A very reasonable and thoughtful statement of the hybrid RC&S position. A well thought out and engineered rib scale is the foundation of a not only the load-bearing imperative but of stiffness-impedance considerations as well. There exists a sweet spot, and then a sweet spot within the sweet spot where tonal power balances longevity of tone. Thus it can be said that any safe and defensible compromises chosen here by the artist-rebuilder is what will determine the range of dynamics that should suit "what the piano literature actually calls for". We all know that hammers cannot draw out of the belly what isn't in there to begin with. NG On Wed, Dec 19, 2012 at 2:10 PM, David Love <davidlovepianos at comcast.net>wrote: > Ron: > > My responses (I've numbered yours below so that will be easier to follow): > > 1. What you said was that there was never a reason to use trichord wrapped > strings. If they sound better, that's a reason to use them. > > 2. I wouldn't consider the Asian lacquer clang the current standard. If > you > are rebuilding a Steinway piano then the best of the Steinway pianos is the > standard unless you decide that it isn't. The scale doesn't change > appreciably, meaning you aren't converting a 155 lb plain wire string to a > 175 lb string or a 145 lb one. So the board will need to be designed > accordingly. We don't need to revisit the inconsistencies of certain > methods and procedures, I think we agree on that. > > 3. Yes they do, we agree on that. > > 4. Yes, here is the heart of the matter. I wouldn't consider my rib scales > light, nor heavy but just right ;-). We haven't gotten into side by side > comparison of rib scales and I'm not sure this is the time for that but I > wouldn't consider my rib scales light at all, but nor are they heavy. They > are calculated to carry the full downbearing load by themselves. Once > major > difference is that I happen to think that fixed ends formulas are a more > realistic approach than you do based on your use of simple ends formulas > and > so and so my rib scales may well be lighter than yours. But I wouldn't > consider them light. > > The boards don't have a lot of compression. If you are thinking that my > panels ribbed at 5.5% and yours ribbed at 6% have a significant amount of > difference in terms of compression at any given time, I think that's > overstating the significance. That amounts to about 5% difference in RH. > This difference between hybrid and RC&S is somewhat artificial to me. Your > 6% board has compression when the humidity is above 35%. Mine has > compression when the humidity is above 30%. I don't want the board going > under tension but neither do I want it in an environment where the humidity > is 80%. Some modest amount of compression is desirable to keep the board > from going under tension. I crown the ribs but not as much as you do. I > just want enough crown that I can flex the board and still have some crown > left. Much more than that is unnecessary, in my view, and may even create > too much stiffness, though I'm not sure as I haven't really ever researched > that, but I've thought about it in light of other assemblies I've made with > tighter radii. Of course with a smaller cutoff, or without one, a tighter > radii can create too much crown so that you have a problem with plate and > bridge height. So I don't see any reason to overdo it. > > Did I say I use light bearing??? I don't think so. The preset bearing > settings I use are 1.5 degrees through the piano. In actual practice the > bearing in the bass ends up a bit lighter when you account for the string > looping and felt placed over bass shelf. This is not particularly light > bearing in fact from what you wrote it's probably a bit more than you have. > I don't see the need to go to 2 degrees in the top of the treble though. > The configuration and rib scale make that area stiff enough. I don't like > jangles. I definitely want the board to be loaded, the spring compressed. > When all is said and done I go through and tweak the bearing based on what > I > hear. Do I need a bit more stiffness here or a bit less. One and a half > degrees, just to clarify, is the preset bearing. The board does deflect > and > the residual measureable bearing will not be less than 1.5%, as it should > be > in my view. That's not to say the load associated with 1.5% has > disappeared, but it has been transferred to the board. This is a broader > topic though. Ideally I would end up with about 1/2 of the preload crown > but it can vary slightly. The rib calculations in the design phase, btw, > will not yield a deflection of 1/2 the crown but something less than that. > The panel (and the bridge) do add stiffness to the assembly. So even with > the board being thinned and the ribs being scalloped, the deflection in > real > life will be less than the beam calculations would suggest. When you glue > on the panel and then glue the panel to the rim, the entire assembly takes > on more stiffness than the rib scale alone would suggest. As it should be. > But if you aren't taking that into account then, in my view, it's very easy > to over design the ribs. > > So taken all together we clearly have some differences in our design > approaches. In my view it doesn't necessarily have to do with cut off bars > or bass floats or the addition of certain redesign features that I've > mentioned before or even the EMC at which we rib the boards, since those > aren't significantly different. I think our differences are more > fundamental and boil down to how we approach designing a rib scale. That's > really at the heart of any soundboard design, the ribs. The other things > add up collectively to impact certain tonal aspects but it's the rib scale > first and foremost. The rib scales I'm using are not light, in my opinion > at all, to restate. They are adequately designed to carry the load by > themselves. Thus I don't worry about panel thinning, in fact I think it > adds to a fuller tonal spectrum. Were I making a compression crowned board > I would definitely think about not thinning the panel except maybe in the > bass. The full thickness of the panel would be needed. But the rib scale > would be lighter as well, likely, or at least they seem to be when you > analyze them. As I said, spring rate is something that I look at but > there > are other criteria that must be used to put the spring rate in context. I > think the contribution of the panel must be considered because no matter > how > you slice it, it contributes. More, if it's thicker, narrower and not > diaphragmized, less if it's thinner, diaphragmized and wider. But it > contributes and, in my view, must be considered in the equation. > > Sadly, at this point anyway, none of us are quite willing to give up our > spread sheets and design specifics because they remain somewhat > proprietary. > Even if we did share them coming to a consensus is always difficult because > we may essentially have very different tonal goals, which is what I think. > Since we can't climb into each other's heads to know what we are looking > for > and or experiencing this is always a challenge. And, btw, that doesn't > bother me but that doesn't mean I don't have a strong opinion about it. > > I think we would both agree that making a rib scale that is inadequate to > the task of load bearing would be a mistake. Where we may disagree is how > much margin there is and far we can go before we have a problem on the > other > end. You have commented favorably before about boards designed such that > they can't be overdriven. But a board that can't be overdriven is quite > possibly a board that can't be driven enough. I think there's as much > danger in that from an esthetic standpoint as making a rib scale that is > too > light. The target is fairly narrow, in my view, if the goal is the maximum > range of expressive possibilities. While we evidently disagree on how > narrow that range can be and still be acceptable my goal is to make the > range as wide as possible even at the risk of being able to overdrive it > slightly (emphasis on "slightly"). And my standard for that is determined > by what I believe the piano literature actually calls for. > > David Love > www.davidlovepianos.com > > > > Nossaman wrote: > > 1. Sure, maybe trichords might actually sound better in some instances, but > I never objected to how they sound tonally. My objections were in the > successful matching and hammer mating of three strings, which is enough for > me when I have the option of avoiding them. > > 2. Yet one of the common observations is that my pianos sound like what the > older folks remember from when they were kids, before the Asian and > lacquer clang became the standard. > > 3. Then they need to try a few things and think for themselves, don't they? > > 4. Okay. Some context. At last this is all fitting into something that > makes sense. You're building a much more nearly conventional rib crowned > board with a very light rib scale and moderate panel compression, loaded > with a light bearing. This explains your preference for a light bearing. > The board couldn't take much more, and a partially panel supported board > (this would be a hybrid RC, rather than an RC&S board) will change more > in tonal character as the load increases than will a RC&S board. That > follows. Eliminating cutoff bar and fish also follows, as panel support > allows this where a light rib scale RC&S board wouldn't support much > load without a cutoff. This follows too. I'm not entirely sure, but I > expect this accounts for your insistence that thinning the panel is > necessary, as you have a minimal bearing load, you need as much panel > flexibility as you can get just above minimal acceptable stiffness. This > also follows, if it's correct. This is also why spring rate doesn't mean > much to you because the rib stiffness isn't nearly as important to > quantify with a very light load and the panel compression doing a fair > share of the work of load support. It also somewhat accounts for your > insistence that the ribs in a CC board are doing the same thing as a RC > board. In a low crown light rib scale assembly, partially panel > supported and lightly loaded, they more nearly are, where a CC board > bears no resemblance to an RC&S assembly where the ribs are supporting > the load. > > Taken all together, I now understand much of what you're doing. Your > preferences in bearing load, rib sizing, bass cutoff and fish, however, > have little to nothing to do with what I'm doing, which as I've said, is > putting a 6% or slightly above MC panel on a rib scale that will handle > a bearing load graduated from 1/2°-3/4° in the bass, to 1-1/2° to 2° in > the treble without any help from the panel. > > Ron N > > -- Nick Gravagne, RPT AST Mechanical Engineering -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20121219/75ceb679/attachment.htm>
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