Concave Tops...

Discussion in 'Guitar Building' started by MendipSlim, Jun 25, 2018.

  1. MendipSlim

    MendipSlim New Member

    Jun 25, 2018
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    Hi, I'm new here and very much an amateur builder. I have succesfully completed one all mahogany flat top, primarily with the help of Jonathan Kinkead's book as well as various other resources. I am now working on two more small guitars as well as doing a bit of restoration on a couple of old ladder braced guitars.

    My problem is that the tops I have made have become concave and I don't know why. They are ladder braced tops which inevitably have a little less comprehensive structural strength but I don't think that can explain it. Both tops are spruce. I have cut and carved spruce braces, with good tight grain perpendicular to the tops. The braces were perfectly flat when I made and glued them. When I returned to them to continue the build they both have a significant dip across (mainly) the lower bout such that a straight edge laid across the edges has a gap of 3 to 5 mm in the middle where the bridge would be.

    I have had a similar issue with one of the guitars I am restoring. It came to me as a bit of a wreck, with the back off and very concave. Two braces were beyond rescue and I replaced them. I reshaped two others before regluing as they were in a pretty bad state. I arched the braces to create the appropriate gentle convex contour in the back. Despite that, the back has ended up concave a few days later.

    My questions for the many more experienced luthiers here are therefore (1) any clues as to what is going wrong; and (2) Am I right to assume that these tops are a write-off and not worth proceeding with?

    Thanks folks...

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