Gluing sound board cracks back to ribs.

[Brian Holden]

I have seen a similar problem dealt with in a piano factory.  A couple of
pianos had been returned because of a cancelled order.  They had been stored
for some considerable time in a container and the humidity had caused the
sound board to partially separate from the ribs.  Because the pianos were to
be returned to stock and eventually sold, repairing with toggles was not an
attractive option.

I don't know how they separated the ribs from the sounboard to put the glue
in, but I did see how they clamped the joint tight while the glue dried.
Concave packing strips were made which fitted the (convex) contour of the
rib in the area which had become separated.  A couple of stiff steel bars
were bolted to the back posts, under which the packing strips were wedged.
Some adjustment was necessary to firmly press the ribs against the
soundboard without affecting the crown.  Once the glue had dried, the steel
bars were unscrewed and the holes plugged.

With quite a lot of trial and error and the skill of these craftsmen, a
sucessful repair was done.

Brian Holden

-----Original Message-----
From: DGPEAKE@AOL.COM <DGPEAKE@AOL.COM>
To: pianotech@ptg.org <pianotech@ptg.org>
Date: Monday, 14 February 2000 18:45
Subject: Re: Gluing sound board cracks back to ribs.


>In a message dated 2/12/00 8:23:28 PM Pacific Standard Time,
>remoody@midstatesd.net writes:
>
><< The problem is a cracked soundboard, and one side of the crack has
> pulled away from the rib about as far as to slip a business card
> through if it were cut in half.    This is in a full sized upright,
> player piano actually.  I must make any repair from the rib side.
>
>    The repair I am most familiar is drilling a pilot hole through the
> rib and SB, then drilling a body hole through the rib, stopping the
> bit with ground down hack saw blade, or old palette knife. Then
> smearing glue into the crack with the thin blade and running the
> screw in.
>    Schaff (new catalog) offers a "sound board toggle" p 82.    Do I
> understand  these are left in the piano after the repair is
> completed?  Or is there a way to remove them and fill the access
> hole with a dowel? On p. 62 is a "soundboard repair clamp".  (wire,
> locking nut and wingnut) But this looks like one must have access
> to both sides of the soundboard.  Is this correct?   Both of these
> appeal to me because it looks like they can draw the seperation
> together with more strength than a screw through a 1/4 inch of
> spruce.
>    If any one has used these repairs and can advise, I would be most
> grateful.  Or perhaps there is something out there I am not aware
>
> of.   I know of the repair in Reblitz using thin bolts and washers
> but  that needs access to both sides which I do not have. On p.
> 128, illus. 7-14 is the exact problem I am facing. One side of the
> crack has curled away, the other seems intact.  Should I screw down
> the other side to be safe?  ---ric
> >>
>
>Soundboard toggles work but not in all circumstances where the bridge may
be
>in the way. So be careful not to drill through the bridge.  They only act
as
>a clamp so remove them and plug with dowel material. To remove them, loosen
>the nut enough to push the toggle through. Go to the other side of the
piano
>and flip the toggle linear with the bolt and push it though.  Then pull the
>toggle out from the other side.  Don't forget to slap some glue between the
>soundboard and the rib before clamping.
>
>If bridge is in the way, look for ideas to install wedges between the
>backpost and rib. Sometimes drilling and installing a screw will work.
>Remove the screw when glue is dry.
>
>Hope this helps.
>
>Dave Peake, RPT
>Portland Chapter
>Oregon City, OR
>