Soundboard installation with hide glue

[Farrell]

>From what I see on their website, they clamp the ribs on a curved surface.  Am I right to suppose that in this case the ribs were shaped curve also?  With the same curve as the clamping surface ?  



Mabe yes, maybe no. I use clamping cauls of the same radius as the rib. Steinway NY uses flat ribs and curved cauls. I don't know what Ciresa does.



If so, maybe they used the standard 60 ft radius?  



Wereas I will agree that many shops likely use a 60 ft radius for their ribs, I don't know of  anything really "standard" about it. I've never cut (or laminated) a 60 ft radius into a rib. I don't have a 60 ft radius caul.



As for the MC at ribbing, I don't know, but I will look closely at the conditions when my board is flat again.  I suppose it is a combination of rib and compression crowning.  I'll know more when they answer my inquiry.  But if they indeed glued the curved ribs on a curved surface, then the MC at gluing time would be that when my board has the same curve as their hardware, not?



Yes indeed - you are correct. Sorry 'bout that. I didn't have my thinking cap firmly attached for the last email. That is also true if the ribs were flat and pressed in a curved caul. So you're right - no way to tell what the ribbing MC was by looking at soundboard curvature.



Anyway, there is no advantage in drying more than when the board is just flat, if I get you well.  So first I must do is bring the board back to flat.



Yeah, I think we can say that safely - if the board inverts, it is too dry! Also, if the ribs do have a radius, then if you dry the board down to a point where the rib radius is less than that prior to gluing to panel, you will be putting the panel in tension - kinda the same as reverse crown as far as the panel is concerned.



But get info on how much to dry from someone who does that. I don't dry my soundboards prior to installation - so what do I know?

 

How long do I have to do the board fitting in the piano before it swells again ?  I suppose that any fitting done when the board changes dimensions again is of no value.  Or is this overkill ?  Relative humidity in my working environment is about 40 % at this time of year and global warming process.



That just all depends on the differential in RH between the hot box and the shop. Best way to tell is to let board equilibrate with shop, measure crown, and then stick it in the hot box and measure crown at regular intervals. That will give you a fair idea of how fast the process will go the other way.

 

Incredible how you can read tons about a subject, you only learn really when you put your hands on it.



Scary sometimes!



Terry Farrell

  ----- Original Message ----- 
  From: Stéphane Collin 
  To: 'Pianotech List' 
  Sent: Wednesday, January 16, 2008 1:01 PM
  Subject: RE: Soundboard installation with hide glue


  Hi Terry.

   

  Thanks for chiming in.

  I think I will definitely use the cold liquid hide glue.  There is only one try for the process, other than ordering a new board if I mess up this one.

   

  I don't know the data you ask about the board (I promise next time, which will be soon, I will ask this first).  The board has been made by Ciresa in Italy, intended to be a close copy of the original, which was a 7'2" Bechstein piano board from 1873.  They did ask me for specifications, but I told them to do their usual standard routine (I believed that they knew better than I, and still believe so at the time I write this).  I will ask them how they proceeded.

  From what I see on their website, they clamp the ribs on a curved surface.  Am I right to suppose that in this case the ribs were shaped curve also ?  With the same curve as the clamping surface ?  If so, maybe they used the standard 60 ft radius ?  As for the MC at ribbing, I don't know, but I will look closely at the conditions when my board is flat again.  I suppose it is a combination of rib and compression crowning.  I'll know more when they answer my inquiry.  But if they indeed glued the curved ribs on a curved surface, then the MC at gluing time would be that when my board has the same curve as their hardware, not ?

  Anyway, there is no advantage in drying more than when the board is just flat, if I get you well.  So first I must do is bring the board back to flat.

   

  How long do I have to do the board fitting in the piano before it swells again ?  I suppose that any fitting done when the board changes dimensions again is of no value.  Or is this overkill ?  Relative humidity in my working environment is about 40 % at this time of year and global warming process.

   

  Incredible how you can read tons about a subject, you only learn really when you put your hands on it.

   

  Best regards,

  And thanks again.

   

  Stéphane Collin.
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