rib dimensions...Ron N.

[Brian Trout]

Hi Ron,

You brought to mind a whole slew of stuff for thinkin' about again.  :-)

You ask:
How is it possible with a constant radius rib unless you taper the rib?

Now that I think about it, I never thought about whether other people are
making their ribs the same thickness from end to end (not including the
feathering, that is).  I've always made mine flat on the bottom, and crowned
on the top.  Never really thought about it too much.  It seems that it would
make the most difference in the center of the board (the section where the
ribs are longer, that is), and much less at the treble end where my thinking
says it's more critical.  If one did make the ribs the same thickness from
end to end, I guess it would be a bit ridiculous trying to find the thickest
spot.  :-)

Actually, Ron, I haven't gotten as far as you have yet on the structural
design of the ribs, and have tended towards putting things back in similar
fashion to what they were with exceptions that I probably shouldn't go into
here.  (Wouldn't want to misguide anyone...)  I hope to learn more in years
to come.  (As I write this, I'm only about 8 months into [piano related]
self employment, so much of my time is occupied in trying to develop a
business and less time than I'd like in studying / research / tinkering /
formulating / hypostulating...  but it'll happen eventually.)

A couple of things I have tried to pay attention to when making a set of
ribs are grain direction, how tight the growth rings are, whether the grain
is perfectly vertical (or how far off it is), and at what part of the
soundboard that particular piece of wood will be used.  I've mostly gotten
my soundboards from North Hudson and when I order them, I order rib stock as
well, plus maybe an extra piece or so.  One thing about rib stock, it seems
that rarely are two pieces alike.

Anyway, so here's what I usually do.  I'll lay them all out so that I can
easily see them all.  I set them so that the growth rings are vertical
(looking at the ends).  I note which of them has the tightest and most
vertical growth rings, and those are the ones that get earmarked for the
treble end.  The ones with less vertical growth rings and wider growth rings
are sent towards the bass end of the soundboard.  I lay out what ribs get
cut from what piece of wood.  That can be fun, especially when you realize
that it would have been much easier if you had ordered just one more piece
of rib stock, but you didn't.  And after they are cut to (slightly over)
length, they're just square blocks yet, I look at them from end, sort of
like a carpenter would look at the 2X12s he's using when building a floor or
a roof, looking to see if there's  a natural crown to the board.  Being sure
to maintain the growth rings in vertical fashion, I then mark them so that I
machine the crown on the side that has the most crown already, if you know
what I mean.

I don't know if any of it is exactly earth shattering, but there's just a
few of the little things that go on when I'm laying out a set of these
things.  I don't think I remember of anyone actually telling me to do these
things.  They're just things that I've come to do.  No doubt there'll be
more get added over the years.  I've heard of some people actually dropping
the rib stock to try help them decide how that piece of wood will vibrate.
(I assume a higher pitch vibration would go towards the treble, but I don't
know.)  Haven't done that one yet.

But it's all fun.  I'm happiest by nature when I'm building something.  And
I'm forever learning new stuff, some of which sits on a shelf up in the back
left hand corner of my brain and occasionally throws piano parts at me.  But
that's ok.  :-)

I gotta get back to work.

See ya,

Brian T.