I think you need both (crown with load and without load) along with the bearing measurements before and after as well. An analysis of the rib scale is also helpful even with pure compression crowned boards and certainly with hybrids. The ribs still do a fair amount of work even in compression crowned boards once glued into the rim. Measuring the crown under load doesn't tell you much. You could have negative crown on a board that's way overloaded that might respond ok once the load is adjusted to the proper level--damage aside. The crown with bearing measurement tells you more, but still not enough. Measuring the crown with tension and without tension and the bearing change with and without load tells you quite a bit about how the board is responding and whether it can withstand any significant load or not. Insuring that your limited and randomly chosen measurements actually reflect the reality of the load distributions is another matter. More is more in this case. David Love www.davidlovepianos.com In the many instances of trying to diagnose soundboard problems in pianos, nearly everyone, certainly every manufacturer's rep, has told me you can't tell the condition of a soundboard under string load. I find this to be entirely backward. An unloaded board will tell me virtually nothing about it's load capacity, while a board with positive bearing load retaining positive crown is an indication of a structurally viable board. Anything an unloaded board seems to be telling you is untrustworthy. Ron N
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