Design Help

[Neil H]

Re: Design Help

Neil,

I believe you are building a barrel, so the two layers are not near as complex cutting as a dome. The total brick thickness is just under 5" so a little thicker on the barrel and quite a bit more on the floor. It may take a little more fuel to fire the oven but you use what you have to work with. I have no scientific documentation but the word of mouth is Vcrete is about 1/2 the thermal efficiency of a CF blanket. So 6" Vcrete equal to about 3" CF. Again, like Gulf says and your latest sketch, insulate the barrel, floor, and walls away from the reinforced concrete hearth.

Thanks UtahB, yes i am building a dome. I will put as much Vcrete as i can on the base ...

[UtahBeehiver]

Re: Design Help

I guess nomenclature confusion, dome to me is an igloo, vault and barrel to me are the same so if you are building a vault or barrel then you brick work will be much easier with the two layers of brick.

[Tscarborough]

Re: Design Help

I built my vault out of 2 layers of 1-1/2" firebrick. I also cut them in half lengthwise to reduce the gaps even more. Be sure to fully bed the second layer onto the first; any gaps will act as an insulator.

[UtahBeehiver]

Re: Design Help

Ahh, Tscar's, pic shows more than words can describe.

[Neil H]

Re: Design Help

Thanks for the comments and support guys.

Attached is the latest version of my design

this is a schematic and not strictly to scale

the chimney is not shown on the sketch but will come out of the entrance arch as shown in the blue arrow.

the insulation is thicker than shown and will be a Vcrete mix

also not shown is the vcrete over the outside of the vault itself

At the moment I have built the stand and thrown the concrete slab, this weekend will hopefully be the Vcretre, wall buttress and base laying ....

[mrchipster]

Re: Design Help

Stagger the bricks if possible (running bond) it will make for a much stronger roof. Etc. is just repeat pattern.

Running bond should also be used for the back wall.

You may also wish to add a reveal at the entrance to the flu arch to provide a lip to seal on for your insulated door.

[mrchipster]

Re: Design Help

Photo of a nice reveal is attached.

[Neil H]

Re: Design Help

Stagger the bricks if possible (running bond) it will make for a much stronger roof. Etc. is just repeat pattern.

Running bond should also be used for the back wall.

You may also wish to add a reveal at the entrance to the flu arch to provide a lip to seal on for your insulated door.

Thanks for the suggestion, I was wondering whether to use a running bond on the barrel itself but it makes sense that it would be stronger .... would you stagger the firebricks (tiles really) as well?

I like the reveal idea, I will incorporate this into my build for sure !

[Neil H]

Re: Design Help

As you may have seen on my sketch, on the floor of the oven I had intended having the layer of Vcrete, then a layer of clay brick then a layer of firebrick tiles (25mm or 1 inch thick) but I am just wondering if the layer of clay brick will actually do anything? they are not needed for strength, my thought was that they would act as a heat sync and would aid in radiating heat back for cooking after the fire is out (I intend using the oven for roasts and bread etc as well as pizza) but will they actually do anything? would the firebrick layer of 25mm be sufficient?

would I be better off using a thin layer of compacted sand to get the base 100% level before I put the layer of firebrick tiles down???

[UtahBeehiver]

Re: Design Help

Mr. C and his drawings are right on with a running bond. IMHO, the 100 mm clay bricks under your 25 mm fire bricks will give you additional thermal mass to ensure extended cooking heat after the fire is out. I would continue as you originally designed.

[mrchipster]

Re: Design Help

Thanks for the suggestion, I was wondering whether to use a running bond on the barrel itself but it makes sense that it would be stronger .... would you stagger the firebricks (tiles really) as well?

I like the reveal idea, I will incorporate this into my build for sure !

Yes and also alternate the layers of firebrick and your clays so the joints alternate.

[Tscarborough]

Re: Design Help

The floor tiles should be laid in at a 45 degree angle so as not to catch the edges of the peel.

[Neil H]

Re: Design Help

Yes and also alternate the layers of firebrick and your clays so the joints alternate.

The firebrick is a different size to the joins with it will seldom line up with the clay brick joins.

I have heard that the join between the back wall and the barrel is a weak spot

I have planned on keying in the firebrick and joining the clay bricks, i.e. the back wall will not be a floating structure but will be tied into the barrel brickwork .... is this the right way to go about things?

[Neil H]

Re: Design Help

The floor tiles should be laid in at a 45 degree angle so as not to catch the edges of the peel.

I have read about this and plan on laying them at a 45deg angle. in order to make this layer as flat as possible (it sits on top of a layer of clay bricks), I plan on putting a very thin layer of plaster sand down (like 2-5mm) to ensure a smooth base for the oven

[Neil H]

Re: Design Help

In terms of the chimney, I have been eying a pot out in the garden, of course my better half has no idea if the impending confiscation of her pot, but the pot is about 80cm high and has a diameter of maybe 250mm tapering to around 200mm, if I cut the bottom off then it will make a very good looking chimney, but will it perform well? is there a formula to calculate the required chimney diameter?

Edit: a friend has offered me a 6 inch steel pipe 1.2m long as a second and much lighter option which I am VERY tempted to go for... any thoughts?