Hopefully Del will respond to the other issues you raise but re the ribs, laminated ribs takes care of the variability of stiffness and weight that comes from trying to select solid pieces of wood for that component.
David Love
www.davidlovepianos.com
David/Del
Being a bellymen and a panel maker both, I find this is an interesting discussion to which I have given the issue of mass/weight & thereby stiffness some thought as well. In my experience 10 factory original model B Steinways can have a board/panel thickness which tells me there is really no standard. However thick it was when it came out of the panel sander it had a starting thickness with out consideration to grain count/weight. This applies to the pre-war boards of (softer)Eastern spruce or the post war boards which at some point were Sitka spruce.
As you stated Dell,....the weight issue was not considered, and yet I find the tonal response in this variety of same model B to be really varied. Yes , many things contribute to that varied difference but pertaining to mass I am thinking of one 1970s B that was formerly CD dept that we rehabbed a bit. It was a particularity lively and delightful sounding B and the panel itself was alarmingly thin. If memory serves approx .300 in the thickest spot. For comparison my eyes have witnessed average thicknesses ranging somewhere between .330 to 370. in Bs but not .300. And this B being a C.C. board it had some hefty compression ridges. The point is this got my my attention haven't forgotten it.
Hoadley states that there can be as much as a 25 % difference in strength with in the same species of wood base depending on the grain count. Ie. 10 grains an inch versus 30 grains per inch.
Being that I have quite a good stock of spruce with varying grain counts it would be interesting to lay up a few soundboard panels of the same model, choosing one to be a primarily a tight grain, ie. 22 to 28 grains per, and the other in the 14 to 18 grains per inch..... set the panel sander up to do both the same thickness, cut each to the same shape and then measure the end weight. Is there anything to be learned from this?
Really though the short version of this thought to me is that a tight grain panel should be perhaps be no more than. .300 to .330. and the wider grain to be at last .330. And for the sake of discussion let's assume these will become rib crowned or RC & S board and no significant compression levels
Seems to me the entire discussion involving a carbon fiber panels is uniformity of stiffness with out the annoyance of material movement under climactic changes. Steingraebbers example sports a really thin panel carbon fiber panel approx 1/8 th inch. It sounds really good.
Where am I going with this. I'm not exactly sure but I have some spruce that is literally 40 grains an inch. In an RC&S board system or a modest rib crowned board, so considering that its weight will or may be heavier why could that panel not be made to be .250/1/4 inch since compression will be of little affect, And being stiff but lighter would it not possibly present a more lively sound or as lively a sound as the carbon fiber board or a laminated board for that matter?
One last fly in the ointment. Even if we get rid of spruce panels we still have wooden ribs. Same issue of grain count, species, and resultant stiffness and weight come into play. Now it gets interesting.
Any thoughts?
Dale S. Erwin
www.Erwinspiano.com
Custom restoration
Ronsen Piano hammers
Join the Weickert felt Revolution
209-577-8397
209-985-0990
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ptg.org/pipermail/caut.php/attachments/20110212/fc2fcac3/attachment.htm>
This PTG archive page provided courtesy of Moy Piano Service, LLC