Hi I'll second this request for information along these lines. And while y'all are at it I'd like to throw an idea out and ask for feasibility comments. The idea of grain going perpendicular to the bridge has grabbed ahold of this unschooled mind and I keep thinking about ways of exploiting its assets. A panel is stiffer along the grain and orienting the thus on the surface of if seems not to be such a dumb idea... aside from the fact that evidently it is not stiff enough in the treble, and the long ribs in the that area that are necessitated by the grain orientation aren't going to be able to help matters enough. Yet this same orientation seems to make for a very lovely bass sound... if I understand things correctly. So... back to the basic idea of a laminate board with all laminations going in the same direction. What if you laminated such that you graduated crown to increase to a maximum in the treble and nearly flatten out in the bass area, and keep the high part of the crown as close to the treble bridge line all the way as possible. For example visualize a panel laminated thus to a 55 (or so) foot radius in the top octave and a half area that gradually moves to an 80 foot radius at the bass bridge. The relative short ribs on the bass will provide all whatever stiffness is needed there and the long ones in the treble would just add somewhat to whatever stiffness the short radius laminates up there establish. Ribs will be of course basically parallel to the bridge so in any case their main role will be to even out cross grain stiffness instead of supporting crown... yes ? So... is this a feasible idea or am I out to lunch again ?? :) Cheers RicB --------- David Love wrote: There is another issue to be raised. How should one match the scale tensions and anticipated downbearing angles to the rib scale. There are choices to be made. I presume that you want a certain amount of deflection of the soundboard assembly and that given a certain scale with a certain downbearing load, you can calculate the panel assembly stiffness and preset crown (in and RC&S board) to achieve that amount of deflection. But there are yet various ways to achieve that amount of deflection. For a given assembly you could increase the scale tension and lower the downbearing angle or decrease the scale tension and increase the downbearing angle. You can design an assembly with greater stiffness to go with a lower scale and greater downbearing or a lower stiffness to go with a higher scale and less downbearing, for example. Each combination, I presume, will produce its own unique tonal characteristics and, probably, require a hammer of different density and/or mass. Those of you who are designing boards, how would you characterize your goals and why?. If we can produce a RC&S board that will be able to accommodate any particular variation in load, what is so magical about the .5 - 1.5 degrees of downbearing that seems like it came about mostly due to the limitations of compression crowning. Further, in an RC&S board, what combination is most likely to give the general tonal characteristics of your successful CC board. And let's allow ourselves to speculate even if we haven't actually built each variation. David Love davidlovepianos@comcast.net Overs wrote: Richard, The downbearing (vector) force on the sound board is equal to the SIN of the angle of deflection times the string tension.
This PTG archive page provided courtesy of Moy Piano Service, LLC