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Post by rene020 on Mar 18, 2019 19:12:50 GMT
thanks for the help much appreciated!
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Post by martin0777 on Mar 21, 2019 0:43:31 GMT
Make sure you insulate adequately between the supporting slab and the floor bricks. i am trying to do it on a tight budget and am using reclaimed marerial where possible. i am thinking on the base paving slabs then vermicrete in hearth and bricks around that but maybe stick some airated concrete (thermoblock) down instead of the vermicrete as i can probably source that for free. Do i really need a ceramic fibre board under the hearth or is there an other insulating material that will be good between the vermicrete and the heat storage blocks. Would a 3mm layer of ceramic fibre paper do the same kind of job? I've done the same. 9inch grinder with so.ond disc. Dust is a killer |
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Post by martin0777 on Mar 21, 2019 0:48:59 GMT
thanks, slight problem they are toplite blocks, aerated concrete weigh 700kg/m3 is this a problem? That would be denser than I'd prefer, but if they're free go for it. A mix of 5:1 vermicrete, considered strong enough for the job has around 500 kg/m3.Likewise my insulating firebricks are the same density (some vary considerably). Maybe stand the toplite blocks on edge so they're at least 4" thick, or cast a thinner vermicrete slab either under or over the hoplite blocks. Perlite is lighter...      |
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Post by downunderdave on Mar 21, 2019 21:18:11 GMT
insulate around the clay pipe or it will crack.You can build around it with 8:1 vermicrete or perlcrete to prevent this. See attached video link. youtu.be/bxOkwQyY-2w |
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Post by downunderdave on Mar 25, 2019 21:41:21 GMT
Whilst perlite is a little lighter than vermiculite, once you start mixing water and cement with it the resulting density difference is negligible. Vermiculite doesn’t have the irritant dust like perlite and it mixes better with cement and water. I actually find a 50/50 mix of perlite and vermiculite works best.
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Post by rene020 on Apr 5, 2019 19:12:20 GMT
Thanks! they are already 4” thick when not layed on edge so i think its the way to go! If i put lets say an inch of vermicrete either on top or the bottom of the toplites do i still need to use a ceramic fibre board or cal sil board or would you recommend a buget friendlier option, before i put my heater storage bricks down in the hearth? No cal sil board. The extra 1” vermicrete together with the aerated concrete blocks should be enough insulation. It must be mixed in the correct proportions. 10 parts medium grade vermiculite, 2 parts cement, 3 parts water. by volume. Mix dry ingredients well then add water slowly whilst continuing to mix. Best done in a barrow rather than a mixer. So i have been making some slight progress and maybe need a bit of advice regarding my hearth base. I had the idea to put 4” thermolites inside my brick frame and then level that up with percrete and add storage heater bricks on top of that and another row of bricks to level it out. Would i need to make holes in the wall or base to let moisture out? also is it a good idea to cover the whole square with the storage heater bricks and build my oven on top that, the storage heater bricks on the outside would get tiled/ rendered to let no moisture in the percrete. Or should i render/ tile straight on the percreate slab and just put the storage heater bricks under the hearth and build my oven around that? I dont know what is better.... Any advice more then welcome, thanks.  |
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Post by downunderdave on Apr 6, 2019 1:12:47 GMT
Rene,
You want to encapsulate the whole oven in insulation, so following that principle don’t extend the floor bricks out past the inner oven walls. Not sure how thick your floor bricks are, but 2-3” is plenty. Any thicker then it takes longer to heat them as well as more difficult to maintain the high pizza temps. There should be plenty of thermal mass in the dome for retained heat cooking if that was what you were seeking.
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Post by rene020 on Apr 6, 2019 8:33:18 GMT
Thanks Dave,
i will not extend the heat holders past the oven., they are 2” so should be good. Can i extend the percrete past the outerwall to make life a bit more easy and to have a level surface wich i can then render/tile?
How long does 1.5”-2” perlite take to dry in uk cold rainy climate? Will obviously keep it dry as best i can.
Below the vermicrete I was planning aerated concrete blocks, can i lay them dry or fix them in place to the slab with some kind of mortar?
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Post by downunderdave on Apr 7, 2019 3:20:15 GMT
First Q yes
2nd Q ages and longer than you’d think.. Probably a couple of months in ideal conditions, but the more you can let it dry from the weather the better, as the moisture under the floor is usually the last to be eliminated from firing. You will find the oven performance to slowly continue to improve as you use it over months and around 20 firings. Try to keep any rain off the vermicrete while it’s drying in the weather.
3rd Q They’re not going anywhere, lay them dry.
Once you’ve severed ties with EU your oven may be all you can afford to cook on.😋 At least it uses carbon already in the system.
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Post by rene020 on Apr 7, 2019 9:18:39 GMT
Right, maybe perlcrete is not the way to go in this case as i was hoping on starting building the dome soon. I have 300 liters of perlite how much do i need for a 28” dome with 50mm of blanket on top? I just thought i would have enough left for an inch in the base, but if not then maybe have to come up with somwthing else instead, thinking this I might have to abandon the percrete plan in the base altogether. i can get 2 calsium silcicate boards for £40 delivered mesuring 610mm*500mm*50mm each, would that be worth the money and would it be enough?
Thanks so much for your help so far, much appreciated!
Fingers crossed ties with EU wont get cut, however can’t wait for another independence referendum an cut ties with these fingerpointing “southeners” and hopefully stay in the EU. It would be nice to have a deep fried mars bar and eat it too.
I got my outdoor eko stove alrady on the go so if we travel back in time what seems like it witch theese chimney sweeps in charge i should survive. Speaking of surviving: the wild garlic is out better go and pick some!
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Post by downunderdave on Apr 7, 2019 19:51:39 GMT
Rene, you will get a shock about the price of cal sil board and it is the reason most people use vermiculite or perlite and cast their own slabs. Actually £40 delivered is not too bad, but if it were mine I’d be making up a 1” perlcrete slab. Calculate volume required height x width x depth. On mixing with water and cement there is a reduction in volume of around 20% over the dry volume so add more to compensate for this. You can start building over the stuff after 24 hrs, but it will just take longer to drive out the water. As it’s only 1” thick you shouldn’t have too much of a problem.
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Post by rene020 on Apr 7, 2019 23:13:37 GMT
It was actually £20 a board so £40 in total with delivery included- that why kept me thinking that it may be a good idea after all... However i might just go the percete way. temperatures are low here at the moment 5 degrees celsius at night and below 10 at day time, besides that there is a lot of rain at the minute so still weighing the pros with the cons.
200 liter pelite enough for the 28” dome? i find it very hard to calculate that...
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Post by downunderdave on Apr 8, 2019 3:31:34 GMT
It was actually £20 a board so £40 in total with delivery included- that why kept me thinking that it may be a good idea after all... However i might just go the percete way. temperatures are low here at the moment 5 degrees celsius at night and below 10 at day time, besides that there is a lot of rain at the minute so still weighing the pros with the cons. 200 liter pelite enough for the 28” dome? i find it very hard to calculate that... My calculations say you’ll need around 40 litres of perlite for under the floor of the oven including the entry and out to the perimeter of the outer shell, assuming it’s one inch thick. Add more if it is to go all the way out to the walls of the stand. |
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Post by rene020 on Apr 8, 2019 6:54:15 GMT
Dave ,i can work out how much i need under the oven (length*width*depth+20%.) covering the dome is what i struggle with is 200 liters enough for that?
Thanks
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Post by downunderdave on Apr 8, 2019 11:41:44 GMT
Dave ,i can work out how much i need under the oven (length*width*depth+20%.) covering the dome is what i struggle with is 200 liters enough for that? Thanks Yes that should be plenty, but it depends on how thick your walls are (brick or casting), whether you are planning on a ceramic fibre blanket layer and if so, thickness of that layer, and finally how thick you intend to make the perlcrete layer. Once those are known the volume of any layer can be calculated using volume of a sphere (using outer radius) less volume of a sphere (using inner radius). Divide the result by 2 because it’s a hemisphere. The volume not required where the door is will be about the same as the extra required around the entry so just work it out as though it’s a complete hemisphere. The formula for volume of a sphere is V=4/3 x pi x r x r x r |
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