laminated ribs

[Ron Nossaman]

> *Ok, stiffer from the git go & a steady reduction of resistance over 
> time also changing it's impedance*

Right, which tends to show up worst in the highly loaded 
killer octave and treble.


> *  Yes but Define steep progressive spring rate.  I assume we're 
>  talking non linear *

Yes, non linear. Beam deflection is linear. Twice the load on 
a beam produces twice the deflection. Panel compression makes 
the system non linear so twice the load produces less than 
twice the deflection. The spring rate increases as it's 
loaded. A purely compression crowned board has a much faster 
rate of increasing spring rate than a rib crowned assembly 
with only mild panel compression.


> *       Yes and perhaps assumptions are being made in my case too.  I've 
> been ribbing at about 6% lately so my evolutionary process continues. 

Ah, then you're getting down into super soft hammer country 
where you'll be adding lots more ribs very soon now.


>At 
> what point is panel compression a virtual non factor any way?  

When it's not needed to hold up crown. The required MC levels 
will depend on the climate, naturally, and there will be some 
panel compression whatever you do. It just won't be a big 
factor in the soundboard function. I'm using 6% MC too, which 
seems to me to be about right for the area. With rib support, 
it just becomes a whole lot less critical.


>I find my 
> overall Crown compression to be  a bit more in the tenor area than in 
> the treble and  I've measured  2.5 to 3 mm residual crown in the killer 
> octave lately & I continue to monitor this. I think variable amounts of 
> rib radius designs are getting pretty common so were likely to  document 
> more similar results.*

Good!


> *  I'm typically using the Ronsen Wurzen or Steinway hammers with a 
> medium density feel to the felt when I needle.  Anyway hammer stiffness 
> is another cool way to bench mark belly assembly stiffness.*
> *  Dale*

It is. Very interesting stuff.
Ron N