smaller oven

[dingodan]

I'm starting to build soon and only have room for about a 28 inch diameter oven. Any recommendations on dome height? Door width and height?

I'm a total newbie and any advice would be greatly appreciated.

Thanks

[the_dr_masuess]

Re: smaller oven

Hi dingodan,

First of all welcome and I suggest checking out many of the threads listed in the newbie guide to construction. There are tons of resources online which can help you and when you have trouble finding something or have a question... just ask.

28" diameter is definitely a small oven. Are you able to provide us with some more information? such as your dimensions of oven placement and proximity to house/yard?

To answer your question using few words if your oven is only 28" diameter and you wish to make a hemispherical dome then your oven would have an interior dome height of 14" and your door height would need to be 9 1/2".

If you are only able to build a certain diameter but can build deeper you may want to consider a Barrel vault oven.

Let me know if you have any other questions.

[dingodan]

Re: smaller oven

I actually started building a huge barrel vault oven at the same time as a friend. He has since finished his oven and is unhappy with the amount of wood it takes to heat it up. So I decided to switch to a smaller dome. Unfortunately, I had already built the base for the barrel oven, so now my base is too skinny to build a bigger dome.

My plan right now is to build a 28" dome that has an 18.5 interior height. That puts a 14" dome on top of my 1/2 brick soldier course.

Thoughts?

[Greenman]

Re: smaller oven

Welcome Dingodan

A good starting point is this thread started by Lburo and it contains lots of treasures.
http://www.fornobravo.com/forum/f2/n...res-15133.html

It contains information that will answer many of your questions including the formula for dimensions of door openings etc.

Good luck with your build and my advice would be to plan carefully to make sure that what you build will suit your needs and end up looking like what you want.

There are plenty on the forum who have expertise to share.

[deejayoh]

Re: smaller oven

One thought - an oven doesn't have to be hemispherical. It can be taller than a half dome. The key to getting it to work is the ratio of the door height to dome height. You could make it 16" tall if you want, in order to have a larger door area.

There are several builders on the site (David S comes to mind) with smaller ovens that can give you and idea of the tradeoffs.

[texman]

Re: smaller oven

i would look at the Napoletana Oven style oven and copy those dimensions to make it work.
http://http://www.fornobravo.com/res...en/casa2g.html

Texman

[wotavidone]

Re: smaller oven

28 inches isn't a big oven. I built mine at 30 inches, and I'd go bigger if I built again.
However, I consider the Forno Bravo Andiamo a very desirable oven, and it comes in 28 inch and 24 inch versions. So if you only have room for a 28 inch oven, it is still a very worthwhile exercise.

For a basic hemispherical dome you'd end up about 14 inches internal height, 9 inches high door gives 0.64 dome to door ratio - close enough to the magic 0.63, and go a little more than half the diameter as door width - say 16 inches.

Are you basing your size calculation on a "conventional" brick construction? i.e. 4 inches of brick wall, 4 inches of vermicrete and a half inch or so of render on the outside? If so you might be able to crib an inch or two of extra room inside.
If you could use ceramic blanket or other high-tech insulation, the reduction in insulation thickness could translate directly to extra diameter.

Doesn't really matter though. 28 will work, and won't take much wood to heat.

[david s]

Re: smaller oven

Oven design is similar to boat design, there are advantages and disadvantages for individual characteristics. For a small oven some of the advantages are: a smaller footprint, no need to build a bomb shelter for a stand, less materials required which means less $ and less labour, less fuel required to get to temp. On the downside a smaller oven requires rather more clever management, and will have an oven door proportionally larger which leads to greater heat loss. If you want to cook a whole pig or a 12Kg turkey you won't fit it into a small oven. My oven is 21" internal diam and we cook a roast for the family on a regular basis, or a few loaves of bread (how much bread can a family eat?). It will just fit a 5Kg turkey. For pizza parties it's fine for groups up to around 35, any more and sharing whatever comes out of the oven works ok, but we'll be cooking for two or three hours. We often fire it up for just three people because it uses so little fuel. I designed it with a relatively wide mouth and very shallow entry for easy access and use it also as a fireplace for comfort during winter. This also enables the use of short handled tools. To my mind it is perfectly adequate for the average family. I think most oven owners grow into their ovens and therefore believe that whatever size they have is the minimum that they'd want or could handle.

[wotavidone]

Re: smaller oven

I think most oven owners grow into their ovens and therefore believe that whatever size they have is the minimum that they'd want or could handle.

I haven't tried a smaller oven than my own, but I expect there is some truth in what you say.
I have tried bigger, and they are easier to operate, simple as that, but the trade off is much more wood needed to heat them, and lots more materials needed to build them.
Of course, there is then more mass for retained heat baking, too. But like you say, "how much bread can a family eat?"
Even though I say I wouuld go bigger than my thirty inch oven, it'd only be a couple more.
So it is whatever floats your boat really.
28 inches will be a mighty fine oven, and will definitely keep the family happy.

[vertigopilot]

Re: smaller oven

I actually started building a huge barrel vault oven at the same time as a friend. He has since finished his oven and is unhappy with the amount of wood it takes to heat it up. So I decided to switch to a smaller dome. Unfortunately, I had already built the base for the barrel oven, so noe my base is too skinny to build a bigger dome.

My plan right now is to build a 28" dome that has an 18.5 interior height. That puts a 14" dome on top of my 1/2 brick soldier course.

Thoughts?

My barrel-vault oven is 31.5W x 40"D x 18"H with 4.5" firebrick, 4" of concrete cladding and 4" - 14" of vermicrete insulation. That's a lot of mass, but only takes 2 hours to hit 1000F and holds usable temps for a long time. If your buddy's oven is using excess wood, I'd bet that he didn't insulate it well enough, or it's still too damp to judge its long-term performance. Mine needed 20 days of heat to dry it sufficiently to get a sense of its potential.

IMO, if your base isn't big enough for the oven you want (including plenty of insulation), knock it down and start over.

[dingodan]

Re: smaller oven

Great info and advice everyone. I'll post pics soon as I hope to lay row 2 tomorrow.

[dingodan]

Re: smaller oven

I put on the second row. As you can see, the walls of the dome sit slightly over the edge of the hearth. When I switched from barrel to dome, my base was slightly too skinny, but I didn't want my oven to be too small. I know I'll lose some heat, but I'm hoping it is not too much.

The hearth is sitting on almost 4" of insulating perlite/concrete and the oven wall bricks are mostly on the hearth, so, we will see.

[david s]

Re: smaller oven

Hard to tell from your photos, but it looks like your floor height will be pretty low. The standard is around elbow height. You might have to do some stooping, but you get used to whatever height you've built. Looking good so far. You might lose a bit of heat conducting from the floor to the outer perimeter bricks, but not too much to worry about. Because a smaller oven is so much more economical with fuel (consumption is proportional to oven volume), it's no trouble to use a little more fuel or refire.

[dingodan]

Re: smaller oven

Good eye on the height. The oven is built into our back slope so it looks low, but it is actually elbow height.

Thanks for your opinion on the heat loss. I was hoping it'd be like you said, but it's nice to hear an expert agree.

[vertigopilot]

Re: smaller oven

I put on the second row. As you can see, the walls of the dome sit slightly over the edge of the hearth. When I switched from barrel to dome, my base was slightly too skinny, but I didn't want my oven to be too small. I know I'll lose some heat, but I'm hoping it is not too much.

The hearth is sitting on almost 4" of insulating perlite/concrete and the oven wall bricks are mostly on the hearth, so, we will see.

Dingodan:
I'm not an expert, having only built a handful of ovens so far, but I've been at the same juncture where you are now with your build: wondering whether the reduced insulation envelope will much affect overall efficiency, or whether it would be worth the effort to do some re-working at this point.

From my past experience comparing the results of build decisions, I would say that only 4" of perlcrete under your floor, reduced insulation space around the perimeter, and the thermal bridging that will come from the decorative bricks around your oven floor, will all add up to considerably faster rates of heat loss than you would guess.

If wood is plentiful and cheap - and you enjoy stoking the fire more frequently - then it won't matter much. But if you look forward to extended baking and roasting sessions post-firing, then you'll want to make the necessary design modifications now while it's still easy. You might consider removing the floor perimeter bricks, adding a another row of block or brick wall around the perimeter of the base to provide support for an enlarged wall area, and extend the perlcrete out wider so that your dome insulation will connect with the floor insulation to fully envelope the oven without unnecessary thermal breaks.

It all depends on what your goals are. The most important thing is acting on your ideas. There is undeniable magic in Action!