Sound board repair/ Was it something I said?

[jolly roger]

Hi Ron,
            I have had good results using the Spurlock Air Router, and
Boldoc shims. Since opening the crack this wide, seems to remove any
compressed and damaged fibres, the groove is perfectly tapered right down
to the ribs.  We dry the board and shims down, with 2 X 50 watt damp chaser
bars for several days.
The piano is covered and draped to the floor with moving blankets. The pre
cut and fitted shims are left sitting beside theire respective cracks.
After a few days the board and shims are just warm to the touch.
We quickly glue them into position with hide glue. Then apply pressure to
the shims with go bars and leave for 24hrs. I think Bill Spurlock wrote
some articals way back in the Journal??????
We also notch the shims so that the bottom of the shim will pass the ribs.
That way we know that the crack is completely filled with the shim.
To my knowlege, there has not been a failure.
Like you I will never go back to the supply house shim tools, they just
compress and tear a groove that is doomed to failure from the start.
Hair line cracks along glue seams.  We dry the board down, tape the crack
with PVC electrical tape, from the bridge side of the board.
 Turn the piano face down, and use high viscosity West system epoxy from
the rib side. Once cured it leaves a very thin, ( about a thin pencil line)
repair, that requires little or no clean up on the bridge side.
If you use masking tape, the high viscosity epoxy tends to wick into the
tape, and leaves a mess.
Clean up of the crack is less critical on the bottom side of the board. But
is very easy if the epoxy is trimmed after about 3-4hrs when it is in a
semi plastic state. Trying to clean up the epoxy after 24hrs and it is rock
hard is no fun.
Again no failures to my knowlege.
Most boards in this dry climate that are cracked, also have some kind of
seperation of glue joints around the liner. Fixing the integrety of the
liner glue joints has a much larger effect on performance than the board
cracks. On grands the belly rail joint in the top two octaves seems to be a
frequent weak spot.  A .010" spatula is need to test every inch of these
joints, plus tapping and aurally checking. I have checked a number of
boards where I thought they were secure, then rechecked after 2 days of
drying down. suprising how many problems show up.
It is prudent to check and recheck the liner before starting to shim.
Regards Roger  

>I shim, but don't see anything wrong with epoxy either. I just enjoy wood
>chopping. Supply house shimming knives belong to the supply houses. Let
>them keep theirs and make a nice sharp one that works for yourself. You
>have to cut or scrape, rather than compression wedging the V. If the board
>and shims are properly dried, the V is cleanly cut, and the shim goes the
>full depth of the panel thickness, the incidence of cracking later is low.
>Most of the time, when I see cracked shimming work where the rest of the
>panel isn't cracking up too, the shim depth was less than the panel
>thickness. Shims cut from old panels aren't deep enough, in my opinion, and
>that's why I make mine from new stock.
>
>Just another opinion.
>
>Ron N
>