> Remembering a discussion from some years back where Del stated in pretty > clear text that a carefully removed and de-ribbed old compression damaged > board could be re-ribbed as a RC & S board and perform pretty much > identically to a brand new panel assembled in the same manner. Yes, I believe I have heard him say the same thing. > Then reading a study from one of the departments of the Finnish equivalent > of the USFD which shows that wood that is artificially aged in a > particular manner... in which the cells are compressed makes certain gains > with regards to stiffness and the speed of sound which travels across the > grain is higher. Again, crush the wood into smaller volume, you may well increase stiffness. Hard maple is stiffer than spruce. But Sitka Spruce has the highest strength (I guess I am assuming strength is something pretty close to stiffness) to weight ratio. > I dont mean to literally mush the thing into pulp as Terry puts it. But > what would be so wrong about getting it just past the point of the cells > elastic limit... and then ribbing the thing. Well, for one, I don't think that is going to happen. Each annular ring is composed of spring/summer wood (very low density) and fall/winter wood (very dense). Actually, it is a continuum - the least dense in the early spring and the most dense in the winter or fall. So as you compress the board, you will push the low density zones (stripes of spring wood) past their elastic limit - but the more dense stuff will require more pressure. I really don't know how it would all shake out, but I suspect by the time you applied enough pressure to push the dense wood past it's elastic limit, the spring wood would indeed be pulp. I think your board would fall apart. I think there is little doubt it would crack all over the place. > It would seem to me that one advantage of ribbing an old board thats gone > through all this already... is that ... well its finished with that. > Crowned as an RC & S assembly wouldn't this be as about as stable as they > can come ? My thought on this is that the old panel has gone through SOME of this - enough for the board to have lost its crown, etc. But if you want to abuse it more, I suspect the average old board has all sorts of potential to fall apart further. That's why I say that IMHO a better way to avoid compression damage to a soundboard panel is to build a well designed rib crowned and supported soundboard assembly, install it into the piano, and then don't abuse it by subjecting it to extremes of humidity. Terry Farrell ----- Original Message ----- > Ok you two... I really did ask the question seriously. Remembering a > discussion from some years back where Del stated in pretty clear text that > a carefully removed and de-ribbed old compression damaged board could be > re-ribbed as a RC & S board and perform pretty much identically to a brand > new panel assembled in the same manner. Then reading a study from one of > the departments of the Finnish equivalent of the USFD which shows that > wood that is artificially aged in a particular manner... in which the > cells are compressed makes certain gains with regards to stiffness and the > speed of sound which travels across the grain is higher. > > I dont mean to literally mush the thing into pulp as Terry puts it. But > what would be so wrong about getting it just past the point of the cells > elastic limit... and then ribbing the thing. It would seem to me that one > advantage of ribbing an old board thats gone through all this already... > is that ... well its finished with that. Crowned as an RC & S assembly > wouldn't this be as about as stable as they can come ? > > What am I missing here ? > > Cheers > RicB >
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