bridge repair

[Ron Nossaman]

>Encountered a 1928 Knabe (5'8").  The bridge cap, which extends down through 
>both capo sections, is cracked and delaminating with some bridge pin 
>migration.  The rest of the bridge is solid, uncapped and in good condition. 

In these old Knabes, the bridge cap grain angle through the treble sections
was something like 60-70° off parallel to the bridge centerline. There
wasn't anything else they could have done but crack. I wouldn't expect to
be able to epoxy the resulting mess back together successfully, so I'd plan
on recapping.


>  The board is good.  The piano has been restrung within the past 20 years.  

This sets off all kinds of alarm bells. Is there measurable crown in the
killer octave and above? What's the bearing in that area? Twenty years ago,
the most common scenario was to shim the board, ignore the presence or
absence of crown, and lower the plate to get bearing - regardless of how
much negative crown was forced into the board as a result. 


> I am trying to determine if 
>its feasible to recap the upper part of the bridge without removing the 
>plate.  Is it possible, or reasonable?  The plate struts do not get in the 
>way of the pinning or notching, but I am trying to figure out how to get 
>around the planing problem. 

The planing problems can be relatively easily gotten around with a bull
nose plane and a plane iron used as a slick (big wide long chisel). There
is absolutely no way the plate struts won't be in the way for drilling and
notching though. How will you get the pin angle on the front row just above
the struts, and the back row just below?



> Any thoughts.  Budget limitations and the 
>overall value of the piano are considerations.  Any thoughts?
>
>David Love

My thoughts are that the piano is worthy of rebuilding, and shouldn't get
another half way patch up regardless of budget limitations. The last guy,
after all, didn't fix the bridge cap or replace the pinblock when he took
his shot, probably because of budget limitations, which is why you are
looking at what you're looking at now. Another patch up at this stage will
make you the next "last guy".


Ron N