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  • james
    started a topic Oven opening size

    Oven opening size

    You are working to balance two conflicting requirements with your oven opening.

    First, the smaller the opening, the better your oven is at holding heat. If the size of the opening relative to the volume of the oven is too large, it will be difficult to keep your oven at high heat, and it won't hold heat for baking. There is a U.S. made commercial oven that has this problem, and I have heard numerous restaurant owners and pizza chefs complain about it. I had a small (26") oven at an Italian house, and the opening (16" x 10") was too large (relative to the oven volume), and it just couldn't hold heat.

    Second, the opening needs to be big enough to easily move food in and out of the oven. If the opening is too small, it can be a pain just using it. I have that problem with my Scott oven.

    For the opening width, 18"-19" is pretty standard. It gives you room to work (and as Robert says) see the fire, without over doing it. You can go a little wider, but I wouldn't go past 20". That width will let you get just about any pizza in and out of the oven.

    Opening height does depend on dome height, and 60% is an OK rule of thumb -- though it is something of an urban legend. There is no perfect formula, and I have never seen it used in the context of an Italian brick oven. For example, the ancient ovens have really high domes (you can almost stand up in them), so the opening height to dome height ratio on those is tiny. Equally, as brick ovens gets larger and the dome gets higher, there is no reason to make the opening taller than 12"-13" -- the size you need to get a roast in and out. So in that case the ratio of opening height to dome height gets smaller and the ovens simply perform better.

    If you have a 42" oven, with a 20" dome, an 19"W x 12"H opening should work nicely. Good access, good thermal characteristics.

    If you have a 36" oven with a 17"-18" dome, an 18"W x 11"H opening would be good.

    If you are building a Volta Bassa (low Naples style dome), you should bring your opening down an 1" or so -- but makes sure you can still fit in a turkey.

    If you want to maximize heat retention, you can always arch your oven opening (higher in the middle for a roast), but lower on the sides for heat retention.

    If you are really into maximum design, you can have a local metal fabricator make you a cast iron door opening like this:

    http://fornobravo.com/commercial_piz...istorante.html

    Wide at the bottom, high in the middle and closed in at the sides. Now that is cool.

    James

  • madhatter1138
    replied
    Re: Oven opening size

    Glad to hear this! Since its arched from 9" (not 9 1/2" like I said earlier) to 12" I can take comfort in the math that it averages out 10 1/2" of height..which is right on the money

    Leave a comment:


  • david s
    replied
    Re: Oven opening size

    Don't sweat. It makes far less difference than many people would lead you to believe. Just fire your oven as it is, you'd find no noticeable difference if you rejigger it to 63%

    Leave a comment:


  • madhatter1138
    replied
    Re: Oven opening size

    Building a 32" oven. Dome height is 16". Oven opening is arched. 12" in the centre arched to 9 1/2" to the sides. Width is 18". I'm worried that height (at 75%) is way off the mark. Should be around 10.5"...BUT if I add a row of half block then it gets really tight on the ends...
    Any thoughts? Apparently I missed the 63% rule in the plans!? I figured it was ball parked etc etc...

    I only looked into this today after completing the arch and it just looks to big....

    Leave a comment:


  • david s
    replied
    Re: Oven opening size

    Originally posted by FrankHawkins View Post
    Ok, I think it's 8x5 inches at the moment. So I may have to open it up a little as mine is a 39 inch oven.
    Here are the pictures of my opening. Does it all
    Look about right?
    That's ok, just make the cross section of the chimney a little bigger. The restriction at the bottom where the smoke enters will just work as a venturi making the smoke accelerate at that point.

    Leave a comment:


  • FrankHawkins
    replied
    Re: Oven opening size

    From another angle.

    Leave a comment:


  • FrankHawkins
    replied
    Re: Oven opening size

    Ok, I think it's 8x5 inches at the moment. So I may have to open it up a little as mine is a 39 inch oven.
    Here are the pictures of my opening. Does it all
    Look about right?

    Leave a comment:


  • david s
    replied
    Re: Oven opening size

    Originally posted by FrankHawkins View Post
    Cheers thankyou!
    Also I'm building the chimney vent out of bricks. What size would be best to make the internal diameter of it.
    Depends on the size of your oven.
    A 24" oven needs 20 sq in
    A 30" oven needs 30 sq in
    A 42" oven needs 50 sq in

    Leave a comment:


  • FrankHawkins
    replied
    Re: Oven opening size

    Cheers thankyou!
    Also I'm building the chimney vent out of bricks. What size would be best to make the internal diameter of it.

    Leave a comment:


  • david s
    replied
    Re: Oven opening size

    I've found the correct ratio of water is 3 parts water for every 10 parts vermiculite, although if you have the fine grade you need more water. As the addition of cement decreases the insulating capacity drastically I use a 10:1 mix, vermiculite, cement. Any less cement than this makes it difficult to get a good workable mix. Adding a little powdered clay to the mix will help to make a lean mix more workable.

    Leave a comment:


  • Greenman
    replied
    Re: Oven opening size

    Hi Frank - The 'vermicrete' insulation is just vermiculite and cement. A ratio of 8:1 by volume works ok.

    The trick is to get the moisture level right and too much water is an issue. It will end up like wet rice bubbles and is not a 'fun' material to work with. I found that working from the bottom up, balling it up and applying it in one 'smear' and moving on worked for me. Messing with it after you place it caused grief in the form of crumbling away.

    I had chicken wire over the blanket and it helps hold the vermicrete too. It is perfectly stable once it hardens but I found it an 'interesting' medium. I did, however, use it on subsequent builds.

    By the way, it is best to mix it in a barrow with a hoe rather than a mixer. The vermiculite maintains its integrity that way and you can better judge the moisture level. Good luck with it.

    Leave a comment:


  • FrankHawkins
    replied
    Re: Oven opening size

    Cheers, pictures were really helpful!
    My next question is about the vermiculite insulation that I will be costing around my insulation blanket. Do you just use cement and vermiculite or do you add sand?
    What ratios also?

    Leave a comment:


  • yorkshireknight
    replied
    Re: Oven opening size

    Hi again Frank hope these pics help you to see your idea os recess and chimney.
    YK

    Leave a comment:


  • yorkshireknight
    replied
    Re: Oven opening size

    Hi Frank,
    Your oven is looking great.

    Your idea seems to be exactly as I did mine. A slightly large opening into the vent area will allow for a recess to put a metal door up against it. Great!
    your chimney will sit on top of your vent, so yes all sounds good.
    Looks like you are over the hard part and not far from completion. good luck and well done!

    Paul aka Yorkshireknight

    Leave a comment:


  • FrankHawkins
    replied
    Re: Oven opening size

    Hello guys. Here is my pizza oven so far....
    Once I finish the dome, I will be building the front entrance.
    I was going to make this slightly wider and slightly taller than the entrance in the photo so that I can push a metal door up to it.
    I was also going to build my chimney into the entrance chamber.
    Does this all sound about right?
    Interested to hear any feedback!
    Thankyou!!

    Leave a comment:

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