Untapered Soundboard Ribs

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Erwinspiano@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: July 19, 2002 8:22 AM
  Subject: Re: Untapered Soundboard Ribs


  In a message dated 7/19/2002 7:18:05 AM Pacific Daylight Time, =
caute@optusnet.com.au writes:



    Subj:Re: Untapered Soundboard Ribs=20
    Date:7/19/2002 7:18:05 AM Pacific Daylight Time
    From:caute@optusnet.com.au
    Reply-to:pianotech@ptg.org
    To:pianotech@ptg.org
    Sent from the Internet=20

           Hi Tony


        Thanks for the post. Interesting trip?  I don't think this all =
that new. I've seen Baldwin L grands with the same deal. It might be a =
Del Fandrich idea but I'm not speaking for him of course.  Actually when =
you think about it that little piece of thin rib that goes into the =
liner is only a small part of the equation as far as the strentgh needed =
to hold the board on the rim. The glue is doing 95% of .the work. Radio =
speaker thing and labor saving method. No fitting notches to the rib and =
the board can float a bit during installation hhm not good.
             Dale

No, this was Baldwin practice before I got there. The only problem with =
this practice was found along the inside curve on the treble side where =
the soundboard grain angle roughly paralleled the inner rim--there was a =
propensity toward soundboard cracks just inside the inner rim. That is, =
between the end of the ribs and the inner rim.=20

The practice of inletting the ribs to the inner rim is a holdover from =
the animal hide glue days. If the glue wasn't kept fresh and used =
properly--very difficult to do in high production--they tended to pop =
off as the glue aged and turned brittle. Originally the ends of the ribs =
were fitted so that the thickness of the feather was exactly the =
thickness of the notch in the inner rim. In other words, the rib would =
be glued to the soundboard and clamped between it and the bottom of the =
notch where it would also be glued. A practice rarely seen today. These =
days the notches are most often routed in to a depth that will easily =
clear the rib and the rib does not actually touch the bottom of the =
notch.=20

The practice does add stiffness to the soundboard system which, in some =
cases may be desirable. I designed the Walter 190 soundboard such that =
the top seven ribs (toward the treble) were set into to notches both =
because I wanted the additional stiffness and to avoid the cracking =
problem the Baldwin M, R and L models were having. (The SF-10 and SD-10 =
ribs were fully inlet to notches.) The rest of the ribs I floated =
because I did not want the added parameter stiffness.=20

I've always puzzled over the practice of thinning part or all of the =
outside parameter of a soundboard and then running a bunch of ribs over =
the thinned portion and onto the inner rim. Only Marketing Logic can =
explain the thinking behind that practice.

There is no reason to inlet the ribs of a laminated soundboard to the =
inner rim. There are many reasons to not do so.

Re: your last comment:  Only the glue between the soundboard and the =
inner rim/soundboard liner is holding the soundboard to the inner rim. =
It's doing 100% of the work. The notch in the inner rim/soundboard liner =
is only detracting from there being a continuous glue bond holding the =
soundboard to the inner rim.=20

Del

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