My design for a wood-burning outdoor oven

[Corbs]

Hi guys, I am looking for any constructive criticism of my fledgling design for a wood fired oven as I think an LBE has a much higher risk of me blowing myself up, and we have the room/materials for a wood oven at home.

What would you recommend for constructing the sort of plinth it sits on? I have large-ish flagstones, but they are a bit too rough and not large enough.

Cheers,

Corbs

P.S. the pictures are cross-sections starting at the front (loading end)

[widespreadpizza]

Corbs,  first off,  have you been to the forno bravo site,  tons of info there.  Second do not use sand above the dome.  It will act as mass that you have to heat,  weigh too much,  and not be the insulation you need.  If looking for a loose insulator use perelite or vermiculite.  In Italy,  they would have used pumice years ago I believe.  Insulate the heck out of you floor.  So much more info is available at the forno site,  I would read over there for a few weeks, and proceed slowly.  Then give them your drawing to critique.  That is the path i chose and have a very functional oven as a result.  Do fret over every little detail.  I am happy to help with questions,  but most of them have already been asked and answered over there.  Good luck,  it is worth the time. -marc

[Bill/SFNM]

Insulate the heck out of your floor. 

marc,
Can you please elaborate on this? I do not understand it. Much of the heat lost by the floor will be back into the oven. What function is being performed by large amounts of floor insulation?

As I've mentioned elsewhere, a big goal in the design of my oven was to maximize the thermal mass of the floor to maintain its temperature after the fire has been moved to the side. I insulated the heck out of the dome to reduce heat loss from the cooking chamber but there is relatively little insulation in the deck. The log storage area underneath the deck barely heats up.

Thanks for any insight you can provide.

Bill/SFNM

[widespreadpizza]

Bill,  I stressed insulating the floor because I have read many times about people who did not insulate it at all.  This leads to a situation where there is too much thermal mass and the oven floor wil never reach the desired temp(s).  In these paticular drawings the there is no indication of of a floor type at all.  In my case I have used one single layer of standard medium duty firebricks on the.  2.5 inches which is the same thickness of my dome.  But under that is 3.5-4 inches of "concrete insulation"  meaning a high ratio of perelite,  to concrete.  This isolates the deck form the stand and allows a pretty quick heat up,  in fact,  I preheat my oven on the side,  not the floor.  This does not mean at all that more mass is not better,  but my oven has enough mass to cook pie after pie,  I think because it is well isolated.  Anyhow,  again my point was to make sure that there IS insulation under the deck.   -marc

[Corbs]

Corbs,  first off,  have you been to the forno bravo site,  tons of info there.  Second do not use sand above the dome.  It will act as mass that you have to heat,  weigh too much,  and not be the insulation you need.  If looking for a loose insulator use perelite or vermiculite.  In Italy,  they would have used pumice years ago I believe.  Insulate the heck out of you floor.  So much more info is available at the forno site,  I would read over there for a few weeks, and proceed slowly.  Then give them your drawing to critique.  That is the path i chose and have a very functional oven as a result.  Do fret over every little detail.  I am happy to help with questions,  but most of them have already been asked and answered over there.  Good luck,  it is worth the time. -marc

Thanks for that, I used sand as I wasn't too sure yet. I will have a look over at FB.

[Matthew]

Bill,  I stressed insulating the floor because I have read many times about people who did not insulate it at all.  This leads to a situation where there is too much thermal mass and the oven floor wil never reach the desired temp(s).  In these paticular drawings the there is no indication of of a floor type at all.  In my case I have used one single layer of standard medium duty firebricks on the.  2.5 inches which is the same thickness of my dome.  But under that is 3.5-4 inches of "concrete insulation"  meaning a high ratio of perelite,  to concrete.  This isolates the deck form the stand and allows a pretty quick heat up,  in fact,  I preheat my oven on the side,  not the floor.  This does not mean at all that more mass is not better,  but my oven has enough mass to cook pie after pie,  I think because it is well isolated.  Anyhow,  again my point was to make sure that there IS insulation under the deck.   -marc

I am in the process of having my oven constructed by "Canuck Jim" (the author of the Pompeii oven plans on the FB site). The dome of my oven will be insulated with 3 inches of ceramic batting & 3'' of matrilite.  My oven engine came prebuilt on a 4" thick slab of concrete & is going to sit on a stand comprised of steel tubing.  In between the oven floor & the stand there will be a 2" thick slab of high heat insulation board.  Jim insists that this is necessary for the reasons stated above by Marc & also to withstand the winter frost.

Matt

[widespreadpizza]

Matt,  Tell Jim I said thanks for the pompeii plans as I relied on them heavily for my oven design and construction.  It came out very nice and his plans out everything in perspective.  -marc

[Matthew]

Matt,  Tell Jim I said thanks for the pompeii plans as I relied on them heavily for my oven design and construction.  It came out very nice and his plans out everything in perspective.  -marc

Will do Marc.  Jim is quite a craftsman/Artisan.  His Breads are incredible.  Every year in May he has a Bread Bash at his place that draws quite a large crowd. People come from all over the world for his bread making seminars. Do you have some photos? 

Matt

[JConk007]

Corbs,
Do the Forno site. The vast amount of info there was not available when I built mine. I have the same oven as Bill/sfnm Oven sits on 1 1/2 " bakers tiles 1" of lean cement ( thats mostly sand and a bit of cement ), and 4" concrete floor. On top I used perlite insulation beyond the recommended spec and filled the entire cavity/space between walls and dome with as much as possible. There is no substitute for good insulation top or bottom.  800 degree temp = cool to the touch outside 

Now for the Bread. I plan to focus more on the bread this season. Using residual heat from the oven I often have 400 degrees plus the next morning. Hardest part for me is to start earlier so I am not baking bread at 11 pm at night after multiple glasses of  Cabernet.
I may refire in the am and try to control the temp that way . Any thoughts?
Thanks
JOhn

[perna]

Second do not use sand above the dome.  It will act as mass that you have to heat,  weigh too much,  and not be the insulation you need.  If looking for a loose insulator use perelite or vermiculite.

Perlite is basicly sand that is cooked in a furnace until it pops like popcorn. So using it instead of sand give you the same inslation with less mass and it takes up more space.

[Corbs]

Thanks Perna, I hadn't heard of it.