36" build in heart of Europe, Czech Republic

[mrotter]

Just sand should do, but I think a 50/50 sand clay mix is less likely to move around under the bricks. Some builders apply it wet which will make it set hard and stop any movement, but that introduces moisture under the floor which has to be removed as well as making brick removal difficult should that be needed down the track.
Maybe not much difference, what do others think?

I used pure Si sand, seems to be workable. I plan to finalize one more course (first fully round course), then cleanup inside of dome more and level bricks. I also replaced bricks with best ones I found with smoother surface.

See photos below.

I mortared 6 bricks of next course, plan to continue today, finish course, maybe do some little leveling adjustments with angle grinder. I struggled a bit with cuts on those dome bricks which touch top part of inner arch, had to use some extra mortar, but backfilled any big spaces with firebrick scraps.

Oh, also, I removed inner arch form.

Any opinions welcomed.

JRPizza
UtahBeehiver
david s

[mrotter]

Also, here is my floor heat-brake, just placed in place.

EDIT: Floor bricks are not yet leveled, I just applied thin layer of sand under them, and will fine-tune leveling later.

[david s]

That looks like some steel rolled hollow section, if so it will be fairly heavy and conductive, exactly what you don't want for an insulating section.. If aluminium it's even worse. Insulating value is the reciprocal of thermal conductivity. The attached table might help.

https://idoc.pub/documents/thermal-c...s-d47e3p7g7yn2

[mrotter]

That looks like some steel rolled hollow section, if so it will be fairly heavy and conductive, exactly what you don't want. If aluminium it's even worse. Insulating value is the reciprocal of thermal conductivity. The attached table might help.

https://idoc.pub/documents/thermal-c...s-d47e3p7g7yn2

Yes, it is hollow, I planned to fill it perhaps with perlite or parts of ceramic fiber blanket.

I do not really see any alternatives. It is made of steel. What other options are there?

[david s]

A better solution IMO is to bevel the underside of the landing brick so that it only contacts the floor brick at the tip the triangular void can be filled with blanket or 10:1 vermicrete or perlcrete. I did a sketch but it's slow to load onto the cloud, I'll post it later.

[MarkJerling]

Either David's solution, or a tiny gap, filled with ash over time is far better than a conductive hunk of steel. Many other options have been tried but a small gap is really the easy solution.
Thermal Break Materials - Forno Bravo Forum: The Wood-Fired Oven Community
In fact, doing nothing would be better than the hunk of steel.

[david s]

Try this

[david s]

In my builds the gap (around 8mm) acts as an expansion joint as well as eliminating heat flow by conduction. It allows the inner oven castings to expand freely without putting stress on the outer decorative arch. I've seen enough ovens with cracked outer arches to know that this is a good innovation. I fill the gap with thin slices of blanket, sealed off at the top with som 6:1 vermicrete.

[mrotter]

Try this

OK, I will do exactly this. Thanks. Luckily that piece of steel pipe costed like 3 USD.

[UtahBeehiver]

I agree with David S. The thermal K value of carbon steel is much higher than refractory brick. Although I installed a thin wall SS channel on my build 10 years ago I would go with David S suggestion now.

[mrotter]

I agree with David S. The thermal K value of carbon steel is much higher than refractory brick. Although I installed a thin wall SS channel on my build 10 years ago I would go with David S suggestion now.

Ok thanks. Will definitely go with that AIR/insulation gap with beveled brick.

[mrotter]

Almost finished next course, I had to bevel bricks at their full length now to avoid inverted V. Will finalize tomorrow and post pictures. According to my calculations, there are 3-4 courses to keystone, holy ****.

[mrotter]

Btw, I had 150 firebricks at the start, about 35 remaining, it seems it will be enough (except vent arch where I plan to buy new bricks for better view).

Also, I had 75 kg of mortar mix, now about 30 kg remains, that should be more than enough.

[mrotter]

In my builds the gap (around 8mm) acts as an expansion joint as well as eliminating heat flow by conduction. It allows the inner oven castings to expand freely without putting stress on the outer decorative arch. I've seen enough ovens with cracked outer arches to know that this is a good innovation. I fill the gap with thin slices of blanket, sealed off at the top with som 6:1 vermicrete.

Thanks, I plan about the same gap. Will have to buy rope to fill it.

[mrotter]

Photos. 9th course is basically complete, I cleaned inner side of dome with wire "cleaner" a bit, also leveled the floor bit more. At this point it is fair to say that mortar is giving great job. Initial adhesion of the brick is helping quite a lot, but still I have to support bricks with wooden sticks, at least like for 10-20 minutes.

Also, bricks are getting narrower and narrower, I cut bricks into thirds (about 7 cm wide), next course from rought measurement I made it seems I will be able to cut each brick into fourths, each about 5.5 cm wide to achieve proper brick staggering.

I will upload more photos below.

Also, it seems i relatively managed to avoid droop. I made some compensations and also made length adjustments to IT as I was aware that my pivot point was bit above the floor (like 1" at max), so I am checking my IT length before each course and make it few milimeters shorter.

Please, guys, if you see any problems or have recommendations, let me know. It seems that two more regular courses and then final keystone. What encourages me is that my father in law thought that I would not even be able to reach the phase I am in and also neighbours seem to ve quite interested in the WFO.

JRPizza
UtahBeehiver
david s

and other. Thanks for your assistance.