Hi ron, Was thinking of raising the board as wedge was driven in to create crown. The kerf would as you say create negative crown. The victim is an old upright with a cracled plate. Havent pulled it away from the wall for an examination of the back post area but think that they have given. The design is a 3/4 plate still in good shape with a 1/4 cast plate over the pin block area with big crack at the bass tenor break. Joe Goss RPT Mother Goose Tools imatunr at srvinet.com www.mothergoosetools.com ----- Original Message ----- From: "Ron Nossaman" <rnossaman at cox.net> To: <pianotech at ptg.org> Sent: Thursday, January 29, 2009 9:59 AM Subject: Re: [pianotech] FW: laminated ribs again > > > > Hi, > > Dont know so Ima goina ask. > > Is there a crown ridge that sort of follows the bridge line? > > In a rib that's a constant radius circle segment, the high > point is ALWAYS in the center of the ribs. That's geometry, no > matter what sort of "logic" and body english is employed to > try to make it not so. If the bridge is centered on the rib > then yes, the bridge is on the high point. If not, no. With > non constant radius crowning (parabola, sine, catenary, or > multiple radii), you can put the high point anywhere you like. > > > > Could one cut kerfs in the ribs radiating away from the bridge line > > and glue in wood shims > > to induce more crown? > > Sure, if you really want negative crown, unless you kerf and > wedge from the panel side. More geometry. > > Ron N >
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