Down-Bearing for Old Board

[Farrell]

Thanks for your response Dale. My comments are interspersed below:

----- Original Message -----
From: "Erwinpiano" <Erwinpiano@email.msn.com>
To: <pianotech@ptg.org>
Sent: Thursday, February 01, 2001 10:19 AM
Subject: Re: Down-Bearing for Old Board


> Terry
>     I,m sure there are many differing veiws on the subject you raised but
> the answer will probably contain similar threads.  A very fine 4 part
sereis
> of articles printed in the P. T. J. around august ,sept.of 1995 By John
> Hartman has been an enormous help in applying downbearing principles to me
> and others. I beleive the series was called downbearing and the affects on
> tone.  This article includes some guidelines for setting up old boards as
> well.

As soon as I get my CD roms of the Journals I will look it up. I know John
has a lot of good info to share. I took his belly class in Arlington - or
was it NC Regional this past year. I only joined the PTG three years ago, so
I do not have those articles.

>        My advice is od not apply more bearing than is needed to compress
the
> board to a flattened  position after it is strung and up to pitch.  The
fact
> that you're in florida means that the moisture content in your board is
> probably high or could be.

Nope. Piano has been in my humidity-controlled shop for over a year. Never
gets below 40% RH, never above 50% RH.

> I think saftey dictates dampchasers be run  with
> humistat for for many  days before making the final determination on how
> much crown was actually acheived(have never had much luck reintroducing
> crown through shimming and I've tried).

That should not be necessary given above.

> How much crown is there really ? This should be meas. after drying to
> 45% r.h. to get a real figure.

Right in the middle of the board I have a full 1/4"

> If a newfully crowned   board exhibits 1/4"
> to 3/8" in the unstrtung condition at 45% how does that compare to what
your
> seeing?

Full 1/4" in middle, full 1/8" everywhere else away from the rim.

>  Usually what is typically described to me by others as" alot  of
> bearing" is a board in fairly flattened or flat condition.   I.E. it has
two
> m.m. of crown.

This board is by no means flat. You shoulda seen me trying to attach
aluminum channels to the board to guides in routing out for shims. I could
only do half a crack at a time because there was so much crown in the board.

> Then you can see thats not much but if thats all you have
> then by all means try to use it to your advantage but do not put more than
> two or three m.m. bearing on the board or something safe.  Remember
> compressing the board changes this light weight structures impedance
(which
> is a good thing) and makes it a more effeicent sound producing device.
> (moving more air / sound waves)
>  Just food for thought and hope it helps
> Dale Erwin
>

So as you can see, I have the crown similar to a new board. BUT, my question
is: Do I adjust my targeted downbearing from that of a new board just
because I am dealing with 80 year old wood here? I'm just thinking of maybe
I gotta go lighter on the downbearing because of the age of the wood? Or
maybe the old wood is stiffer than new, and maybe I should give it more
downbearing? Less? More? Same? Maybe less IS more? Is there an accepted (at
least by some) direction to go with old wood?

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com