Pianotech

I have a 1925 Nordheimer grand piano with a front rail that touches the keybed only at the ends.  There is a gap in the middle of approximately .050".  When I slide out the action and test the front rail against a straightedge, I get a gap of about .033", using front fail punchings as measuring gauges.  The front rail has positive crown, and the key bed has negative crown.

We have wide seasonal swings in humidity here.  The piano has a Dampp-Chaser system with an undercover, but the keybed is outside of its zone of influence, as I see things.

I have read posts about kerfing and shimming the front rail to remedy warpage.  I have also read that some rails are intentionally left flexible.

I am inclined to kerf the front rail at regular intervals along its length, starting at the bottom and coming up about 2/3's of the thickness, or even alternating bottom and top kerfs.  I am also inclined not to shim but to simply allow the rail to follow the keybed if it moves seasonally.  I have regular access to this piano throughout the year, so I could adjust glide bolts seasonally if necessary.  I could also glue in shims at a later date if it seemed to be beneficial.

Any feedback here?  Am I going to regret doing this?

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Floyd Gadd
Regina SK
306-502-9103
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Floyd,

I have a 1907 Chickering 121 here with the issue, though not quite as bad (.025" - .030"). I chose to glue veneer shims all along the front so as be able to do my fitting with that. Worked quite well. I considered precisely what you are and decided shimming was less intrusive and just as effective.

Pwg

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Peter Grey
Stratham NH
603-686-2395
pianodoctor57@gmail.com
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Original Message:
Sent: 06-01-2018 19:00
From: Floyd Gadd
Subject: Kerfing the front rail?

I have a 1925 Nordheimer grand piano with a front rail that touches the keybed only at the ends.  There is a gap in the middle of approximately .050".  When I slide out the action and test the front rail against a straightedge, I get a gap of about .033", using front fail punchings as measuring gauges.  The front rail has positive crown, and the key bed has negative crown.

We have wide seasonal swings in humidity here.  The piano has a Dampp-Chaser system with an undercover, but the keybed is outside of its zone of influence, as I see things.

I have read posts about kerfing and shimming the front rail to remedy warpage.  I have also read that some rails are intentionally left flexible.

I am inclined to kerf the front rail at regular intervals along its length, starting at the bottom and coming up about 2/3's of the thickness, or even alternating bottom and top kerfs.  I am also inclined not to shim but to simply allow the rail to follow the keybed if it moves seasonally.  I have regular access to this piano throughout the year, so I could adjust glide bolts seasonally if necessary.  I could also glue in shims at a later date if it seemed to be beneficial.

Any feedback here?  Am I going to regret doing this?

------------------------------
Floyd Gadd
Regina SK
306-502-9103
------------------------------

I've make kerfs with non-parallel sides. A matching tapered shim can be inserted to the degree that is needed to flex the front rail. Make the shims long and trim the excess. A sparring amount of glue on one side allows for future adjustment if needed.

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Regards,

Jon Page
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Original Message:
Sent: 06-01-2018 19:00
From: Floyd Gadd
Subject: Kerfing the front rail?

I have a 1925 Nordheimer grand piano with a front rail that touches the keybed only at the ends.  There is a gap in the middle of approximately .050".  When I slide out the action and test the front rail against a straightedge, I get a gap of about .033", using front fail punchings as measuring gauges.  The front rail has positive crown, and the key bed has negative crown.

We have wide seasonal swings in humidity here.  The piano has a Dampp-Chaser system with an undercover, but the keybed is outside of its zone of influence, as I see things.

I have read posts about kerfing and shimming the front rail to remedy warpage.  I have also read that some rails are intentionally left flexible.

I am inclined to kerf the front rail at regular intervals along its length, starting at the bottom and coming up about 2/3's of the thickness, or even alternating bottom and top kerfs.  I am also inclined not to shim but to simply allow the rail to follow the keybed if it moves seasonally.  I have regular access to this piano throughout the year, so I could adjust glide bolts seasonally if necessary.  I could also glue in shims at a later date if it seemed to be beneficial.

Any feedback here?  Am I going to regret doing this?

------------------------------
Floyd Gadd
Regina SK
306-502-9103
------------------------------