>1)I have experienced now that compression crowned boards loose very much >crown by unstressing them; so if you want to work this method you should >carefully dry the panel so the wood will swell and taking crown by the >change of humidity. And you also have to "overbend" the ribs to keep some >crown after a few days, weeks. That's the only way to be shure to keep >some crown. Unless you crown the ribs. That's still the surest way. >Problems then are : how can one attach the bridges to the board? By >puching more you also bend the board in the direction it may not bend. If >you have crown and you puch with more force, the board is going flatter >which will allow to have the bridge full contact with its complete surface. The bridges will contact the surface quite easily no matter what crown you have in the panel, and regardless of whether the bridge is flat or crowned. It isn't a problem. There was an extensive discussion about this on the list a couple of months ago. >So if you want to know, I'm going to restart, ie taking of the ribs whith >a plane and placing new crowned ones, drying the board and the ribs >carefully to a MC as low as possible and then gluing and clamping them >together. >The "only" problem I still have: how much crown should I give to the beams >of my press: none, and arc of +/-18m for the longest ones and +/-15 for >the shortest ones, (like the ribs are precrowned), + for >having more crown at the end? (How much should one have with a new >board anyway?) Can somebody me tell that please? I only know that the >uncrowned beams of my press give about one cm of crown when I'm blowing >the hoses. Sorry, I can't help here. I've never made a compression crowned board. Ron N
This PTG archive page provided courtesy of Moy Piano Service, LLC