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Warpage of flat back piece/ HOw to flatten?

Discussion in 'Setup & Repair [DB]' started by basswraith, May 25, 2004.


  1. basswraith

    basswraith

    Mar 10, 2003
    Boston
    I have a flat back bass in pieces. One side of the flat back is detached from the glue line. Over time this flat piece of wood has warped and is no longer flat. Now my problem is how do I get this piece of wood back to flat or near flat? The warpage is significant. I was thinking of placing it on a flat hard board and placing heated sand bags on the wood, as well as a bracing system that will keep it flat until I need to glue it. Just an idea. What do you guys think? Any suggestions? :meh:
     
  2. You will probably get more help here if you let us know something about you by filling in your profile. Then, tell us what experience and/or training you've had in bass luthiery.
     
  3. basswraith

    basswraith

    Mar 10, 2003
    Boston
    I worked in a shop on the east coast for a little while, now I do set up and repair at a university in Texas.
    Thank you very much for your interest.
     
  4. Without actually seeing the instrument, it's hard to diagnose the problem accurately, but 90% of the time, flatbacks with this kind of problem will usually require that you replace all of the back braces before you glue it back together. The wood in the backs of flatbacks is usually pretty thin (5/16" or less) and any warpage will be flattened out by the new cross braces when you clamp and glue them. Naturally, this means either the back or the top (if you have the deep clamps to work from the top) will have to come off first. If the problem was caused by water damage, then you may have to resort to steaming or rebending like you were bending new ribs for a bass. If you already have the sandbags, the heated bags and a little moisture might work as you suggested. If not, try a old steam iron (keep it moving). The proper method to use will likely depend on weather you are planning to revarnishing afterward. Too much heat or moisture will ruin the varnish on the outside.
     
  5. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    If you could get a couple of digital photos of this bad boy, then we could give you very specific, helpful advice.
     
  6. basswraith

    basswraith

    Mar 10, 2003
    Boston
    I will see what I can do about the pictures..
     
  7. basswraith

    basswraith

    Mar 10, 2003
    Boston
    James Ham gave me a great solution to my warped side of flat back. We just put it out side on the grass. There is moisture under one side and heat from the sun on the other. In 2 hours the piece of wood had bent it self back to its original position. No sand bags or nothing...just mother nature. This was way easier than I thought.
     
  8. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    Mike, that is a great idea I never would have thought of. Kudos to Mr. Ham!
     
  9. This from the man who straightened my Juzek by filling it with water.




    Well, almost.