WFO CNR Build - Darwin

[terratree]

Hi All,

Thought I's share some pics of the build to date, while the hearth cures.

Hopefully give me time to finalise the plan - work out inner and outer arch placements, final insulation layer/calsil plan and orientation of first course now that I have a brick saw.

My plans are very similar to Gregs build below in Canberra however, my fire brick dimensions are a little different @ 230 x 114 x 70. (Purchased from Littlehampton in Adelaide, about 10 years ago)

https://community.fornobravo.com/forum/regional-forums/australia/391738-fnbrokens-corner-wfo-in-canberra-australia

Jay

[UtahBeehiver]

Great start. Pivot point of IT works best when at floor level. This can be done by building a wood block to be placed where the center brick would be. See Gulf's build.

[terratree]

Thanks Russell. Have been over your build (and Gulfs) some time ago, very nice !

i need to go over these builds again until I fully understand the TDC brick placement. It seems this is the first step for the inner arch ?

[Gulf]

Hi Terratree,

You wont find much on my build about inner arch placement. I placed mine too far forward and also used 8" firebrick. 9" brick for the inner arch give a little more play. I ended up splicing my inner arch brick to make up for the difference. It's difficult to do but, it was either that or work it out with a beaver tail later. The TDC brick (and it's shape) is what you use to decide the proper inner arch placement. I think that JRPizza 's build will help explain that. He and Russell may also be able to reference you to some more recent builds conserning that.

[terratree]

Thanks Gulf !

The amount of information on this forum is ridiculous - and yes I'm scouring thru JR's build too.

Re. the inner arch - Deejayoh's calc (how good is that ?) puts the door height at 13" (330 mm). I'm assuming the "Door Height " in the spreadsheet = bottom of the inner arch. JR's is 12.25", which is similar to a few other 39'ers. I think I'll start with that to build the footprint, and play around with it

My bricks are 9" x 4.5" x 2 3/4", and I have 200. I'm still debating which way to run the first course orientation given the slight height reduction of my brick, and the quantity. Fairly certain I read that running a full Sailor creates a weak point somewhere. Also I thought standard bricks were 3", not 2.5 " as per spreadsheet ?

Appreciate the help !!

J

[JRPizza]

Ideal door height is supposed to be around 63% of interior height. Since I was building a 39' I took the dimensions from the FB plans (36, 42) and interpolated. Thought it was a good sign that it came out to 62.82%

	ID	Height	Width	Height
36"	36	18	19	12	66.67%
39"	39	19.5	19.5	12.25	62.82%
42"	42	21	20	12.5	59.52%

[terratree]

Thanks JR,

Was just looking at your IT, and your pivot is directly above the rotation (bearings). Mine is not central, will this matter at all ? Pic attached.

Also, whats the go with the paper under the first course ?

I think I'll be laying my first course (half brick and flat) directly on the insulation/around the cooking surface. Any pros/cons of doing this verse laying on the cooking surface as you have done ? Am hoping to reduce mortar and make cuts (Chipsta Jig) as needed.

Trying to validate the 1st course quantity with that spreadsheet, doesn't seem to add up - pic attached. Physically 28 bricks as sailors fit exactly around my ID 39" (1000mm) - I'll keep playing with it - Im doing something wrong. I note it says soldiers on the spreadsheet too, but changing the brick width does change the brick count ...

Was going to make my WFO with no door lol - think I may have answered this after checking on the template. 32 bricks on first course as per last 2 pics, seems a little more aligned. This comprises inner arch floor (6 1/3 ish) and where inner arch meets dome (4).

Thanks again all - very helpful info.

J

[UtahBeehiver]

By not having the IT pivot point at floor level, the dome will be taller by the amount that the pivot point sets off the floor. Not a major problem but need to be aware, More important, by not having the pivot point on at floor level, you will need to adjust the radius of the IT (needs to be adjustable) to get a seamless mating of a tapered inner arch and the dome. During my build my IT pivot point was not at floor level so I had to make manual adjustments mating the tapered arch to the dome.. IMHO, I would lower the pivot point to floor level.

Paper - beats me

By placing the first course on the dome floor rather than around it , you do not need to be as precise with you perimeter cuts on the floor brick.

The DeeJayho spread sheet is an estimator, you need to have some contingency bricks anyway.

The arch seems too far in, use your IT to determine or confirm the intersecting point.of the arch form and the dome

[terratree]

Thanks Gents,

Great info. Will read those posts, and adjust the tool if needed, as I intend to have it at floor height.(IT Pic in first post) .

By placing the first course on the dome floor rather than around it , you do not need to be as precise with you perimeter cuts on the floor brick.

Excellent - never thought of that !

Will also adjust the inner arch placement. Have to reacquaint myself with sketchup to visualise the build a little better

Much appreciated

Jay

[JRPizza]

OK, now I see your IT pic. It will take some creative placement to get that pivot point at the floor level, but if the base of it is at the same plane as the lower surface of your floor bricks it might work - securing it there might be a problem. While you are getting ready to build you may want to look to see if you could come up with something more low profile and centered but I am sure you can make yours work either way.

[terratree]

Has anyone used a tapered refractory brick (more like a proper kiln block), with dimensions of 380 x 150 x 65/75. (14.96" x 5.91" x 2.56"/2.95")

I now have 90 of these puppies weighing 11.6 kg (25.57 lbs) each. Made in Japan by Krosaki. All stamped KRD-SS8 G12

Pics against a standard brick for comparison.

When I purchased them sight unseen I assumed they were a normal size....

Welcome any advice on how best to utilise these. Unsure of their heat spec/application, but have contacted head office

[UtahBeehiver]

I used industrial size and grade fire bricks that were tapered from to back vs side to side, From the pics the taper appears slight so it would work for the dome as long as you use an IT to guide you. The dome wall will be a little thicker abt 4.3/4" but not a deal killer. Only cavaet, high probability these bricks may be super duty, hence hard on diamond blades.

[terratree]

Thanks Russell,

That was my thinking.

I assume I can cut each into threes, and utilise the three different bricks(thicknesses) as the dome progresses. Would there be a preference for having a thinner/thicker brick(facing the floor) at any course given my three different size bricks, when cut??

In any case, should equate to less mortar back end , I think ?

Appreciate the help

Regards

Jay

[UtahBeehiver]

Metric always messes me up so after calculating the brick dimensions again, the depth of the bricks are 5.9 inches (150 mm) so cutting them in half for the dome makes the walls a little less than 3" (75mm), this is on the thin side for a dome and I am not sure there is enough mortar joint to make a stable dome. Not cutting the depth makes the dome on the high side of the spectrum (5.9") which means more mass to heat up, hence more fuel, So I am going to back track when I said it should be okay. I now think your option is a full depth brick but cut in threes along the 380mm length.

[terratree]

Yeah apologies Russell about the metric and yes cut in three makes each brick close to 5" (126.6 mm). So thicker wall, more fuel and hopefully a longer cook time ?

I'm planning to use these for the floor as well (less cuts), but raising them level will be interesting. Playing with them on the hearth, and it seems it will be easier if I do not "herringbone" them, as I'd have raise different areas. Would a length of ~1/4 " (5mm) fire brick split be ok for this ?