Bob, Having worked with many laminated bridges I can not agree with your idea that spring back has damages the soundboard. After removal from the soundboard the amount of spring back is minimal. Removing the cap does not effect this either. So the purpose of the cap is not to stabilize the laminated bridge. Neither do I believe that protecting the glue lines is a valid point; hide glue is very reliable in this situation. As a rule most glue line failures are in reality due to the stresses of wood movement due to changes in moisture content, not poor adhesion. In fact I would guess that the soundboard cracks you mention are also caused by the same wood movement problems. The soundboard panel moves across the grain but the long grain bridge restrains it. Stresses build up and cracks are formed. John Hartman
This PTG archive page provided courtesy of Moy Piano Service, LLC