Was Buttr. Arch. Q for Ron N - increasing rim density

[Overs Pianos]

Fenton and all,

At 6:57 AM -0700 16/4/06, Fenton Murray wrote:
>How about treating the inner rim with a penetrating epoxy?

Yes that would work, but you need some means of hydraulically driving 
the glue into the wood. A slightly less messy solution, which I've 
used for light density rims such as Luaun, is to drill a series of 
holes into the top face of the inner rim, spacing them about 12 mm or 
0.5" apart around the perimeter, drilled to a depth of around 25 mm. 
The drill diameter is chosen such that the resultant holes are a 
slight press fit for maple hammer shanks (a couple of test samples in 
a piece of scrap will allow you to determine which drill size is the 
most suitable). The drill must be very sharp or it will glaze the 
surface of the hole, preventing glue from moving into the wood pores. 
For this type of work it is most important to have a series of drills 
in 0.1 mm diameter increments from which to choose. We have drill 
sizes from 1.0 to 10.00 mm in 0.1 mm  steps. They can be purchased at 
quite reasonable prices in sets. One set from 1.0 - 6.0 mm, and a 
second set from 6.0 - 10.00 mm. Fill the holes right to the top with 
Titebond and drive the hammer shanks home to the bottom of the holes. 
Glue comes out of wood pores everywhere. The clean up is very easy 
compared to epoxy and the density increase overall is fantastic. A 
Japanese pull-saw can be used for trimming the excess hammer shank 
length flush with the top surface of the inner rim after gluing.

If the belly rail is similarly light-weight, it can be treated in the 
same manner. Its quite an effective fix for pianos which were built 
using trash-wood for the inner rim.

If you use this method, don't forget to leave the case for a couple 
of weeks to dry out before fitting the new sound board, or it will 
take ages for the piano to normalise after the rebuild.

This technique, for hydraulically driving glue, can be used for 
bolstering back beam joints by drilling holes which diagonally 
intersect joints, including back beam joints with the rim/belly rail. 
Before a case is fitted with a new board all joints can be 'injected' 
using this method from above and below to make sure that the entire 
length of the joints are 'sound' (flip the case and treat the lower 
part of the joints, then set it right way up to treat the top part of 
the joints - all before fitting the sound board). Once you try this 
it will surprise you how many joints, which look to be OK, really had 
gaps all over the shop. I suspect that poor back brace joints will 
suck up energy which might otherwise be helping the sustaining 
qualities of an instrument.

Look forward to meeting you in Rochester Fenton.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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