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Sinking top plate on ply bass

Discussion in 'Basses [DB]' started by fdeck, Jan 25, 2005.


  1. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Sorry about another pesky plywood question. It's just that you guys have been so helpful.

    My 1962 Kay was an old high school bass, which I saved from a trip to the Dumpster in 1982. It was in very bad shape, but my dad and I restored it. This included making a new sound post, as the old one was nowhere to be found. I wish I could remember how we did this with a radial arm saw.

    The belly has a noticeable depression under the G side of the bridge. There is a less pronounced bulge on the back. It was that way when I got the bass -- don't know if it has gotten worse in the past 20 years.

    Is this a symptom of all ply basses? Currently there is roughly one sound post's width between the sound post and the bridge foot. Will this continue getting worse until something really bad happens? How about carved basses?
     
  2. AMJBASS

    AMJBASS Supporting Member

    Jan 8, 2002
    Ontario, Canada
    If it doesn't appear to be getting worse, I doubt you will have any significant problems. The top can't crack like a carved bass. I wouldn't be too worried. An older carved bass could be more of a concern.
     
  3. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    I beg to differ. I've repaired several ply's where the soundpost was coming through the top and the area under the bridge foot was sinking badly. Ultimately cracking can occur. Some of the Kays had thinner tops than others--one reason for the boomy sound. Anyway, if it's stable you might be OK. The cure is to remove the top, press out the affected area (if possible) and install a soundpost/bridge foot area patch. But if the area is badly de-laminated, a through-patch may be the only option. Or, you could get a new top from Engelhardt...
     
  4. B. Graham

    B. Graham Guest

    Aug 11, 2002
    The problem with mine seems to be that at one time, or for a long time, the sound post was to far south of the G bridge foot. The foot created a little depression for itself to live in. This depression isn't even the right place and is well above the f-hole notches.

    I'm not sure that buying a new top, and the labor fees associated, would be worth it financially. It's a tough call because there's something kind of special about some old Kay's.
     
  5. KSB - Ken Smith

    KSB - Ken Smith Banned Commercial User

    Mar 1, 2002
    Perkasie, PA USA
    Owner: Ken Smith Basses, Ltd.
    My good Friend Peter Eibert makes a Sound post patch on the Top and back in Maple and or Spruce to re-inforce and spread the tone of plywood Basses. You may also need a BassBar if it is loose or not helping the top anymore. .. Listen carefully to what Arnold is saying. He is one of the best out there....
     
  6. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    You mean Albert Einstein? Man, that guy could do a neck graft, set a soundpost, and figure out general relativity all before lunch...
     
  7. AMJBASS

    AMJBASS Supporting Member

    Jan 8, 2002
    Ontario, Canada
    Yes I agree if it is badly sunk there is a risk of a crack. However if it is only sunk a little, and has been stable for a long period, I wouldn't think it is too much to worry about.
     
  8. ctxbass

    ctxbass Supporting Member

    Nov 6, 2003
    Central Texas
    My 62 Kay also had a depression where the bridge foot had settled in. It, like Bill's, was well above the f hole notches. This seems to be fairly common with Kay basses. I think that with many of these school basses the bridge was moved to shorten the 42" string length. Lacking support from the soundpost, the tops sank under the pressure of the bridge. I would guess that moving the bridge back to it's proper position would eliminate the cause of the problem. In the 23 years I had that Kay, the condition remained stable.
    If there is a bulge in the back of your bass, it is possible that your soundpost is a bit too long. My bass had a wooden reinforcement disc on the back where the soundpost rested.
    It also had a thicker (5 ply) top than the 37 Kay I have now(3 ply).

    I have to add that in my case there was no de-lamination
    or splitting of the wood.
     
  9. AMJBASS

    AMJBASS Supporting Member

    Jan 8, 2002
    Ontario, Canada
    Just a question Arnold....if you were to remove the top of a plywood that had major depressions and press it back into shape, would you need to add wood inside to strenthen it?
     
  10. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The bulge on the back is very slight -- I cannot see it, but it is noticeable if I run my hands over the back. There is a reinforcement disk on the back. There is no apparent splitting on either the front or the back.

    The length of the soundpost is potentially an interesting issue, since my dad and I had to guess how long it should be. We made it barely fit with the strings off the bass, as per instructions from an old book on violin repair. Also, this bass had a detached and split bass bar when I got it, and a cracked neck block. We had no idea that a Kay bass was of any potential value, but we were curious to see if we could make it playable. And my main instrument was 'cello at the time. This bass literally turned me into a bassist, and it has held together for more than 20 years.
     
  11. Aaron Saunders

    Aaron Saunders

    Apr 27, 2002
    Ontario
    How exactly does one put IN a new soundpost? If I'm reading this correctly, it's a wooden post meant to support the bridge, from the inside, right? So that would involve...what, taking the top OFF of the bass?
     
  12. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    Fitting a soundpost is a bit like building a ship inside a bottle. The top of the bass is already on, and a spruce dowel (soundpost) is fitted and placed with an "S" shaped tool, a mirror, and whatever tool the repairperson desires. All of the work is done through the "G" side f-hole.
     
  13. Aaron Saunders

    Aaron Saunders

    Apr 27, 2002
    Ontario
    Sounds...terrifying to try. I think I'll let the professionals handle that one!
     
  14. but how do you get the post inside with the top on
     
  15. Aaron Saunders

    Aaron Saunders

    Apr 27, 2002
    Ontario
    Good question.



    Also, guys, I have one last question. Sorry to derail the thread, but this is a big concern for me. Well, I'm borrowing the school's upright this week and last, and because of this thread, I thought "Hmmm, let's see what this sound post dealie is all about." So I looked inside the f-hole, and the side of the soundpost that's supposed to be under the bridge foot on the treble side is a good inch and a half/two inches back towards the tailpiece, and there's a buldge in the top (you can feel it, but it's not visible.)

    So, should I be scared for this bass, or what? I'm pretty concerned here.
     
  16. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    You get the soundpost in through the G f-hole.

    The soundpost doesn't sit directly under the G foot. Rather, it sits a bit "south" of the foot, towards the tailpiece. A general rule of thumb is "a soundpost's distance away" from the back of the bridge foot. However, slightly different placement changes how the bass responds and sounds. There is quite a bit of info in the archives about this...