[pianotech] FW: laminated ribs again

[Farrell]

One needs to cut the plies from a number of different planks, shuffle the deck and them glue them up.

Zactly! That's one thing I've been doing for a long time. I maintain a very large stack of Sitka laminations. When I glue up a slab of ribs, I choose laminations from a variety of different planks.

You're right with your other idea as a way to gradually change the strength-to-weight ratio of the rib wood. I guess I'm just not much of a designer though - I agree with you that some extra mass up in the high treble is generally desirable, but I wonder if it makes a difference whether that mass in put in the bridge or in the soundboard - I suspect it does. Neat idea though - maybe it is a good way to go!

Terry Farrell
  ----- Original Message ----- 
  From: David Love 
  To: pianotech at ptg.org 
  Sent: Wednesday, January 28, 2009 7:23 PM
  Subject: Re: [pianotech] FW: laminated ribs again


  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 different 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

   

  From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of erwinspiano at aol.com
  Sent: Wednesday, January 28, 2009 2:39 PM
  To: pianotech at ptg.org
  Subject: Re: [pianotech] FW: laminated ribs again

   

  Hi Marco
    I have used laminated ribs infrequently. Although I agree with the big boss as to a more stable Modulus of elasticity 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

   

   

   
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