Increasing Crown

[Lesher, Trent J.]

Terry,

With all due respect, I don't think the original suggestion specified a "haphazard" method of applying the treatment, or in applying it to a board that is "shot."  If there are some boards that can be improved with reasonable treatments, then they are not shot, and it may be better to improve them than not.  The questions are "can they" and "how best" and "if not, why not." 

As to your questions "will you get enough crown?" and "what effect will [the added mass] have?" those would depend partly on the material used, which I believe is what the original post was looking for recommendations about.  

However, without even knowing the wood to be used, it would seem you could guess at the magnitude of the effects of the added mass -- including ribs and bridge, the average mass per area of the soundboard system won't be changed more than a few percent by increasing a rib from about 25mm to 28mm.  Further, independent of crown, increasing the height of the ribs may help stiffen the board significantly.  Adding 3mm from end to end would have more effect on the boundaries of the panel where the ribs are shallower, though

"In logic, a tautology is a statement which is true by its own definition, and is therefore fundamentally uninformative."  Your statement "I guess I just don't have any real interest in haphazardly applying band-aids to a soundboard that is shot" seems almost to qualify.

Respectfully,

Trent Lesher

-----Original Message-----
From: Terry [mailto:terry@farrellpiano.com]
Sent: Monday, March 14, 2005 10:08 AM
To: Pianotech
Subject: Re: Increasing Crown


I didn't answer because I didn't know quite how to respond without sounding
sarcastic.

Sooooo, not meaning to sound sarcastic.........

Yes, I suppose if you wedge up a flat board and glue on some auxillary
laminations, you might be able to get the structure to retain a bit of
crown - but will that do any good? You are increasing the mass of the ribs.
What effect will that have? How much crown do you want? Will it get you
enough crown?

I guess I just don't have any real interest in haphazardly applying
band-aids to a soundboard that is shot.

Terry Farrell

> I am currently fiddling with the idea of gluing
> auxilliary laminations to the spine of existing ribs,
> while the two are flexed together, along with a
> backing caul, by a jig secured to the back of the
> piano.
>      I asked Terry Farrel to recommend a
> laminate--perhaps 3mm thick, 3 ply, but have not heard
> back from him yet. Anyone else care to comment?
>      Thump




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