Richard Brekne wrote: > Hi List > > I wanted to try and better explain why I am having difficulty in > accepting that the ribs in a CC board do not support crown against down > bearing. Please follow the following reasoning and diagrams and you will > see where I am stumped. > > First is a panel that is simply bent across the grain and held into > place with a cable appropriately attached on the ends of the panel. > Obviously, when down bearing is applied, the outward pressure on the > cable is increased. This entire situation is going to be the same if one > first dries out the soundboard, then securing that same cable tightly, > let the panel take on enough MC to form the same crown. Richard, Have you actually tried this with real materials. If you had you would find that the cross grain panel will bend locally when you apply a force to it like down bearing. Also because the cross grain is compliant in relation to the cable it will absorb the force by compressing and collapsing. In any case very little of the force will be transmitted to the cable. What you have drawn here bears little resemblance to a soundboard. Once the ribs are glued on the panel and ribs work as one. John Hartman RPT John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] Rebuilding Steinway and Mason & Hamlin Grand Pianos Since 1979 Piano Technicians Journal Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015]
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