[pianotech] Pitch change, etc.

[Scott Nelson]

Some time ago I inspected a Seiler grand that had beeen traded in. Overall it was in good shape, but I noticed what looked like hairline cracks around the bridge pins. Upon closer inspection, looking down the long bridge from the lower tenor end (with the lid off), I noticed the cap was horizontally laminated, possibly Delignit. Admittedly, this is an isolated example, and I know that other makers, like Schimmel, use some form of horizontal structure as well.
 
What was interesting was under favorable lighting conditions, you could see the horizontal lams statring to split apart and lift at many of the bridge pins, almost as if the pins were leveraging the cap apart where it was weak. I used to think that the laminated structure would be stronger, but apparently the material was yielding in this case.
 
Could this be an example of the Delignit bridge capping material you were referring to? If so, it would seem that your use of veneer or thinner plies with epoxy saturation would indeed be more structurally sound.
 
Scott Nelson
--- On Wed, 4/7/10, Ron Nossaman <rnossaman at cox.net> wrote:


From: Ron Nossaman <rnossaman at cox.net>
Subject: Re: [pianotech] Pitch change, etc.
To: pianotech at ptg.org
Date: Wednesday, April 7, 2010, 8:32 PM


jimialeggio wrote:
> I think it would be useful to try and determine if there is any advantage of  the various maple epoxy laminations over a delignit cap.
> 
> Do we have any data on this?

Not directly, but Delignit ought to make a first rate cap. The stuff sold by Delignit for bridge capping is, I think, not hard and dense enough. It's a little over 70% the density of the pinblock stock, and noticeably less hard. The only real benefits I see to epoxy/veneer laminations over Delignit pinblock stock are that it looks less like plywood because of the grain direction of the laminations, and it's less abrasive to edged tools when you notch.

If you want to try a pinblock grade Delignit cap, I have 9mm material.
Ron N
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