?? Has anyone ever made a piano with two boards. Parallel to eachother with different stiffness factors? Joe Goss imatunr@srvinet.com www.mothergoosetools.com ----- Original Message ----- From: "Ron Nossaman" <RNossaman@cox.net> To: "Pianotech" <pianotech@ptg.org> Sent: Sunday, July 27, 2003 7:28 PM Subject: Re: Rib overkill > It can. A more flexible board will tend to be generally louder, with > shorter sustain. A stiffer board will tend to be not as loud, with longer > sustain. Will the bass suffer? > > Yes. If there is to be any hope of getting a fundamental out of the low > bass, the board needs to be flexible down there, and the back scale needs > to be long, and the core wire needs to not be the diameter of an 8d nail. > At the same time, the treble needs to be stiff or you will get the > percussive attack and short sustain of the "killer octave" through the last > two octaves or so. Stiffness requirements are widely different from one end > of the scale to the other. > > > >I think I also remember Del mentioning something about a board giving too > >much of a percussive sound and not as much string sound. Is this with a > >board that is too stiff? > > Probably too flexible. > > > >How does the thickness of the board relate to how much load it can support? > > It depends on the crowning method. A compression crowned board will be > stiffer with a thicker panel, and support comparatively more load than a > compression crowned board with a thinner panel. With a rib crowned board, > assuming it is really rib supported and not just a compression crowned > board with machine crowned ribs, the panel thickness makes much less > difference. With a rib crowned, rib supported board, there is no need for a > thick panel if the rim is solid. > > > >And in relation to the rib thickness? > > Again, it depends on the crowning method. Compression crowned boards tend > to have ribs wider than they are deep, because they start out flat and the > panel expansion has to bend them to form crown. Rib crowned and supported > boards will have ribs less wide, and deeper, regardless of panel thickness. > Ribs get stiffer in proportion to their width, and to the cube of their > height (and inversely to the cube of their length), so a little bit of rib > height makes them a lot stiffer. > > > >I'm sure all these things are interrelated. What are the trade-offs? > > Those are some of them. > > > >Next, I'm sure the size of the board is a factor. A smaller piano will > >have more support from the rim, because the there is more rim per area of > >board. Yet another factor to consider, aye? > > Absolutely. Soundboards, contrary to manufacturers' marketing literature > bragging about how their soundboards have more area than their > competitors', are for the most part already too big. Redesigns I do > typically lose something around 20% of the existing active soundboard area, > depending on what I started with. > > > >How does one judge or weigh the trade-offs? There are so many variables. > > A bunch of variables, the most critical of them not the ones we have always > been taught were all important. One can either put in a couple of hundred > soundboards, making incremental-to-major changes in virtually everything > until he works out a set of priorities and effects of design features, or > he can do what I did and start rethinking what I thought I knew against the > good fundamental science and physics based advice and guidelines of someone > who did do the basic R&D from scratch. That would be Del. > > > >There's no real point here to my questions. I am always trying to learn > >more about my trade. And who else do I learn from other than the folks > >who do this every day? > > > >Mike Bratcher > > Every day's a new day for all of us isn't it? There's always something to > learn - and heal up from. > > Ron N > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives
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