sunken top on a '51 Kay

Discussion in 'Setup & Repair [DB]' started by bassmandan81, Jul 13, 2013.

  1. bassmandan81

    bassmandan81 Supporting Member

    Apr 2, 2009
    Anchorage, AK
    I am restoring '51 Kay M1-B that has a sunken top extending about 2" above and below the bridge. Upon taking off the top, I discovered the spring of bass bar had delaminated the innermost layer over about half its length. I am curious - is the plywood on my '51 laminated with hide glue? When did Kay switch to synthetic glue? Is it okay to reglue this with titebond? As for the repair, I'm wanting to feather a patch (as described in Traeger's book) of 1/8" material to the underside of the top. Should I use maple or spruce? Any advice as per how to clamp this? Should I use titebond for this too? Any advice on this repair is greatly appreciated.
    Danny Booth
    Frank Solivan & Dirty Kitchen
  2. I believe they stopped laminating the plies with hide glue in '52. Ask Roger Stowers.

    So the bass bar has detached and taken the inner laminate with it? That's always fun. If that is the case I'd lay the belly face down on a heating pad set to low, lightly mist the inside of the top with water and clamp the bar back into place to re-arch the top.

    Once the top is back in round you can remove the old bar, repair the inner laminate and fit a new, unsprung bass bar. Linen patches soaked in hide glue can be used to reinforce the bar without changing the sound. Some folks elect to fit a spruce belly patch, which will change the voice.
  3. bassmandan81

    bassmandan81 Supporting Member

    Apr 2, 2009
    Anchorage, AK
    The old bass bar seems to be properly sprung. Is there a reason that I should make a new unsprung bass bar? Seems like that would only help the top return to its sunken position. Traeger recommends adding a patch to all old laminate basses, and says it will improve the sound (increased midrange and more "center" to the note). Is this your experience when adding a patch? It seems like it would keep the top from re-sinking as well.
  4. I've never added a belly patch. A bass bar is about the limit of my ability.

    If you re-use the existing sprung bar you run the risk of the bar separating again and tearing more of the inner laminate loose. That's advice Arnold Schnitzer gave me.
  5. Jake deVilliers

    Jake deVilliers Commercial User

    May 24, 2006
    Crescent Beach, BC
    Owner of The Bass Spa, String Repairman at Long & McQuade Vancouver
    Hey Dan, hide glue is what you want to use to re-glue loose laminates on your '51 Kay.

    The breast patch is a good idea - it really adds a lot to the sound of a plywood bass. Don't count on it to keep the top from sinking - if the top is sinking with the bass bar and plies properly attached, you'll need to make a raised saddle to take some pressure off the top - or use guts.

    Use old, dry spruce for the breast patch, chalk-fitted to the top and glued with hide glue. If its a good fit it won't need much clamping. I put the top on a piece of 3" foam and weight the patch with a 25 lb bag of shot.

    Carve the patch down to a maximum of about 1/4 - 5/16" up against the bass bar, feathered to nothing. You can hold the top up and tap tune the bar first and the patch later on.

    Its worth the trouble! ;)

    Good luck, Jake
  6. bassmandan81

    bassmandan81 Supporting Member

    Apr 2, 2009
    Anchorage, AK
    Thanks for the advice Jake & Kungfu! I figured hide glue would be the right choice... That & being my first belly patch a reversible job is probably a good idea ;) I wasn't planning on making one so thick but it's good to know you can w/ good results. Any suggestions as to where to find good n dry spruce? ...or am I delving into the secret lutherie handshake territory? Jk... I'm just having a hard time finding dry material that size, and if you have any ideas I'm all ears (&eyes). Thanks! -Dan
  7. 360guy


    Apr 28, 2006
    Lansing, MI USA
    I have some very well seasoned spruce for patches. You can contact me if you like.

    [email protected]
  8. Jake deVilliers

    Jake deVilliers Commercial User

    May 24, 2006
    Crescent Beach, BC
    Owner of The Bass Spa, String Repairman at Long & McQuade Vancouver
    Kays tops are typically around 1/4" thick, so if you add another 1/4" you're only at half an inch. Let the tap be your thickness guide. You'll be planing off most of the patch but you'll need something to work with.
  9. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc

    I've been off the grid for a couple of weeks; all of your pms have been responded to.

    As for the Kay belly patch- you betcha'! the thickness depends upon what you are after for both structure and sound, and more important, what type of spruce you are using and its individual characteristics. I range from 0.090- 0.150"; most often about 0.120" West Virginia or North Carolina red spruce, sometimes applied in two layers , bent with a heat blanket system and always glued in with hot hide glue and a matching caul on both sides that is the curvature of the original factory arches, maybee 10% over.

    A 1/4" of weak Engleman spruce can be bent by hand to a 3" radius with no problems. A 1/4" of hard red spruce additional belly patch would be like putting a titanium plate inside the bass!

    Do you have copies of last year's American Lutherie magazine with the 2 issue, 20 page article spread on vintage ply bass restoration? It gives a bunch of helpful ideas and photos for this process; your best bet until the vintage ply restoration book comes out next year!

  10. mmoehring


    Jun 25, 2012
    East Texas
    Hey Dan,

    These guys have given you some great info! I Love listening to these knowledgable people chat about our favorite subject. I have done the belly patch described in traegers book. It worked out well. It added a much more direct mid range to the bass. It helped add evenness throughout the basses range. I hope it works out for you. Use the sand bags or shot bags. My first attempt I used 6 large c clamps, terrible idea. Use the bags! Good luck