More on soundboard crown

[Richard Brekne]

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Delwin D Fandrich wrote:

>           No. Compression set continues until some
>           neutrality is reached. I.e., the point at which
>           there is so little compression left within the
>           panel that in practical terms the wood fibers no
>           longer deform. At this point compression and crown
>           and stiffness will be at their minimum point.
>
>
>      RB:
>      AH !!... Thankyou... That was what I was after. So....
>      stiffness then is in a sense a function of how much
>      compression there is in the board, but if the degree of
>      compression is beyond what the wood can handle it will loose
>      both?
>
> If the degree of compression is beyond what the wood can handle--i.e.,
> it is stressed beyond its proportional limit--the wood fibers will
> crush immediately. If it is compression stressed below its
> proportional limit compression-set will work to reduce that
> compression stress slowly over some period of time. In both cases
> there will be forces at work to reduce compression, in the first
> situation it simply happens faster.
>
>
> Del
>

Thanks Del.. this clears up what I was mostly after in all this very
nicely. Double checking then... Whatever degree of compression-set has
taken place determines the boards stress limits at any time. So as more
compression set devolopes the board will have a harder time dealing with
tension when MC gets low seasonally... leading to cracks. And
compression set also lowers the panels compression stress limit... which
as seasons continue to go by exhasperate the situation. An in the
process both crown and stiffness is lost. Yes ??

I am still a bit unclear on how stiffness is related to the degree of
compression, but I suppose I can pick that up later on.

Thanks muchly...

RicB

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html


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