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Correcting the curve of a neck blank

Discussion in 'Luthier's Corner' started by Cerb, Feb 13, 2005.


  1. Cerb

    Cerb

    Sep 27, 2004
    Indiana
    Not to long ago I glued up a wenge/purpleheart/maple/mahogany/maple/purpleheart/wenge neck blank. Just a few days ago I noticed that it has a slight curve it it. The blank is about 52" long. With a straightedge touching both ends, the gap at the center is about 2-3 millimeters. I figured I would be able to correct it by routing down the center following the curve (the center piece of mahogany is 1/4 " thick, so I would use that as a guide), and then forcing the truss rod into place. The more I thought about it, the more I figured that it was a really bad idea. Any suggestions on how to correct this?
     
  2. Flip the blank over and make the other side the top?
     
  3. Cerb

    Cerb

    Sep 27, 2004
    Indiana
    Do you mean use the wenge as the top of the neck and have everything stacked vertically? Maybe I didn't explain well enough. From left to right, the neck is laminated wenge/purpleheart/maple/mahogany/maple/purpleheart/wenge. Looking at it from the top (that is, being able to see all of the laminates) it has a slight inward bow on the right side. Here's a picture I threw together quickly in paint to show what I mean.

    [​IMG]
     
  4. Sorry, it wasn't clear from your first post that the arch was lateral and not longitudinal.
     
  5. Cerb

    Cerb

    Sep 27, 2004
    Indiana
    Any ideas on how one would go about fixing such?
     
  6. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    I think Cerb's neck blank has more what you would call "crook" rather than "bow" if it were a piece of rough lumber as it's movement is side-to-side. In any case, I echo what Ken said in that (a) now is the best time to decide whether or not to scrap it (b) the critical section is going to run about 27" in the fingerboard area and (c) don't glue a fingerboard onto a bowed side.

    Now, given that [i assume] you are not aiming to sell this bass for thousands, I would think you'd want to try and work things out. In all liklihood it can still be made into a great bass. I would, as has been suggested, try to true it up on the jointer. 3mm over 52" is not insurmountable. Get it true and then clean up the other side on the planer. Let the neck sit for about a week and see if it stays straight. Then proceed as planned. The keys are that your channel does not cause the truss rod to bind up and that the neck has done all the moving it is going to do before you put it into service.
     
  7. phatcactus

    phatcactus

    Apr 2, 2004
    Chicago, IL
    Couldn't a bend like this be fixed using the same principle that allows wood to be permanently bent for acoustic guitar sides? Moisture and a hot, flat plate, perhaps? Or does only work with thin slices of wood?
     
  8. budman

    budman Commercial User

    Oct 7, 2004
    Houston, TX
    Formerly the owner/builder of LeCompte Electric Bass
    I'd be tempted to rip it down the middle to see if it springs back. If it does spring back then use a joiner to eat away the leftover mahogany and glue in a new piece. If it didn't spring back I don't know what I'd do.
     
  9. Cerb

    Cerb

    Sep 27, 2004
    Indiana
    Thanks for all of the suggestions. I believe that using the jointer and the planer would be my best bet. I'm still definately open to suggestions, though.
     
  10. phatcactus

    phatcactus

    Apr 2, 2004
    Chicago, IL
    Ooo, Budman gives me an idea. Rip it down the middle, then flip one side of it and re-glue it. Then the bend will be cancelled out against another equal-but-opposite bend. You'd prolly wanna replace that mahogany with a super-straight piece, too.

    Terrible idea? Would it spring apart later on? If wood glue is as maaagical as I keep hearing it is, the wood would theoretically pull itself apart before the glue joint would. And I'd imagine the fingerboard would help keep it together, too.

    Hmmm?
     
  11. Cerb

    Cerb

    Sep 27, 2004
    Indiana
    That was my first idea, but I wasn't sure about how to break the pieces apart.