Help Please - about to start work!!

[mmmhumous]

Finished the lintel, front arch and first course of bricks for the chimney. Also put a layer of vermicucrete (and some chicken wire) over the oven arch.

So it's pretty much operational now (and looking like anoven) . Just need to finish the enclosure and chimney.

I think I read somewhere (not sure it was on this forum though) that the height of the chimney is important for the draw. Is that right - or doesn't it matter?

[Frances]

Yep, the higher the chimney the better the draw.

Erm, and that would be because of the difference in pressure at higher altitudes...? Hot air rises and so, er...

But you definately did read it on this forum and as far as I know it is also true

Although some ovens have no chimney and still work, so it must be realtive.

How much vermiculite did you put round your oven by the way? Its looking really nice - lovely archway there - but it looks a tad too slender to my mind. As it says somewhere on this forum (like just about every second thread ) you can't have too much insulation.

[mmmhumous]

Cheers Frances.

Good stuff, think I'll be adding about 50-70cm to the chimney (maybe more).

For the insualtion, theres about 5cm of vermicucrete round the sides (I'll be adding 5cm of loose vermiculite once the enclosure walls are finished).

There's slightly more vermicucrete on top and as well as loose vermiculite, I'm addin a roll of mineral wool insulation too (had some left over from insulating my loft).

Basically I'm using as much insulation as I can fit in (like you said the advice given on every over thread) - Total: 5 inches below, 4 round the sides and loads on top.

[Frances]

Sounds as if you've got that bit well sorted out then.

[mmmhumous]

Hopefully

[mmmhumous]

Got to love wikipedia!

Looks like it's worth me using vericucrete in the 'porch' bit oven the oven (what is that part called - under the chimney?), to try and keep the smoke hotter too.

Chimney - Wikipedia, the free encyclopedia



where:
Q = chimney draught/draft flow rate, m³/s
A = cross-sectional area of chimney, m² (assuming it has a constant cross-section)
C = discharge coefficient (usually taken to be from 0.65 to 0.70)
g = gravitational acceleration, 9.807 m/s²
H = height of chimney, m
Ti = average temperature inside the chimney, K
Te = external air temperature, K

[mmmhumous]

First pizza going in within the hour!!!!!!!!!

Had a fire going for the last 2 1/2 hrs and been at well over 350°C (limit of my cheap oven thermometer) for the last hour and the soot has now burnt off..... yey!

Vericucrete does make a substancial difference ~30°C less than the bits which aren't covered.

See what everyone means about wood/fuel consumption...... and there was me thinking my wood stores were too big! ...."gonna need a bigger boat"

Notice a slight flaw in my design. the front arch is a bit too high, so not all of the smoke is directed up the chimney...never mind, thinks I'll go for a slpit (stable style) door across the front arch which should rectify the problem. Anyway was is got hot there wasn't that much smoke any way.

[70chevelle]

mmmhumous - can you tell me the cooking floor dimension of you oven?

[mmmhumous]

Hi 70chevelle

Hearth was done with fire bricks and is 900mm wide and 765mm deep. The oven walls sit on top of these bricks. Thie interior dimensiona are 640mm wide and 540mm deep (up to the lintel at the front). Hope this helps.

[dmun]

Just a little translation for us meter challenged: 25 3/16" * 21 1/4"