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Post by gream0604 on Jun 14, 2015 16:25:31 GMT
So I thought that I would start a build thread so I can start to document my progress on the build. I am in the process of building the base for the oven, and am fairly limited for space. A quick question. Will it make a huge amount of difference whether I lay the bricks like this: or like this: The reason I ask is because I am fairly limited on space, laying them like the last photo will allow me a slightly bigger floor space? I am guessing that the difference will be that the top photo would have slightly more thermal mass. Will I notice a massive difference though, or am I overthinking it? Keep an eye out, and I will post more photos as the build progresses! Matt
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Post by chas on Jun 15, 2015 8:15:20 GMT
Hi Matt, never had two otherwise identical ovens to trial, but my guess is your guess is good - less thermal mass, less insulation, more heat 'leak' with the bricks on edge, probably 100% better laid flat. That said, if by laying on edge you have room for more ceramic blanket or any other insulating jacket, you could be better off... I started with 4.5" flat laid and no insulation and am in the process of fitting some because heat loss was noticeable: ukwoodfiredovenforum.proboards.com/thread/2187/give-pompeii-retro-fit-insulationThe other thing worth mentioning is that wherever your bricks end up on the base, there is no reason why the insulating jacket can't oversail them - in fact there is an advantage: fill the available oven floor with brick and oversail the covering and water will run off harmlessly to the ground, not onto the floor! Chas
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Post by gream0604 on Jun 17, 2015 13:31:52 GMT
Quick question about the Mortar for the arches, as I have read a few conflicting things. Do I need to add powdered fire clay to the mortar mix, or can I stick with cement, sand and lime? Some posts I have read on the FB forum have said that the clay is only used to help with the workability of the mix. I already have some plasticer left over, so could I use that?
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Post by oblertone on Jun 17, 2015 18:15:24 GMT
Apparently the mortar burns out at the temp of a WFO so mixing powdered clay is recommended to provide a fixative at higher temperatures; this is only my understanding but I used 'home brew' at 3-1-1-1 (sand/cement/lime/clay) and it seems to be doing the job so far.
ps - If you need more heater blocks then I've got a dozen left, yours foc.
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Post by gream0604 on Jun 19, 2015 7:19:53 GMT
Dry run of the Thermalite blocks ready to fix in place.
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Post by cobblerdave on Jun 19, 2015 9:29:12 GMT
G'day With a vaulted oven it's better to build the arches at each end then build the vault ceiling over the ends. Reason being the ends are then trapped under the vault ceiling which will minimize the tenancy for them to expand outward. The round vault is the strongest configuration rather than the taller type as the forces follow the bricks evenly back to the base. The taller type the forces still want to push outward at the point where the structure straitens and leaves a weak point. You could buttress this at the sides but this adds extra mass. The vaulted dome is strongest when it is done of brick bearer pattern like a brick wall of overlapping bricks. A series of single arches is weakest as it doesn't lock into the whole structure. Just my thoughts on how I would build a vaulted oven Regards dave
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Post by gream0604 on Jun 19, 2015 10:10:40 GMT
Thanks Dave,
That's really helpful information. I was planning on the round vault type, as you say so the forces go straight down through the base of the oven, instead of pushing out. My Oven is going to be fully enclosed by Thermalite blocks, with loose vermiculite poured round for insulation, then all will be rendered.
I'm still trying to figure out how to create the door opening area with chimney etc at the moment!
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Post by cobblerdave on Jun 19, 2015 11:30:50 GMT
G'day My bestest mate has a vaulted oven it's a great oven though im the first to admit he cooks in it best. His has no entranceway which I get tricked by and have lost a few hairs to the hot gas out the front. With the oven mouth. Like the all ovens 63 per cent the hight of the internal roof. Width as wide as is usable not 1/2 the width like the dome oven rather more. The length of the entranceway I'd try to keep it at a brick and a 1/2 ( roughly 12 ins) so you aren't trying to operate you long oven though a long entrance way Regards dave
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Post by gream0604 on Jun 28, 2015 15:32:14 GMT
Been doing a bit more work over the weekend. Forgot to take pictures as I was going though!! The arches are up, and back wall built yesterday. Seems to be pretty strong, although I was a bit worried when I took the form out this afternoon!! Need to pickup some more bricks tomorrow to start on the entrance way. Its not huge, but should be plenty big enough for what I need. Also starting to think about insulation. I have about 120mm around the sides and 115mm around the back to insulate. Also want to try and keep the cost down as much as possible. What are peoples thoughts on just ceramic blanket for insulation, and rendering straight on top. How thick would I need the blanket? I was thinking 50mm, or could go up to 75mm. Or would it be better to go for 25mm blanket and 50mm vermicrete? Around the back of the oven I am pretty tight on space, as I have gone up against the fence. I was thinking of using some 13mm blanket, then thermalite blocks. Do people think that will insulate enough? Or could use loose fill vermiculite instead of the 13mm blanket?
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Post by cobblerdave on Jun 29, 2015 2:33:30 GMT
G'day 50 mm of ceramic blanket or 100 mm of vermiculite/cement is a good standard. The vermiculite/cement is best at a ratio of 5 to 1 cement. Loose fill vermiculite is more efficient than when its mixed with cement. So 115 mm gives you heaps for your insulation and render. Ceramic blanket is easy to apply and you don't have to wait as long for your oven to dry, but its the most expensive. Vermiculite/cement is a bit harder to apply and you have to dry out quite a bit of moisture but its certainly a lot cheaper. Both will work equally well at the thicknesses I gave, so its up to you what's important. Regards Dave
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Post by gream0604 on Jun 29, 2015 6:07:06 GMT
So can I apply the vermicrete directly onto the red brick then?? Won't it get too hot and start to break down the concrete, or does it not get that hot on the outside of the oven??
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Post by cobblerdave on Jun 29, 2015 7:03:31 GMT
G'day Yes it doesn't break down as its insulation and the heat is trapped in all those small airspaces in the vermiculite. Same with airated cement block. You'd think that it would break down being cement but it doesn't again because the heat is trapped and slowed down in the airspaces. If never truly understood what is going on, but it works and you have to except that Regards dave
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Post by gream0604 on Jun 29, 2015 7:57:42 GMT
Haha. Thanks for that. I don't really want to understand! Just want to know that it will work, and not fall down!! Thanks again. More pictures to follow once I have started on the entrance way, and insulation!
Matt
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Post by gream0604 on Jul 29, 2015 7:36:11 GMT
Made lots of progress over the last few weeks, but unfortunately forgot to take photos along the way. Here is the stage I am at now. Vermicrete has been completed, and is drying out, and I am just waiting for the 5inch flue to arrive. Lit the first fire last night to help in the drying out process. Out of interest, how long do people leave the vermicrete before rendering over the top?
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Post by cobblerdave on Jul 29, 2015 11:22:37 GMT
G'day Well done that's a heathy thickness of pearlcrete over the dome! Sorry it will take many weeks to dry fully. Protect it from the rain at all costs. A piece of plastic over a section and check it in the cool of the mornings. If it has condensation under it, it's still not dry. Sorry any oven takes time to dry. Regards dave
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