Brisbane Build

[Hatzi]

Can I add
5. Cover the cement rendered layer to hold moisture in it to enhance its strength. For a week
6. Allow to dry for a week before firing.
7. Cook a few roasts for a few firings (chooks are fantastic) before racing straight to pizza temperature.
8. Treat the exterior with a waterproofing layer of the oven is exposed to the weather.

Thank you for the response.

I think that I really want to follow oasiscdm build by putting the perlite under the thermal blanket - this makes sense (especially when reading his arguments for this). I also think that you can not go wrong either was as i am building a backyard oven and not an industrial one.

[Hatzi]

At this point I need to turn my attention to the landing and the vent.

I have decided that I will not use a flared landing.

This is where I need help please (have already mailed utahbeehiver and oasiscdm)

I think that I will be using a double layered flue, with an internal diameter of 200mm. My reasoning for this is that it is a bit safer as the external flue will not get as hot.

I am not sure what size the vent opening should be nor the landing.

I am wanting my vent to be similar to oasiscdm's as seen in his posts 600, 629, 633

Waiting for approval from oasiscdm to post his reponse to my questions. However would love to hear other peoples ideas.

Sorry guys, it been a while since I got my response and have simply forgot to post it.

If you look at the photos the inner arch of the Vent and landing are determined by the Oven entry arch. I cut the bricks to fit around the outside of the Oven entry arch. They are not attached to the oven entry, as i attached fire proof fibre cloth around the Oven entry arch. This option maximises the landing width at the oven entry.

The outside arch it is important that

1. The front top of outer arch is lower than the bottom of the inner vent arch so is flatter.
2. The width of front landing arch is determined by a line drawn out from the middle of inner landing arch base brick drawn 90 deg.
3. I used 2 bricks length remembering inner brick warps around the outside of the oven entry arch
4. The brick angle is determined by angling the landing arch bricks outside of the line drawn above so effectively is half brick wider on both sides of the oven than the inner landing arch.

It is important to have the front arch lower this redirects the smoke up the flue and prevents staining the front of the oven with carbon.

The landing arches inner and outer are determined by your own oven and oven entry arch. My flue gallery for 8" flue was cut out of a 300 mm square tile tapered wider at the mouth than the top. I think it was 8.5" and 10"opening. If you check photos you will get the idea.

The length of landing arch was 2 bricks so 460 less the overlap around your oven entry arch for me was 60mm
Exact dimensions as I said above are determined by your own oven I have described the method for you to determine the sizing. My oven was bigger than yours and also without knowing details of your ovens entry arch my measurements won't work for you.

Also cutting the bricks is really tricky to get proper alignment when using a tapered landing, until you get to the gallery vent.

Strength and a greater width to work in. I cook in the entry opening I intentionally left the 2 separate less cracking due to the heat variance. But once rendered it really doesn't matter.

[MarkJerling]

I saw someone in South Australia use them. Once i did some research about the properties of Hebel bricks, it made sense to use them.

Very much so. My goal has likewise been high insulation values. Best I can tell, my oven takes 2 days to reach ambient temperature after firing, but I need to do more tests with a smaller fire over 4 hours of heating versus a large fire over 2 hours of heating which is what tried so far.

[Hatzi]

Very much so. My goal has likewise been high insulation values. Best I can tell, my oven takes 2 days to reach ambient temperature after firing, but I need to do more tests with a smaller fire over 4 hours of heating versus a large fire over 2 hours of heating which is what tried so far.

what layers have you put on the outside of your oven and at what thicknesses?

[MarkJerling]

what layers have you put on the outside of your oven and at what thicknesses?

I have 1" of furnace insulation blanket over the lower sides and over the chimney gather and sloping sections of flue, 2" of furnace insulation blanket over the upper sides of the dome and then 6-8" of regular fibreglass insulation over the top of the whole thing, R3.2. Over that, the heavy duty foil and over that mesh and 35mm-75mm of 3-coat cement plaster, with the lower two layers being regular plaster and the outer layer being waterproof plaster. Near the door opening (outer arch) the plaster and mesh layer thickens to over 150mm to help buttress the outer arch, but the rest of the plaster layer is relatively thin. It is completely cool to the touch, even when the oven is at it's highest temperature. The furnace insulation is alumina silicate spun fibre blanket rated to 1400degC from ThermalSolutioNZ.

Under the floor, there's about 50mm of compacted iron rich casting sand and under that 75mm of Hebel aerated autoclaved panels. That layer extends all the way out to the inside of the brick surround. The "gap" between the outer edge of the (under-floor) dome walls, up to floor level and the outside brick course is filled with empty glass bottles and a vermiculite cement mixture up to the oven floor level. One of those glass bottles would have been perfect for a time capsule but I forgot!

[Hatzi]

hi guys,

its been a while since i last posted.
Unfortunately life got very bus and there was little time to work on the oven.
Was busy running around on the weekend with my son after he was selected in QLD Futsal team. So pretty good excuse not to be working on the oven.

[Hatzi]

Recently have made some progress on the oven.

Have been working on vent area.

The granite landing has been selected to tie in with the stacked stone and the granite pool coping that we have.

[Hatzi]

Work then started on the domes for the vent. Thanks to everyone who provided advice on specifics for the vent landing etc

[Hatzi]

I know that i probably should not have done the next thing.

But could not wait to see if the vent was big enough and if my outer most arch was low enough to direct smoke up the vent. So had to test it..... the only way to test it was with a "small fire"

As can be seen in the pic.... smoke was directed up the vent opening, However at times there was some smoke coming out the front. From what i have read, i am hoping that this will sort itself out when I add the chimney flue which will increase the updraft. Flue is going to be 150mm diameter (I know it should of been 200mm - but this is what my dad could get me) and about 2m tall ( to clear roof line.

[Hatzi]

Preparation for the chimney flue ...
Now have to get the "old boy" to make me one, now that he understands what i am after. God knows how long this will take .... but when you are getting it for free you can not complain

[Hatzi]

After much research and consideration I decided to place a perlite layer 50mm (will go on in 2 x 25mm layers) thick under my ceramic blanket.

Well I seriously underestimated how much of the perlite ( well i am using "maxilite) I would need.

So i travelled all over Brisbane to try and get some more ..... guess what ? Could not find any!!!!!

Pretty annoyed and frustrated at the moment!

[Hatzi]

Is there anyone in Brisbane that knows where i could get more of this from?

[Hatzi]

On the positive though...
Today I found a supplier for perlite and vermiculite in Brisbane ---- 100Litles of vermiculite for $40.

So question for you guys.

if i was to purchase the vermiculite what recipe would I use to cover the dome?

what ratio of vermiculite: cement: sand: clay ?

Also for the Brisbane builders, what suppliers do you use for the clay?

Any help would be greatly appreciated and would alleviate my high degree of frustration.

[Hatzi]

On the positive though...
Today I found a supplier for perlite and vermiculite in Brisbane ---- 100Litles of vermiculite for $40.

So question for you guys.

if i was to purchase the vermiculite what recipe would I use to cover the dome?

what ratio of vermiculite: cement: sand: clay ?

Also for the Brisbane builders, what suppliers do you use for the clay?

Any help would be greatly appreciated and would alleviate my high degree of frustration.

Ok, so just saw on another thread from UtahBeehiver that a ratio of 10:1 vermiculite:cement is good enough for the dome. Is there sand and or clay in the mixture and is "normal" cement appropriate to use?

[david s]

The vermicrete mix over the blanket is to restore the hemispherical form, insulate and to provide a firm enough substrate to support the outer tendered shell. The lower the cement content the better it will insulate. Some go as low as 13:1, but I find 10:1 is about as lean as I can go and still have a workable mix. Even a 10:1 mix has more weight in cement content than vermiculite. I also like to use a 50/50 mix of perlite and vermiculite, it makes a more workable mix than either alone.For improved workability I also throw in a handful of powdered clay for every litre of cement added.
So my brew is 5 litres vermiculite, 5 litres perlite, 1 litre cement, a handful of powdered clay and 3 litres of water. Mix dry ingredients then mix in 1/3 of water, knocking down any lumps, add second 1/3 of water, mix and finally add last 1/3 of water. Place from the bottom up making a flat ledge onto which you can build another layer until you get to the top.
You’ll swear it’s not going to work when you place it but in 24 hrs it’s fine.
If needed you can then carve away high spots or fill low spots with the same mix.