard coated steel (Colourbond) for the outer pipe, inner one stainless. You just need a cowl at the top that is made to take the two different diameters. I also stuff some insulating blanket between the two pipes for the first foot or so of pipe height.Kindled with zeal and fired with passion.
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Originally posted by P3 Stoaker View PostG'day All, thought I'd post a few picks as the pics others have posted have been a great help throughout planning each stage of my build. Going slow but still progressing.
RegardsMy 42" build: https://community.fornobravo.com/for...ld-new-zealand
My oven drawings: My oven drawings - Forno Bravo Forum: The Wood-Fired Oven Community
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Originally posted by P3 Stoaker View PostGday all. Has anyone ever considered the weight of the bricks added on top of the entry arch so as to form part of the fluing? Initially I planned to cut curves to form a flat top, which I’ll still do but I was going with one more layer on that before installing the metal flue. I haven’t actually weighed the bricks but that could add to nearly 50 kg, or even more around 110 lbs.
Appreciate any thoughts or experiences.
Regards
Greg.
My 42" build: https://community.fornobravo.com/for...ld-new-zealand
My oven drawings: My oven drawings - Forno Bravo Forum: The Wood-Fired Oven Community
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G'day All,
Russell, David S and Mark, many thanks for the comments and advice, greatly appreciated.
I've cut some full bricks so as to form a flat surface. They will convert from the rectangle shape, wider than needed to a round shape about 1.25 inch greater diameter than the 8 inch i eventually want, and the next layer will reduce down to correct flue size. Not sure if it would have been an issue but I didn't want flat horizontal spots in the vent brick work where exhaust would tend to slow or be trapped. Probably an overkill but bow it will smoothly transition from rectangle to 8 inch. Photo's to follow. in the end around 100 lbs.
Regards
GregAdelaide, Australia.
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G’day all
can anyone tell me what a typical thickness of render might be for rendering a vent arch? My thought is for the upper horizontal layer of the vent brickwork to over hang ???5-10 mm (quarter inch ) or so to accomodate the thickness of the render.
Im going for 2 inch of blanket over the dome, then 2 inch vermiculite over that with render then over the the lot including the vent/arch brickwork. I understand there is no need to insulate the vent brickwork.
Thanks in advance.
Regards
Greg.Adelaide, Australia.
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G'day All,
Previous post questioned typical render thickness. I ended up going with about 10mm (1/2 in) for the top layer of the vent, photo no 1.
Not sure if it was a huge overkill but I wanted the vent brickwork to transition from the rectangle, in the actual arch to round by the top of the vent brickwork. I will be covering the top with a stainless plate, sides turned down around the edge and a riser welded to the plate that the flue can sit over. The oven is outside so any water running down the flue will be directed away and not end up on the vent floor. The relatively smooth transition from rectangle to round should encourage the exhaust UP, with any luck. I wasn't sure if the top stainless plate was over a larger rectangle with an 8 inch exhaust hole in the middle, if the exhaust would cavitate or circulate and resist heading where I want it to?
Thanks again for all the assistance and idea's, lots of those in place as seen below.
Kind Regards
GregAdelaide, Australia.
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G'day All,
Well the time is near and I've read up on curing fires. I plan to run the series from around 100 deg f through to about 700 deg f from memory before I insulate the dome. That will allow me to see the cracking and address/repair area's if needed. I'll then run a few more fires and eventually insulate, 2 inch blanket and 2 inch perlite.
One question for the wisdom of the forum, I read conflicting approaches to the duration of each fire. Some say get to the target temp and let it burn out/cool, whereas others say to keep that target temp for a while, presumably a few hours if possible.
Interested in your thoughts/recommendations.
Kind Regards
GregAdelaide, Australia.
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WOW - a guy takes a hiatus from the forum and comes back to AMAZING work!! Greg - you're work is EXQUISITE!!! The cuts, the build, the thinking - and THANK YOU for sharing the pics and questions - you are helping us all so much. Grateful for your build questions here - when we get out of the winter and I'm back to building - I will be at the vent arch stage and this work here will help immensely!!
Wondering about the notches you cut in the brick? Is it to provide more hold when mortaring?
As for firing - I've seen many schools of thought - blanket and burn and others being burn - then blanket - then finish burn (as you suggest).
Given the purpose is to cure and release moisture as well - I think your approach will work ... and like your build and Russell's advice to EVERYONE that starts their cures: GO SLOW! Small fires, slow and steady over time.
Honestly - Happy for you mate! Great stuff!
YOU GOT THIS!!!
BarryYou are welcome to visit my build HERE
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G'day Barry,
Many thanks for your comments. I've quite enjoyed design and build of the entry, much more than the dome. The cutting was really quite straight forward and I did what I could on the petrol saw but its quite old, vibrates a lot, moving the work and the table isn't all that accurate, but it worked well as a bit here and there doesn't matter. I also cut a lot freehand and dry with a 5 inch.
The grooves are as you say, my attempt to get things to hold together a little better. I figure even if the hairline cracks appear, as expected, the grooves might help to keep it all in place. I figured probably couldn't hurt ??
Please keep in touch and sing out with any questions.
Kind regards
GregAdelaide, Australia.
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