Soundboard Evaluation

[Richard Brekne]

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Delwin D Fandrich wrote:

>      4 The across grain compression strength  that maintains
>      crown in compression crowned boards is inherently weak
>      and will dissipate over time. (relatively short ??)
>      (regardless of such factors like such as climate ??)
>
> Yes. It is both time and stress dependent. The more compression
> stress the wood fibers are under, the faster the resulting
> compression-set will occur. The longer the wood fibers are under
> compression, the more they will be permanently deformed.
> This is climate dependent to the degree that during dry periods
> moisture will be drawn from the wood fibers and the panel's
> internal compression will decrease. During humid periods the wood
> fibers will absorb moisture, try to swell, and the panel's
> internal compression will increase.
>
>

Does this mean that the a compression soundboard assembly can hold
crown as  long as RH is held at high enough levels to sustain
internal compression ? Or do you mean to say that the assembly fail
anyways...perhaps more slowly. ?

>      I am not quite sure why a compression board is said to
>      be "damaged" (fiber compression damage) when in essence
>      this damage is meaningless in as much as all one has to
>      do is re-rib and reconfigure for a rib crowned assembly.
>

As you and Ron both make the same very valid points here, I dont
need to go further then to say that that subject matter, important
as it is in itself is another matter. Certainly in that perspective
the assembly failing due this kind of damage has meaning..and lots
of it... no one is going to argue that point me thinks..


One other thing... you mentioned somewhere along the line I
believe,  and I think Ron has echoed this in another thread a while
back... that in a best case scenario for a compression board... the
sound can be in some sense better or more powerfull... or something
of this nature then in a non compression board..... but that that is
of little use because it is so short lived amoung other reasons...
or have I mis-understood you here.?



--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no


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