28" homebrew cast oven in walled enclosure Belgium

[Mullster]

Kris S one tip I would give is to think about your total sand needs including for the dome to cast over. I have been left with a lot of leftover sand from the dome because I bought the coarser (builders) sand. I’m not sure but I think it would have been possible to use the finer sand (plasterers) for the dome to cast over and then remove it and reuse for the final layering of the outer layer on the oven.

Having said that you are going for enclosed aren’t you - so you may be able to reuse it anyway on building your enclosure.

anyway - point still stands - think about total sand needs unless you want to end up with a lot left over when you empty out the sandcastle you cast over.

[Kris S]

Thanks David S & Mullster for your tips.

Any left over sand from the sandcastle will go straight to the children's sandbox

[Kris S]

Dry stacked the hollow blocks, later filled every other hole with concrete.

[Boogie-D]

Looking good Kris... I hope to be at this stage soon...

[Kris S]

Poured the table top...

[Kris S]

I also dropped my tape measure in one of the hollow colums of stacked blocks

[Kris S]

I’m thinking a few steps ahead now, but for some reason I can’t wrap my head around how to place the chimney pipe on the flue gallery.

I want to go the David S route with simply resting my (single walled) chimney on top of the flue pipe and rendering up to it (with a cardboard spacer in between) with Vcrete.
But I don’t really understand the advantage of cutting and bending 3 tabs at the bottom of the chimney to put it on the flue gallery over the hole. Can’t you just make the hole of the gallery a little bit smaller (1cm?) so the chimney can be put on top without it falling through and without the need for the tabs? And rendering up to up with vcrete for 8 inches high or something?

I would think the gallery hole always has to be a bit smaller than the chimney diameter so the pipe can’t fall through? So are the tabs just there to ‘anchor’ the pipe more in place because they will be covered with Vcrete, thus giving more stability?

Maybe these drawings make it more clear what I mean:

[Kris S]

How long do the PP fibers need to be?

The ones I found online are about 1/2 inch long and 20 µm thick.

The same manufacturer (Sika) also makes about 2 inch long and 0.7mm thick fibers, but I can't seem to find a seller...

Will the short ones do the job?

[david s]

The ones I use are Sika PPM 48/19 and come in a pack of two types of fibres, the short ones 19mm are finer than human hair, the longer thicker ones are 48mm and around 0.7mm. Only the fine ones should be used as burnout fibres. Sounds like you have the right ones. You can test them out by placing a pinch of them on a saucer and pop it into your kitchen oven at 180C. They should melt at 160C. You can use the larger fibres in a normal concrete slab. being plastic they don't corrode if on or close to the surface like steel fibres do.

[david s]

I also dropped my tape measure in one of the hollow colums of stacked blocks

Sorry, can't help you

[Kris S]

Thanks David S for confirming the type of PP fibres I found are the right ones!

Something else: I read somewhere (can't remember where anymore) that the length of the chimney should be about 3 to 4 times the door height.
For me that would be 3 or 4 times 22cm, resulting in something like 70 - 80 cm.

I realize the longer the chimney, the better the draft / less smoke escaping throught the front opening, and it also depends on the diameter, wind etc. but just wondering what you guys think of this. would 70 - 80cm be enough in your experience?

For my 28" / 70cm oven I think a diameter of 6" / 15cm for the single wall chimney would do.

[david s]

6” (150mm) is the correct diameter for your oven. The height doesn’t matter as the flue is only there to get the smoke away from your face. The taller the flue the greater the draw.if it’s really high it requires stays. Generally around 3 ft works pretty well without stays. I use one 900mm length for most ovens.

[Matthijs]

The chimney is tricky.... I think the tabs in the end of the flue pipe give you a bit more stability (at least this worked for me. But also more touch point with the oven and risk of cracking the stucco.

The photo shows my nice cracked stucco (one layer) in the front of the oven chimney. The stucco does not touch the chimney in any place.
(I had to redo my stucco on the chimney anyway due to unremovable cardboard....)

[Kris S]

Poured the 10cm (2.5") thick 50/50 vermiculite/perlite insulating layer.
Used a 5/5/2/3 volume mix of verm/perl/cement/water. Dry mixed the solids first before adding water as advised on the forum.
Vermiculite is the brown stuff, and Perlite the white lumps in the picture of the wheelbarrow.
Have to let it dry for 3 weeks now before continuing.

[Kris S]

Forgot to add I also drilled three 10mm weepholes through the conrete, I could immediately see it's advantage as there was a little water seeping through after I put the Vcrete on.

Getting way ahead of myself again and stocked a bit of future firewood under the oven.
I've got a sheer endless supply of willow and oak, but read that fruit woods are considered excellent for cooking with. I have a little bit of apple and plum (close up picture) and also stocked some cherrywood.

I intend to only use these if and when I get the hang of firing and cooking half decently.