It’s important if you are doing RC&S boards where the rib provides the support without help from panel compression. If you base deflection and stiffness characteristics on the ribs then they need to be predictable. A good rib maker should be able to slice and shuffle to get pretty good uniformity where the variations will be pretty minimal. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of erwinspiano at aol.com Sent: Wednesday, January 28, 2009 5:51 PM To: pianotech at ptg.org Subject: Re: [pianotech] FW: laminated ribs again Still ,now mater how you slice the deck, shuffle the cards or glue up the ribs. There will be some variations. Just not as many. How to measure that & what to do with it is another matter. My point is I think the tendency is to look at these things with a microscope when a magnifying glass will do. Know what I mean? Dale I think it’s not so much an issue of stability but rather of tossing a salad of different lots so that there is a greater likelihood of blended uniformity from rib to rib. If you just cut all the plies from one piece of wood and then glue them back together that would defeat the purpose of lamination. One needs to cut the plies from a number of different planks, shuffle the deck and them glue them up. That insures greater uniformity and thus predictability (the real goal) between ribs. I do wonder, however, since added mass in the treble seems to be a goal, why one wouldn’t use a heavier wood or better yet a graduated blend of differen t woods to make up the laminations so that you could gradually increase the mass coefficient as you ascended through the treble. Rather than just switching the type of wood, as has been done in the past, you could simply gradually add one, two, three plies of a heavier would in each consecutive rib as you moved into the treble. David Love www.davidlovepianos.com <http://www.davidlovepianos.com/> Hi Marco I have used laminated ribs infrequently. Although I agree with the big boss as to a more stable Modulus of=2 0elasticity they can still vary a great deal depending on the grain density/wood density you laminate with. Laminating two sets of identical Stwy B ribs using wider grain wood on one & very tight grain on the other, indicated a definite and marked difference in the strength of those two sets. The denser grain was a stiffer set of ribs. I believe it important to make note of this difference & make an informed decision about stiffness parameters. Ie. how deep/wide/crowned the rib should be...cutouts. The next best thing to Laminated ribs is good set of stiff Sitka ribs cut from the same cant of wood, which, will yield a more even M.E. than ribs selected willy nilly as the to grain count. Wood density/stiffness will be more uniform. I know it's always something. I'm open to hear more comment on this. Dale _____ Which stars will make the biggest headlines in 2009? Get <http://toolbar.aol.com/popeater/download.html?ncid=emlweusdown00000027> Hollywood news, celebrity photos and more with the PopEater Toolbar. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20090128/0e7b97c1/attachment.html>
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