Scotty's 36" Build on the Sunshine Coast, Australia.

[david s]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

For your sized oven you should burn at least one full bottle of gas. As your temps indicated, there is still tons of water in the lower part of the dome and floor. Some kind of makeshift door, partially closed, that will still allow some oxygen in will help to keep in heat. I use one made of ss as shown in the thread on curing.

Regarding the ss door you plan on making, remember that ss warps way more than mild steel when heated, but I think 6mm will prevent that. Heavy uninsulated steel doors provide a good path for conductive and radiated heat loss.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Hey David,
Thanks for the tips. I was thinking that the lower walls were cooler cause the heat from the burner went straight up thus heating the roof first? I did go thru a full bottle, amazing actually I got about 28 hours out a a already partially empty 9KG bottle, I was quite surprised.
Now as for your comment of the door, "Heavy uninsulated steel doors provide a good path for conductive and radiated heat loss"
is that a good thing or bad?? Will the bit of 6mm cement sheet do the job of insulation or should I use a thicker sheet or something else?
Thanks a heap for you help tho.
Scotty

[david s]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Scotty,
When you get rid of most of that water the oven will heat more evenly. It is a bit like a wet sponge sitting outside to dry. The top half will dry out while the bottom half is still wet- have patience.
6mm of any insulator is not thick enough. Cement sheet will not cope with the heat and the fibres it contains may not be safe. An uninsulated door will work, but not as well as one that is insulated. Traditionally Italian ovens had wooden doors. These work quite well as wood is a way better insulator than steel. The trick was to soak itin a bucket of water to reduce charring. Another trick they used was to stuff wet newspaper around the door to make a really good seal.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Bloody good point on the fibres. I had not thought of that!
Ok back to the drawing board for the door, I have 2 laser cut door coming anyway one in 6mm and one in 3mm, Im sure I can come up with something to use the stainless.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

wrapped with an inch of ceramic blanket.



First layer of render nearly done, for this im using 10 sand/6 Fire clay/3 lime/2 cement. the same mix I used for the brick mortar, but I used 5 water/1 Bondcrete for the water to mix the mud. At the moment its about an inch thick.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Came home tonight after about 9 hours since I did the above rendering and there are some substantial cracks in the render and it feels a bit loose or it seems to float on the blanket still. It is still a bit wet so I know its still setting, but will the cracking eventually stop on the render? I assume I have to do a few coats of this stuff, how thick should it go??
Cheers
Scotty

[Aussie Pete]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Hey scott, build looks great, with your issue with the door, i think the norm is to sandwich a board of calcium silicate inbetween 2 sheets of steel. I suppose if you did that, you could do a 6mm steel back of door (facing fire), then the silicate board,then you could have the stainless facing outward if you wanted the stainless look.
You can get the board pretty cheap around Brissy. Its only about $25 for a 1" board 1000 x 500mm. Just use 2 layers to get 2" thick insulated door. thats similar to what i'm thinking of doing anyway.
Keep up the great building.

[brickie in oz]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Came home tonight after about 9 hours since I did the above rendering and there are some substantial cracks in the render and it feels a bit loose or it seems to float on the blanket still. It is still a bit wet so I know its still setting, but will the cracking eventually stop on the render? I assume I have to do a few coats of this stuff, how thick should it go??
Cheers
Scotty

It looks like there is too much clay in the sand, you need washed sand for render, its the clay shrinking that causes the cracks.

[OzOvenBuilder]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Hi Scotty,
Great looking job so far!
This might be what you're describing regarding the door design. All mild steel and works great!

Cheers,
Russell.

http://www.fornobravo.com/forum/f28/...ign-17110.html

[david s]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Slump cracks can be avoided by the following

Render layers should be applied to about 1/2" thick.
No clay in the mix.
Make the mix thick (not too much water)
Wet the substrate before applying the render.Skip this point because there would be no point wetting the blanket.
Use sharp sand not grains that are rounded. I use silica sand.
Add fibres to the mix.

I use 4:1:1 silica sand, lime, cement.This is a well tested and recommended recipe.
You should not do the work if it is exposed to sun or wind if possible.
I also wrap the whole thing in cling wrap, for one week, to hold in moisture while it dries and to increase strength.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Ok so I have pressed on with the build this week. Have reduced the qty of Fire Clay in the mix to see if that reduces the cracking, and it seems to have worked. I have 3 layers of render on there now each with less FC and each showing less cracks. But yet to fire it up for a big burn yet. Its only had a couple of small burns and the original 30 odd hours of gas burner heat.
Here is the sandstone that Im intending to do the bench with.

I have a nice laser cut stainless facia on the front

I was thinking of going for Blue as the dome colour, but after seeing it I have changed my mind, will now try a dark charcoal.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

I have a door being welded up today. its 6mm stainless on the fire side with 2 inches of calcium silicate sandwiched in the middle and 3mm stainless on the visible side.
Yes it is a bit heavy!! but will give me a good bicep workout when I use it.


And a perspective shot of where the oven is.

[brickie in oz]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Render is always sharp washed sand with no clay otherwise the clay content will shrink and crack.

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

Doug if you look at the perspective picture you will see a nice big stainless fridge, that is my beer and wine fridge!!

[scottsummers]

Re: Scotty's 36" Build on the Sunshine Coast, Australia.

I ended up choosing Dark Charcoal for the colour.

The door, its a little over engineered Weighs in at about 15 KG..... whoops. Oh well workout time.

Door in the hole.