Butt-Jointed Ribs

[Farrell]

I had written:
> > 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?

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).

Del, said further:
> 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...

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.

Terry Farrell
  
----- Original Message ----- 
From: "Delwin D Fandrich" <pianobuilders@olynet.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Friday, November 22, 2002 12:11 PM
Subject: Re: Butt-Jointed Ribs


> 
> ----- 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
> 
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