Fender neck bend at the high frets: how to cure

Discussion in 'Guitars in General' started by bgwicks, Feb 1, 2008.

  1. bgwicks

    bgwicks Member

    Messages:
    146
    Joined:
    Feb 1, 2007
    I have a 1966 Fender Coronado which is actully a nice guitar. However to get the action to work I had to shim it. As I have looked closely at the guitar I can see that the neck has bent slightly at the point it attaches to the body.

    I assume what happened was someone left the guitar under tension with way too much relief in the neck. As the neck bowed it actually bent at the point the neck attches to the body. When I tightened the truss rod, which was completely slack when I got the guitar, the neck straightened except for this last bend.

    Having the bend of course tilts the neck up requiring the shim.

    The end result has been a guitar which plays very well except down on the body. The frets here completely choke the strings.

    Does anyone have any advice on how this is fixed?
     
  2. hogy

    hogy Member

    Messages:
    11,360
    Joined:
    Jan 4, 2002
    That's called a "raised tongue" and it's fairly common. It's caused by the string tension as well as the fact that the neck absorbs moisture through the end grain (the butt of the neck) causing it to swell.

    The bad news is that the only proper fix is to remove the frets, plane the finger board, and refret the neck.

    The good news is that it is likely as swollen as it can be giving the age of the guitar. That means once you fix it, it won't ever come back.


    Hogy
     
  3. Dana Olsen

    Dana Olsen Gold Supporting Member

    Messages:
    7,631
    Joined:
    Oct 2, 2002
    Location:
    Santa Barbara, Marin, Chico, CA
    Just for support, Hogy's exactly right (which is common for him).

    Dana O.
     
  4. bgwicks

    bgwicks Member

    Messages:
    146
    Joined:
    Feb 1, 2007
    Thanks for your help!
     
  5. mc5nrg

    mc5nrg Supporting Member

    Messages:
    8,070
    Joined:
    Mar 15, 2004
    Location:
    DC, Philly, Asquared, Upper Michigan
    I assume you put the shim at the far end of the neck pocket?
     
  6. walterw

    walterw Gold Supporting Member

    Messages:
    33,090
    Joined:
    Oct 16, 2006
    thirding dana, who's seconding hogy, the other factor is the shim itself. dropping a shim into the body end of the cavity and then cranking the neck down creates a bending force on that section of neck, pushing on it right at the point where it's already prone to kink up into the string path. other than making a fancy full-length wedge-shaped shim, the trick is to use another, thinner shim to support the neck between the main shim and the headstock-side edge of the pocket. use a straightedge to determine where the middle shim should sit to take equal pressure with each end of the pocket, then use a little spot of superglue to stick it in place so it doesn't slide out of alignment upon re-installing the neck.
     
  7. Vince

    Vince Member

    Messages:
    1,551
    Joined:
    Jan 8, 2004
    Location:
    St. Louis
    This might go against the common thinking on the causes of the symptom, but it's not from the tongue swelling. It's a function of the fact that string tension only acts on the neck from the nut to about the 15th fret, at the point where the back of the neck meets the neck pocket. On a strat or tele, it's 3" from the neck pocket butt. That's the "hinge" or break point for the flex in the neck caused by string tension, and why you're seeing the bend there.

    Because the tongue of the neck is supported by 1 1/8" inch of wood between the 15th and 21st fret, neither string or rod tension affects it. So, what happens is that under tension, whether compensated by the rod or not, the neck will flex at the 15th. If you were looking at the neck from the side and brought it to pitch (say with the body laying flat and clamped to a table), you'd see the the nut come up from the table and fingerboard start to arc. BUT, since the neck doesn't flex where it's bolted into the neck pocket, it stays parallel to the table. If you imagined that the arc of the neck continued from nut to the end of the neck, you'd see how the non-moving part of the neck creates a chord line inside the arc and cuts into it, creating the rise and the problem.

    Check out this geometry diagram. It's exaggerated, but illustrates the problem. If A is the nut, X is the point where the neck attaches to the body and line XB is the neck from fret 15 to 21, you can see how that part "rises" into the arc of the fingerboard (arc AB) at X.

    [​IMG]

    The only solution is to dress a certain amount of "fall away" into the upper frets, so that it dives a bit and extends the neck arc correctly, mimicking what would happen above in the arc between B and X. This is what we do as part of the fingerboard prep, planing and sanding of every Vinetto neck, of course prior to fretting.
     

Share This Page