Forno Bravo Forum: The Wood-Fired Oven Community

Forno Bravo Forum: The Wood-Fired Oven Community (http://www.fornobravo.com/forum/)
-   Getting Started (http://www.fornobravo.com/forum/f6/)
-   -   Before pulling the trigger, in need of criticism (http://www.fornobravo.com/forum/f6/before-pulling-trigger-need-criticism-19114.html)

giol 03-20-2013 06:08 AM

Before pulling the trigger, in need of criticism
 
Hello all,
I am a newbie in this forum and after reading a lot of content here for the past month i decided to make a WFO on my balcony.
Some background first i live in Greece in an floor/aparment at the top floor of a 3 storie building. I have a good location for the oven that can hold the weight and the smoke will have a clear path away from buildings. My balcony is quite big but my wife's tolerance is not so i have secured a 40x55 inch space for the oven.
I am going to use a metal base that size to put the oven on (with heavy duty wheels so i can move it few feet back and forth ico).
My idea so far is to build an oval kindoff pompei oven with cooking space dimensions 36 inch deep x 26 inch wide. The ceiling will be at 13 inches . The door opening will be 16 inches wide and 8 inches tall.
The thermal mass of the firebrick is going to be 5 inch (the firebricks i found are 9x5x2 '').
Outside the firebrick i am going to use a Medium cement castable insulation concrete reinforced with chickenwire. i expect to use 2-3 inch of this since it is very high quality (i have tested it on my gas bbq -bulit a pizzahacker kind of dome- and with 800F degrees inside the outside was cold). Below you can see a rough sketch i made.
The chimney is going to be 8x10 built with the refractory insulator and the gases will be routed over the front top of the oven and will exit from the top of the dome vertically with stainless steel flue.
The metal base will be covered with a metal plate with 5 inch high sides in order to make the cement casting easy. I am going to use 3' of ytong blocks and on top i am going to use the insulating concrete. Above that, fireclay slurry and the 2 inch thick firebricks.
Please if you see something wrong with my plan tell me before i start.
Thank you.
https://docs.google.com/file/d/0B3EI...it?usp=sharing

ATK406 03-20-2013 09:55 AM

Re: Before pulling the trigger, in need of criticism
 
Sounds like a really interesting project. I hope you can share some pictures when the time comes, yours is a unique design and build site.

If it doesn't complicate your design in any way, you might want to consider rotating your cooking surface by 90 degrees (making it 36" wide x 26" deep). I only suggest this because when you are cooking pizza, roasting or smoking meats you will need to have a small fire (or smoldering ashes) burning inside the oven. It might be a little easier to manage the fire if it is on the side vs in the back of the oven. A fire on the side also reduces the chances of pushing your pizza into the ashes with your peel since you aren't actually pushing the food toward the fire. I know there are some people who prefer to place their fire in the back so in the end it is really just a matter of choice and small one at that.

Good Luck
AT

PS - Is that really an insulating cement (as in it does not absorb heat) or is it a refractory cement that would add thermal mass, like adding another layer of firebrick?

giol 03-20-2013 12:07 PM

Re: Before pulling the trigger, in need of criticism
 
I thought of making it wider than deeper but i suspect that the draft will be severely comprimised and i would have stale smoke on the sides. But you got me thinking that maybe i am wrong.
The cement is used for insulation of high temp furnaces up to 2000F . It does have some chammote in the mix which adds thermal mass (i suppose). It is lightweight -less than 1 gram per cm3. And the Thermal Conductivity at 600C is 0.25.

ATK406 03-20-2013 02:58 PM

Re: Before pulling the trigger, in need of criticism
 
I don't see why your draft would be compromised either way. It sounds like your vent will be plenty big enough in area - as long as you can extend you chimney up about 1 m you should be fine (you might even be able to get away with less if you wanted to). You are venting to open air above? I.E. you don't have a roof over head - sorry but I had to ask.

I read somewhere that the thermal conductivity of a 4:1 mix of Vermiculite and portand cement is ~ 0.16 which is about the same as the cement you are planning to use. If you find that cement to be cost prohibitive (I've not seen anything like that here), mixing vermiculite or perlite with cement is a proven method here (you can even go with a leaner mix if you are not too concerned about compressive strength - but it can get crumbly if you don't get it right).

shuboyje 03-20-2013 06:19 PM

Re: Before pulling the trigger, in need of criticism
 
Quote:

Originally Posted by giol (Post 148270)
I thought of making it wider than deeper but i suspect that the draft will be severely comprimised and i would have stale smoke on the sides. But you got me thinking that maybe i am wrong.
The cement is used for insulation of high temp furnaces up to 2000F . It does have some chammote in the mix which adds thermal mass (i suppose). It is lightweight -less than 1 gram per cm3. And the Thermal Conductivity at 600C is 0.25.

I assume the 0.25 is in metric? The 0.77 for Vermicrete is in Imperial units. That converts to 0.036 Metric. As you can see what you have here is not an insulator, it would be considered thermal mass in the US. A lot of materials considered insulators in Europe are not actually insulators, and are not considered to be in the new world countries.

brickie in oz 03-20-2013 10:50 PM

Re: Before pulling the trigger, in need of criticism
 
Ive used the so called insulating refractory concrete and if you can find an alternative insulating material for similar price I would grab the alternative.

giol 03-21-2013 12:33 AM

Re: Before pulling the trigger, in need of criticism
 
There is no roof above.
The concrete does contain vermiculite and the TC is in w/m/k which coverts to 0.14 btu/hr/ft/sqft. I can get an even better insulator if needed. I was thinking that the AAC block below the concrete will finish the job since it is also insulating.

giol 03-22-2013 02:46 PM

Re: Before pulling the trigger, in need of criticism
 
I just bumped on wfo shape i have never seen before http://fireworksmasonry.com/wp-conte...8761715989.jpg
How do you think this oven works with two different levels?
Maybe i can go for something like this?

brickie in oz 03-22-2013 02:49 PM

Re: Before pulling the trigger, in need of criticism
 
Quote:

Originally Posted by giol (Post 148330)
AAC block below the concrete will finish the job since it is also insulating.

Insulation below the concrete is all wrong, it needs to go on top of the concrete unless you own a forest of firewood. :)

giol 03-22-2013 02:55 PM

Re: Before pulling the trigger, in need of criticism
 
The concrete i am going to use is castble insulating of very high quality. The AAC will be additional insulation below a layer of 5cm. The company engineer that suggested the concrete told me that 5 cm would be more than enough but i thought "you can never have enough".
What do you think about going for a wider than deeper wfo?


All times are GMT -7. The time now is 02:23 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC