Cracks and ridges

[Brent.Fischer@asu.edu]

>> Dear Mr. Hartman,
>>
>>    It is to  what degree of ridging in a Steinway soundboard that
>> concerns me mostly, since to duplicate their processing methods, which
>> deliver maximum tonal impact  and output, it is to be expected to have
>> wood joint compression. I am not in favor of excessive ridging but the
>> act of crowning a soundboard with flat sugar pine ribs into a
>> fifty-five foot radius caul at around percent 5% MC  is going to result
>> in joint compression.
>
>Brent,
>
>Could you explain this?  I don't understand how this would cause
>compression.  It almost seems to me that the opposite condition would
>result.  Thanks.
>
>Paul Stephens, RPT


Dear Paul,

     Let,s defer to the PTG Journal for good advice.  Del Fandrich
talks about soundboard systems in the Febuary issue.  The
explanations suggest that the Steinway board is a combination of
compression and stress crowning while pre-crowned ribs create less
internal compression in the board. The key is the use of a flat
and flexible sugar pine rib.  A  straight spruce rib will lessen
compression because it will retain more memory after being
removed from the press.  Read  his article carefully  because
it is excellent writing and is well substantiated. The one and only
exception I take is his belief that all ribs should be pre-crowned
to some degree since I think that would reduce the gusto of the
final result. Brent







Brent.Fischer@ASU.EDU
Arizona State University/Tempe