Butt-Jointed Ribs

[Delwin D Fandrich]

----- Original Message -----
From: "Farrell" <mfarrel2@tampabay.rr.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: November 22, 2002 6:37 PM
Subject: Re: Butt-Jointed Ribs


> Del responded:
> > 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!)
>
> Well yes, but that is commonly used on either a hull plank that is a
single thickness, or perhaps a spar that is made up of two halves. Here we
are talking about a laminated product. My thinking (guessing) is that
burying the a lamination butt joint within several laminations might just
make it unnoticeable.  And if it were noticable, maybe just a low ratio
scarf would take care of it (make it unnoticable).

I only said that because so much of early piano construction came from the
wooden boatbuilding industry of the day.


>
> You have used it with a 4:1 scarf where? You say you would not want to use
it next to the soundboard - as in scarfing or butt jointing a lamination on
a rib? Just curious.

Yes, I was talking about laminated ribs. I like a continuous strip of wood
next to the soundboard -- one with no scarf joints at all. This is where
most of the tensile stress is. If I were butt jointing a solid rib I would
prefer to use a good finger joint or at least an 8:1 or 12:1 slope. There
can be a lot of steady-state tension up there.

Del