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-   -   Thinner dome (http://www.fornobravo.com/forum/f8/thinner-dome-5515.html)

dlgeis 11-06-2008 05:33 PM

Thinner dome
 
Hi

I built a Scott medium oven 3 years ago and it is a wonderful piece but I have only used it 6+- times because it takes so long to fire and I simply don't have a need to bake 30 loaves at a time. The walls are 4 1/2 thick firebrick with 4" of concrete cladding and it is just too much mass for a couple of pizzas, 4 loaves of bread and the occasional turkey.

I have decided to either add a Pompeii 30" or tear my Scott down to the support and rebuild (it hurts but what good is an oven I never use).

My thought is that cutting the bricks in half like the plans show and placing them sideways so that the dome is only 2 1/4" thick would still give me plenty of mass, fire quickly, and reach very high temps while using just a little more than 1/2 the wood of the standard Pompeii.

Am I going too far the other direction or would this be enough mass to cook a couple of pizzas and/or one load of bread.

Doug G

nissanneill 11-06-2008 07:53 PM

Re: Thinner dome
 
Hi Doug and welcome to the forum,
I feel for you and your oven but it is not such a huge job to dis-assemble it provided the mortar is not bonded to the bricks like steel.
A few members have actually made their Pompeii ovens with third bricks rather than 1/4 bricks but there is no reason why you can't.
Do you have a rendered or an enclosure over your Scott oven?
The reason I ask is because once you build it and find that maybe you have gone a bit too far, you could always remove your insulation and add a little extra refractory mortar to increase your thermal mass.
I would think that your plan would be fine, it would heat up in around an hour, (mine is a 40" Pompeii with 4 1/2" thick dome and 3" thick hearth and heats up in around 1 1/2 to max 2 hours depending on how fierce I make the fire and I burn around a wheelbarrow of split red gum.
I can cook as many pizzas as I like because you keep the fire going albeit around the edges, scrape out the coals, let the oven cool, do a batch of bread, rolls and spicy fruit buns and then the evening roast.
Better to modify it and get the use fromit!

Neill

dlgeis 11-06-2008 09:03 PM

Re: Thinner dome
 
Neill

Thanks for your quick response.

I am actually thinking about using 1/2 bricks set sideways so the largest face is facing the inner/outer circle. I would of course cut wedges out for a close fit. I am concerned that such a wide face on a small base would not be stable enough and maybe using 1/3 or 1/4 bricks is a better idea but if it would work the 1/2 brick set sideways would build so much faster.

Doug

nissanneill 11-07-2008 01:07 AM

Re: Thinner dome
 
Doug,
provided you build your dome, whether semicircular or not will be structural stable IF you make the shape to fit a chain which you hang from each end, those ends at the width or diameter of your intended size and hanging down the depth that you intend to make your dome.
Get a sheet of ply and put 2 nails say an inch down from the horizontal top edge and 40"a apart if you plan on a 40" oven. Now adjust the length of the chain to hang down the same distance that your plan your dome height. If you want a semicircular dome, then it will need to be 20". If you only want a low dome of say 16", then reduce your chain droop to 16".
Draw a line around the chain shape. It is this shape that must run through the cross section of your dome brickwork to be sure that it will be self supporting and at it's maximum strength, irrespective of the dome thickness.
I would then draw a line that would run through the centre of the chain then cut the plywood along so that that line would be in the centre of your bricks. So, if you were to use 3" thick bricks, I would jig saw it 1 1/2" inside the line.
This then becomes your template for building your dome.
I hope this is not too confusing.

Neill

arevalo53anos 11-07-2008 03:49 AM

Re: Thinner dome
 
5 Attachment(s)
Half bricks with 2 inches of cladding will do the trick.
The one in pictures reachs the 900 F in 1 1/2 hours top and is on the 350/400 12 hours after end of fire.
See the vanes solution to build the dome.

FIREANDFLAMES 11-07-2008 06:18 AM

Re: Thinner dome
 
[QUOTE=dlgeis;44428]Neill

"I am actually thinking about using 1/2 bricks set sideways so the largest face is facing the inner/outer circle. I would of course cut wedges out for a close fit. I am concerned that such a wide face on a small base would not be stable enough and maybe using 1/3 or 1/4 bricks is a better idea but if it would work the 1/2 brick set sideways would build so much faster."

this is how i built my oven and it works great! also a lot less mass(wieght) and materials were used. i spent a whole day(morning till evening) slowly curing my oven and i did not get one crack.

dmun 11-07-2008 06:36 AM

Re: Thinner dome
 
I built my dome the thickness of the brick (2 1/4") and I'm not convinced it's worth the trouble. I used no exterior cladding and got quite a few cracks, none more than hairlines. It still takes me the same hour and three quarters or two hours to fire my oven as those with the 4" thickness.

I am now convinced that an arched structure should be thick enough to enclose the catenary curve which makes the strongest shaped dome, as shown on the first picture on the linked page. The thinner your dome, the more you depart from this ideal.

Just my opinion, but if I built another oven, it would be 4 inches thick.

Frances 11-07-2008 02:09 PM

Re: Thinner dome
 
I'm with dmun - if you look at those diagrams a 4" thick oven has many advantages. And they do work really well. I mean nothing against experimenting, but if you want an oven which you know will work, go with the regular plans.

james 11-07-2008 02:48 PM

Re: Thinner dome
 
Quote:

Originally Posted by dlgeis (Post 44411)
Hi

I built a Scott medium oven 3 years ago and it is a wonderful piece but I have only used it 6+- times because it takes so long to fire and I simply don't have a need to bake 30 loaves at a time. The walls are 4 1/2 thick firebrick with 4" of concrete cladding and it is just too much mass for a couple of pizzas, 4 loaves of bread and the occasional turkey.

I have decided to either add a Pompeii 30" or tear my Scott down to the support and rebuild (it hurts but what good is an oven I never use).

Doug G

Doug,

I can feel your pain. I went to dramatic lengths to deal with my Scott oven (also 9" in the dome) -- we moved. :eek:

Seriously though, if we had decided to stay in the house, I had resigned myself to taking it out.

After working with a lot of folks who have built the Pompeii Oven, plus lots and lots of folks who have installed FB oven kits -- along with our newly gained experience with the Primavera oven -- I don't think going thinner is a problem from an oven performance perspective. There is no doubt that thinner ovens hold more than enough heat for backyard baking.

I think the bigger question is construction and stability for the brick-by-brick oven. I would not go thinner for thinner sake, to where it becomes more difficult to actually build the dome.

Hope this is helpful.
James

dlgeis 11-09-2008 07:36 PM

Re: Thinner dome
 
Thanks for your advise it looks like the 4 1/2" thick dome with no cladding wins.

Doug


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