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Post by cannyfradock on Sept 3, 2012 19:13:03 GMT
Hi Pete Didn't understand.... "oven dimensions for a 30" hearth oven build if anyone can help." A few of our clay oven builders have used bottles below their hearth, but I don't understand this system. Oh dear....I'm not doing very well so far. If it wasn't for the front overhang, and didn't want to pour a slab I would have suggested thermolite blocks directly on top of the RC lintels. In fact your system with the heavy slabs would still work with thero blocks....here's how I used them I shall be using the 2" CF blanket from Liam on my next build.....I think this is the one.. kilnlinings.co.uk/ceramic-fibre-blankets/cf-blanket-1260gd/cf-blanket-1260gd-3.66m-610mm-x-50mm-density-128kg The number of bricks needed vary from member to member. For my 90cm internal diameter oven I used about 120 fire-bricks in total. My hearth was laid "on flat" (3"). For the dome the bricks were simply bolstered in half. Only the internal arch was fire-bricks...not the entrance arch, and the fire-brick hearth stopped at the internal arch. The landing to the entrance arch ....and the entrance arch were both built with clay bricks. Hope you get a bit more feedback on this. Terry P.S....Your wish is my command.....thread now moved to the Pompeii section
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petec
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Posts: 232
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Post by petec on Sept 3, 2012 21:31:55 GMT
Hi Terry - many thanks , this is really helpful.
I like the thermo block idea and could do this on top of the 500mm pavers, including the overhang. Nice easy insulation base for the hearth ! Like it.
Will any thermolite blocks do the trick or is there anything I should look for ? So looks like the beer and wine bottles can go to recycling then !
Picking up the 50mm thick pavers from Milfords tomorrow - so work can resume. Going to order rest of the firebricks, blanket etc from Liam this week too.
Many thanks for all the advice - really appreciated Cheers Pete
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petec
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Posts: 232
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Post by petec on Sept 3, 2012 21:37:49 GMT
Ah the bit about "oven dimensions for a 30" hearth" ...
what I meant was how big from rear to front of the finished oven dome and entrance/landing. I need to make sure my entrance/landing will fit.
Looking at various build photos it doesnt look as though you need much room for the vent and external arch. I just wondered if I could get a rough idea.
With the front overhang I will have a total available front to back dimension of 1350mm + 150mm = 1500mm to use.
Rgds Pete
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Post by faz on Sept 4, 2012 6:33:18 GMT
My 31" oven is 68" from front of entrance to rear of oven. My entry is two full bricks deep, so you could save a few inches by making it a bit shallower.
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petec
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Posts: 232
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Post by petec on Sept 4, 2012 11:34:55 GMT
many thanks faz, cheers pete
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Post by bookemdanno on Sept 5, 2012 12:43:14 GMT
Welcome to the brick build crew, Pete!
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petec
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Posts: 232
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Post by petec on Sept 5, 2012 14:06:32 GMT
cheers,
following Terry's advice/example I ordered my thermalite blocks (and 50mm flags ) today along with another couple of bags of vermiculite.
I will end up with a hearth plinth with max dimensions of 1350mm wide by 1500mm deep front to back , due to the opportunistic overhang of the 50mm deep pavers at the front. They give me 150mm overhang beyond the 1350mm base.
Onto this go 14 of 620mm x 215 x 100 lightweight thermal blocks. This will form the underfloor for the hearth and will actually cover most of the plinth including the entrance area which I will brick over.
What I need to work out next is how much entrance space I have to work with based on a c.31" oven floor.
Roughly speaking I have 31" + 9" of 1/2 firebricks + 4" of ceramic blanket + 6" Vermicrete (2 lots of 3" - hope that thick enough ? ) 1 2/2" of outside render . So, all in all diameter of 51.5" or 1308mm sitting on the 1350mm width.
So its now all about the dimensions of the entrance / chimney area.
I read that for a 27-36" oven the flue needs to be about 6" diameter for good draught. I reckon thats just over 28 sq inches in area, so I am trying to work out what vent opening I need between oven arch and entrance arch . I guess a half brick and 7" wide vent would do it.
As my internal arch will extend forwards to 15.5" + 4.5" radius from my centre point , i.e. 20" or 508mm, it seems I have 750mm less 508mm to play with for the entrance and vent area. Sooo..., about 242mm or about 9" , or a bricks worth. Hope I got all that right !!! Now to work out how to do it - might have to do that "live" when I get to that stage.
I'm sure other people must have built larger than 31" ovens with entrance areas on 1.5m front to back plinths ? I'm sure I've read that here somewhere !
If anyone can see any crazy errors let me know !
cheers Pete
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Post by cannyfradock on Sept 5, 2012 18:07:02 GMT
Pete You just start to build an arch as normal except, the last 3 bricks at the top of the arch are not full bricks. They are 1/4 or 2" bricks either side of the hole. This will create a vent of 4" x 8" (ish). It's easier to make a square hole...or round hole come to that if you han a brick and a half to play with. Vic's build on the old forum was short of space so he just overhung the bricks over the slab to get his 1 and a half bricks in... woodovenukforum.forumup.co.uk/viewtopic.php?t=1079&postdays=0&postorder=asc&start=20&mforum=woodovenukforum It really helps with these tricky stages to spend a little time and look at the vent construction of all the Pompeii builds on the new AND old forum.....pictures say it better than words. Still keep shouting if you need advice. Terry
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petec
WFO Team Player
Posts: 232
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Post by petec on Sept 5, 2012 19:51:17 GMT
Thanks Terry - I'm getting the idea about the external arch and vent.
I'll keep looking at all the other builds. Anything special about allowing for expansion at the entrance or between internal and external arches ?
Cheers Pete
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Post by bookemdanno on Sept 5, 2012 20:01:12 GMT
Just re-read your last post a few times Pete! Lots of numbers! I think your not allowing for the fact that the Oven Arch usually bisects the diameter slightly. Meaning that the overall length, front to back is not fully diameter plus brick and a half for the entrance. Your tight for space but, this may mean your oven can move slightly more forward perhaps allowing an extra inch or two into the radius! Best best is to sketch it all out to scale. I did this many times over last winter before starting out. WH Smith should have plenty of Back to School offers for Geometry Kits! Good luck!
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petec
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Posts: 232
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Post by petec on Sept 5, 2012 20:43:51 GMT
good thinking ... ooh...more girth ......would be good. I'll work out what space I will save because of the "chord" across the front of the oven curve. just realised that the opening is roughly same as the radius so there is an equilateral triangle outlined from the edges of the inside of the arch opening to the centre point. So i should be able to work out how much space saved inside the diameter If that makes sense ! Google is my friend..... calculator.tutorvista.com/math/67/chord-of-a-circle-calculator.htmlI just need to solve for d in the formula below. Or I could just draw it to scale !! Formula for chord length = 2 r2−d2‾‾‾‾‾‾‾√ r = radius of the circle. d = perpendicular distance from the chord to the circle center. from the chord of the circle to its center. Anyway, it turns out that the length is 13.85 inches. So a little bit more space gained - maybe get away with a 32" inside if I can squeeze the entrance arch in. Once I get the thermalites down this weekend I will start mocking up with cardboard templates etc. No substitute for seeing it in situ. Cheers Pete
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Post by tonyb on Sept 6, 2012 8:14:58 GMT
Pete, I think I've followed your musings and don't see any particular problems, but make sure you mock it up in situ before laying any bricks
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Post by faz on Sept 6, 2012 10:55:02 GMT
It is good to see that you're also getting assistance from StarWars - I see R2D2 makes an appearance in your post above!!
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Post by bookemdanno on Sept 6, 2012 12:10:50 GMT
Even in these computer CAD days, Formula 1 Cars usually get a "mock-up" during the design. It always helps to see with your own eyes!
Blue Peter!
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petec
WFO Team Player
Posts: 232
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Post by petec on Sept 7, 2012 17:46:20 GMT
more materials arrived today for a bit of progress tomorrow, fixing the paving slabs and thermalite blocks on top of my blockwork base.
Quick question regarding DPC.
I put a DPC layer over sand on top of my hardcore before I poured my base. But I didnt put any DPC in any of the courses of blockwork in the stand.
I wondered whether I should fit DPC on top of my lintels, under the flag slabs before I do my thermalites and hearth layer.
Daft question - but does it not matter that the mortar doesnt bond to the layer below ? Does the weight just pin everything down effectively ? So, do I need to bother with any more DPC ? cheers Pete
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