an analysis of downbearing, etc.

[David Skolnik]

Phil-
I will try to find the information you mentioned.  Any idea as to the 
thread titles? In the mean time, maybe I'm really suffering from something, 
but what is being said here?  That there is no particular need for crown 
and downbearing?  That the board impedance that was talked about very 
recently will exist whether the board is being compressed or tensioned? 
Positive, negative bearing...it's all the same?

David Skolnik

At 09:30 AM 2/15/2004 -0700, you wrote:
>David,
>Comments interspersed.
>
>>
>>>Could the sounding board have a negative crown (like a dish), and the 
>>>downbearing be "upbearing?" From a physical standpoint, yes. There would 
>>>be no difference in the behavior of the system, though the bridge would 
>>>peel off the sounding board pretty quickly and the design of the bridge 
>>>pins would be interesting.
>
>I agree that the design of bridge 'pins' would be interesting. However, 
>agraffes would work in this configuration.  Why would the bridge peel 
>off?  Stress level on the joint should not be that high.
>
>>>
>>>Or, in another possible configuration, could the sounding board have a 
>>>negative crown and the downbearing still exert force downward?  Again yes.
>>>(The bridge would have to be rather high.)
>
>The amount of crown (or dish) on a board is not that much.  I don't see 
>that the bridge would have to be outside the range of bridge heights that 
>you typically see.
>
>>>   The sounding board's wood would be in tension and the rim of the 
>>> sounding board would tend to be pulled away from the frame, but again 
>>> from a purely physical standpoint the system would work about like a 
>>> normal piano.  Structurally, of course, this configuration would be a 
>>> disaster, but the sounding board and strings would behave pretty much 
>>> normally if the whole works didn't peel apart.
>>>
>>>Mark Kinsler
>
>Why a disaster?  Dale Erwin has a Sohmer in his shop with exactly this 
>configuration.  It's in good shape even after several decades.
>
>>Is there general agreement that these statements are correct?  I myself 
>>find it hard to reconcile.
>>
>>David Skolnik
>
>There was an exchange about this a few months ago.  You might want to 
>check the archives.
>
>Phil Ford
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