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Post by faz on May 6, 2012 6:09:16 GMT
Looks pretty sturdy! It's good to see someone else making a oven that can be used as a hurricane shelter if it's ever needed
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tapir
valid member
Posts: 45
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Post by tapir on May 6, 2012 14:55:33 GMT
I was about to saw up loads of wood to shore up the ply board that the slab will be cast on, when I had a moment of inspiration. I've used an old pallet to support it and rested it on bricks. I've put wedges on top of the bricks to make it level & to make it easier to get the bricks out. (too dark & wet for a photo though). Make sure that if the pallet gets wet or damp, and expands, you've still got enough give in your wooden supports to knock it out
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Post by pete123 on May 6, 2012 15:49:11 GMT
Thanks Tapir, My son reminded me of the same thing so I've put some wedges in.
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Post by pete123 on May 6, 2012 19:33:46 GMT
Last view before the concrete goes in. No medals for carpentry skills! Attachments:
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Post by pete123 on May 6, 2012 19:38:25 GMT
A close up of the improvised metalwork support (a piece of slab). Shutter depth is 110mm or thereabouts. ....I did put damp proof in but only to stop any cement falling through the cracks, it will come out when the board is taken down. Attachments:
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Post by pete123 on May 6, 2012 21:46:47 GMT
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Post by faz on May 7, 2012 6:35:54 GMT
They have a 4/15ths (approx 27%) lower conductivity, so you'll either lose 27% less heat through the base of the over, or alternatively you could achieve the same insulation value with a 27% thinner layer, if height was important to you.
I suspect they have developed them to take advantage of high insulation values required by the newer building regs (not that those requirements apply to a WFO!).
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Post by tonyb on May 7, 2012 8:24:19 GMT
I'm not sure its as simple as that. The thermal conductivity is often quoted within a 'working' temperature range which for all these types of block is going to be pretty much ambient temperatures and much less than the blocks will see in a wfo situation. If it is a simple linear relationship then all other things being equal, if they cost less than 27% more than standard blocks and you can afford it then why not. I suspect that the additional conductivity benefit is probably due to more voids in the construction ie air As an aside, i trained as a chemical engineer, (though did little if any during my career), one thing I remember being told at university was that a 'holy grail' for chemical engineers was to produce goods that consisted of as much air and or water as possible! Or maybe that was marketing not chemical engineering
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Post by pete123 on May 7, 2012 17:52:05 GMT
Thanks both of you. That's very knowledgeable and will help me make my mind up.
I finished the base and stand today- Not the bricks around the base though so I don't get cement & home-brew on them. I may have a few more questions coming soon prior to me buying fire bricks & insulation.
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Post by pete123 on May 7, 2012 18:19:40 GMT
I started relatively early in case I had to rush off & buy some more ballast. It eventually took 18 bags of ballast & 6 bags of cement. I sprinkled the sides with a bit of water to stop them sucking all the moisture out of the mix. I understand that it's best to cure slowly, so I'l cover it with a sheet tomorrow when it's dry. Attachments:
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Post by pete123 on May 7, 2012 18:28:55 GMT
Pretty pleased with the result. There was the odd light shower so back up with the Heath Robinson Tarpaulin. I think this concludes phase 2! So home for an early bath & a tin of beer or two & some more research prior to ordering bricks etc. Attachments:
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Post by pete123 on May 9, 2012 14:52:32 GMT
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Post by pete123 on May 9, 2012 14:56:45 GMT
This is what Liam sent me in relation to some questions I had.:- Thank you for your e-mail. Calcium Silicate board is what I would suggest as a suitable insulation between the concrete foundation and the firebrick hearth. This has been tried and tested by hundreds of wood oven builders to date. The 50mm seconds pack should be fine as you don't see the cal sil once its laid as its hidden between the base and firebricks. A little tip. To keep the board waterproof and therefore keep its insulation values, most builders wrap the cal sil in aluminium foil prior to laying the bricks. It just means if any water goes beyond the bricks above , the board stays dry. The boards are not usually fixed to the slab, the weight of the bricks above keep them in place. Bricks required for the hearth and dome of a 36" oven I would guestimate at around 200 based on previous sales. The size most purchased for the job is 230x114x76mm The chimney will get extremely hot and so you would need to use either Firebricks or something that can withstand such heat such as a high grade stainless steel chimney or similar. The fireclay is a powder as you say. Fireclay has little if no binding properties and is usually mixed with Lime and cement and sometimes vermiculite I believe in making the home brew mortar. The LBP HT blanket is the usual choice as its user friendly (Non - Carcinogenic) the thickness and size roll is up to yourself. Personally I would go for 25mm 128kg 1200GD. I would be unsure on the quantity of Fireclay needed as I haven't done the home brew mix myself. Bricks 200 approx. 1 or 2 blankets. Boards 50mm thick enough to cover the hearth. I hope this helps and if I can assist you further please let me know? Thank you and Best Regards Liam Proprietor Kilnlinings www.kilnlinings.co.ukinfo@kilnlinings.co.uk
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Post by pete123 on May 9, 2012 14:58:34 GMT
Rather than Foil... how about the hypothermia space blanket that runners use? Any thoughts anyone?
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Post by pete123 on May 10, 2012 8:22:48 GMT
200 Bricks, Clay, Blanket & Calsi Board now ordered.
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