----- Original Message ----- From: Paul <tunenbww@clear.lakes.com> To: <pianotech@ptg.org> Sent: May 03, 2000 5:55 AM Subject: Re: Grand Rim Construction > Brian > You may get several replies on this. Here's my take on it : instead of the > rim being bent with several layers of wood, saw cut are made almost through > at a right angle to the length of the rim piece. By the spacing and the > depth of these cuts, the rim piece becomes flexible so it can be formed > around a mold with very little stress. If I remember correctly, Bosey glues > this rim piece directly to the inner rim. After it is dried. they install a > face veneer to the inside of the rim piece to cover the saw cuts, fill the > ends of the saw cuts with wedges and add an edge banding to hide all the > joints. A lot of putzing to get a rim. They claim it is stress free and adds > to the singing tone of the piano. > > Paul Chick -------------------------------------------------- Your description of the Bosendorfer rim is correct. The cuts are spaced fairly close together where the rim curve is of smaller radius (a tighter bend) and further apart where the bend is more gentle. This is a time-honored process used in the furniture making industry to make various curved pieces. It has been largely replaced in furniture manufacturing by the bent lamination process because the latter is stronger, more stable and easier to accomplish in production. Still, for a one-off bent piece for a bow front chest or whatever, it is fast and fairly easy to do in the small shop. No process used to create bent furniture components is really stress-free. But they are correct that this type of rim construction does result in less stress than do others. At least initially. I'm not sure this is an important issue in piano construction, however. The stresses imposed on the veneers used to make a bent laminate rim are basically dissipated after the rim is a few months old. I have encountered several piano rims in which the original hide glue had almost completely failed and the rims had almost fully delaminated but which had still retained their original as-pressed shape. Del
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