Soundboard drydown for installation

[Jude Reveley/Absolute Piano]

Hail Dale, (Sorry had to return the rhyme), et al,

I come from the land of a very strict adherence to the doctrine of CC boards. Speak up if I offend any neighbors here on the list, but I think I am the only heretic in this part of the land that has abandoned the CC for a hybrid and even gone as far as experimenting with the RC & S. Currently, I have settled on a hybrid. I think the primary reluctance to abandon the lower ranges of MC (3.5-5%) has to do with the knowledge that most households here range from RH in the low teens in winter to the high 80s in the summer. We just can't count on our customers maintaining the RH in their piano room, hell we're lucky enough if we can get them to move their $80,000 investment away from the fireplace, heating register, window and exterior wall (like my piano for example, not the price just the situation). We know our wood can withstand the compression set of the expanding board better than the contracting board so we ere on that side and deal with the compression ridges. Udo Steingraber also mentioned that their drying schedule had more to do with protecting the wood from the driest environs than promoting crown. Some speak of the ethereal qualities and tonal color that only a CC board can yield but I'll leave that one alone :).

Using my handy-dandy "Crownulator," [see archives] the other thing I've noticed is that my traditional CC brethren, that rely on low MC and forced crowning (i.e. in a dish) to promote crown, end up with way more crown than they thought. Their go-bar decks may measure 60' radius, but by the time the board is glued in, they usually have about a 35' to 40' radius which is more than what I've seen in some rebuilders' boards that are pre-crowning their ribs, unless of course they are using a more ambitious radius in their rib scale from the get go, as I am. This is all measured in the unloaded state across the grain. Loaded states are even more interesting, but I would like to collect more data before making any statements.

The back bass corner seems to flatten out on all boards due to the fact that we are all unlimited by the inner rim unless we are manufacturing our own pianos. This is what really interested me about the Steingraber's inner rim profile. They also custom taper their boards by placing sand on each board and tapping the board in the middle until all the sand moves towards the edges of the perimeter of the board.

I'm not sure how much sense the crowned bridge makes to me or any crown along the grain. I'm more concerned with the apex of crown being centered under the load across the grain, and in this regard the Steingraber has a very symmetrical design. Observe that straight treble bridge (no hockey stick), placement of impedance devices in the low bass and treble and the bass cut-off if you get a chance.

The other point I wish to make is that we have to remember that we're not dealing with one board glued at each end, but rather several planks glued together and then mounted all the way round. Ron's experiment is a good one but it would be good to try to repeat the concept of the experiment using a model that comes closer to a piano soundboard. We should note that the individual planks within the soundboard have a mind of their own depending on the grain and how the panels are glued together in regards to radial and tangential shrinkage.    

It is all very interesting, and paraphrasing Udo, how can we expect one piano to satisfy the whole repertoire from Scarlatti to Thelonious Monk and beyond. Still, I won't be happy until I can say that this species of wood with such and such modulus of elasticity, given x amount of load, with y rib scale and design, and so and so's hammers yield this type of sound. Yeah, dream on...

Back to work,
 
Jude Reveley, RPT
Absolute Piano Restoration, LLC
Lowell, Massachusetts
(978) 323-4545
  ----- Original Message ----- 
  From: Erwinspiano at aol.com 
  To: pianotech at ptg.org 
  Sent: Sunday, January 20, 2008 5:20 PM
  Subject: Re: Soundboard drydown for installation


  Hey Jude dude
       I spoke with Udo Steingraeber Friday night at a private party/ Reception, in Which his new & 7 ft & 7inch piano was showcased by five of the most awesome & prodigious L.A. First call, A list pianists & Jazz players.  BTW...Jude , he confirmed many things you state below.
     The piano sounded awesome.  T'was Dark, clear & singing & powerful.  No duplex scaling behind the bridge & each backscale length was nice & uniform as it rested on a half round brass bearing bar. 
    I checked the residual treble bearing to be evenly about 1 1/2 degrees.  The rear lengths were ,in my opinion, adequate for bridge freedom.  
      It's tonal pocket is very similar to what I'm trying to achieve thru an entirely different form of Sound board building. In my experience any board dried to 4 % before ribbing would show compression rumpling a cross the panel after stringing but none was in evidence on this piano. It had 15 taller than wide ribs & a nice sweeping cutoff bar & aquite a thin panel as best as I could tlel by peeping thru the nose bolt holes. Udo confirms using flat ribs in a dish of sorts &  palced a big emphasis about crown along the bridge.  In fact he had never heard of checking the crown along the ribs with a String.  I was honestly baffled by this. Certainly a certain amount of crown is expected across the ribs but perhaps it was all propreitary which is as it should be.
    
  Whatever.  The on going lessons for me are that, .....many things work & some of them work really well.  What I do know is the piano sounded truly awesome & personally inspiring & also.  It would only let me play minor key stuff at first & sounded familiar to a certain D I once rebuilt but .....that's another story.
    David & Tanya put on a elegant & wonderful party for the Steingraeber crew & friends  & he can elaborate as he wishes.
    Dale Erwin

  As for Steingraber, they seem to be the only company that is really trying 
  to preserve a dome shape to their boards. Not only do they glue a 
  pre-crowned treble bridge to an unribbed board, they also custom fit the rim 
  all the way round, which makes more sense than assuming a 1 degree angle on 
  three sides will yield anything except more stress (not that I'm saying more 
  stress is undesirable). The Germans seem to have done copious research on 
  stress in soundboards as a tone-producing ingredient, according to Sauter. 
  There are many texts in German which have yet to be translated into English.

  The Steingraber bass bridge is attached after the board is installed because 
  of the many centemeter variations in the plate casting. The bass bridge is 
  therefore hallowed out at the root to allow it to flex onto the crown of the 
  board.

  Regards,

  Jude Reveley, RPT
  Absolute Piano Restoration, LLC
  Lowell, Massachusetts
  (978) 323-4545 







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  Start the year off right. Easy ways to stay in shape in the new year. 
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