more board question

[Farrell]

Hi Gene,

I keep my shop right between 45% and 50% RH. My soundboards have 
equilibrated with shop conditions when I set my bearing. I see no reason to 
dry things down to glue-up MC.

I don't know what kind of soundboard design you are working with, but with 
any system the goal would be to have stable, repeatable conditions. Once you 
learn your soundboard design characteristics under certain environmental 
conditions, you can then proceed with some degree of confidence that your 
procedures with produce predictable results.

Setting bearing on rib crowned soundboard assemblies will be less affected 
by small changes in RH/MC. I would presume stable, repeatable environment RH 
would be rather critical in setting downbearing on a compression crowned 
soundboard system. I presume you are working with a rib crowned soundboard 
here - my guess from your relatively high MC at rib/panel glue-up. If yours 
is rib crowned, who designed it?

Where are you doing this work? In your shop? What kind of climate control 
systems do you have? What kind of RH monitoring system do you have? What 
range of RH does your shop experience?

I have simply never observed bearing conditions in the new board change over 
time because I keep my shop environmental conditions very stable. I find 
that helps keep things predictable and keeps me from pulling my hair out. I 
find my shop RH range to be ideal, because I install Damp-Chaser systems on 
all pianos that I put soundboards in, and thus, presumably soundboard MC 
will stay close to my shop conditions - that way, wherever I set bearing, 
bearing should remain constant.

Hope this helps.

Terry Farrell

----- Original Message ----- 
> Getting ready to set bearing tomorrow and am very curious how many people
> try to get the board/rib/bridge assembly close to or at the % moisture
> content that was in the board when the ribs were glued on as a preparatory
> step.
> When taking the bearing measurements that will determine how high the
> bridge will be, it would appear to be important to do this?
> The reason I ask is that I have observed the available bearing in the new
> board change over time depending on the relative humidity.
> The mc was about 6.5% when ribs were glued on.
> Any thoughts would be appreciated.
> Gene Nelson