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Thread: Quarter sawn braces, or not ...

  1. #1
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    Default Quarter sawn braces, or not ...

    I have always adhered to the practice of making sure that the grain lines in a brace run up and down (quarter sawn brace wood) as opposed to across the brace (the flat sawn equivalent). I did always wonder how much of a difference having a quarter sawn brace would make, stiffness wise. So, I conducted a little experiment.

    I set up a dial indicator, a place to hold brace wood, and a pivoting dowel on which I could hang a weight to load the very center of the brace, over the dial indicator. I cut some samples and ran them through the thickness sander side to side, so that the cross section is square. I put a brace in the holder, zero'ed the dial indicator, applied the dowel weight, and read off how far the brace had deflected.

    I tried this with a variety of woods, 6 pieces total, I had around the shop, and tried a single piece a couple of times to check for repeatability. The repeatability seemed to be on the order of .003-.005. The data is an image below. (I can not figure out how to get this text to make a table. It seems to compress out blanks.)

    So there is almost no difference between having a quarter-sawn brace or a flat sawn brace. In fact, with the reproducability of around .003-.005 there is no difference at all. (This may account for the Alaskan Yellow Cedar appearing stiffer on the flat sawn.

    The test setup, not elegant but worked pretty well
    Attached Images Attached Images
    Last edited by jupiteruke; 05-21-2021 at 12:30 PM.

  2. #2
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    This squares with what I've read in sources that discuss guitar building. Thanks for posting your test results!
    Last edited by saltytri; 05-22-2021 at 03:37 AM.

  3. #3
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    I wonder if we added time to the equation whether there would be a difference? It's often over time that we see a soundboard under load start to deform. Maybe a soundboard with flatsawn braces would deform whereas one with quarter sawn braces would not. I also wonder whether a quarter saw brace copes better with moisture changes?
    Last edited by greenscoe; 05-21-2021 at 09:25 PM.

  4. #4
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    Fascinating. What if you used thinner pieces (like the actual dimension of a brace) and then added weight until the piece broke (ruptured). Would the difference between the two be more apparent?

    Anyway, it appears that hey, it really doesn't make a difference. Rocket science comes to ukulele making.

  5. #5
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    I use flat sawn spruce bracing but turn them sideways...if you know what I mean. Edge up.
    http://ukulele-innovation.tripod.com ebay i/d squarepeg_3000 Email timmsken@hotmail.com

    If you can believe that moving images and sound, can fly through empty space across the universe and be seen and heard on a box in your living room ?.. then you can believe in anything.

  6. #6
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    That's cheating!

    John Colter

  7. #7
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    My experience over the years of doing repair work has shown me that quarter sawn braces over time will perform better. If the bracing stock is marginal or of poor quality in guitars or ukes, the top plate will suffer over time. My advice is to use the best quality Sitka or Red spruce you can fine. The stock should be well seasoned, stiff, quarter sawn and light weight.

  8. #8
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    It's my understanding that a quarter sawn board will, with changes in moisture, expand or contract up and down, whereas flat sawn will expand side to side. If it's glued to the surface and trying to expand side to side, it's trying to break the glue or itself to do that. Quarter sawn doesn't have that problem.

  9. #9
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    Quote Originally Posted by Matt Clara View Post
    It's my understanding that a quarter sawn board will, with changes in moisture, expand or contract up and down, whereas flat sawn will expand side to side. If it's glued to the surface and trying to expand side to side, it's trying to break the glue or itself to do that. Quarter sawn doesn't have that problem.
    The braces are two narrow for the expansion and contraction to make much difference.

    Both quartered and flat sawn material will perform roughly the same and the least stiff arrangement is at 45 degrees. With flat sawn braces the grain line might have a greater tendency to split and peel if you have scalloped braces. There was also another mechanical problem using them but I can not remember it right now.

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