Oven opening size

[mikku]

Re: Oven opening size

Thank you Wiley,
I understand what you are saying about the distance from the inner door to the outer door - (landing) or transition - as a distance of convenience. Now lets call the distance from the inner door to the dome interior (or location) the "throat maybe". In your opinion is there any optimum distance or range that you must deal with?
I cast my dome in two pieces and a separate piece I call the transition. When I began layout for making an oven base it appeared like the "throat" was longer than what I see on all the photos at FB Forum. I spent a lot of time making the mold from wood but it would be modified easily for a future casting if this does not work out. Just trying to understand the mechanics of design...Now am beginning to understand the art of firing as well.
Still a very long way from puting a fire to anything. I can imagine it at best right now. Thanks again and Thank You Forno Bravo for hosting this forum--unbelievable wealth of information available!

[Wiley]

Re: Oven opening size

Mikku,

The height of the opening relative to the height of the interior of the dome is for optimum airflow. IMHO the depth of the oven plays an important part for proper airflow. One would expect that there is an optimum range for this distance but honestly I know of no study that has been done to determine this optimum.

There is skill and art to firing a WFO. The size of the fire and dryness of the wood being burned is important. Once the smoke leaves the interior of the WFO it is not really participating in the airflow inside the WFO; excepting if the flow is restricted to the point of choking the exhaust exiting the WFO. Regardless if the WFO is well designed and built, if the fire is producing a larger volume of smoke than the chimney can handle it will spill out the front. This a variable controlled by the person firing the WFO.

I see no problem with your referring to the area between the exterior opening and the interior opening to the oven itself as the landing.

The height of the exterior opening is IMHO more a matter of practicality in ease of working the food and fire and aesthetics of the builder. When I am firing my WFO I use a draft door and the opening is a bit over two inches high. It causes the fire to draw extremely well yet would be very impractical to try and cook thru this small an opening.

It is my feeling the depth of the landing has little to do with the performance of the WFO, with exception of how easy it is to manipulate whatever is being cooked in the oven thru the entrance and tend the fire.

The width has been discussed before. I suspect a controlling factor is one of support and construction in a traditional WFO built of bricks. The wider entrance allows for larger pizzas (provided we are talking of round pizzas).

Hope this helps,
Wiley

[mikku]

Re: Oven opening size

Back to the issue of opening size.
I have a question on actual placement of oven opening in relation to the inside of the oven. The pompeii oven ebook shows the oven opening tangent to the arc of the interior of the oven dome. Is there any critical dimension to worry about? All discussions are about ratio-dome height to opening height-width not important. If a tunnel is present making the oven opening 8" from the point of tangency then a transition made to the vent chamber, will there be a problem with venting of the smoke? Is the landing considered the place between the oven opening and the outer surface of the vent chamber?

[david s]

Re: Oven opening size

I disagree with your method for mixing the insulating concrete. The cement and water should be mixed first to form a slurry. Strict attention to the water to cement ratio must paid. Additional water beyond the specified amount will weaken the concrete. Once the slurry is formed add the aggregate. Perlite is a slightly better insulator than vetmiculate so that's what I would use. Both are fine though.

Rent a tumble mixer for this and make your life easier.

Both vermiculite and perlite tend to break down if mixed too much. I've tried using a mixer, but not found it an improvement. The mix sticks to the sides, you can't inspect the mix easily and judge your water addition and you have to scrapeoutworn the sides with your hands anyway. If mixing in a barrow or large bucket you can see the mixing process better and clean up is easier.regarding water content I have tried the "mix a cement slurry first" but have gone back to mixing the vermiculite or perlite with dry cement before adding water.The correct amount of water is critical. If you end up with water pooling at the bottom then you've added too much. It seems to simply wash the cement off the grains and takes the cement with it to the bottom.
I've also found the ratio of 10 parts vermiculite or perlite to 3 parts water is about right for the layer over the dome (use a 5:1 mix for the insulating slab under the floor), but this does vary with the grade of stuff you get. Fine vermiculite for example needs about 4:1
The other thing I discovered was that a 50/50 vermiculite, perlite mix works up to a much more workable mix than either of them alone, have no idea why, but it works well for me.

[Optionparty]

Re: Oven opening size

http://www.fornobravo.com/forum/3/an...tos-690-2.html

I had a hard time finding them too. (Used Google to search fb site)

Carl

Well meaning workmen, worked on my oven while I was in the USA.
It still works, but it has lost it's beauty. Just brickwork to them.
Sorry

Carl

[dragonsoup]

Re: Oven opening size

I disagree with your method for mixing the insulating concrete. The cement and water should be mixed first to form a slurry. Strict attention to the water to cement ratio must paid. Additional water beyond the specified amount will weaken the concrete. Once the slurry is formed add the aggregate. Perlite is a slightly better insulator than vetmiculate so that's what I would use. Both are fine though.

Rent a tumble mixer for this and make your life easier.

[Optionparty]

Re: Oven opening size

tried to see you pics but fb says it cant find it

http://www.fornobravo.com/forum/3/an...tos-690-2.html

I had a hard time finding them too. (Used Google to search fb site)

Carl

[smallholder123]

Re: Oven opening size

tried to see you pics but fb says it cant find it

[Optionparty]

Re: Oven opening size

Door hight from 61.8% to 63% will provide a good compromise of heating to draft.
Door width effects rate of burn and loading/unloading.

Plan ahead, consider your options once operating temperature is reached.
(Just an idea, maybe some type of sliding door, or a Venetian blind design)

Carl

[sonomacast]

Re: Oven opening size

According to Forno Bravo sales literature 22" wide is the perfect width of an oven door.
Forno Bravo Modena2G Oven Opening Size

[connie kokiousis]

how about the vent opening

Can anyone tell me what size vent opening I should have for a 11.5" x 19" opening on a 36" oven with a dome height of 20"?
Thanks!

[connie kokiousis]

Re: Oven opening size

Thank you so much for the answer to my question. I will post pictures of our progress soon.

[asudavew]

Re: Oven opening size

Definitely use firebricks.
Your local brick yard should have them in stock. ( I found them at ACME for $1.11 each, I used about 220 bricks.)
They tend to be yellowish in color. But can also be found in lighter reds.


Insulating concrete is made of a mixture of Portland Cement (not Quikrete), and vermiculite/perlite. Portland comes in 94lb bags and can be found at Lowe's or Home Depot. Vermiculite/perlite comes in 4 cubic foot bags. It is usually found at garden/horticulture stores or at local pool supply outfits.

The normal ratio for insulating concrete is 5 parts vermiculite to 1 part Portland cement. (by volume)
Mix the two together first, and then add enough water until it holds together.

The structural concrete should be poured first, followed by the insulating concrete. I would suggest that you pour a 5 1/2 inch insulating layer.

After it "hardens" after a few days, (it will feel like cork) then begin laying your hearth layer.

Good luck!

And we enjoy pics around here!

Dave

[connie kokiousis]

building an oven, my first posting

Hello,
I was inspired by this site to build an oven too. My husband and I are very excited about it. We have the base nearly complete and are finding lots of tips from the postings here. I am working with a contractor who has never built a pizza oven before so we are all learning together. The brickyard that sells the firebricks told him that he should use common clay bricks because they retain the heat better. This is completely contrary to the FB instructions, which clearly call for firebricks? Also, what is insulating concrete?
Thanks,
Connie

[Wiley]

Re: Oven opening size

Bruce, I think I understand what you are getting at. It seems most people try to contain the ovens heat within the oven area itself rather than include the entry area. I can see some downsides to including the entry, the biggest being the fact that it wasn't heated in the fireup so as the WFO "normalizes" there will be greater overall temperature drop ....the heat used to heat the previously unheated entry.

I too am planning on being able to shut off the chimney from the airflow when "closing up" for the night and wanting to retain heat for the next days cooking. My plan is to remove the chimney and insert a plug in the hole. I have designed my WFO so the chimney can easily be covered for storms and periods of non use. To do this easily means simply lifting off the chimney and inserting the plug/cap. This will lessen the loss from the chimney as the uninsulated direct path to the outside world for heat from my dome is thru the entry and thru the refractory which is part of both the dome and the chimney.

So I will have a door for the oven itself and a plug for the chimney. I'll probably set the smoke door mentioned previously in place both as a place to store it and to keep the passing raccoon from finding the warm area too inviting and so wanting to curl up and make himself at home :-)

Wiley