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In a message dated 10/11/2003 10:18:55 AM Pacific Daylight Time,
RNossaman@cox.net writes:
> As you say It doesn't seem the panel is going to compress
> significantly with these minor increases from downbearing. I typically
> dry Sitka panels before ribbing between 5.5% to 6% EMC out here in
> Calif. Many go to the bay area with higher average moisture levels than
> the central valley where I am. I have followed many of these pianos over
> timed see no sign of compression ridges, cracks bulging etc. With other
> kinds of spruce with less strength across grain , or containing too much
> soft spring/early wood, it could be a problem.
But then neither you nor John are building compression crowned soundboards
with flat ribs, so the comparison isn't of much use.
>>>Well , uhh, not xactly. Early On I dried some panels down to what was
probably 4.5% to 5% with lightly crowned ribs with very little if any addition in
height. The only one that had a problem with a bulge was an eastern spruce
board with a huge plank of early wood in the bass corner. With the damp chasers
on it diminished significantly.
Not only that but I do rib a bit drier than some folks (I know my
climate) and the backs of the ribs do bow some even though they were machined
straight. Primarily its the longest ribs. As you well know all boards have some
compression componenet. I've stated it before that I prefer the sounds of a board
with a bit more compression based on what I hear in my own boards & in others I
prefer I prefer the sounds of. My philosophy is that if a board sounds
really good for 50 yrs. isn't that long enough? Obviously most hybrids will
persevere longer than that & besides, Uhh I won't be here... probably.
But no in general I crown my ribs 60ft & more in the treble, it depends on
the piano.
> >>> So then it looks like a safe level of E.M.C for panel crowning could
> range from 5.5 % to 6%emc
In purely compression crowned boards, the overall compression is the
problem, not the starting MC. Similar panel compression levels can be
gotten by either severe drying, or pressing the assembly in a deeper dished
caul. If the resulting crown is the same, the panel compression is the same
no matter how it was arrived at.
>>Panel Moisture content at ribbing equals overall panel compression. As to
the latter my press caul is steeper(45 ft.) than most of the rib radii I use as
well but the rib backs are straight when it comes out of the press so I'm not
sure how much steeper it'd have to be to make this true.(speaking of panel
compression)
> If anyone has had the idea that only a highly modified board is an
> exceptable and legitimate attempt at quality piano rebuilding just isn't so.
And as far as I'm aware, not a living soul has made that claim, so I can't
help but wonder why so many people repeatedly and specifically make this
point against a claim that was never made.
>>> When an idea has so dominated discussion on this list it is possible to
conclude that a thing has been said or assumned, even though unstated. People
draw perceptions in a variety of ways. I wasn't pointing any fingers just
making clear that there are a variety of different ways to be succesful doing this
work.-Most all are valid-Regards-Dale
I also note that my original request for an explanation still hasn't been
approached. John said that the ribs of a compression crowned soundboard
supported most of the crown, and the panel supported very little. I'd still
like to know how that can be when it is panel compression that is bending
the rib in the first place, thus supporting both the rib and the bearing to
retain crown.
>>> Angled rim joint has an effect though not one you'd obviously build a
whole concept around This
Ron N
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