My first attempt for 42" oven / changed to 36"

[Greenman]

Re: My first attempt for 42" oven / changed to 36"

Hello George - Yes measure by volume and mix it carefully so as to keep as much air in the mix as possible.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Hi,
Why need air in the mix?
I will mix it with cement mixer, is it good method?
Thanks

[Greenman]

Re: My first attempt for 42" oven / changed to 36"

The more air you can retain in the perlite mix the better the insulation value. I mixed mine in a barrow with a hoe. The air in the perlite is the reason for using it.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Can i use cement mixer?

[david s]

Re: My first attempt for 42" oven / changed to 36"

Can i use cement mixer?

Overmixing tends to abrade the grains of the perlite and if you use a mixer this is more likely to happen. The stuff, being so light also does not mix well with a mixer. It tends to stick to the sides and paddles of the mixer. I always mix in a barrow, that way you can fold it gently and see exactly what's going on. 8:1 is pretty lean for an underfloor slab, 5:1 makes a better mix. Throw in a little powdered clay to improve the mix too. I use 3 parts water for every 10 parts perlite. Also have found a 50/50 mix of perlite and vermiculite makes a far more workable mix than either of them alone, I think this is because you get a good variety of grain size this way.

[NCMan]

Re: My first attempt for 42" oven / changed to 36"

Can i use cement mixer?

It's best not to. You want to keep the Perlite in as big of pieces as you can. Do not over mix it. I used a shovel and just kept flipping it over until it was mixed, trying to avoid chopping it up.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

OK i will use 5:1 ratio and i will not use the cement mixer.

Thanks for your replies!
Really helps me with your replies because i haven't much experience.
Best regards

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Today i had shopping
I bought 50 bricks for start and floor base plates.

Bricks size is 22x11x6 cm (or 8.6x4.3x2.3 inch)
Floor plates are 50x25x6 cm (19.6x9.8x2.6 inch)
I get this plates to avoid to use more bricks.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

I have a question about the entrance size.
For a 36" oven what lenght must i make?
I want to calculate the total lenght to center the oven on the slab before starting the perlite insulation layer.
Thanks

[Tonyp]

Re: My first attempt for 42" oven / changed to 36"

I have a question about the entrance size.
For a 36" oven what lenght must i make?
I want to calculate the total lenght to center the oven on the slab before starting the perlite insulation layer.
Thanks

Kind of up to you George. Don't forget that the dome arch will extend roughly 4" into that entry area of your drawing. So from there you have an arch on the outside of the dome arch, then an area which will collect the smoke and extend up into the flue, and then the outer arch. Minimum I would estimate around 20" if you are measuring from the inside face of the dome arch. That would leave you with space for the 3 arches at 4" = 12" and 8" for the smoke/flue area which gives you a nice base for a 6" stove pipe/chimney. You can adjust for your particular brick size..For example 4.5" thick bricks add 1.5" total for the 3 arches.

The bricks you picked up look nice too!

Tony

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Thanks Tony!
Between the perlite insulation layer and oven floor must I put some material or I can build the oven floor on it?

[Laurentius]

Re: My first attempt for 42" oven / changed to 36"

Hi George,

You construct your hearth and oven dome on your insulation layer.

[david s]

Re: My first attempt for 42" oven / changed to 36"

Thanks Tony!
Between the perlite insulation layer and oven floor must I put some material or I can build the oven floor on it?

The usual is to put down a layer of 50/50 sand, clay either wet or dry, as a leveller between the vermicrete and the floor bricks.

[George_M]

Re: My first attempt for 42" oven / changed to 36"

Due to bad weather conditions i stopped the activities for now.

As for the total external size is:
36" cooking floor + half bricks 4,3" + 6" insulation = 46,3" ???

My calculations is correct or i missed something?

Thanks for your replies!

[Tonyp]

Re: My first attempt for 42" oven / changed to 36"

Hi George,

What are you planning to use for insulation outside? The type you use and how important it is for the oven to stay cool to the touch and hold heat will make a big difference on the thickness of your insulation.

I am using ceramic blanket and planning on at least 4"+, although a few snug spots it's more like 2.5-3". If you are not as concerned about the oven getting warm on the outside and holding heat for as long as possible then you don't need as much insulation.

The external size is cooking floor + 2x the wall thickness. Wall thickness is brick thickness + insulation layer. If you are planning to put a coating directly on the outside of the insulation you have to add that in to wall thickness also.