soundboard stresses

Richard Brekne Richard.Brekne@grieg.uib.no
Tue, 14 Oct 2003 17:59:56 +0200


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John Hartman wrote

> >What I said is that the crowning process does not damage the panel as long
> >as it is kept within the elastic range. Your putting the ceiling at 11%
> >(witch is equivalent ot 60% RH) is exactly what I said earlier.
>
>

Given that we are dealing with 5.5 % instead of 4.5 % this either all gets
adjusted upwared to 12 %,  which pushes RH up a bit as well, Or you are looking
at a 0.8 % overall compression, which what...needs to be modified to take into
consideration the effect bending via crowning has.

I am under the impresseion that the 0.8 % compression rate is really just what
is the compression level at the interface with the rib, and that as you move
towards the top side of the panel this is significantly less... tho I dont see
yet how to figure this damage. This would seem to lower the overall damage
threshold further.... tho I am not sure yet as to how much.

Still trying to figure where Ron got 580 psi as perpendicular to grain FSPL for
Sitka when it says 710 psi in the table on page 79 of Hoadly's book. Thats
about a 20 percent increase strengthwise.

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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