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Correcting a back bowed neck

Posted by Brent Kasl on January 25, 2020 at 5:22pm in Building Secrets, Tips, Advice, Discussion

I made two necks out of walnut with scarf joints, seemed nice and straight prior but now I notice a back bow of about 1/16" rocking, once a fretboard is glued on and secured with substantial clamps and heavy bracing top and bottom, could this be corrected?

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Replies

  • Myron Joe Hickel January 27, 2020 at 11:27pm

    It sounds to me like the wood acclimated to the environment of your shop. Cutting a scarf did not cause the walnut to bow. Your idea that it can be corrected by using a straight cull to clamp it together will work. However since you know it has enough tension to cause it to bow a 1/16th just making it straight is not taking the spring back into consideration. You are making a simple basic laminate glue up. I would recommend putting a back bow in the reverse direction at minimum at least the thickness of two pieces of blue painters tape. After the glue has dried release the clamps let the neck sit for a day or two. It should be straight.

    • Brent Kasl > Myron Joe Hickel January 28, 2020 at 6:27am

      Thanks

  • Taffy Evans January 27, 2020 at 4:34pm

    Hi If I can just make an comment here......a truss rod or reinforcing bar is usually used to prevent a neck from bowing up, so using one on a back bowed neck may defeat the purpose. 

    Jerry's first option is the proper way to do it, and if the necks not on yet, eazy peazy. I feel a thin fingerboard fighting the pull of a thick neck is going to lose, in long run.

    Taff

  • Jerry Jordan January 27, 2020 at 12:51pm

    That has happened to me when the wood had too much moisture content, and then it dried a little., you can sand it or plane it out, back to being flat, but I would not expect the strings to correct it with tension., I have heard of heat pressing a neck to flatten it, but it building a neck from scratch I would level it myself.,

    • Brent Kasl > Jerry Jordan January 27, 2020 at 1:20pm

      thanks

      gluing fretboard on while blocked both sides with aluminum bar wont help?

      • Jerry Jordan > Brent Kasl January 27, 2020 at 3:32pm

        I suspect you could make it work, but there lots of different kinds of truss rod material out there. If the neck was flexible enough, and the bar stiff enough, in a tight channel, and you clamped it till it was dry. It just depends on how you want to approach it. I had a whole batch of neck blanks go twisty on me and I just discarded them. I think the whole lot only cost $10.

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