I am currently fiddling with the idea of gluing auxilliary laminations to the spine of existing ribs, while the two are flexed together, along with a backing caul, by a jig secured to the back of the piano. I asked Terry Farrel to recommend a laminate--perhaps 3mm thick, 3 ply, but have not heard back from him yet. Anyone else care to comment? Thump --- Michael Spalding <spalding48@earthlink.net> wrote: > William, > > I'm a relative newcomer compared to others who I > hope will join in to > clarify or refute. My perspective is that of a > mechanical engineer turned > piano technician. But as I see it, crown is a > means, not an end. In other > words, what you need from a soundboard is > appropriate > stiffness/mass/impedence that endures for the life > of the piano. ( Refer to > archives about impedence matching SB stiffness to > string wt/frequency in > the different regions of the SB.) Crown is a > construction feature which, > in combination with traditional materials and design > features, tends to > produce the desired effect. There are other ways to > achieve this, > including Del's epoxy surface coating. I have > noticed, in my brief career, > big improvements in treble power, clarity, and > sustain in small pianos, > without doing anything about crown. What you do > have to do: re-attach > separated ribs, shim or fill SB cracks, cap or epoxy > the bridges, install > new bridge pins, re-surface the v-bar and agraffes. > Control your shop > humidity at the lower end of the normal seasonal > range. Trying to put > crown back into an old board by radically drying > before shimming, or > pushing up on the underside before shimming, only > ensures that during next > summer's high humidity the soundboard will compress > and crush, and the > following winter the cracks will come back. Bottom > line: if you want more > crown, install a new board and/or new ribs. If you > want to increase the > stiffness of the existing board, try the epoxy > surface treatment. If you > want noticeable improvement with low risk, do the > basics with precise > attention to detail. > > JMHO > > Mike > > > [Original Message] > > From: William R. Monroe <pianotech@a440piano.net> > > To: Pianotech <pianotech@ptg.org> > > Date: 3/13/2005 7:42:17 AM > > Subject: Increasing Crown > > > > List, > > > > I am currently working on rebuilding my own little > piano to gain some > > experience, and have a question about improving > the crown, function of the > > soundboard. I had heard of shimming up the SB > from underneath, prior to > > shimming, or doing anything else on top (Bridge > repairs, etc.), in hope > that > > by doing these repairs while the board was shimmed > up, they might act to > > improve the crown, even a very little bit. > > > > My question is about flowing epoxy over the > surface of the board, as was > > discussed here a while back, and I'm wondering > what you all think about > > having the board wedged up & flowing on epoxy. My > concern is about what > may > > happen when the wedges are removed - cracked > epoxy?!?!? > > > > What say you? > > > > William R. Monroe > > > > > > > > _______________________________________________ > > pianotech list info: > https://www.moypiano.com/resources/#archives > > > _______________________________________________ > pianotech list info: > https://www.moypiano.com/resources/#archives > __________________________________ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/
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