rim separations & beam cracks

[Ron Overs]

>. . . Put another way, am I being too "sensitive" in expecting some effort
>in filling the gaps in the rim in a structurally sound manner?
>Patrick Draine

I don't believe so Patrick. I believe that it is inappropriate to 
rebuild any grand piano with a de-laminating case. There has been 
much written on this list about certain pianos having potentially 
inferior tonal characteristics due to having luaun rims for example, 
but a grand piano with a de-laminating rim will have significant loss 
characteristics regardless of the wood quality used for its 
construction.

The problem with repairing certain de-laminated sections of an older 
grand piano rim is that the entire rim was constructed with the same 
glue and has been subjected to the same climatic conditions over 
time. Therefore, with some de-lamination already evident, it is 
likely that any repair carried out on the case may prove to be akin 
to rearranging the deck-chairs on the Titanic. More de-lamination 
will be inevitable. This is why whenever we are called in to rebuild 
a piano with a de-laminated case, I recommend that the owner disposes 
of the piano and acquires a suitable shell. Sometimes this provides 
an opportunity to dispose of a brand name piano with a poor scale 
design, changing it for one with a brand name of less repute, but 
with a scale design which is very close to best practice. This will 
enable the rebuilder to create an instrument of far greater musical 
worth.

In the case of this piano, it may be worth injecting glue into the 
de-laminated areas. There's no guarantee that other parts of the case 
won't de-laminate in time, but since it has been fitted with a new 
board something needs to be done. We use un-thinned Titebond Extend 
(when thinned, its gap filling qualities are not as good) and maple 
hammer shanks. With the rim laminations clamped together and the case 
inverted, we drill close tolerance holes up from the bottom edge of 
the rim to almost the full depth of the de-lamination. With the 
clamps loosened a bit, the holes are filled one at a time with 
Titebond. A hammer shank, without glue-escape grooves, is driven in 
the full depth of the hole. Glue flies everywhere. As the dowels are 
progressively driven home the rim behind is clamped together and the 
excess glue cleaned up. This process gets the glue deep within the 
rim to ensure a proper repair. The excess hammer shank is trimmed 
after the glue dries and the bottom of the rim refinished. We've done 
this repair many times. It is also a useful procedure for pianos 
which have an otherwise good rim which has been dropped. While this 
process works very well, I remain reluctant to recommend rebuilding 
de-laminated cases and using this process. There is always a chance 
of original glue joints de-laminating at a later date.

Ron O
-- 
OVERS PIANOS - SYDNEY.
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron at overspianos.com.au
_______________________