Dale responded to a question I had about his rib crowning jig. Here it is. Terry Farrell > > Subj:Re: Dale Erwins----/Rib Crowning Jig pic's > > Date:2/11/2002 4:42:02 AM Pacific Standard Time > > From:<A HREF="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A> > > To:<A HREF="mailto:Erwinspiano@aol.com">Erwinspiano@aol.com</A> > > Sent from the Internet > > > > > > You wrote > > Hello Dale Erwin. Thank you for the rib crowning jig pics. I have a > > question. From the picture I can easily see how you make your first cut on > > the rib. After this first cut and you let the rib relax, you are left with > > a rib that has a straight edge on the uncut side and a convex curve on the > > other. Obviously, the convex curve will be glued to the soundboard back. > > How do you then cut the other side of the rib so that you end up with a > > constant-thickness rib? > > > > Terry > > Your very welcome > > > I was wondering if any body saw the pictures as this is the first > > question I've fielded. > > All the rib crowning rebuilders I know do not care that more beef > falls in the > > middle the rib or under the bridge. This idea is in line with the > > diaphramatic concept in that the majority of the soundboard mass is in the > > middle of the board. > > I frequently add 1mm to the overal depth at the thickest part of the > > longer ribs because the rib ends are losing some mass due to the > > aysemtrical thickness. Does that make sense? > > If you wish to have a constant thickness rib you can. After the crown is > > cut the next step is to run the backside of the rib thru a large radius > > router bit This puts the usual half moonish radii on it. Use a fence and > > feather board.if you value your fingers. The rib is still thicker in the > > middle at this point. After the ribs are glued on to the board use Dana > > Mazzaglias rib radius plane which has a radius blade. It is a simple matter > > to plane out the extra mass in the middle if this is what you decide you > > wish. > > A question you didn't ask. With this jig it is easy to put the highest > > part of the crown under the bridge. Make a mark indicating the bridge > > location on the rib. Install the rib on the jig where the C clamp is. This > > will become the highest part of the crown on the rib. This has limitations. > > The high treble ribs for example are too short but wherever the bridge > > travels thru a wider part of the board it is feasible. > > > > If you wish post this to the list as others may have the same question. > > Hope all is well with you. By the way I just recieved the Roseland Sitka > > soundboard panels and they are really beautiful. Seamless joints, great > > color match. They are a higher quality board than most I've tried > > >>>>>>>>Best--Dale Erwin>>>>>>>>>... > >
This PTG archive page provided courtesy of Moy Piano Service, LLC