Spurlock shimming method.

[Delwin D Fandrich]

----- Original Message -----
From: <JIMRPT@AOL.COM>
To: <pianotech@ptg.org>
Sent: May 05, 2001 10:39 AM
Subject: Re: Spurlock shimming method.


> <<"The rim is not part of the crowning mechanism; the crown is in there
>
> before it gets glued to the rim.">>
> Bzzzt...wrong answer...want to call a friend? :-)
> On a "compression formed board the rim is a major part of the crowning
> mechanism. On a rib crowned board it is 'somewhat' less of a factor but
still
> a factor.

Sorry, but no. The rim does not have much, if anything, to do with either
forming or maintaining crown. Not even in the M&H with their fancy Octipital
Tension Resonator. Do the math. Or look back in the Journal where I've done
it for you.



> <<"But there are situations where, for example, a piano is breaking
strings
> and the owners want to extend the life of their 100-year-old hand-me-down
> but don't want to pay for a new board because it sounds just fine to them.
> In that case, I would most likely shim the cracks because it would be the
> technically thing to do">>
>
> I agree.
>   There are situations which call for a shim for other than cosmetic
reasons
> and one of those is what I will call 'continuity of surface'.

Up to this point I agree as well. There are times when shimming is called
for, even in cases where the board clearly needs to be replaced. I see
nothing wrong with shimming or epoxying an old board to make it look better
in these cases. I do have a problem with what follows:



> ... A board with
> numerous cracks in it will not be as efficient at its job as an 'amducer'
> (amplifier/transducer) as a board with a solid surface/body sans cracks.
It
> seems to me that a board with numerous cracks would lose some of its power
by
> only the ribs transferring the vibrations from panel to panel without help
> from the panels having solid connections to all the other panels
otherwise.
>  Said another way a board with 'continuity of surface' will perform better
> than one without.

Shimming will not add to the performance of the finished product. It will
look better and the piano will sound better. It will sound better because of
the rest of the work done. The resetting of the plate, the new strings, the
new hammers, the rebuilt & regulated action, etc. This 'continuity of
surface' will have had nothing to do with that.



>  Now finally.......can more crown be added to a boards by
shims?....probably not.

No.



> Can more tension/pressure/compression be added to a board by 'well
executed'
> shims?....definitely.

Only to a very nominal degree if at all. And then only very temporarily. We
like to speak in terms of decades when we describe our rebuilding work. Any
possible improvement from the above will be dissipated in months, possibly a
year or two at the outside. Again, no problem as long as the customer is not
told that this soundboard is being improved and its character and/or voice
is somehow being restored and/or improved in ways that are not technically
possible.




>  Are the 'technical' effects of said shimming as long lasting as the
cosmetic
> effects?......................???????
> Del says probably not, at least in the long run.

Del says no. He does not say "probably not." He says no.



> Richard says he gonna redo the ribs and skirt the whole issue..hopefully.

Actually, this idea has some merit. But what you end up with, if you are
doing it the way it was described by our friend Arnold Duin, is a
rib-crowned board still using the original panel. There is no reason why
this will not work since there are no additional stresses placed on the wood
comprising the panel. Otherwise you simply end up with another
compression-crowned board except that now you're depending on wood that has
already suffered considerable compression damage to support crown. Again, it
won't last.



> I say....if a board is otherwise sound and any needful shimming is done
> "properly" (whatever that means:) that the board will be, 'technically and
> cosmetically', a better board. Not a 'new' board or a 'recrowned' board
but a
> "better" board.
> Course I have been real far off base before............

Well, at least we agree that it will be a cosmetically better
board...usually.

Del