Minne"snow"ta castable build....... I think?

[fox]

That is interesting as virtually everything is cheaper in the States compared to the UK but I but I just worked out that I pay around $6-7 sq ft. for 2’’ thick 1200c CFB.

[jakeanderton]

That is interesting as virtually everything is cheaper in the States compared to the UK but I but I just worked out that I pay around $6-7 sq ft. for 2’’ thick 1200c CFB.

Yeah, not sure what the issue is.

david s I talked to my KS-4 supplier, and they stated there are no fibers in the Ks-4. nor would they sell me any steel needles for reinforcement - due to the liability of them falling into food for my application. They also stated that they recommend a minimum 3" thickness for the dome size I am building, and for my size he emphasized doing 4" of thickness.

[david s]

The stainless needles are not mandatory, and because they are difficult to work with (sharp) you can skip them. If they are embedded there's no problem with them falling out. You could lay up a thin layer first without them and apply a second layer containing the needles. Try to access some AR fibreglass fibres instead. The most important ones are the burn out fibres. If the product doesn't contain them (I'm surprised it doesn't, perhaps your supplier was thinking reinforcing fibres rather than burn out fibres). Check yourself by sieving some of the product with a tea strainer. If not add the very fine polypropylene fibres, you don't need much but they require very thorough mixing to disperse evenly, you don't want them clumping.

[david s]

For the last big oven I built, I used cal sil board on (a 55" internal oven) I used two layers of 40 mm board which ended up costing A$480 @ A$48 /100 x 61cm sheet.
That's $79/m2 or $7.31/sq ft.
Vermiculite and perlite here around $30/100 litres
To cast a vermicrete slab of the equivalent area 4" thick would cost around $100

[Americana]

I’ll sift some KS-4V Plus this eve and show results.

[Americana]

It seems to be a kind fiberish.... Like heavy lint. in the KS-4V Plus. Seems plenty strong for a pizza oven application as it came out of bag. SS needles seem to be hard to mix in and clump when used for wet casting.
I have used this product from the bag a fair amount with good results and my rep for the product recommends it highly. david seems to have a good understanding on ovens so I would have to defer

More pics coming.

[jakeanderton]

For the last big oven I built, I used cal sil board on (a 55" internal oven) I used two layers of 40 mm board which ended up costing A$480 @ A$48 /100 x 61cm sheet.
That's $79/m2 or $7.31/sq ft.
Vermiculite and perlite here around $30/100 litres
To cast a vermicrete slab of the equivalent area 4" thick would cost around $100

My cost is about $95, due to some leftover perlite I am using from the garden. The KS-4 is going to set me back nearly $700. So, I need to keep costs down where I can

[jakeanderton]

It seems to be a kind fiberish.... Like heavy lint. in the KS-4V Plus. Seems plenty strong for a pizza oven application as it came out of bag. SS needles seem to be hard to mix in and clump when used for wet casting.
I have used this product from the bag a fair amount with good results and my rep for the product recommends it highly. david seems to have a good understanding on ovens so I would have to defer

More pics coming.

Very interesting to see. Thank you for sharing! I'll be picking up 13 bags of the stuff this week. Still torn on using any additional fibers or just going with the KS-4 straight out of the bag. What would you say your castable to water ratio was for applcation?

[Americana]

For reference I used 11 bags for my oven at 2" The water ratio was used per manufacturer. But seemed to always add more as I went along. It was a real dance 2 bag casts and getting each layer to bond but not slide down. Not perfect but seems to work.

[jakeanderton]

For reference I used 11 bags for my oven at 2" The water ratio was used per manufacturer. But seemed to always add more as I went along. It was a real dance 2 bag casts and getting each layer to bond but not slide down. Not perfect but seems to work.

Wow!. With that in mind, I am worried that my 13 bags wont make it as I attempt 3-4" of thickness. My mind immediately thinks I might need to make a form for each layer, maybe going up in ~5" increments the entire perimeter of the sand mold. Your forms look wonderful!

[Americana]

I would stick with 2” of castable and 4” of insulation.
You will notice my front piece was a little layered at 3 bags 1 3/4 hrs. 65 degree shop. They progressively got better.You have to move reasonably fast.
Maybe score your cast when done…. Create a known expansion joint.

[jakeanderton]

Create a known expansion joint.

Agreed. My thought is that my 3-4 layers will have a built in expansion joint between them just due to the process I will undertake.

For my previous build, I had the top of the oven at 66% of the height of the dome. Yours appears to be a little lower? Curious what you and david s have to say on the correct ratio. What would you say yours is and off which plans (if any) did you base your design?

[david s]

My conclusions about the door height to internal height ratio being some kind of magic number for optimum operation differ from that of many members here, particularly after modifying one of my ovens to change the ratio considerably and finding it made no discernible difference to firing or operation. Interestingly the Golden Ratio of 1:1.618 (62%) is pretty close to that which the Canadian study of the average ratio found in a number (don't know how many) of ovens. This is not a scientific study of these ovens operation or efficiency, but does provide some good information about what practical use has determined.
The optimum fuel to oxygen ratio for the most efficient combustion is around 10:1. When using wood as a fuel it only becomes fuel when the wood is heated sufficiently to release its gas. The reduction of the air intake will increase the efficiency of the fuel/air mixture but results in two major drawbacks. Firstly it reduces access to the oven and secondly raises the temperature increase to levels vulnerable to the brick or refractory to cope with the sudden rise in thermal expansion. Far better to allow the oven to increase slowly and absorb the heat gently. It would be the equivalent of a potter firing a kiln at full blast from ambient. The two most vulnerable zones are ambient to 300C, when water elimination is the most likely to cause damage and the 500-650C zone where many of the materials in either brick or refractory have different thermal expansion rates. All potters are well aware of these two danger zones and ensure the rise is low (no more than 100C/hr) for these zones. Most oven owners either ignore or are unaware of this information and fire at around 300C/hr from ambient. Now an oven is not a kiln, and pottery wares are not bricks, but the same principles apply.

For my ovens the ratio is 64% and the modified version 70%

Here's an interesting thread which discusses the issue.
https://community.fornobravo.com/for...g-size#post764

[UtahBeehiver]

I am not sure if the thread is talking about door opening height relative to internal dome height or dome height relative to oven ID. Can the OP clarify?

[jakeanderton]

I am not sure if the thread is talking about door opening height relative to internal dome height or dome height relative to oven ID. Can the OP clarify?

Door opening height relative to internal dome height.