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Who gets the most cracks? Square vs Angled cuts

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  • splatgirl
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    The super meticulous people who cut their bricks so that there are the tiniest of joints are also the people who obsess about cracks. Those of us that that were less meticulous have no idea whether we have cracks or not

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  • Tscarborough
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Good point, Dino. Unless the crack is at a structural joint (like the center of your arch) and is getting bigger, then it is no big deal. Some cracking is to be expected.

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  • Dino_Pizza
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Originally posted by WoodchuckDad View Post
    just cut the bricks in half and use them and blob on tons of mortar and they don't say anything about cracks. So who gets the most cracks and the most stable build?
    This sounds good to me! I've come to really appreciate the simplicity of doing this. From the inside of the dome, it looks exactly the same. From the outside...quite different until you insulate. But you use a lot less bricks, less diamond blades but more refractory mortar. But I say this just for comparing building methods....(I went with mostly tight joints, lots of tapering)

    As for does it affect cracking? I don't know. I got a few hairline cracks in the dome (as viewed from the outside before insulating) and 1 big thermal-shock vertical crack that split my bricks due a curing "accident" on my 3rd curing day that was easily avoidable. Other than than that, no cracks that you can SEE at the arches or arch walls. Those may or may not happen as Tscarborough said: due to too wet mortar or shifting problems.

    IMO I wouldn't pick the building method based on hairline cracking. I would be more likely to pick on other just as hard to pin-down criteria: Do you believe the tighter joints make an oven with slightly better heat retention having 90% firebrick instead of 85% firebrick/15% refractory mortar? Does the extra work make a difference?

    I think the most important decision is spending time on good vent transition design that is stable and sized large enough to draw excellently. Hairline cracks disappear for all kinds of reasons (insulation covers it, soot masks it, oven weight closes them) but smoke out the front is always...smoke out the front. If obtaining your bricks is easy to do, you could install your floor, soldier course, the 1st row of half bricks, then your inner arch, by then you can decide if you think the 2nd row and the rest will be larger joints or not.

    Lastly, make both inner/outer arches tight. Cut them slightly pie-shaped and fitted well. The cracks there tend to come from rectangular pieces slipping slight which cannot happen if they are all slightly wedge shaped (especially near the top of the arch).

    You'll be really happy with whichever method you choose, Can't wait to see it!, Cheers, Dino
    Last edited by Dino_Pizza; 05-21-2010, 01:45 PM.

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  • Tscarborough
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    There are several causes of cracking, and they are not mutually exclusive or additive.

    1. The number one cause is shrinkage from too wet of a mortar/too wet brick at placement.

    2. The number 2 cause is thermal shock. As a rule, this one will be less with wide joints, more with thin joints that can not absorb as much movement.

    3. Structural movement. Also more common with thin joints.

    As you can tell, thin joints are not a good thing with the exception of refractory applications, where the advantage of protecting the joint is greater than the possibility of movement and cracking.

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  • fxpose
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    My joints are very, very wide on the outside of the dome using homebrew, but the joints in the dome are fairly tight where it really counts.
    Regardless, I'm looking forward to getting some cracks once the curing process begins...

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  • WoodchuckDad
    started a topic Who gets the most cracks? Square vs Angled cuts

    Who gets the most cracks? Square vs Angled cuts

    I see some folks with exacting cuts and nice tight mortar joints.....and at the ed of their build they talk about cracks. And I see some who just cut the bricks in half and use them and blob on tons of mortar and they don't say anything about cracks. So who gets the most cracks and the most stable build?
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