#1  
Old 03-21-2005, 01:25 PM
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Default Pompeii oven vent design

hi everybody,

since i just finished the dome this last saturday, i myself too, feel
that i am done building my breadoven and are now able to start
cooking......
it took me much longer than i had thought, but i know every bit was
worth it at the end. knowing that i am a bit of a perfectionist, i do
intend to finish most of it this year however, not letting myself
getting used to the idea that i can use it just like that.

i have another question however, concerning the vent and chimney?
can i get the steel vent and flue at home depot or do i have to get it
custom made? i know some of you just did it yourselfs, cutting steel
and welding it together. it looks easy enough, but i don't know how to
welt yet. (learning to weld is a project for some other time).
would a chimney of 2 feet lenght be enough or would 3 feet be better? i
am intending on using a 8inch steel round chimney.
also, can i use the same portland/fireclay/sand mix to cement the steel
vent & chimney in?
has anyone some piece of advise? what i should avoid?

any advise is very much appreciated!

thanks to all of you to get me so far

simone
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  #2  
Old 03-21-2005, 01:31 PM
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beautiful job (and child) simone.*i really love the circular base. my two cents:

i pondered long and hard about the vent. i really wanted a cantilevered vent but it just wasn't in the cards.**a cantilevered *vent allows a greater working angle from the left and right when placing the peel in and makes the oven more attractive as an outdoor fireplace because it allows a wider angle of fire viewing.*but i didn't see any way to attach*a cantilevered vent hood*to the oven and still have the strength to hold up the weight of the hood, chimney, mortar and insulation. i toyed with the idea of pouring two solid concrete pillars on either side of the opening**to be used to hold*the vent hood and provide chimney support but chickened out.

in the end i went with the traditional "mouth" of bricks holding up the chimney. it was just cobbled together (i'm more impatient and not much of a perfectionist). *i used plain heating duct parts from home depo. i'm certain that in a few years i'm going to have to make repairs to the vent portion because with the thin metal, the heat will just burn right thru it. i think i can get three years from the existing vent hood. at that time i'm going to more seriously reconsider the concrete post support idea. the chimney, itself on my oven is removable so that's not a problem. after it deteriorates i will just get a new pipe and insert it in the "chimney slot".*

the taller the chimney the better in my opinion. although the area occupied by your oven looks well sheltered i would still think that 3 feet would be a minimum.*its really helpful in keeping the smoke out of your face and the taller height seems to increase the draw. is that a eucalyptus tree in the background? a spark arrester is going to be vital!

i went the 8 inch chimney diameter route but the throat of my chimney where the chimney hits the hood is a little constricted by mortar so i have a fair amount of smoke that comes out the front opening. i think that without the constriction, and with a relatively tall chimney the 8 inches would have been ok.

my pictures are at <http://www.cpsusa.com/ebay/pompeiioven.htm>www.cpsusa.com/ebay/pompeiioven.htm
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  #3  
Old 03-21-2005, 01:42 PM
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i just posted 2 pictures in the yahoogroup photo section.
> thanks so much for your helpful input.
> i will check out home depot today....
> more questions later.
>
> thanks again
> simone

Very nice. I like the round base.

Looks like you won't have a problem getting the chimney installed. You
can corbel the bricks from the side pillars you have until you close
in enough to support the chimney pipe. (Corbelling is done by stacking
the bricks on top of each other offset by about a 1/3 of the brick
width on each row as you go up.)

Keep the very front opening a tad larger than the oven side. That will
let you make a 1 piece door that will still be able to fit in.
Otherwise you have to finagle to get it in diagonally or you need a 2
piece overlapping door to seal off the oven when you're ready for bread.

Jim
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  #4  
Old 03-21-2005, 01:44 PM
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Jim will remember these pictures.

I just posted a handful of the photos that Jim and I used when he was
building the first oven. It's a professionally made brick oven that a
neighbor just bought (that he is rightfully proud of).

Simone, the photos show both the oven opening and vent landing, which
might be helpful visualizing your design. It also shows some very
nice dome brick work.

There are 7 photos, starting here. If you want higher resolution
pictures, you can email me:

http://www.fornobravo.com/pizza_oven...ens/Colle.html

I think there are two ways of going about the vent and vent landing.
You can either attach the vent to the oven enclosure wall, and leave
the landing complete open, or you can build brick sides to the
landing, and rest the vent on the vent landing walls. There are
pluses and minuses to both. The open plan give you more landing
space, might be a little harder to install and might not draw as
well. The closed plans gives you a more constricted landing, but is
easier and draws well.

The vent walls are built into the prefabricated ovens.

I will post a new page on the Pomepeii plans with a couple of line
draws showing the two styles.

James
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  #5  
Old 03-21-2005, 01:48 PM
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hi jim

if i corbel the bricks in from the 2 supporting walls, the front arch and inner arch, would that do instead of a metal vent?
how about the 'terraced' look from the inside of the ventlike structure? would that possibley change the airflow and weaken the draft?

also, if i can avoid the steel vent and built it from brick instead, i might just get a terra cotta round or rectangle pipe for the chimney on top of it.

i have no experiences with airflow and drafts at all and would like to be sure whatever vent/chimney structure i am building will work very well, so i am not ending up having smoke coming out the front arch. i understand that for my 36inch dome a 8inch chimney pipe is o.k., but would a 10inch pipe give me a even better draft or does that not matter one way or the other.....

thanks for your time and advise
simone
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  #6  
Old 03-21-2005, 01:51 PM
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if i corbel the bricks in from the 2 supporting walls, the front arch
> and inner arch, would that do instead of a metal vent?

### Yep. The corbelled brick act as the vent.

> how about the 'terraced' look from the inside of the ventlike
> structure? would that possibley change the airflow and weaken the
> draft?

### Not substantially. The thing with these ovens is that they are
burning so hot that the draft gases are very very hot. They want to go
up. Corbelled flues have been used for a long time in fireplaces
without real issue as well. But, that's also one reason I suggested
the 8" pipe instead of the 6" pipe. The flue capacity will pull the
draft gases up. Also, when you fire it, start the fire at the front of
the oven just behind the flue. This will help warm the stack (in fact
you could start it right under the chimney). Then as you add larger
pieces of wood you push the whole thing back into the center of the
oven. By the time you have the largest pieces on it'll be in the
center and the chimney will be drawing it right out. Oh, and if it's
windy where you are, add another foot to the height of the chimney to
help reduce any downdraft.

>
> also, if i can avoid the steel vent and built it from brick instead, i
> might just get a terra cotta round or rectangle pipe for the chimney on
> top of it.

### That's a good idea. The standard clay/terra cotta flue sections
just sit right on top of the brick then. Don't mortar it together as
there are serious differences in thermal activity of both materials
and your flue will be cracked from the first fire.

>
> i have no experiences with airflow and drafts at all and would like to
> be sure whatever vent/chimney structure i am building will work very
> well, so i am not ending up having smoke coming out the front arch. i
> understand that for my 36inch dome a 8inch chimney pipe is o.k., but
> would a 10inch pipe give me a even better draft or does that not matter
> one way or the other.....

### There's a point of diminishing returns here. An extra foot or two
of height will have more effect than a bigger chimney. Also too big
and it won't draw well at all as there will be a hot column of air
surrounded by a much cooler layer. The 9x12 flue I used is actually
8x10ish inside dimensions.

jim
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