Difference in wood requirements based on size.

[guiriguiri]

I'm wondering if anyone has any idea how to quantify the difference in wood requirements in 36" (39") and 42" ovens? I've already built my stand for a 42" oven but am now debating going down to a 36" to save on fuel costs and heating time, leading to more use in the future. However, after combing the forums, I can't really get a handle on how much of a difference this will make in terms of time and fuel. I realize this is research that should've been done several steps ago but I've pretty much got a late August deadline when all my free time ceases to exist, so I pretty much broke ground as soon as I mentally committed to the project.

Also, If I go down to a 36", I'm thinking of just using the extra space up front as an 18" or so brick counter. Any reasons I would regret this?

[david s]

As a rule of thumb fuel consumption is directly proportional to volume. Although a larger oven is more efficient mainly because the oven mouth is much the same size.Just like a 4 litre motor will use way more than a one litre, but not by four times.
A 42" oven has 16 % more diameter than a 36", but 40% more floor area and a whopping 60% more volume, so you can expect quite a saving on fuel consumption if you drop from 42 to 36. More importantly you save a lot of effort cutting and splitting wood.
There's little difference in heating time between the two because the larger chamber allows for a larger fire and the wall thickness remains the same. In practice both ovens will take the same time to get to temperature.

[jimkramer]

I can't add to the science of it, but I'll say I definitely don't use most of the capacity of my 42". I could probably handle making 3 pies at a time, but I have only done 2 at a time. I can also say that although I can heat my oven up somewhere around 2.5 hours, I have been lately heating it for 5-6 hoursto make sure it's all saturated with heat before we have guests over and make 10 pies. This might be overkill, and I'll try something in the middle, but with less time, the floor cools down a lot in between pies. The long and short of it is that this takes a lot of wood (which I have and isn't an issue for me) and so I think you'll be very happy with a 36" and it will probably save a lot of wood, if that's a factor.

[guiriguiri]

Thanks for the advice!

I've got my ply board in place and my rebar frame built. Now I just need it to start raining, so I can build the external frame and pour the hearth. I'm planning on laying a 3.5" hearth with a few 3/4" drainage areas near the center. Then casting a much smaller 5.5" insulating hearth once I map out exactly where the oven floor bricks will lie.