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Post by wolvisfamily on Jul 17, 2017 5:39:29 GMT
It all started with a bread-making course at the E5 bakery last year, and now here we are building what is going to look like a giant flint hedgehog next to a field in Norfolk. Our heads are spinning with dome dos and don'ts, but I'm realising that we need to design the bit at the front too. So far this seems to be the main info I need to take into consideration, but any advice from members experience would be welcome. I'm assuming a 6 " flue, but is there any optimal size for the chimney? I want to use the oven to bake bread, so I guess it would help to have a damper on the chimney to help keep heat in when the fire has died down? Has anyone had experience of making one. As for the chimney itself, I can see that double wall steel would be expensive but efficient in terms of being able to buy fittings, but my wife may have views about antique chimney pots, in which case I am sure that will be a whole other game. Has anyone ever put steel pipe inside an old chimney pot to disguise it? We'll need a door too, obviously. I'm assuming we'll end up with a home made one that we push into whatever opening we construct - or are there a range of doors out there we could build to fit to? I have picked up that whatever the size of the hole we should allow a rebate all around so that the door can push fit snugly. Then comes the positioning of the chimney hole, presumably it is centred in whatever we construct for the snouty bit of the hedgehog/igloo, at the moment we are thinking about a brick and a half's worth of snout.   |
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Post by chas on Jul 17, 2017 7:51:46 GMT
It all started with a bread-making course at the E5 bakery last year, and now here we are building what is going to look like a giant flint hedgehog next to a field in Norfolk. Our heads are spinning with dome dos and don'ts, but I'm realising that we need to design the bit at the front too. So far this seems to be the main info I need to take into consideration, but any advice from members experience would be welcome. I'm assuming a 6 " flue, but is there any optimal size for the chimney? I want to use the oven to bake bread, so I guess it would help to have a damper on the chimney to help keep heat in when the fire has died down? Has anyone had experience of making one. As for the chimney itself, I can see that double wall steel would be expensive but efficient in terms of being able to buy fittings, but my wife may have views about antique chimney pots, in which case I am sure that will be a whole other game. Has anyone ever put steel pipe inside an old chimney pot to disguise it? We'll need a door too, obviously. I'm assuming we'll end up with a home made one that we push into whatever opening we construct - or are there a range of doors out there we could build to fit to? I have picked up that whatever the size of the hole we should allow a rebate all around so that the door can push fit snugly. Then comes the positioning of the chimney hole, presumably it is centred in whatever we construct for the snouty bit of the hedgehog/igloo, at the moment we are thinking about a brick and a half's worth of snout. Ok... if you have the sort of door that you push forward through the entrance to a reveal in the brickwork, you'll have pushed past the chimney above, so no cap/damper on the chimney needed. If, like me you fit a reclaim cast iron door at the entrance, then you do. You're also heating the entrance way instead of just the oven proper once it's closed, and leaking some heat through the iron and up the flue... not having both types to try, I'm not sure if that's a huge relevance. If I was particularly bothered, I could arrange some form of ceramic insulation on the inside of the door. If I was building again I'm not sure I'd use the iron door - but at the outset I was only interested in pizza (ie door open) cooking and only became more concerned with insulation/sealing as I developed an interest - encouraged here - in other uses. Yep, the chimney is conventionally forward of the dome and formed from lower down than the top. This helps ensure heat rolls over the entire oven floor on its way out - when, of course it's lost. My experience is that if you cover the oven with anything other than a permanent roof or a custom-made tarp, a tall chimney is a handicap. So, keep it stubby. The exhaust is very hot, you may have 'cracking issues' with anything terracotta - I mention this because of the likely cost at a reclaim yard. So, if a tall, elegant chimney is the chosen way, then yes, line with steel. Twin wall would help isolate the pottery, but single with a jacket of vermiculite poured down from the top would do. Chas ps - if you're anywhere near Acle and want to look at an oven... |
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Post by oblertone on Jul 17, 2017 7:54:37 GMT
Your 'snouty bit' is there for two main reasons; first to help ensure the ratio between the dome height and door height is correct (at 63% or thereabouts) and secondly to provide a firm base on which to stand your flue. Whereabouts your flue sits isn't too critical but if it's too close to the dome you may end up interfering with the dome insulation. Some sort of plenum or shaped chamber to gather the smoke would be good, but is dependent upon how thick the arch material is. As to size and material, twinwall with a 6" internal diameter would be OK for your 36" internal oven; you can often find single lengths on eBay or gumtree for not much money. Any clay pipe or chimney piece will crack as they are designed for the top of a flue and not the business end where the temperatures are fierce. Someone did do an internal metal sleeve with the gap packed with vermiculite but the you have the issue of sealing the top; so it can be done.
There is no need for a damper as you pointed out, using an internal door to seal the oven against a lip is the best way forward. Any external door is purely decorative and may make working your oven difficult by constricting the entrance.
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Post by chas on Jul 17, 2017 13:38:09 GMT
It all started with a bread-making course at the E5 bakery last year, and now here we are building what is going to look like a giant flint hedgehog next to a field in Norfolk. Our heads are spinning with dome dos and don'ts, but I'm realising that we need to design the bit at the front too. So far this seems to be the main info I need to take into consideration, but any advice from members experience would be welcome. I'm assuming a 6 " flue, but is there any optimal size for the chimney? I want to use the oven to bake bread, so I guess it would help to have a damper on the chimney to help keep heat in when the fire has died down? Has anyone had experience of making one. As for the chimney itself, I can see that double wall steel would be expensive but efficient in terms of being able to buy fittings, but my wife may have views about antique chimney pots, in which case I am sure that will be a whole other game. Has anyone ever put steel pipe inside an old chimney pot to disguise it. This might help - it was posted to my thread but disappeared, tracked it down:  Chas |
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Post by jagnut on Jul 17, 2017 20:33:19 GMT
 sorry i think i just messed up your post here is a pic with steel liner which i add a extra 1 1/2 meters to when cooking see my post if you need more help i will send you more pics |
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Post by oblertone on Jul 18, 2017 6:27:53 GMT
Duplicate posts removed for clarity.
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Post by wolvisfamily on Jul 18, 2017 11:51:24 GMT
 Interested in what the community think about the following dilemma. - I have only ordered enough Fibre Board insulation (50 mm) to totally support the oven floor, but not the dome walls. - Do I a) use the two pieces whole and have an insulated square, filling the rest in with perlite and or vermiculite concrete? Worried that the difference in structural support might end up destabilising the whole structure. - Or b) cut round the shape of the oven floor and use the fibre board as a circle under the floor, embedded in an oven shaped island of perlite concrete? - or , I suppose, c) bite the bullet and buy more FB board and pay the absurd delivery costs on top? |
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Post by wolvisfamily on Jul 18, 2017 11:52:31 GMT
ps the picture shows 2 of the 3 flinting elves at work. The third is off mixing pug trying to keep up with them in mortar supply.
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Post by oblertone on Jul 19, 2017 9:30:56 GMT
You've bought it, so use it ! Leave it as pictured so your outer layer of insulation will connect with it, thereby totally enclosing your oven in insulation. Filling the gaps with vermicrete or perlite cement will take care of the 'snouty bit' and edges. Once the dome is built then the compressive forces will be spread evenly so I don't think you'll have an issue with stability.
Flinting elves look like a useful extra, but likely to be expensive in the long term !
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Post by wolvisfamily on Jul 20, 2017 11:24:22 GMT
Ha ha, wise words, but we love them: it's all got very arty down there,(see pic) while I am still trying to work out how to guarantee a rebate for my door, and not actually got a brick laid yet!  |
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Post by oblertone on Jul 21, 2017 7:09:30 GMT
Arty indeed; as to the rebate, build the dome, then add the arch leaving a little lip. I used my oven for a year before adding the arch/flue and it worked perfectly well, albeit a trifle hot and smoky to operate.
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Post by wolvisfamily on Jul 24, 2017 9:36:49 GMT
Sounds like good advice, thanks. Hope to start the dome this week.
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