Good questions, and good thoughts. I think you are correct that my original glue up process enhanced the bow of the multi-lam. I didn't take before measurements. I just know that the after measurement was extreme and unacceptable to me. I think that the gluing setup needs refinement also. As to the original, I clamped up without a bottom caul, and with a top caul of 6/4 maple that had a bow opposite the bow in the multilam. So I am thinking that the current glue up is better, but not ideal. By the way, prior to this glue-up I removed the original delignit cap which did not relieve the bowing in any way. After resawing the multilam, the two pieces bowed to an even more extreme. In this glue up, they went back together with the bows opposing. I acknowledge your observation about unequal clamping pressure. The cauls, however, are 60 - 80 mm oak, so the issue may not be as extreme as you perceive. I also used whatever bow was present in the cauls to advantage and placed the convex edge down. The table is extremely rigid and flat, which of course why I used it this go around. Last night after doing this glue-up I did some searching of prior posts on hybrid boards here. I saw some gluing setups that are far superior to what I used -- both vacuum and mechanical. It's great to have all the input available. The experience of others is invaluable. Experimental results and observations will be available tonight! In any event, for the next pinblock, I don't expect to have such an adventure. Duane McGuire 801-830-5858 http://blog.duanemcguire.com On Wed, Apr 7, 2010 at 6:32 AM, jimialeggio <jimialeggio at gmail.com> wrote: > I was thinking about your original glueup problem...I would bet that a good > part of what happened was caused by the way you clamped your stock. > 1- did you clamp the multi-lam and delignit together without flat cauls top > and bottom > 2- looking at the clamp setup in your new glueup, the clamping cauls > reaching across that wide presumably flat table are exerting unequal > pressure, ie lots of pressure at the edges and considerably less in the > center. As well, the clamps reaching over that wide distance will tend to > deform (cup) the previously flat gluing table. The clamp pressure above and > below should be right on the piece not offset. > > Just some thoughts..hope its helpful > > Jim I -- > Jim Ialeggio > grandpianosolutions.com > 978- 425-9026 > Shirley, MA > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100407/b2095a4a/attachment.htm>
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