Structural Slab for new WFO

[david s]

Re: Structural Slab for new WFO

Usually you only need a double thickness insulated chimney if you are going through a roof. Is that so or did you have another reason for wanting it double? It does double the cost and is not worth the expense unless you have a reason IMO. If the expense of stainless is an issue you could consider brick or stone.

[mikku]

Re: Structural Slab for new WFO

Chimney decisions and high costs!
Someone once said that you must keep a chimney hot to draft properly.
Package stainless steel do just that, but all the parts add up in a real hurry.

Made two stops today, sheetmetal shop- friend said stainless steel in .5mm available any length to 15m x 1 meter width. About $30/running meter.
Thought of making a chimney.

Second stop: metal fabricator: He said, buy ready made spiral pipe SUS304.
Says any lengths available-cuts O.K., also flanges, tees, elbows etc.

He is checking 150 dia and 200 dia, will know tomorrow.
Plan on putting one inside the other, use some spacers to keep centered and fill with pericrete. I think the factory chimneys use a dry fiber but this should work.

Anyone have thoughts on this? I am thinking that a one meter chimney, this pattern complete with flange will be around $30. Flange is .8mm (weldable thickness), use a plasma cutter to make the flat base-rest is all .5mm no welds necessary.

Once the chimney idea is decided, the rest of the dome insulation can begin.
I've searched the threads but so far no advice if there should be a barrier between dome and pericrete??

[mikku]

Re: Structural Slab for new WFO

Ran into a snag a couple of days ago, when I altered the firebrick hearth from one that would sit inside to setting the dome on top...had to order a few more brick. Only 6! The shop that I ordered from was happy to take the order, but I did mention that the first bunch was thinner than the size they originally said they were supposed to be.. 61mm/vs 65. I told them it did not matter, EXCEPT, please make sure I get the same again. No communication problem--I heard him talk to the supplier--they said no problem- bla bla. A couple of days later when they arrived. Wrong thickness! 65 instead of 61! The "lady taking the order-swore they were the same!" So trot back to the house, photograph them, e-mail to store, store e-mails to supplier, supplier apologizes and sends a special truck with only 6 brick to the store! Got there at 6:30PM same day!!!

Special service! Wow! And I am in no way a big client at this store...just a regular walk-in sometimes customer. But I know the people by sight and everyone gets a chuckle at my rotten attempts at Nihongo- "the Japanese language".

So, today was my put things together day. Everything went great! Cut a few brick, this time dry. They were the right thickness-base was level --as is!

Did the "Egyptian-Pyramid Block-moving technique" with fine sand and got the other 1/2 dome section (100Kg) 220# set in place. Was able to do so without messing up the brick positions. Had pieces of thicker plywood on top of the brick, thin plywood that the block slid on top, then used a lever (made of wood) to raise the casting enough to get the plywood out. Worked like a charm!

I had a chance to communicate with my "special build consultant" for a bit and listened to his words of encouragement and advice. (Always appreciated!)

Friday, I received the trowelable castable --so today was also buttering up the joints on the dome??? Who knows if they will hold, but at least the cracks are filled. Even though I wet the dome sections, you could see right away that the water was being sucked out quickly. My hope is that at least a percentage of the trowelable will adhere properly and maybe the pericrete insulation will prevent the patches from falling anywhere when the firing/curing and future using occurs.

Lastly, had a little bit of perlite left over from below hearth insulation--so mixed that up 5:1 again to fill in the void between the firebricks and the structural slab.. This brings the outside practically level. This time, I did not have vermiculite to mix in. I do not know why, but the mixing required a lot more water than before. Over 50% more if I calculated correctly. I tried to get it to a consistency that it would retain its shape when squeezed and still not be able to squeeze any water out. What it actually looked like this time---was like a good mix of beach sand and water... suitable for sand castle building.

I really do not know how the 10:1 mix will work for dome insulation but probably just a little fluffier. If it is the intent when mixing cement into the perlite for the dome cover to simply provide a measure of adhesion and stability until a render coat can be applied, then probably this next job should be as dry as possible again!

Oh! Trouble now. The wife just called down and asked if I am "Still at the keyboard"!

Time for a few photos:
Sorry if my posts resemble a novel or short story... But just in case someone else right now is facing the same issues..maybe my long explanation can be helpful!

[mikku]

Re: Structural Slab for new WFO

Thank you, kind words will get you everywhere!

Maybe that should be my nickname- "Mr. One of a kind"! That is the way I feel when going to a shop looking for something, the people probably say "Look out-Here comes "Mr. One of a Kind"!" because I am always looking for something nobody ever orders, so the shopkeeper needs to research it.. If they do finally locate something similar, its always not quite right! Or too expensive--I say-"its on amazon for cheaper BUT amazon is usually too high" that means they are way too high!

Forno Bravo must have done a lot of research and prototype building before offering their precasts to the public!

IMHO, Nobody in their right mind would use my casting; unless they had easy access to a forklift, unic type boom truck, or a whole lot of help! The weight is excessive for any simple action!

So far, I am just winging it. My results may be a very heavy smudge pot?
Really believe that there should be a fiber mat below the hearth, but cannot swing the extra $400 right now. (value vs performance?) Probably should have larger interior as well, but our household is only two.

If anyone wants to comment on dimensions, please give advice:
-750mm inside diameter
-445mm height at center of dome
-oven opening; 400mmx295mm high with corners clipped 100x100 each way.
-transition to chimney outlet size 145x160mm, plan to use 6" round chimney (150mm), initial height 3' (914), probably stainless insulated.
-dimension - center of dome to center of chimney (650mm)

These dimensions are now "set in stone" or "more accurately AGC CA-13S", but are open to modifications if I had to do again.

What is the recommended next layer over the dome (IF) not using ceramic fiber blankets? Something to break any bond? to pericrete?

[banhxeo76]

Re: Structural Slab for new WFO

I am very impressed with your built so far. Truly one of the kind! People at Forno Bravo is getting nervous because your designed is very impressive.

[mikku]

Re: Structural Slab for new WFO

To tell you the truth, sometimes with a lot of difficulty. What appears to be the case is sometimes an illusion. Orderly and conformity are very similar. Creativity is sometimes a byproduct of disorder, or thinking outside the box. A western saying "The squeakie wheel gets greased", An eastern saying "A nail that sticks out, gets hit down!"

I like to think things through before proceeding, but if every option must be thought through to the nth degree of accuracy...nothing gets accomplished except the actual act of thinking. Sometimes I get caught up in this cycle and that is when the "patience" runs out!

I once took eight years to completely restore a sports car. Learning all the techniques, measuring--testing to return things to "as built spec's" or Better. Sometimes waiting until a part would show up in Hemmings. When it was finished, it was too beautiful to drive!

Great results but not the intended outcome! Cars are meant to be driven --not simply looked at like a great painting! I think "balance" is more important but also difficult to achieve!

[UtahBeehiver]

Re: Structural Slab for new WFO

How do you survive in Japan, everyone seems so patient and orderly. Yes it is so easy to get impatience when you are on a roll with these ovens but take a deep breath and step back and do it right. You will be glad you did. We did take the Nozomi from Tokyo to Kyoto, zoom zoom.... and the trains are so clean too.

[mikku]

Re: Structural Slab for new WFO

Thank you for the attachment.
Your data and what I encountered are very similar.
Mixing quantities- first batch used identical size containers. The bucket measured 6.5 liters.
5 buckets (10-6 mix) Perlite/vermiculite
1 bucket portland cement
6.5 liters water. Had a 4 liter plastic jub that (shochu) - a type of clear alcoholic drink comes in. One full and another market to 2.5 liter level--so always same proportions.


The pericrete in the plastic bag is still sealed. I assume that setting is like for normal concrete, better to keep moist.. 28 days is a good set but 81 is really a better time for max strength.

Right, a lot of compressive strength; much lower tensile strength.

My structural slab form had a layer of plastic on the lower plywood so no absorption downward; greased perimeter forms; and when the pericrete was placed--again covered with a poly sheet (and a bucket of water under the cover sheet to compensate for water absorbed by the first concrete casting.

It really is funny to work with. It resembles what tile people call "crumbly mud" as a material for doing sloped bases in showers. But that is sand, cement, water---also very dry--but strong.

Interesting--thanks for sharing your data!
There is a page about pericrete used for insulated roof decks that listed some of the values for compressive and tensile strengths--alot out there on the web!

[david s]

Re: Structural Slab for new WFO

Mikku,

Here are some results of a test I did with vermicrete that could be useful for you.

[mikku]

Re: Structural Slab for new WFO

I attempted the "Easter Island - Head Moving" technique this afternoon using 1/2" PVC water pipe.

But there is a second issue to overcome: I have to raise the dome section 16" to get it from floor level to the top of structural slab. When using the PVC dowels, I cannot control the weight enough to place additional dowels as you go up the incline. Wow this is heavy! And dangerous!

The pipe pieces were also starting to chip the brittle casting as it rolled--so really gave up on that because of safety.

Now it was time to try "The Egyptian Pharaoh - Pyramid Block moving technique".

This "one man show" operation does not compare to the time in Egypt where there was an almost unlimited supply of skilled and unskilled workers!

First I fastened a piece of plywood over the brick area--this prevents anything from coming in contact and dislodging their location.

Next, a plywood ramp (Japan style) 3x6 15mm plywood, with some 2x4's under to strengthen them. This was ramped from floor level to the top of the slab.

Next, I was able to maneuver a thin sheet of plywood beneath the cast section and with the "lubricant" -- super fine sand. Called "micro tsuna" or micro sand, spread a little on the ramp--jockeyed the block close and was able to pull the casting up the ramp using a rope without a whole lot of effort! The sand acted like "mini ball bearings" but still enough resistance not to slide backwards.

On top, a little more sand and got it positioned exactly above its final location--but with a layer still separating it from the bricks.

Now I need to run a long 4x4 through the casting and block each end up. With the aid of a car jack, I can lift it enough to pull the plywood out and lower it to its final position.

No pulled muscles, or squashed pinkies or toes...So far.

Probably much better with more people to help, but also a better chance of more people getting hurt.

I never anticipated the weights that are involved in building a WFO.

I guess every build runs into the same, but usually block by block/ brick by brick--not these pre-cast masses!

One down and two to go... sounds like play by play for baseball... Just slower, but more exciting than watching!

Thank you... all who have commented or checked in... For those of you who have completed one of these ovens....you must have a great feeling of satisfaction. A total brick build really has to test patience and build character.

[mikku]

Re: Structural Slab for new WFO

Thank you Laurentius,
Your ideas and advice are always greatly appreciated!
Can hardly wait to fire up the oven. But still a ways down the road.

[Laurentius]

Re: Structural Slab for new WFO

Nice work, Mikku.

[mikku]

Re: Structural Slab for new WFO

Struck out on the brick, different manufacturers are different thickness.

The stuff I had ordered last week and received yesterday was supposed to be 65mm thick x 114 x 230, ended up being 61x111x128- Other place had a few brick but all 65. Ordered the (6) only as well as a "trowel on refractory" for closing the seams on the dome. But have to wait a few days. Patience is not one of my virtues. I really need to work on it.

The newest fast train is called "Nozomi" and that thing almost flies. That particular arrangement is for long routes heading out of Tokyo- to west Japan (Nagoya, Osaka, Hiroshima, Hakata in Kyushu). If you do come for any length of time, make sure you purchase a "JR Rail Pass" before leaving USA. It can be picked up here once you enter. A much cheaper way to get around for foreigners for limited time. (1 wk), (2 wk). Still a little expensive, but one quick round trip- Tokyo to Osaka would pay for the entire pass!

China has a new train that is significantly faster!

USA would be nice to have a system similar but the population is not dense enough to warrant the huge initial expenses--most places elevated over other roads and rail networks! Really an unbelievable undertaking, suited for Europe maybe USA --Florida to Boston corridore.

Have to try out the dowel system, sounds like a winner!

[UtahBeehiver]

Re: Structural Slab for new WFO

Use could use some wood dowels and roll the oven in place the remove them one at time. Kind of like how they moved the volcanic sculptures on Easter Island. Will have to check you area out. BTW those JR Bullet trains are an engineering marvel.

[mikku]

Re: Structural Slab for new WFO

If you are planning on coming this way again, you might enjoy some of the World Heritage sites around Nikko. It is about an hour by train (either JR) originating at Tokyo station or (Tobu Line) originating at Asakasa Station. If I have time, would gladly show you around!

Thanks-I am on my way to get the rest of the brick. Thinking now about using a very thin layer of plywood (1.5 to 2mm) to slide the castings over the brick. Then just leave it in place to burn away during the curing.