WFO in Utrecht, the Netherlands

[Mr. Slowhand]

After this, the timing was to put the morgan superwool around the oven. I did 3 layers everywhere, plus fourth layer on the top, close to most of the dome.




Around the entry is currently only one layer. This is due to the fact that I have mixed a bit more homebrew with the fibres, and reinforced from inside some places where the casted flue was not straight, and did another round of cement around the base of the chimney holder, to be more reinforced.



So, starting with vermicrete later today, I hope. This one will last for some time, as I will do layer by layer.

[Mr. Slowhand]

Great job. I think you'll be happy with the solution. That form would have been nigh on impossible to build with brick units and taken 10x as long.

Absolutely right. Just yesterday, I removed the sand and newspaper from the inside of the oven. Looks pretty smooth. I had the misfortune of putting the chimney bit wrong way around. So had to remove it, it was stuck super tight. After removing it, rotating it, I could attach the rest of the chimney.



It is a bit crooked on this picture, but that is because it is not fixed. I put it just to see that the fittings match.

[david s]

Great job. I think you'll be happy with the solution. That form would have been nigh on impossible to build with brick units and taken 10x as long.

[Mr. Slowhand]

Was a bit busy with the removal of the arch form, cleaning the oven entry, and putting the arch for the flue mold. I than started building this form, out of sand. Never ever I did anything like this, so it took me a while to get the right consistency of the sand, so it can stay OK. I added a bit water (don't know if that is the route). Ended looking OK









Afterwards, covered it with wet newspaper. I see why this needs to be done. Otherwise, the concrete will embed a lot of the sand in the actual casted cement.



At the end I put a chimney in the concrete, and than built the enclosure around it. This is to be able to have the cimney "sit" in a concrete opening with the right size. After some 1hour, I wrapped the entire thing in cling film, that is a good idea.
I got some bazalt fibers. The characteristics state that they are good up until 1,200 degrees celsius. The ration was approx 3% of the mass. I tried to determine this as much as closely possible, so for this amount I had to use approx 800 grams of the fibres. In addition, I put some PP fibres for steam spalling. Tried to use the guidance of quantity on that one as well. Not a lot was needed. The amount of concrete was approx 2/3 full wheelbarrow. I think it was enough. If not, I will add another layer, we will see how that goes.
So, following the excellent guidance of David s, I tried to do this. If it does not go through, I can always remove it, and build one from bricks, hopefully does not go there.
All of the isolation has arrived, I might finish this soon as well. Hopefully putting the blankets and vermicrete on sunday!!!

Marko

[Mr. Slowhand]

So, I noticed some cracks on the front arch. Let's just clean them a bit, so I can push some new mortar there.....



Oh, there is another one somewhat towards the base..




And before you know it:





One big chunk came off.
Nothing to it, I cleaned the mortar of the bricks, mixed some mortar and put it back together.
The issue is, I made the arch, and left for holidays. Maybe someone should have come and put some water over the arch.It did not fall apart when I removed the arch support. I just it is a bit loose, and could take it out with my hand. Even if I had not fixed it the fact that above it I would put mortar to cast the flue, it should have kept it in place. But, no sense in not repairing it now.

Anyhow, now it is fixed, tomorrow I am casting the flue. I could only find the bazalt AR fibres, not the normal AR fiberglass fibres. And got the normal PP fibres, so it will be an interesting experience.

Hope to finish it tomorrow!!!

Marko

[david s]

If you make the mix to the right consistency it will stand up vertically. Too wet and it will slump, to dry and you’ll get voids. The consistency is described as “ball up” ie throw a ball of the mix 2 feet (600mm) in the air and catch it. Either too wet or too dry won’t work. There are plenty of cast builds on the Other Ovens section that describe fibre additions, read as many as you can. Obtaining the ideal consistency and wriggling the mix against the mould should eliminate nearly all the air, although an outside mould and vibration is superior, it is far more complex to create the moulds as well as creating more difficulty in placing the mix.

[Mr. Slowhand]

Try this thread for starters.
https://community.fornobravo.com/for...803#post413803

The flue gallery does not really see direct flame impingement so the homebrew (3:1:1:1) as used for mortar is quite adequate. Using castable refractory which is expensive and less user friendly is probably not an ideal material for a first time home build. The fibre reinforcement is also not mandatory but does increase strength therefore allowing a thinner casting. The AR (alkaline resistant) fibreglass fibres as used by the concrete countertop builders work well for this application and are user friendly. The very fine polypropylene fibres as used in concrete help the safe elimination of moisture, reducing the possibility of steam spalling.

Another thread that may help you on a similar problem is the rebuild of a front arch. I retained the three corses of the original arch as they were pretty solid.

https://community.fornobravo.com/for...723#post435723

Excellent idea, just to be sure the 3/1/1/1 with the AR fiberglass and the PP fibres both? Is there any instructions on how much to use? Do you make any outside mold, or it just sticks?

marko

[david s]

Ok, after a brief overview, definitely going to cast the flue gallery.
The inner mould is done with sand, I understand that one. The outer mold, I presume you do with some sort of wood planks. Without it it would simple run down? Not understanding how that is done.
I have a couple of questions, if anyone can assist:

1. Refractory castable. I am in the Netherlands, cannot seem to find online anything offered. Does anyone have any advice. I have no preference weather to buy, or make some homebrew refractory castable. I cannot seem to find a recipe for one. I definitely see that the homebrew mortar is not a refractory castable material.

2. The needles/fibres for the mix. Anybody now a similar name for what david s and the US builders use?

Or if you can point me to the posts that detail this, thanks!!

Thanks guys

Marko

Try this thread for starters.
https://community.fornobravo.com/for...803#post413803

The flue gallery does not really see direct flame impingement so the homebrew (3:1:1:1) as used for mortar is quite adequate. Using castable refractory which is expensive and less user friendly is probably not an ideal material for a first time home build. The fibre reinforcement is also not mandatory but does increase strength therefore allowing a thinner casting. The AR (alkaline resistant) fibreglass fibres as used by the concrete countertop builders work well for this application and are user friendly. The very fine polypropylene fibres as used in concrete help the safe elimination of moisture, reducing the possibility of steam spalling.

Another thread that may help you on a similar problem is the rebuild of a front arch. I retained the three corses of the original arch as they were pretty solid.

https://community.fornobravo.com/forum/pizza-oven-design-and-installation/design-styles-chimneys-and-finish/637-the-brick-arch?p=435723#post435723

[Mr. Slowhand]

BTW, I went a bit overboard, and see that I bought way more firebricks than I need.
..... well I gues I will be making that tandoori oven next......

[Mr. Slowhand]

Ok, after a brief overview, definitely going to cast the flue gallery.
The inner mould is done with sand, I understand that one. The outer mold, I presume you do with some sort of wood planks. Without it it would simple run down? Not understanding how that is done.
I have a couple of questions, if anyone can assist:

1. Refractory castable. I am in the Netherlands, cannot seem to find online anything offered. Does anyone have any advice. I have no preference weather to buy, or make some homebrew refractory castable. I cannot seem to find a recipe for one. I definitely see that the homebrew mortar is not a refractory castable material.

2. The needles/fibres for the mix. Anybody now a similar name for what david s and the US builders use?

Or if you can point me to the posts that detail this, thanks!!

Thanks guys

Marko

[Mr. Slowhand]

Sorry if I made this sound too dramatic. The guys cutting and installing stone countertops working every day are at a very high risk. You should be fine. I’m surprised your saw didn’t die. Both the switch and motor on angle grinders don’t last too long before a total dismantle and clean is required.

No, you are absolutely correct, and I should take notice of it. I am a seasoned motorcycle rider, having made a trip around the world also, and firm believer in ATGATT rule (all the gear, all the time). So, should have known this.
But, the angle grinder was not expensive, still works OK. The disc was more expensive than the grinder, to be honest, it was around 100 EUR, the grinder was a in-store brand, at around 65 EUR. All work good.

Now, you have me very intrigued with the casting possibility. You say it does not take you a lot to cast a flue. Can you point me to some of your posts where you describe how you cast, and what materials do you use. Thanks!

Marko

[david s]

Sorry if I made this sound too dramatic. The guys cutting and installing stone countertops working every day are at a very high risk. You should be fine. I’m surprised your saw didn’t die. Both the switch and motor on angle grinders don’t last too long before a total dismantle and clean is required.

[Mr. Slowhand]

Yikes! That saw looks like it has no water feed. If so the dust is very dangerous to inhale for the operator or anyone (including your neighbours) in the vicinity. Soaking the bricks before cutting only reduces the dust minimally. If so it's probably too late now because it looks like you've finished cutting all your bricks.

https://www.vent-tech.co.uk/blog/sil...short%20period.

Double yikes, did not know it is that serious. I was wearing, for at least 80% of the time the mask, and 100% of the time the eye protection. Plus the cutting station was located next to a box type wall, so most of it stayed there.
Anyhow, thanks for the info. Is there any info on any of the amateur builders ever developing anything from this? As I have seen a lot of builds with just a miter saw type contraction, without a water source.
Thanks for the info David, the cutting is thankfully done

[david s]

Huston, we are vertical!!!



The build is going great!. Yesterday was one of the most productive days.
I used a wire wheel mounted on a drill to clean the inside walls, and managed to lay approx 2.5 rows (3 rows over the entrance arch, as there was a gap), plus 2 on the entire one

Also started to taper the bricks, avoiding as much as possible the "wee" joints



My son adores working on it, looks quite adept as well!.

So, for tapering and other compound curves, using a clamp

Yikes! That saw looks like it has no water feed. If so the dust is very dangerous to inhale for the operator or anyone (including your neighbours) in the vicinity. Soaking the bricks before cutting only reduces the dust minimally. If so it's probably too late now because it looks like you've finished cutting all your bricks.

https://www.vent-tech.co.uk/blog/sil...short%20period.

[david s]

That looks like an excellent solution, although I’m not surprised it took you two days. Just to make you feel worse, it takes me 45 minutes to mix and lay up a flue gallery casting and because it’s one piece and fibre reinforced, is probably stronger than one made of individual bricks.