Modulus of Elasticity

[Ron Nossaman]

At 11:53 PM 11/18/1999 -0600, you wrote: 
>
> Does anyone happen to know, or know where I can find, approximate typical
> values for the modulus of elasticity for spruce both along the grain (the
> rib) and across the grain (the soundboard)?   This comes up because the
> technician installing the new soundboard for me wants to decrease the width
> of the new ribs yet leave unchanged the stiffness of the soundboard/rib
> assembly.  Obviously, the new ribs will need to be taller, but how much? 
> Armed with enough facts, I am confident that I can figure this out with some
> practical degree of accuracy.
>  
> Wasson Kerrick, RPT
> Owensboro, KY
> <mailto:wkerrick@mindspring.com>wkerrick@mindspring.com
>  


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.

There are lots of reference books out there with all sorts of other beam
deflection formulae, but this is about the most straight forward. 

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