41" low dome WFO build

[SinoChef]

Well it seems obvious that Italians don't know s@#%t about bbq!

That is funny!

[Jackie Tran]

That is looking really promising JD.  I knew you wouldn't have any issues with it.  As long as you have a live fire going, I don't think you even need insulation.  But I guess you'll find out soon enough.  Keep us posted.  Looking really good Gene.

[Jet_deck]

.... That's cool, how well did it maintain the heat? Did you bake any pies?

The dome has absolutley no thermal mass, so it does need a live fire to provide any top heat.  I didn't cook this time, but soon.

[Jet_deck]

I put up a video of the fire last night. A video of a fire in the wfo?  I've got the pizza disease real real bad.

<a href="http://www.youtube.com/watch?v=X5xTgqSGotA" target="_blank" class="aeva_link bbc_link new_win">http://www.youtube.com/watch?v=X5xTgqSGotA</a>

[parallei]

Well it seems obvious that Italians don't know s@#%t about bbq!

Hey!  I resemble that remark

Very cool Jet Deck and a wonderful piece of work.  Can't wait to see the pies you make with it.

Paul

[Jackie Tran]

Cool video Gene.  That looks like a lot of fun.  My oven is being put together tomorrow. 

[scott r]

WOW!

[Jet_deck]

I decided late in the day yesterday to do a test cook on the wfo.  I picked up a 30 lb. bag of Grade A1 Mexican Mesquite lump charcoal.  I dumped 10 lb of it in the oven along with 3 arm sized logs.  After 2.5 hours and 3 more logs, I still needed more heat.  The oven floor was about 200* to cold.

I made an emergency dough and used the cake yeast i picked up at RD.  It wasn't anything special for sure.  Polly O fior di latte and some doctored crushed tomatos that included Pace Picante sauce were used.

I would grade the pizza at 60% by forum standards, probably 96% by the general public standard.  The oven being on the trailer at shin level and underfired were the biggest obstaces to getting better results last night.  None the less, my first wfo pizza.

[Jackie Tran]

Gene 2 things.  The pizza and crust looks good.  I don't know yet, but I keep getting the feeling that my favorite wfo pizza will be in the 3-4min range.  So I'll need lower temps like where you were just at. 

2nd - you are one of the few to use lump coal for a fire and posted about it.  I've only seen one other person mention lump coal.  So I'm curious to know.  It sounds like you used about 15lbs or roughly half of that bag for a 3 hour burn.  What was your final hearth and dome temps and how long was that pie baked for? 

Thanks,
Chau

[TXCraig1]

Congrats on WFO pie #1!

You must be loosing a ton of heat our the top. That was my biggest problem with the BBQ mod. It took 10 layers of pyroblankets to hold enough heat in. I would not reccomend them for your WFO. It would be way too hot for the material directly above the flame.

How about welding a 6-8" (or whatever makes sense) rim around the steel oven top and weld up a snug-fitting cover. Then you could fill the top with loose vermiculite?

CL

[TXCraig1]

I don't know yet, but I keep getting the feeling that my favorite wfo pizza will be in the 3-4min range.  So I'll need lower temps like where you were just at. 

Chau,

What makes you think that? The best pies I've ever eaten were all in the 1.5-2 min range. When baking pies in my grill, the closer to 2 min I can get, the better they seem to be.

CL

[Jackie Tran]

Gene would a 2-3" layer of sand over the dome help hold the heat in?

Craig, it's just a gut feeling I have.  I'll have to do a lot of testing to know for sure.   I'm looking for a certain hydration in the dough to get the open moist crumb but I also know it takes a bit more time than 90 seconds to bake off the moisture.  Perhaps I'll settle on a 2.3-3m bake,  or perhaps my new favorite will be a 90 second bake.  Just not sure yet....

Chau

[shuboyje]

If you decided you want to add some thermal mass to the dome, I would personally try fireclay.  I'd mix up a dry "mud" with some water and put a couple inches over top of the dome then fire it to drive off the moisture.  I would bet it would have very similar thermal properties to firebrick or castable.

As for fire the oven with lump charcoal, I would throw that idea out.  Lump charcoal is wood that has had it's volatile gases removed via pyrolysis.  Those gases hold btu's so you are already at a disadvantage over wood, and in a WFO it's an even bigger issue.  A WFO needs open flame licking the dome, and those open flames come from pyrolysis of the volatile gases in the wood...the same gases that are gone in charcoal.

Chau,

I don't post much, but read a lot and am pretty sure I have a good idea what you are after.  I would highly recommend firing the oven to 900+ on the hearth.  Once you get the initial spring from the high heat and the crust begins to set a bit I would then move the pie to the cooler area of the oven right in front of the door to drive off the moisture and crisp it up a hair.  There is something magical that happens with a high hydration dough and a 900+ hearth IMHO.  With this method you can get the best of both worlds, I would certainly give it a shot, it is my go to method for a more american style pie.

[Jet_deck]

Chau, I would say that the hearth was around 750° and the bake time was just over 3 min.  I used about 10# of lump and no more than 5 arm sized logs.

Craig, I think your idea has merit even if it does have enough insulation.  With the roof on the way it looks now is very Beverly Hillbilly-ish.  A solid roof would clean up the looks alot.  Just above the dome I have 1 layer of 2" thick ceramic insulation rated for high heat.  Above that is a 6" thick bat of regular houshold fiberglass without the paper backing.  The first burn had a pretty funky smell happening, but none last night.

Shuboyje-  Thanks. I never thought about the lump not being able to produce as much heat as wood.  I have used it for several years, but at much lower temps.  When all was said and done last night, I had almost the same size pile of coals as the first test.  So I'm sitting there scratching my head wondering wth happened.  Now I know.

While experimenting with dough I will put another non-lump fire in it and try it again.
I have decided to put this thing on my bbq trailer.  I will have to add another axle and extend the tongue, but the trailer already has amenities that are nice for food prep.

[parallei]

JD- I'd loose the regular houshold fiberglass.   Not sure what'll happen if it gets wet!

Some R-Values:

Vermiculite, loose fill   2.08
Perlite, loose fill   2.7

Not sure about sand, but I think its R is about 0.6 or something.   Perlite is also much, much lighter than sand......

Can't imagine fire clay having a better R than the loose fills, but I could be wrong...........
 

[Jackie Tran]

If you decided you want to add some thermal mass to the dome, I would personally try fireclay.  I'd mix up a dry "mud" with some water and put a couple inches over top of the dome then fire it to drive off the moisture.  I would bet it would have very similar thermal properties to firebrick or castable.

As for fire the oven with lump charcoal, I would throw that idea out.  Lump charcoal is wood that has had it's volatile gases removed via pyrolysis.  Those gases hold btu's so you are already at a disadvantage over wood, and in a WFO it's an even bigger issue.  A WFO needs open flame licking the dome, and those open flames come from pyrolysis of the volatile gases in the wood...the same gases that are gone in charcoal.

Chau,

I don't post much, but read a lot and am pretty sure I have a good idea what you are after.  I would highly recommend firing the oven to 900+ on the hearth.  Once you get the initial spring from the high heat and the crust begins to set a bit I would then move the pie to the cooler area of the oven right in front of the door to drive off the moisture and crisp it up a hair.  There is something magical that happens with a high hydration dough and a 900+ hearth IMHO.  With this method you can get the best of both worlds, I would certainly give it a shot, it is my go to method for a more american style pie.

Shuboyje, I wish you would post more.  Excellent.  Thank you for answering 2 questions I've had on my mind for some time.  I did think about that technique briefly awhile ago but it's impossible to know without a WFO, so I'm glad to know that it does work.   I will definitely try it out.  Thank you.  

Chau

[buceriasdon]

Paul, Gene and others, My concern with a setting clay on top of the steel would be the very different rates of expansion leading to severe cracking, plus the fact clay can't adhere to steel. Gene, if I understand correctly you plan on trailering the oven and that would lead to even more cracking.
Don
 

JD- I'd loose the regular houshold fiberglass.   Not sure what'll happen if it gets wet!

Some R-Values:

Vermiculite, loose fill   2.08
Perlite, loose fill   2.7

Not sure about sand, but I think its R is about 0.6 or something.   Perlite is also much, much lighter than sand......

Can't imagine fire clay having a better R than the loose fills, but I could be wrong...........
 

[shuboyje]

In a WFO you basically have two things, Thermal mass and Insulation.  An open space surrounded by thermal mass surrounded by insulation to be exact.  I was recommending the fireclay as thermal mass if the OP decides it is needed, not as insulation which is where R-value comes into play.  I envision the "mud" being placed on top of the metal dome and then some form of metal lath being placed into the top of it to loosely hold it in place.  In this installation if it cracks so be it, mass is mass cracked or not.  It will still store heat the same. 

That said this is all only if the OP decided it is needed, as I see it the jury is still out of metal ceilings with no mass.  I don't think we've seen enough to give up on the concept, although I do have my doubts which I expressed in other threads about metal dome ovens.  As a sheet-metal worker by trade with all the skills and tools to fabricate metal ovens quickly and easily and heaps of scrap metal at my disposal I hope I am wrong and it works great!

[buceriasdon]

In my other life I was a member of the Sheet Metal Workers of America, hopefully in another year I can collect some pension if any money is still left.  Yes, if some method can be devised to hold the clay together it would help retain heat.
Don

In a WFO you basically have two things, Thermal mass and Insulation.  An open space surrounded by thermal mass surrounded by insulation to be exact.  I was recommending the fireclay as thermal mass if the OP decides it is needed, not as insulation which is where R-value comes into play.  I envision the "mud" being placed on top of the metal dome and then some form of metal lath being placed into the top of it to loosely hold it in place.  In this installation if it cracks so be it, mass is mass cracked or not.  It will still store heat the same. 

That said this is all only if the OP decided it is needed, as I see it the jury is still out of metal ceilings with no mass.  I don't think we've seen enough to give up on the concept, although I do have my doubts which I expressed in other threads about metal dome ovens.  As a sheet-metal worker by trade with all the skills and tools to fabricate metal ovens quickly and easily and heaps of scrap metal at my disposal I hope I am wrong and it works great!

[scott123]

While I think that some extra thermal mass is a good idea, cracked fireclay on a sloped surface is going to slide off.  Welding a lip, as Craig mentioned, would support the fireclay, but... welding stainless is a major pita.

I've actually been contemplating a way of keeping refractory on top of a sloped metal roof for some time now.  Something that just came to me is taking heavy duty steel wire and forming it into a big loop.  When your form the fireclay on top of the roof, make it into sections (like slices of a pizza), forming a flat exterior edge with a groove for the wire.  With all the pieces in place, the wire acts like a harness, preventing the refractory slices from sliding outwards.  The slices also need not be too form fitting to make room for expansion.

You probably wouldn't want to drive with the slices in place, but it should be easy enough to assemble/disassemble. I'm thinking maybe 1" thick refractory wedges or possible some perlcrete that's a little heavier on the 'crete to give it more thermal mass.