Frank Weston wrote: > > OK engineers: > > The soundboard assembly must withstand a substantial amount of downbearing > force, no matter how it is constructed. A so called "compression" crowned > soundboard in an unloaded state will have the fibers in the top half of the > board subjected to tension and those in the bottom subjected to compression > (it's the rule, you got to have both). Frank, What you got to have is a difference in compression. The top and bottom can both be compressed relative to an unconfined state, but if the degree of compression is different, the board will curve, relative to that unconfined state. Gluing the dried board to ribs and then allowing it to expand causes the board to be compressed everywhere because of the confinement of the ribs. However, the compression will be greatest at the point of contact (the glue joint) and less on the top, where it is somewhat freer to expand, causing it to curve. A minor quibble, actually. Paul S. Larudee, RPT Richmond, CA
This PTG archive page provided courtesy of Moy Piano Service, LLC