help a beginner measure mc in wood with confidence

[jimialeggio5 at comcast.net]

Terry,

>But why would you be drying a keyboard blank down past room EMC (a room that 
>has desirable RH that is - 40% to 50% or so).

I was'nt clear on my intentions here...all I'm going to do is record the overall 
width of the blank so all work  across the grain happens at the target 
mc/dimension. As you say, target mc in this case is simply ambient mc in a room 
with desirable RH.  

>That is correct. However, I don't need the reference after the panel is 
r>ibbed. I'm building rib crowned and supported soundboards. Even though I 
>usually do put a ribbed soundboard in my hot box before gluing into the 
>piano, it's more for protection against being broken than to dry down the 
>board. The ribs pretty much lock in the panel dimension, so what difference 
>does it make whether I dry the panel down to 6.5% MC prior to installation 
>or just let it acclimate to my shop and come up to the 8 or 9% EMC? 

OK.

>I keep my shop right between 40% and 50% RH - so I'm always working in 
consistent 
>conditions for downbearing work - its all very contollable. 

Enviable! Since I assume you need to condition your space in the Florida summers 
for personal comfort, the controlled shop RH is quite a nice benefit. Here in 
Boston, summer is not a "conditioned" time of the year mostly. Not only that, 
when its nice out I like the door open...its a cost as well as a quality of life 
issue to some extent. But your controlled RH is enviable. My processes and 
preferences reflect and accommodate the ambient conditions in my shop.  

>If you are building compression crowned soundboards, why would you want to 
>dry the soundboard down to 5% or whatever your ribbing MC was for 
>downbearing work - what does that do for you?

I'm doing RC&S boards...5% is not in my repertoire. For downbearing measurement, 
I'm shooting for around 7-7.5%mc.  Both yourself and Ron seem to be saying the 
crown of an RC&S board is not variable at different mc's.  I'm chicken and will 
have to prove that to myself before I trust it. 

But one other mc frustration I have is that after all is said and done, the 
board ribbed, in, downbearing done, strings up to pitch, I want to come back and 
observe exactly what I have achieved for future reference. IE, have the "as 
built" deflections hit the target crown deflections of the design. Not knowing 
what the mc of the board at this point is, to me, adding a variable which I want 
would really like to exclude. If I prove to myself that the RC&S crown is stable 
in different mc's I may rethink this point.

--
Jim Ialeggio 
www.grandpianosolutions.com
Shirley, MA (978) 425-9026