[CAUT] 1912 B: speaking lengths anyone?

[Richard Brekne]

Hi All

Sorry to have copied so much of Rons last response, but the questions 
are so pertainant I found it unavoidable.  See comments/questions 
interspersed below.

         > Sorry if I wasn't clear Ron, no need to diagnose. Re-capping
        is a foregone conclusion, as the bridges are barely touching, or
        below the > plane of my test string... with no string load.

    Oh? What's the present measurable crown in as many places as you can
    reach? If you set bearing with adequate crown in the first place and
    there's no bearing now, there isn't adequate crown either and making
    the bridge taller won't cure that. So lacking adequate crown, what
    do you hope recapping will get you?

A real large question mark appeared in my mind here as well. First... 
Mark, how do you explain the present condition if crown and bearing were 
good when you originally planned the bridge ? Are you convinced the 
unloaded board just "lost" too much crown due to low winter RH over 4 
years ? And I'd underscore Ron's comment that a taller bridge wont help 
(assuming it is a lack of crown that is the present problem). Probably 
it would be a recipe for reverse crown upon loading.

         > (Our shop is now alarmed (the HVAC e-mails me) at a 20%
        minumim RH, as opposed to previous Januarys, when this
         > board was originally installed, and the engineers calculated
        single-digits... and we still hot-boxed!

    Which means what? What's the current RH%, and at what MC was the
    board ribbed?

Agreed again... no advice from here can really help without knowing 
present RH and the panel MC at ribbing. It might be also nice to know 
what MC the ribs were prior to glue-up.

         > I just wanted to double-check my speaking lengths with Bob's
        before I start carving the cap. Must be the 1/2" of shop dust on
        my  
         > teardown notes making me paranoid.
         > best regards, Mark Cramer

    Again, what do someone else's measured speaking lengths on a
    different instrument have to do with crown and bearing on this
    piano?

    Ron N

I really don't see what the speaking lengths themselves have to do with 
the crown part of this in the first place, and most certainly dont see 
what good another B's lengths or nominal B specs will give you. At best, 
a combination of speaking lengths and back lengths along with the rest 
of the scale information can give you downbearing pressure on a board 
for a given string deflection-

Potentially a very instructive case study here Mark.... but more info is 
required.  What kind of crowning procedure did you use and how much 
crown did you start out with ?  How were you measuring crown ? How much 
crown is there now ? RH and MC figures previously asked for.  We ARE 
talking  about a board with a planned bridge glued onto it aren't we or 
is that still unglued ?

A rare case perhaps of a new ribbed board installed but left unloaded 
for several years and subjected to only climatic changes.... You could 
provide us all with some interesting data here Mark.

Cheers
RicB