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Thread: "H" Bracing for a flat-top Octave Mandolin

  1. #1

    Default "H" Bracing for a flat-top Octave Mandolin

    I have used H bracing on some 10" mandolins, and recently used it on a 11 1/2" wide body (see pic).
    I am now building a 12" wide Octave Mandolin with a 19" scale. Any thoughts out there?
    In the wide body mandolin, the traverse brace was 3/8 x 3/4. I think it was a bit too big, but the but the finished instrument has a nice balance and plenty of volume and resonance.
    I'm thinking of 1/4 x 3/4 for the OM.

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    I carved away quite a bit of the braces.

  2. #2
    Mandolin tragic Graham McDonald's Avatar
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    Default Re: "H" Bracing for a flat-top Octave Mandolin

    Should work just fine 8-)

    Cheers

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  4. #3

    Default Re: "H" Bracing for a flat-top Octave Mandolin

    Graham,
    I thought I read somewhere that you would suggest placing the traverse brace slightly ahead of the bridge location rather than directly underneath it?

  5. #4
    Mandolin tragic Graham McDonald's Avatar
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    Default Re: "H" Bracing for a flat-top Octave Mandolin

    This is a small advantage, I think, in moving the transverse brace 1/2-3/4" in front of the bridge, but it is not huge. More important is carving enough of the braces away to support the top without stiffening it up too much. I might be worthwhile thinking about cantilevering the transverse brace over the longitudinal braces so it doesn't sound them at the intersection. I haven't tried that, but I think it could work.

    Cheers

  6. #5

    Default Re: "H" Bracing for a flat-top Octave Mandolin

    Interesting idea; leaving a gap so that the braces don't touch at the intersection?
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  7. #6
    Mandolin tragic Graham McDonald's Avatar
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    Default Re: "H" Bracing for a flat-top Octave Mandolin

    Yep, that sort of idea. I am thinking that you want to support the longitudinal arch but have some control over the transverse stiffness.

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    Tukanu 

  9. #7
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    Default Re: "H" Bracing for a flat-top Octave Mandolin

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    I have experimented with that configuration recently & so far I like the results. I built a 12" top, 22" scale OM with that bracing pattern & I believe it is one of the best sounding I have built. I used a cross-grained ring around the sound hole & that seems to obviate the need for further bracing in that area. Also I like to bind the sound hole.

    I like the bracing pattern because it puts the braces exactly where they are needed: to support the downward force of the bridge & resist longitudinal buckling. And of course to control stiffness. Unfortunately I did not record (at least I can't find) the dimensions of the braces, but I believe I was in the same ballpark.

    I have built a test rig like James Condino's & plan to continue experimenting when I can get back to the shop. The idea of making the braces independent is quite interesting.

    Earl Tyler

  10. #8

    Default Re: "H" Bracing for a flat-top Octave Mandolin

    Thanks Earl. It is very encouraging to know it works well with the larger top of an OM. I will be building the braces today and hope to get them carved tomorrow.

  11. #9

    Default Re: "H" Bracing for a flat-top Octave Mandolin

    Braces are all 1/4 x 3/4 and tapered toward the top. I left the transverse brace full height to carry the load. The longitudinal braces were reduced by quite a bit, but are still very stiff. There is only a slight bit of give when I stress them. I think that's enough shaping for now.

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    Last edited by Tukanu; Nov-14-2018 at 6:30pm.

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