Bigger ovens

[JayP]

I am designing a pizza oven to be built on a rural community in south Western Australia. The oven is to serve community functions and the community is 15 households is size. We have no shortage of wood (indeed burning reduces the fire risk) or space and I would like to build a big one. Inspired by a photo of one in morocco I thought a 1.75m diameter cooking floor (three times the area recommended for a single household) would be big enough. I simply scaled the size recommended by Forno Bravo to get the following dimensions and will put the flue at the back to make the oven more accessible.

Internal diameter of oven- 1750
Internal height of oven - 650
Opening width - 790
Opening height - 460

Does anyone know much about bigger ovens? I suspect the Moroccan oven is a bread/baking oven, but hope that with insulation the oven will reach pizza cooking temperature and stay there with a decent size fire. Will it be able to do this?

Will try to post a cross section and photo of the Moroccan oven.

[Dutchoven]

Re: Bigger ovens

The size you are suggesting makes it about 68 inches diameter with about 25 inch high dome...most ovens here end in the 50 to 60 inch range but I don't see why this larger design wouldn't work...would take more would to heat up but as you said you have no shortage of fuel...my only concern is that the door opening height seems a bit high in relation to dome height...the ratio you mention is about 70% and most ovens are most efficient in the 63% range...so more like 415 door height...other than that I see no problem.
Best to you!
Dutch

[Ken524]

Re: Bigger ovens

That'll be a whopper! Can't wait to see the build!

[gjbingham]

Re: Bigger ovens

I'm not sure what the answer is for your specific case regarding the size. Larger makes sense to a point, but the oven will stay hot for a long time and multiple loads of bread and food can be cooked from a single firing.

I think you should do a lot of research to make sure that it will serve your communities needs. The Bread Builders, written by Daniel Wing and Alan Scott is an excellent resource and sounds like the type of ovens that you're looking for.

Canuk Jim will no doubt have an authoratative answer for you soon.

[dmun]

Re: Bigger ovens

Hi, Jay, and welcome to the forum. There is no problem with the size of the oven, particularly if it's used often, as a community oven and doesn't have to be started from cold every time.

I'm a litte concerned about the drawing you posted in the photo gallery:



This shows the flue exiting the dome at the back of the oven, instead of over the doorway. This is a really bad idea. Instead of having a circular path of the combustion gasses that heats the dome, all the heat you get from your fire will be sucked out the back. Also, if you do retained heat cooking, it will be impossible to keep it hot for any length of time with a big hole in the back.

I know you say that there's no shortage of fuel, but it's still work to cut and haul it, you might as well make the most of it.

[JayP]

Re: Bigger ovens

Managed to post a cross section and perspective of the oven and James said he would reduce the size of the Moroccan oven pic for me as it was a bit big.

Thanks for the feedback guys, no worries to bring the entrance it down to %63 (thanks Dutchoven). Yes the flue is at the back, I have seen this in pictures of commercial ovens. A factor I considered in the placement of the flue was that it was not above the height of the top of the door and that a damper can be fitted if the flue sucks to much (the flue is 2.5 to 3m). The oven will also have a wooden door that will control the amount air coming in.

Cheers

[james]

Re: Bigger ovens

I think a community oven is a great idea. It reaches back to a time when the oven was the center of the community for bread, cooking, and events; and the gatherings and the food will be great. We have talked about wood-fired ovens supporting community work before.

I would agree with the idea that you should build an oven where the vent is located outside the oven chamber, above the door. It will be easier to manage heat and temperature, it will be better a baking pizza, and more efficient with your wood.

From the perspective of dimensions, check out the FB Ristorante ovens. They go all the way up to 185 cm (nearly two meters). This type and size of oven is used throughout Italy to support large restaurants. My view is that these proportions will work well for both high-heat cooking, such as pizza, and for retained heat cooking, such as bread and roasts for the community. You are in good company here. These restaurants make pizza all day, and then bake bread the next morning.

Here is a link to the oven sizes. The drawings give you floor, dome height, door width and door height sizes.

http://www.fornobravo.com/commercial...orante185.html

Let us know how the project goes.

[Dutchoven]

Re: Bigger ovens

Jay
Just realized this when I read your last post, although you said it in the first I just didn't recognize it...about the flue in the back...I think you would have to make the opening to the flue at the 63% height and the door should be lower(I think) otherwise your exhaust gases will exit the door. I agree with Dmun and think you should use the door as the "exit" for the gases...you could then run the flue over the oven dome toward the center or the back...that could be the best of both worlds!!! I will try to render up a sketch for you tomorrow!
Dutch

[CanuckJim]

Re: Bigger ovens

Jay,

I built my own Alan Scott 4'x3', brick by brick, barrel vault oven for baking bread. From my experience with this build and also installing Forno Bravo ovens for customers, I would very strongly suggest that you completely scrap the idea of the flue placement at the back. This simply will not work with any efficiency. Making the oven more accessible is a misdirection; properly built these ovens do not smoke, and the facade of the chimney will only get warm to the touch. The whole point about these ovens is to get them hot and keep them hot. For a community oven, this would be crucial for people who want retained heat for bread, meats, casseroles. The design you suggest would guarantee, damper or not, that most of the heat would go right up the flue. Stick with the flue in the front model; it's been proven over centuries. True, for you fuel is not an issue, but how long are you willing to wait to get the oven up to heat? With a rear flue, you'll be stoking and waiting quite a bit; then add gathering and cutting into the equation. The time would be better spent baking with a beer in hand.

The 63 per cent figure for door height is the one to go with. I'd use the dimensions of one of the Ristorante ovens or go with a barrel vault design. My oven is a demon for bread baking, but it's not as efficient for pizza, though it can be done with practice.

Also, the mantra here, and it's a tried and true one, is that you can NEVER have too much insulation, both below and above. I suspect you'll only want to build this oven once, so insulate it as thickly as you have room for; you'll be glad you did.

I suggest you revise your drawing and re-post it here. You will get the advice you're after.

Jim

[JayP]

Re: Bigger ovens

Thank you for all the feedback, our pizza oven will be the better for it!

My flue has received the most attention and I would like to explain why I designed a pizza oven with a rear flue and how I believe they work.

The advantages of putting the flue at the back:
? The oven will be easier and cheaper for us to build because we won?t need a hood over the door and can simply put the flue straight into the oven.
? We get our door opening directly onto the cooking floor, an advantage I think that is more applicable to bigger ovens. We would need to be able to reach 1.75m across the floor plus an extra length for the flue, using a 2m plus pizza peel.
? And well?the oven just looks more approachable (see perspective).

How a pizza oven with a low rear flue with damper would work:
? The cook would be able to tune the damper so that the flue draws enough to stop the oven from smoking out of the front, but not enough to suck the hot gases from the dome. To do this you would simply close the flue until the oven starts to smoke from the front, then open it a bit.
? The cook can also choose to shut the flu off which means the oven work like ovens displayed on this site, and vents from the front.
? Using a door you would be able to shut the oven down and retain the heat. You also have the option of shutting the flue.

Perspective @ http://www.fornobravo.com/forum/phot...dex.php?n=1028
Pictures of pizza ovens with the flue at the back - http://www.fornobravo.com/forum/f37/....html#post8640

If the oven will not work like this why not, and has anyone used an oven with a flue design similar to the one I have posted, or the ones in the above link?

Thankyou
Jay

[dmun]

Re: Bigger ovens

The ovens you linked to:



are the twin ovens at "a mano" here in Ridgewood NJ. Those are low dome Naples style ovens, and yes the vent is above the door. The commercial builders of this style of oven angle the vents up from the entryway and take the vent stack up from the center of the dome enclosure. I think this is mostly for aesthetics, but do not be deceived: these DO NOT vent from the inside of the dome, they only look that way.

We've only seen one built example of an vent-from-the-dome oven, built by the father of a member (can anyone help me with a link here?) that wasted vast amounts of fuel, and took forever to heat up. No amount of dampering is going to compensate for having the flue in the wrong place. One additional thing about wood stove commercial dampers: they are designed to cut off only about 80 per cent of air flow when fully closed for safety reasons, and they are just a flap of cast iron - no insulation at all.

Ovens are a lot of work to build, and we're here to help you to build one that will work right the first time. If you decide to do things differently, we're here to cheer you on, and to learn from your mistakes, or to share in your triumphs.

[james]

Re: Bigger ovens

Hi Jay,

There is a style of Italian oven where the vent is located outside of the oven chamber above the door, where it arches back over the oven dome -- and connects to the chimney at the top of the oven. While it looks as though it could be vented in the back, it is the same oven design we describe in the Pompeii Oven e-book.

The Twin Ovens were actually made in Italy, and shipped to NY -- where they use Caputo flour. :-)

The main advantages of the Italian design is that you have much better control of the fire, higher heat cooking and better use of your wood.

Community wood-fired ovens are the wave of the future.
James

[james]

Re: Bigger ovens

Hey David,

I think this is the second time we answered the same question the same way; at the same time.

Great minds....

James

[edschmidt]

Re: Bigger ovens

I love being the devils advocate.....So..... I believe the squirell tail ovens which from my knowledge were built in vermont and other earlier settlements had the flue in the back.

People seem to quickly dismiss this change by saying it was less efficient, but if that was the case why did they do it for 50-100years. It seems to be more laborous to build, so it must have served a purpose right? I know at least one of the ovens built by the MHA (masonary heaters of america) was a squirell tail design. It would seem that giving the exhaust gas a second pass at the masonary would make sence (scents? im on my third labatts). I think there is a way to make an oven in this manner with high tech insulation and have the best of both worlds.

I believe alan scott wrote that domed ovens are old technology which should be relegated to history. I just dont feel comfortable dismissing the squirell tail (or the dome for that matter) as easily.

[Dutchoven]

Re: Bigger ovens

Ed
You are correct in saying many "squirrel tail" ovens vented from the back and then over the dome. I do not however recall the one that the MHA folks built, I would love to see it! I believe that there are ways to create something that would satisfy both needs...I think if the opening to the flue is at the recommended door height and is located correctly I think such an oven could heat up in good time...however...keeping the heat in would be another issue as you have added an additional "drain to the bathtub"...one opening to the oven is simpler and more efficient...has to be...
That's my 2 cents before bed...
Jealous about the Labatt's...have not had one sine I left NY!
Dutch