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Back reinforcement - Typical, or "What the???"

Discussion in 'Setup & Repair [DB]' started by eh_train, Jan 27, 2006.


  1. eh_train

    eh_train Supporting Member

    Jan 12, 2004
    Toronto
    Hi all,

    I am working on repairing a cheap ply bass, and have a few questions. FYI, it's labelled as a Selmer Manhattan, which I think is a Kay with a nicer neck...

    When I got it the top was half off, and seriously collapsed in the bridge area. I have removed the top (see pic below). I know that I can get a replacement top for under $200, but am curious as to whether people have tried to re-shape a ply top, and with what results... My guess is it's a lot of work, but I'd like to hear whether other TBers have done it!

    Also, the back has a rectangular shaped, contoured piece of wood attached to it (under the bridge area). I have had another ply bass with a thin round patch where the post touched the back, but this is WAY more substantial (ie., about 1/2" thick in the centre). I can tell that the post was resting on the treble side of this piece of wood, if that's any help... Does anyone know whether the bass was manufactured this way, or is it a case of someone substantially over-reinforcing this area?? In either case, I'd appreciate any thoughts on whether this extra wood is an asset or a liability, and how easy it might be to remove (it is very slightly lifted on the bass end)...

    Thanks for any suggestions!

    Paul (eh_train)
     

    Attached Files:

  2. ctxbass

    ctxbass Supporting Member

    Nov 6, 2003
    Central Texas
    I recently looked at a '39 Kay Orchestra model that had the same piece of wood in that location. The serial # of your bass (if it's a Kay) indicates the same era (1940), so the part is most likely original.
     
  3. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    Yes, you can reshape a plywood top. You'll need to make a mold of the collapsed area, correct it, then heat up the wood and press it back into shape. This is way harder than it sounds. Once corrected, the area will need a patch that is feathered in around its edge. I've done some plywood top repairs where the deformation was small, and was able to make the press mold from wood. Generally it is made of poured plaster though, especially if a large area is being corrected. Results can be outstanding if done with care and patience.
     
  4. eh_train

    eh_train Supporting Member

    Jan 12, 2004
    Toronto
    Arnold

    Thanks for your post. I have read about the process in the Traeger book, and know it would be a chore...

    With this top, I would say the middle 20% needs correction (ie., 6" above and below the bridge area, and out to the f holes in each direction). The good part is that there's no evidence of delamination in this area. However, there is a little where the top came off of the ribs - I have saved the pieces and can reglue them.

    Does this sound repairable? With lots of patience?? I don't need the bass immediately. On the other hand, would most people opt for the new top and save the headaches??

    Any further thoughts are greatly appreciated!

    Paul (eh_train)
     
  5. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    Yes, you can do it; if you have good tools, good skills, a good shop, good information and lots of patience. In my shop a job like this would likely be prohibitive, as the cost would exceed the bass' value. But if you are determined you can likely make it happen. Step #1 is to make a holder that fits the top's perimeter (with the top upside-down, being held by about 3/4" of the edge all the way around), plane off the bass bar, and put some weight in the suspended top to see what happens over a week or so. If you decide it needs the plaster mold treatment, you may be able to get away with pouring a partial mold. Jeff B. has done many more of these than I have; I hope he chimes in with some tips.
     
  6. Hi Paul;
    I recently restored a 1951 Kay with a badly sunken top. I must say, reshaping the top was the easiest part of the repairs.

    I was very lucky to get away without building a form. With the top removed and face down, I used force from above (2 lally columns) and judiciously bunched-up quilted packing plankets on the work bench, along with strategically placed shims here and there.

    After leaving a damp rag laying on the most deformed area overnight, and using an electric clothes iron, I applied pressure slowly. I found the plywood extremely willing to go back to its former shape. I believe the ease of the reshaping is due to the inherent nature of the laminated pywood. I don't think a carved top would ever have the "memory" that plywood has.

    The only thing I would do differently next time, would be to keep a sheet of smooth plastic against the varnish side in the area that was warmed, since I had to spend extra time buffing out the texture that transferred from the blanket.

    I must add, however, that I wholeheartedly agree with Arnold; such a job would likely be cost prohibitive to have done. I spent far more time doing damage control to the plywood edges and retouching the finish than the bass' value would have warranted. It only paid for me because I acquired the bass for next to nothing, it gave me good experience, and I now have a really great gigging instrument that I am proud of.

    Good Luck!
    Bob
     
  7. eh_train

    eh_train Supporting Member

    Jan 12, 2004
    Toronto
    Thanks, all, for the info. I plan to give this a try, and will likely have some further questions as I go....

    Cheers,
    Paul