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Thread: How to fix a bowed neck on classical guitar or ukulele ?

  1. #1

    Default How to fix a bowed neck on classical guitar or ukulele ?

    I have a baritone ukulele with bowed neck. What would be the best way to fix this problem ? My guess the same technique applies to classical guitars as well.

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    Registered User Greg Mirken's Avatar
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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    If this is an inexpensive instrument you could try heat-straightening the neck. Basically you cook the neck and clamp it into a mild backbow until it cools. It may help to utter magic incantations over it.
    On better instruments without an adjustable truss rod, it can be refretted using wire with a wider tang ["compression fretting"] or the fingerboard removed, then reglued while the neck is again clamped straight or with a slight backbow.
    Shade Tree Fretted Instrument Repair
    Now located in Nevada City, California
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    Registered User DavidKOS's Avatar
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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    Quote Originally Posted by Greg Mirken View Post
    If this is an inexpensive instrument you could try heat-straightening the neck. Basically you cook the neck and clamp it into a mild backbow until it cools. It may help to utter magic incantations over it.
    I've done that more than a few times using an old guitar repair tool, essentially a heating element inside a straight aluminum block. No incantations needed.

    However, some instruments react better to heat than others, particularly old cellulose bindings and such.

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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    Thanks for answering my question with very clear instructions. I will heat treat the neck first, if it does not hold, I will replace the frets. Current frets are too thin. I love fatty frets (on my tenor ukulele and Tacoma mandolin).

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    Registered User Greg Mirken's Avatar
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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    But it couldn't hurt, right?
    I can tell you that old celluloid can react dramatically to heat.
    Shade Tree Fretted Instrument Repair
    Now located in Nevada City, California
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    Registered User DavidKOS's Avatar
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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    Quote Originally Posted by Greg Mirken View Post
    But it couldn't hurt, right?
    I can tell you that old celluloid can react dramatically to heat.
    Ah, you've noticed! That old stuff can be pretty unstable.

  9. #7

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    But it couldn't hurt, right?
    I can tell you that old celluloid can react dramatically to heat.
    The neck is plain wood with frets, no celluloid. Safe to heat treat.
    I think this uke is an inexpensive one that I got for free to (practice) repair.
    It had a lifted bridge which I removed, cleaned and reglued.
    The fretboard now bows and then has a recurve where it lays on the sound board.
    The recurve rises higher causing string buzz when playing fret#10 and higher.

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    Registered User Greg Mirken's Avatar
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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    Uke necks are typically parallel to the soundboard. If it buzzes up at the heel now you will have to raise the saddle when the neck is straightened.
    Shade Tree Fretted Instrument Repair
    Now located in Nevada City, California
    http://www.shadetreeguitars.com

  11. #9

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    I did shim the saddle up. It is very playable now. But I intend to straighten the bowed neck to improve my repair skills. A friend gave me this ukulele as he knows I love repairing instruments.

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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    My "neck-straightening machine" is a length of aluminum I-beam (just because it was on hand) and two leather-faced cauls. Pressure is applied at the appropriate point with a C-clamp backed by another caul.

    Slower is better. The guy who taught me to level houses used to set his screw jacks in place, and then come back and give them a half-turn every other day for three weeks or a month. Move materials slowly and let them stabilize. For bad necks, I've left them clamped up for a couple of weeks, giving the clamp another quarter-turn every day. I like to put the instrument in the sun when possible, which seems to provide just about the right amount of heat. One of the lutherie journals (can't recall if it was GAL or ASIA) published an article from a repairman somewhere in the Deep South. He would clamp up a crooked neck, and then put the instrument in the cab of his pickup truck on a sunny day. That's probably more heat than you need, but it does have a certain redneck appeal.

    Take your time, and it will come out just fine.
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    -Ray Wylie Hubbard

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  15. #11

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    Thanks. I just did as suggested using the edge of the table for now. I will get a straight metal edge before putting in car trunk. I am no rush.

  16. #12

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    I found an old 18 inch Craftsman metal carpenter's level that is basically an I-beam and works well for that purpose.

  17. #13

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    My carpenter level is too long. I just use the straight edge of my metal bench. BTW, I also put towels on the neck and pour hot water on it, 3 times, about 2 hours apart to heat the neck. The moisture also makes the neck softer. This morning the neck looks almost straight, I repeat this hot water again, expect the neck to be really straight in the next 4 hours.
    Two questions remains: how long to wait before restringing ? Will the neck hold straight for good ?

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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    I would wait until the neck thoroughly dries before unclamping it, maybe a couple of weeks depending on the temp and humidity where you are at.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

  19. #15

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    I was wondering what would happen if you used very hot hazelnut oil or something like it?
    Would the oil be absorbed into the wood, and what would that do to tone?
    Are some (heavier) oils better than others?

    You can recondition leather by mild washing it and then oiling, or using hair conditioner on it before it dries, so...

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    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    No water, no oil. Heat and time only. The wet instrument neck will likely require a refret.

    @atsunrise, same reason you don't want to be too frequent or aggressive in oiling a fingerboard. Too much will loosen the frets.
    "And the days that I keep my gratitude higher than my expectations... Well, I have really good days."

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  22. #17

    Default Re: How to fix a bowed neck on classical guitar or ukulele ?

    OK, no more hot water. How about clamping then wrap the neck with a heating blanket set to warm temperature ? I don't want to put in a car trunk exposed to sun light as this could melt all the glue and the uke body and braces come apart.

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