steel liner question

[lovibond69]

Re: steel liner question

Thanks again Wiley,
I was able to get fine white silica sand. I followed your advice and did not add any perlite to the mix. I used the 50:50, fire clay:sand, blend to level the fire bricks and then cut out the form. I didn't end up bending the walls as there was enough space inside. The form felt pretty stiff so I didn't want to mess with it's integrity.

Here is what I have so far...

Any suggestions for that chimney hole on top?

BTW - "lovibond" is a brewing term as I am a brewer (answering the PM I received)

[UtahBeehiver]

Re: steel liner question

You build is interesting to watch.

[cobblerdave]

Re: steel liner question

Gudday
You works looks great .... Real workmanlike.
Regards Adding fibers to the mix . It's an old trick used in oh ovens to encourage excess moisture to exit the oven rather than causing cracking. It makes no difference to the thermal mass of the oven as the very small amount you put in I'd nothing compared to the final thermal mass . What it does it provides really fine capillaries for steam to was escape and not lead to large cracks. 1 ltr of water heated will produce 1600 ltres of steam ... Sobering thought
In you case I would thing you would probably get more cracks from the metal expanding at a larger rate than your mass layer . The result would not be noticeable in your oven as the interior surface is one piece stainless! It's all sealed in and the cracks don't go to the outside!
On the door width. The 63 per cent rule is a rule of oven height to door height not width . The wood fired oven breaths to this ratio. It makes no difference if the entrance is bigger in area because it is wider it will only draw in what air it
needs.
I have a dome oven a friend has a tunnel oven . Both cook a great pizza both cook a mean roast. They are just a bit different to operate . I know my oven best and my mate knows his oven best. I still claim my oven uses less wood but my mate lives on acreage so he just says" wood ... How did you worry about wood !" So I suppose we all just know our ovens best and know what we have to do to operate them best.
Anyway watching your build with interest
Regards dave

[lovibond69]

Re: steel liner question

Thanks UtahB and CobblerD - I really appreciate the encouragement. I looked at both of your builds and all that comes to mind for both is "Wow"! Excellent skills my friends...

Here is where I am today:
I troweled down a 2" layer of home brew refractory and placed some aluminum mesh over to hold in-place. I plan on skimming another inch or so over the top - which will then be covered in ceramic blanket. I will have enough to cover this in a 3" layer of ceramic. Would this be enough or do you think I should cover the blanket with perlcrete as well?

I cut some more stainless to form the entry arch... I think I will fire brick over the stainless.

Still working on the chimney - I'm pretty sure I have that figured out now and may line the refractory chase way with more stainless. I need to find a suitable stack for the top.

What's the best way to seal this from the weather? I have a large stack of red bricks I was entertaining cladding the oven with. Do I need to do anything to the ceramic blanket or perlcrete before mortaring these over? Do you recommend sealing the bricks?

Feel free to chime in. I enjoy the differing perspectives.

Thanks

[cobblerdave]

Re: steel liner question

Gudday
You have been busy.
3 inchs of ceramic insulation.....overkill...which is good. Covering with a layer of perlite/cement....not sure its required as most use it to cover the lumps and bumps left after trying to make the blanket fit over a dome shape. Being a barrel shape I dont think you will have that problem? I suppose theres onl;y one way to find out.
As for covering the dome with a brick exterier, do it! but of course I bias. I would consider covering the insulation blanket with a layer of render so you have something to mortar the brick too thats solid.
Not to sure that hand hole is going to let through enough smoke as a rough rule of thumb it should be 15 per cent of the area of the oven entrance. Again I a bit bias... go big...the smoke has to go up, you just have got to let it do that.
Regards Dave

[brickie in oz]

Re: steel liner question

The flue hole is too small.

[david s]

Re: steel liner question

The hole into the flue can be a little smaller than the area of the flue beyond it with out any problems. It will simply act like a Venturi and suck furiously at that point.if it is significantly smaller ( like 50% ) of the area it will start to choke it and you may start to have smoke issues.

[lovibond69]

Re: steel liner question

Great - thanks everyone for the feedback.

I calculated the minimum flue size based on a method I read on someones post. My entry way is 14" wide by 8.75" high (63%) which requires a vent hole minimum of 4" or possibly 2" round?. My vent is 4" x 2".

14" x 9" = 126"; 10% = 12.6; 12.6 divided by 3.14 (pizza pi) = 4"

After looking at these numbers again - I think I need to take another look at that calculation? Does this look right... last night I came up with a 2" round hole minimum base on my small oven size - now I'm not so sure...

I really do not want to cut away the bent and rounded corners of hand holes (flue holes) as this gives incredible structural strength to these pieces of stainless.

I plan on connecting the two flue holes by troweling refractory to create a chase way in-between the bottom and top flues. I was planning on bricking out the top (above the stainless hole) to open it up the flue interior and create some height (how much?) and then install some stainless pipe above that with a "flapper" through the middle to close off the vent if ever needed.

Are there recommendations as to how tall the stack should be to create the best draw? If I were to cut away 1" holes on either side of the rolled flue holes (without compromising the strength), leaving a small space in-between, would that change the air flow in a positive way... I know this is all speculation. Btw - I was originally going to build this without a flue but after reading more, I thought having a narrow flue is better than having none at all.

Thanks!

[cobblerdave]

Re: steel liner question

Gudday
Is it possible to reverse that entrance piece so that the rolled steel lip is on the outside. This would give you a smoke chamber to stop the smoke from exiting straight out the front. It would also move the vent hole forward enabling you perhaps to fit a 6 in? 7 in?Chimney over the top of your vent hole gaining the Venturi effect as Davids has suggested
Having used on oven with no external chimney before I built mine I can tell you that the chance of missing an eyebrow or fringe is very real and quick.
Regards Dave

[okn]

Re: steel liner question

4" diameter/2" radius is the right number, but you have a 4X2 hole which is much less than the MINIMUM required.

[lovibond69]

Re: steel liner question

Here is what I was thinking of for the flue(s). Any issues with having two ports for venting? The diameter of the two combined is ~5.75". Any recommendations on how tall they should be?

I may do a test fire to see how it flows before making any changes.
Any thoughts?

Thanks folks...

[okn]

Re: steel liner question

You're outside my expertise, but I think the two smoke stacks look coo l

[cobblerdave]

Re: steel liner question

Gudday
Love the look of those pipes! I think you can start to talk in terms of exhaust rather than chimney.
It's good that you are going to experiment with it, you into unknown territory.
A couple of things to keep in mind. All ovens smoke to varying degree at start up as the fire becomes hotter the smoke itself hotter and the chimney hotter the process becomes more efficient.
If you don't have a smoke chamber the smoke will bypass those pipes and follow the path of least resistance straight out the front.
Regards dave

[david s]

Re: steel liner question

For your set up with a front flue I wouldn't go any smaller than a 5" diam flue (which is 19 sq in)

[UtahBeehiver]

Re: steel liner question

Out of my pay rank whether a dual chimney will work but the slanted pipes are very neat, something off a turbo diesel engine!