Soundboard drydown for installation

[John Delacour]

At 10:43 -0500 22/1/08, Erwinspiano at aol.com wrote:

>even my own practice I can see a huge belly before it goes in but as 
>the board conforms to the rim some of that extra crown disappears.

So do you angle the rim to conform to the crown that you're going to 
end up with when the piano is strung or steeper?

>  I think the numbers of radii you state are fine.  I've introduced 
>some pretty steep crown with my methods/press/ribsÊwith no adverse 
>results.  How much is too much.  I dunno

To my way of thinking crown _in_itself_ is of no value, and I know of 
many excellent-sounding pianos that have virtually no measurable 
crown in the finished state.  Take off the strings and up comes the 
crown.  The importance of crowning is the resulting springiness of 
the board which is due to the compression of the summer growth 
initially by the process of drying the board and then letting it try 
to bend the ribs, and subsequently by pushing it down with the force 
of the strings, thus compressing the fibres, most at the top surface 
of the board.  Further compression results when the board takes up 
more moisture than ideally it would be allowed to, and the result of 
this, if the compression of the board is already near the limit, will 
be failure of the least resilient line(s) of summer growth and 
so-called "compression marks".  Although there is some truth, in my 
experience, in the statement that compression marks are the sign of a 
good piano, since I have seen them only in good pianos, there is 
nothing intrinsically good about a compression mark, since it means 
usually that too much compression was created in the earlier 
processes.  All the compression mark does is slightly reduce the 
compression and render the board unsightly. For makers to claim that 
a compression mark is a good thing and a sign that they've done their 
work properly is, to me, nonsense.  It's like a waitress claiming she 
pours a good cup of tea because some of it always ends up in the 
saucer.

As to bridges with concave bottoms and all that,  I ask what on earth 
for?  If the board is compressed as much as possible in order to 
release pressure when too dry without cracking and build pressure 
when too wet without giving way in compression failure, then it is 
going to work well.  Getting that balance right seems to be the 
perennial problem.  At least when a compression mark forms you can be 
pretty sure they were near the mark even if they overshot it.

And I'd like to know what is supposed to be achieved by forcing the 
board to curve along the grain, which has the effect, surely, simply 
of producing a curve for its own sake.  Sure there's nothing new 
about the idea but two makers at least that I know who did this 
stopped doing it in about 1885, presumably for good reason.

JD