Soundboard 60-ft. Arc

[Greg Newell]

---------------------- multipart/alternative attachment
Ron,
    Would you care to describe your method of rib crowning a board for me? Also
could you suggest some reading I could do on the subject? (I don't have the
Journal index on CD) I'm curious to know what I'll be needing. Since I'm heading
to a woodworker show this weekend it might be a good idea to have an idea of what
faces me in the weeks ahead. THANKS!!!


Greg

Ron Nossaman wrote:

> > On a five-foot span I get 0.63 inches of crown.
> >This seems excessive (isn't an unstressed new board supposed to have about
> >1/4" - 3/8" of crown in the middle?).
>
> Your crown height for 60' radius is right by my figures, but how long a rib
> do you plan on having in a piano? That's what cutoff bars are for. The
> compression crowned boards ended up averaging about XX crown at XX length
> (varying widely with material choice and methods) as a consequence of the
> crowning process rather than a design criteria. With rib crowning, you are
> granted the opportunity to make your own decision and build to a much
> closer spec. It's supposed to be whatever you find works to your
> satisfaction with all the other dozens of factors considered in your
> soundboard design, string scaling, bridge configuration, loading, etc. Nor
> is it particularly necessary or (to some builders) desirable to have the
> same crown radius throughout the rib scale.
>
> >Or is it that on the rib-crowned
> >board, you cut the rib to the aforementioned arc, glue it to the board in a
> >caul of the same arc, and when removed from the caul the naturally flat
> >board help the assembly to straighten out a bit to where it has the
> >"?normal?" 1/4" - 3/8" of crown?
>
> Panels are still dried down before assembly in a rib crowned board, just
> not as much as with compression crowning, so the panel is still under some
> compression, and still helps support crown rather than dragging it back down.
>
> >Am I making a boo-boo somehow with my drawing?
> >
> >Terry Farrell
>
> Nope, but there are a few assumptions behind it that you need to decide
> whether or not to accept. <G>
>
> Ron N

--
Greg Newell
mailto:gnewell@ameritech.net


---------------------- multipart/alternative attachment
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/pianotech.php/attachments/66/16/3f/58/attachment.htm

---------------------- multipart/alternative attachment--