Modulus of Elasticity ...Ron

[Wasson Kerrick]

Hi Ron,
    Thank you for your most helpful response to my inquiry about the modulus
of elasticity for spruce.  What are the proper units on each of the
variables in the nice-and-simple formula for beam deflection?  To answer
your questions:
1) Why decrease rib width?  My impression was that the gentleman intending
to install the soundboard was not real comfortable working with ribs so wide
and with so little height as originally on this old piano, which if I recall
correctly are in the neighborhood of 1.5" wide, closely spaced (15 ribs, 7'+
grand), and only about 0.5" in height.  At this point he is not committed to
changing the rib dimensions, only proposing that this be done.
2) How does he know he doesn't want to change the stiffness of the
soundboard assembly?  He doesn't, and neither do I, but I dearly wish I did.
In the absence of further knowledge (or educated guesses), I thought the
best bet would be to duplicate as precisely as possible the original
stiffness.  How can I get a handle on this so that I don't duplicate faults,
but instead improve the piano (with respect to the soundboard assembly) to
whatever degree this might be possible?  Any hints, guidelines, or rules of
thumb you can share?  You (and Del) have given us all hope (in previous
posts and in Del's Journal articles) that there is generally room for much
improvement in soundboard design, especially as it relates to the mid
treble/"killer octave" area of the scale.  What do I need to know,
calculate, measure, determine, buy, borrow, or sacrifice in order to wind up
with soundboards in my pianos of which you would be proud?  Within reason,
I'm willing to do whatever it takes, because I'm sooo sick of dealing day in
and day out for over 20 years with various shades of mediocrity where
scarcely 1 piano in 100 could be called "fun and exciting" to play.
    Hope you have a great weekend and an uneventful finish to this
millenium.

Wasson Kerrick, RPT
Owensboro, KY

-----Original Message-----
From: Ron Nossaman <nossaman@SOUTHWIND.NET>
To: pianotech@ptg.org <pianotech@ptg.org>
Date: Friday, November 19, 1999 8:24 AM
Subject: Re: Modulus of Elasticity

>Encyclopedia of Wood
>1989 Sterling Publishing
>
>It's a revision and reprint of Wood Handbook: Wood as an Engineering
Material
>
>A general purpose simple beam deflection formula for a center loaded beam
is:
>(L*L*L*Load)/(4*E*W*H*H*H)
>Where L=length between supports, W=width, H=height, and E=modulus of
>elasticity, which is about 1,570,000 for Sitka spruce along the grain.
>
>Out of curiosity, why does he want to decrease the width of the ribs? Also,
how
>does he know he doesn't want to change the stiffness of the assembly in the
>process? Just wondering what the intent is here.
>
>Ron N