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