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Splits in the hearth..

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  • johnrbek
    replied
    Re: Splits in the hearth..

    Maver,

    I think it would make sense to hear from someone with an engineering background... Perhaps an engineer could shed some light in absence of any real testing... Otherwise, it's all conjecture.

    Any engineers out there care to weigh in?

    JB

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  • maver
    replied
    Re: Splits in the hearth..

    I understand your question and the idea that layering may have value, but from the insulating standpoint I don't think the idea holds up. The idea of firebrick is to have a material that conducts heat well to help with handling the high heat and to form an even "heat well" to avoid hot spots. By layering bricks you may lose some of that type of beneficial conduction (it's the job of the insulation to put a stop to that) and may have more risk of uneven heating. You also add more potential uneven spots (raised areas) in your hearth which would be annoying with cooking. Layering whole firebricks would make your heat well very deep, maybe ok for retained heat cooking but much harder to bring up to pizza temps.

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  • johnrbek
    replied
    Re: Splits in the hearth..

    Hmmm... remember.. I'm only the messenger here.. but it did get me thinking... it is clear to me that a single firebrick layer works fine... there are just too many ovens in use and with no issues...

    On the other hand, from an academic point of view, could it be better? Could you potentially require less insulation OR have more heat staying in the floor than bleeding into the underlying insulation? It would seem to make sense... just like I think it make sense to run 2 layers of 1" insulation board and overlap seams than just one layer of 2" with the seams.. Sure the 2" single layer works, but...

    Anyway, the purpose of the topic is to consider alternatives.. improvements.. refinements... not to say that the current process is wrong, just throwing something out there for consideration.

    I do disagree with the splits creating a weaker more fragmented floor... the splits are pretty damn strong.. it's not like we're driving a car over them or anything.. in any event, at one to two bucks a brick, it's not rough to replace one if it cracks.. be it a full size or a split...

    On second thought though, doesn't the space shuttle have a single layer of heat shield tiles? Mavbe that's substantial enough reason to leave it alone...

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  • maver
    replied
    Re: Splits in the hearth..

    I can only imagine the seams being a problem if you have an isulation layer that is not up to the temperatures, but that's why we don't use loose fill paper to insulate the floor . I agree with DMUM.

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  • dmun
    replied
    Re: Splits in the hearth..

    I don't understand the point of this. Two layers of firebrick will be too much thermal mass. Two layers of "splits" will only make a weaker and more fragmented floor. Any cracks in the floor, and I haven't heard of this being a problem, will just fill with wood ash.

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  • johnrbek
    started a topic Splits in the hearth..

    Splits in the hearth..

    Was on the phone with a refractory supplier down here and he said it would be a good idea to double up on a the brick in the hearth and put it in running bond so that seams overlap...

    He mentioned using soaps which are he said are standard brick cut down the 4.5" side, so you'd have 2.5 x 2.25 x 9... I'm thinking you would just use them on the sides to set the offset...

    However instead of doubling up on the standard brick and increasing the hearth mass, you could just use splits... and cut splits in half lengthwise to get the affect of the soaps to offset your seams on the bottom layer... I imagine you could also do 2 reverse herrring bones as well..

    Anyway, he said, as much as you can, you want create a fire break and the seams in a single layer give heat more direct access to your insulation layer than if you overlap seems... I hadn't heard of this before, so I thought I'd throw it out there for everyone...

    The downside of using 2 layers, whether they be splits or full size is the additional cost for the hearth floor.. my understanding is that splits costs about the same as full size bricks. Haven't run the numbers, but I wouldnt' think it would be significant in overall project cost terms...

    Any thoughts?

    JB
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