new build in werribee

[Karangi Dude]

Re: new build in werribee

No,

If as I asume you would be using firebricks for the vent hearth, then you could just use the hebel under the firebricks as the vent arch hearth does not get as hot as the oven hearth.
The reason I would use the board is to make it easier to get the same height as what the oven hearth is.

[oasiscdm]

Re: new build in werribee

Hi DOug

I was concerned since the oven is always going to be in the weather, that the calsil board would disintegrate if wet, since there is little heat in vent it might not dry out. I will make a door for the front on oven as well as inner door to help keep dryish. I spoke to field furnace when I ordered tiles and they told me they had trouble with some ovens that have been cleaned out with water. The calsil apparently turns to powder.

My thinking was to not use the calsil for that reason, bit lay the 75mm tiles on Hebel and then 50mm granite on top of that in the vent area enclosing the tiles. Would look nicer too.

[Karangi Dude]

Re: new build in werribee

Colin that sounds like the way to go, the hebel will be fine it can get wet but dries out pretty good.
I like the sound of the granite, there is a man made granite that looks good and is a lot cheaper so keep your eye out for that it comes in a few different colours as well.
The barrel oven I am helping with will be enclosed and will also have a roof over the whole thing so it can be used in the rain, as I said it rains a lot here in Coffs.
Colin I know the DIDS group you referred to, when they were setting up they bought some stationery of us, small world eh.

Colin, if ever you are comming up to Coffs give a PM and let me know, I would be delighted to show my oven and maybe have a coulple of pizzas.

[UtahBeehiver]

Re: new build in werribee

Colin,

Whether you decide to use Hebel or CaSi you can alway put on a thin brick or stone veneer over the Hebel or CaSi to enclose it. I did this with my build. I ended up trimming back the CaSi and Foamglas back 1" from the edge of the hearth brick then mortared in a 1" brick veneer so this insulation material in no longer exposed to the elements or food. Look near the bottom of the pics. Sorry I don't have a better detail.

[SpottedFrog]

Re: new build in werribee

Hi Colin,
I have been watching your posts with interest as I am planning on a similar top structure. So I gather that others feel that so long as you use CalSi board the under floor insulation should be okay; and the hebel should stand up to the weight of the oven.
I was a bit worried about that and was planning on a 2 inch reinforced concrete layer then the same hebel sheets as you then a layer of verimicerete then the calsil. I know you can't have to much insulation but i'm not that tall and wanted to have space underneath to store wood.
looking forward to more photos.

[cobblerdave]

Re: new build in werribee

Gudday Rosemary
A 2in re-enforced slab is to thin to protect the steel properly it needs to be at least 3 1/2 in thick. The re-enforced hebel should be strong enough if correctly supported underneath. A H shaped slab gives you 2 bays for wood stowage which is excellent for access ( trust me a c shape you'll never see the wood at the back). You back up the support in the bays of your H with steel lintels or angle iron.
Using hebel cal sil and pearlcrete seems a bit of an overkill. The hebel will supply you with a good insulation to start with. Protect the hebel with a layer of pearlcrete or cal sil to take the big heat. Remember Portland cement that the hebel is formed from will tend to break down over 330 C . It takes a big long firing for this heat to pass through to the hebel layer however. So a thin layer of cal sil or pearlcrete is your insurance. My own oven does not have this but survives because it has 75 mm of firebrick , it might be 500C inside but by the time this heat reaches the hebel layer it has dropped enough not to have an effect on the hebel.
Hope you have a copy of the Forno plans .... It's a bullet proof oven to build

Regards dave

[david s]

Re: new build in werribee

Gudday Rosemary
A 2in re-enforced slab is to thin to protect the steel properly it needs to be at least 3 1/2 in thick. The re-enforced hebel should be strong enough if correctly supported underneath.

I was disappointed in the Hebel strength. The stuff I used was 75mm thick and reinforced with 4mm steel cast into the middle. This is pretty inadequate IMO. You can make a 50 mm concrete slab stronger. If you feel it's too thin for steel reinforcing then use fibres. Another alternative which I prefer is to cantilever the supporting slab so the span between supports is much shorter. As the centre of mass is not at the perimeter of the dome anyway this makes more sense.

[SpottedFrog]

Re: new build in werribee

Thanks Guys for the info and advice.
I have settled on a stand plan that is a 'C' at the front with a crosswise 'H' behind. Steel lintels across all and a cantilevered top so most mass is above the block work of the stand. Good to know about the thickness of the concrete and the option of the needles rather than reo. I will be sticking with the Hebel, only cost me $20 from the Junction up at the tip.

[oasiscdm]

Re: new build in werribee

Hi rosemary

When you look at the photos of my build. You will notice that the base is based on a B frame at the rear and a C frame at the front. The blocks are positioned immediately under the oven circumference the middle steel lintel 7mm back to back angle iron is positioned under the inner arch.

You simply need to use the calsil board on top of the Hebel panel only. As Dave, Doug and Russell have stated in my own questions to them. Nothing else is required. The Hebel panel will also provide insulation in conjunction with the calsil

Cobbler Dave if I recall is using Hebel as his insulation layer on a concrete base. I feel a concrete base is unnecessary as long as the panels are well supported.

I have checked this out with a Hebel engineer.

Rosemary you are on the right track with your last post. I have not used a concrete base nor do I intend using vermicrete. But the Hebel panel needs to be supported. To hold oven weight.

[david s]

Re: new build in werribee

Hi Colin.
What is the span between your supports under the Hebel? If you are using the 75mm thick Power Panels be careful. Hebel is about the third of the weight of structural concrete so expect a third of the strength. It's reinforcing is pretty light. 4 mm rod if I remember correctly. I hope you told the Hebel engineer how much weight will be sitting on top of the panels.it's fine under compression , but flexural strength is the worry.
Dave

[oasiscdm]

Re: new build in werribee

Hi david

Thanks david for your concern. Just to clear up my base, it is built with 150mm thick Hebel blocks in the form

|--|--|
|--|--|
|-----|
|-----|

with the blocks with two hebel panels making an oven surface of 1500x1600. The oven is supported under its outer diameter by these blocks in the back half of the base. This part of the structure supports the centre of the oven. At the front i have placed two lintels one under the front inner arch this is 7mm steel angle iron welded back to back to form a T . I also have a steel lintel across front supporting the outer vent area and the face plate you can see in the pictures this is 4mm angle iron welded to form this shape LL .

So from back to front there are 4 major supports.

Hope this clears it up. I feel the panel it is very well supported and hence the oven.

Also i told the Hebel engineer it would be holding 2 tonne based on my calculations it will be a lot less than that.

[SpottedFrog]

Re: new build in werribee

Thanks for all the detailed discussion. Mine will I guess look like something like this, the blue bars are the lintels, the black are the block work. Still working on the dimensions. I think I need to make a template like Colin and some others have so I know where the weight is. The top will be cantilevered so the main weight is on the blocks and lintels.

[david s]

Re: new build in werribee

Well done Colin and Rosemary,
Sounds like you both have it well planned.

[oasiscdm]

Re: new build in werribee

Thx David

I have included the photo that shows the supports. Note the extremities of the base fit the dome extremities exactly.

Rosemary looks like a good plan what size blocks i didnt catch if you were using besser or Hebel.

Storage i guess is in the T ?

Just want my brick saw so i can start

[david s]

Re: new build in werribee

You could hide all kinds of things in those two sealed bays? A few refugees, a couple of dead bodies or a briefcase full of money.