Butt-Jointed Ribs

[Delwin D Fandrich]

----- Original Message -----
From: "Farrell" <mfarrel2@tampabay.rr.com>
To: <pianotech@ptg.org>
Sent: November 22, 2002 4:45 AM
Subject: Butt-Jointed Ribs


> Del either posted recently, or I read it the other day in one of his
Journal articles (that I was reading for the umpteenth time) that some piano
manufacturer somewhere had apparently successfully finger jointed short
pieces of spruce together to make up a rib. Obviously a great use for short
pieces of expensive spruce.

It was Kawai. And a good idea well executed from those I saw.


>
> If ribs are laminated, let's say with four to eight laminations, I wonder
what would be the effects of making all the rib laminations out of two
butt-jointed pieces, and spreading the butt joints evenly (or
preferentially) over the length of the rib.

No effect if done right. Well, it better utilizes wood which is a good
effect, environmentally, but --all other things being equal -- there is no
discernable audible difference.


>
> Has anyone tried this? Is a thicker rib required to compensate for any
weakness induced by the multi-segmented laminations? And if so, would
scarfing the lamination butt joint effectively eliminate that weakness? What
ratio of scarf?

Yes. No. Ideally, the slope of the scarf should be between 8:1 and 12:1
(Come on, Terry, you know about wooden boat -- you should know this!)
depending on the wood. In practice we have used something closer to 4:1 with
no problems and less waste. We do not use scarfed wood generally -- we don't
need to -- and I would not want to use it next to the soundboard in any case
(it's under the most tension). Everywhere else it's fair game and I expect
eventually well be doing it on a regular basis.


>
> I think I just dug a hole for myself. Here, I'll save everyone the trouble
of responding:
>
> Terry,
> Please go ahead and field test the idea and report back to list with
results.
> Thanks.


Well, yes, there is always that approach. What a unique concept.

Regards,

Del