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Thread: Bridge problem!  Please advise!

  1. #1
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    I actually already knew about this "problem", but it is starting to manifest itself in a different way.

    I have an MK that I bought just prior to them going to stores. #The only thing I was really disappointed in was the fit of the bridge to the top. #It didn't. #I have described this to you guys before - I think in a discussion of setups. #I plan on it, but I live a good 2-3 hours from all teh suggested places.

    To basically describe its original fit: #The foot on the lower (E string) side of the instrument, only touched the top at one point, the point of the bridge foot closest to the middle of the instrument. #From that point out, the foot remains 'in the air', enough to slide a piece of paper a fair ways under. #The top (G string) side is fit much "better". #MK's reponse to my concern was that they do not fit the bridges to the tops for each instrument.

    Well tonight, I noticed that my brige is LEANING towards the headstock. #Perhaps 10 degrees. #Maybe less maybe more. #But it is noticeable. #It may have to do with my recent string change...however, I do NOT remove all teh strings at once and replace. #I remove and replace two or four at a time, working from G to E. #I was thinking of loosening the strings substantially enough to see if the bridge can be set vertically again.

    I have never had this instrument set up professionally. #I think it sounds geat and stays in tune. #With my chromatic tuner, however, it seems that the higher I play a note or chord on the neck, the more out of tune it appears on the tuner. #

    Well, obviously I could use a setup and a proper bridge fitting. #Perhaps a bone nut and a new tailpiece etc... too.

    I just thought a few of you could relate or share your thoughts. I appreciate it.

    Alan

    PS I SHOULD NOTE that if you look at the mando from the top (side, in cross section so to speak), and study the profile of the mandolin, that teh 'peak' or height of the top does not occur at teh point of bridge placement, but closer back to the tailpiece. I was thinking of searching for some images on this site that might help me with this question. Simply put, the bridge does not site on the 'highest' spot on the top, and this may or may not be applicable, but I thought it might contribute to the leaning I have now.



    Alan

  2. #2
    Registered User jim simpson's Avatar
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    Alan,
    The bridge on a mandolin will often creep forward or lean with string changes or just tuning. You might be able to grip it and tilt it back upright without loosening strings. This leaning will throw your intonation as you have noticed. As far as the bridge goes, I would definately have it fitted properly. If you can't find someone to do this, you may be able to do it yourself (diy). It takes a little patience. I had ran into Roland White many years ago at a festival. He had asked about the mando I had at the time. He looked at it, noticed my leaning bridge and promptly straightened it to it's correct position. He then proceeded to play wonderfully on it. After that I strarted to keep a better eye on the bridge to prevent what you are experiencing. Good luck with it!
    Jim
    Cabin Fever String Band, Bill Gorby and the Musical Mercenaries

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    Alan,

    The physics of proper intonation are based on the length of the vibrating string - so for a given set of frets, your bridge saddle needs to be approximately 2x the distance from the nut to the 12th fret. On your mandolin, I have no idea where that point relates to the "highest" point of the carved top.

    I say approximately, because the precise location is what compensated saddles and moveable bridges are all about.

    The fact that you are noticing intonation problems (I'm guessing that as you play higher on the neck, your notes go sharp?) your bridge most likely tilted when you were restringinging due to the fact that it is not seated on that foot.

    You need to deal with that.

    As Jim notes above, you can simply straighten it up and likely cure the "out of tune up the neck" issue - short term.

    Getting the feet to seat properly simply involves getting a small sheet of sand paper, placing it grit side up where the bridge is supposed to go and then simple moving the bridge back and forth along the axis of the neck in that spot until the bottom of the bridge fits the carved contour of your top in that spot.

    Use short strokes and take your time.

    Make sure that the center of the bridge stays centered on the instrument or you won't be any better off when you go to string it back up.

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    Thanks guys. I did not try to fix the bridge last night, and may try tonight. (straightening it again). #I realize that physics dictates bridge placement, and that the 12th fret would be exactly halfway b/w bridge and nut. #I just wondered if on most mandolins, is the body at it's highest point at that spot. #It appears, from pictures on pages 4, 24, 25 of the "Loar Pic of the Day Thread" that the tops are contoured such that the highest point of the top's curvature, happens to be roughly (or exactly) where the bridge would be placed. #(picture attached is from the Loar Pic thread of Loar #73992) My top seems to have steeper curves than this Loar (and of course I KNOW that I have an MK, NOT a Loar!) I just feel a real bad case of MAS coming on.





    Alan

  5. #5

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    As to the bridge feet not fitting the top, I had an experience one time where a repairman replaced the bridge with the bass side of the feet on the treble side of the mando. Of course the top part of the bridge (saddle) was replaced correctly, but there was a noticeable clearance between one side of the bridge and the top. You'll have to loosen all the strings considerably to remove the bridge, just tilt it over, then take the top off and try the fit both ways with the bottom portion. Sometimes the builder will mark in pencil under one foot whether it is bass or treble side.



    Fred

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    > I just feel a real bad case of MAS coming on

    You say that like its a bad thing




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    levin4now... As far as the question does the bridge always set on the highest peak of the arch? The answer is no. Many mandolin arches are higher behind the bridge.

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    Thanks Mav. It helps to know I'm not the only one.

    Gary, you're right. An Awesome case of MAS! (bad, b/c I could never treat it properly).
    Alan

  9. #9
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    My MK's top is contoured the same as you describe. I bought mine from Elderly and they did a great job of setting it up, the bridge is fitted perfect. I've had the bridge on my Gibson creep forward slightly over time, as previously noted I loosened the strings and adjusted to vertical.
    Lee

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    Quote Originally Posted by (grsnovi @ April 13 2004, 01:10)
    Alan,

    The physics of proper intonation are based on the length of the vibrating string - so for a given set of frets, your bridge saddle needs to be approximately 2x the distance from the nut to the 12th fret. On your mandolin, I have no idea where that point relates to the "highest" point of the carved top.

    I say approximately, because the precise location is what compensated saddles and moveable bridges are all about.

    The fact that you are noticing intonation problems (I'm guessing that as you play higher on the neck, your notes go sharp?) your bridge most likely tilted when you were restringinging due to the fact that it is not seated on that foot.

    You need to deal with that.

    As Jim notes above, you can simply straighten it up and likely cure the "out of tune up the neck" issue - short term.

    Getting the feet to seat properly simply involves getting a small sheet of sand paper, placing it grit side up where the bridge is supposed to go and then simple moving the bridge back and forth along the axis of the neck in that spot until the bottom of the bridge fits the carved contour of your top in that spot.

    Use short strokes and take your time.

    Make sure that the center of the bridge stays centered on the instrument or you won't be any better off when you go to string it back up.
    When you sand the bridge, be very careful. It's easy to "roll" the edges of the bridge. One source I found stressed only moving the bridge in one direction on the sandpaper, ie. pull it a short distance toward you, then lift and replace the bridge and pull it again. I did mine this way and I'm very pleased with the result, but it's not fast. Take your time and do a good job.

    Kathy Wingert suggested to me that to avoid rolling the edges, one might locate the high spots and use a scraper rather than sanding. She said it would be faster and safer (from the not rolling point of view). I didn't take her advice largely because I'm not that conversant with scrapers, but I'm very willing to put in the time to do it slowly and carefully with sandpaper. I'm pretty sure that if I was a builder and was trying to get some production out, I'd need to use a faster method.

    -Raf

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