Backpost delamination

[Cy Shuster]

I tuned a 1980's Wurly studio last August, and brought it up maybe 40 cents 
to pitch.  I measured the pitch before tuning it this month, and this is one 
time that measuring really helped identify a problem.  The bass was maybe 
five cents sharp, but after middle C, it dropped off to 80 cents flat.

I use TuneLab for pitch raises, and as I got to about C5, I heard the 
unmistakeable sound of wood fibers letting go with each movement of the 
tuning hammer (torque was OK).  The bridges were fine, so I looked over the 
top at the backposts.  Each one is made of three sections of oak, and one 
joint had come unglued part way (about 1/4" deep):

http://tinyurl.com/2rhoug
(also see attachment)

I've never heard such an immediate splitting noise in a backpost with 
raising pitch (and there wasn't much overpull at this point).  I'm concerned 
about the pinblock separating, too, but its top is covered with veneer. 
What's the best way to unglue it to take a look?  Just iron a damp cloth? 
Should I look for a plate crack, too?

It seems that a couple three carriage bolts should do the trick.  I could 
wick in some thin CA, too; I don't know if I could work epoxy in.  Is there 
a better fix?

--Cy--


-------------- next part --------------
A non-text attachment was scrubbed...
Name: backpost_split.jpeg
Type: image/jpeg
Size: 31118 bytes
Desc: not available
Url : http://www.ptg.org/pipermail/pianotech/attachments/20070405/4b04ce4a/attachment-0001.jpeg