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Thread: Hairline Cracks under Fretboard

  1. #1

    Default Hairline Cracks under Fretboard

    Hi all,

    I've recently picked up an Eastman 315 and have been having a blast with it. It plays like butter, stays in tune, and the neck is pretty much dead straight.That all being said, I recently noticed a few hairline cracks on the body of instrument beneath the fretboard that follow the grain of the wood that I may have overlooked when purchasing the instrument. Are these cracks symptoms of some sort of structural failure that will end up costing me down the road, or are they a harmless manufacturing cosmetic defect?

    Please see attached images.

    Thanks in advance for any help or advice!

    Click image for larger version. 

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    Click image for larger version. 

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    Last edited by powrmando; Nov-29-2021 at 11:32pm.

  2. #2
    Adrian Minarovic
    Join Date
    Oct 2003
    Banska Bystrica, Slovakia, Europe

    Default Re: Hairline Cracks under Fretboard

    It's impossible to judge from pics reliably so I can offer just few ideas and wild guesses...
    There is chance they are just finish cracks but that cannot be detected from pics. Visit good luthier to check the area under strong light both from outside and inside (with dentist mirrors).
    If they are cracks my bet would be on improperly dried wood. I can hardly imagine any physical way to break the top this way perhaps fall that would put leverage on neck but that usally results into one large crack along edge of support or both, especially on oval hole instruments. On f holed instruments this area is quite rigid.

  3. #3
    Registered User
    Join Date
    Dec 2008
    Greer, SC

    Default Re: Hairline Cracks under Fretboard

    I'd guess they were finish cracks but can't really tell.

  4. #4
    Teacher, luthier
    Join Date
    Oct 2017
    Southeast Tennessee

    Default Re: Hairline Cracks under Fretboard

    It might be nothing to worry about, or it might be a sign that there is a loose glue joint on the neck block, which is large block of wood inside the mandolin that the neck attaches to. A bad glue joint on the neck block is a serious problem, and a difficult repair on an f-hole instrument.

    If the instrument is new, it should be returned under warranty.
    If you bought it used, it should be inspected through the f-hole with a light and a mirror by someone who knows instrument construction.

  5. #5
    Registered User
    Join Date
    Sep 2007

    Default Re: Hairline Cracks under Fretboard

    Agree with those who do this for a living: get it inspected. I bought a new Taylor 714 guitar in 2008 or 2009 that had a similar finish crack I’d missed in the shop. I wanted some additional set up work done (but didn’t know the guys in the shop where I bought it, and it was a pretty good drive to that shop), so I found a local Martin certified luthier who confirmed it was nothing structural and surmised the shop hadn’t been well humidified. As I liked the guitar and there was really know way to prove it happened in the shop (though I’d only had it for 2 days when I noticed it) I had him replace the saddle (the other shop or factory had it way too low), got a case humidifier, and played the stuffing out of it for 12 years or so, after which I sold it in a downsize move.

    It may be nothing, or could portend impending neck joint failure…sorry!!

  6. #6

    Default Re: Hairline Cracks under Fretboard

    Thanks all for your expertise and opinions. The instrument has a satin finish and the cracks definitely extend into wood. As the instrument is a lower end Eastman model, my first thought is that it's just a rougher or improperly dried piece of of wood that was deemed passable since the cracks are small and are mostly concealed by the fretboard. That being said, the cracks being near the neck joint is what worried me enough to make this post, and I will take everyone's advice and get it looked at next time I bring things to my local shop.

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