Untapered Soundboard Ribs

[Delwin D Fandrich]

----- Original Message -----
From: "Phillip Ford" <fordpiano@earthlink.net>
To: <pianotech@ptg.org>
Sent: July 19, 2002 7:43 PM
Subject: Re: Untapered Soundboard Ribs


>
>
> On Fri, 19 Jul 2002 10:26:13 -0700 Delwin D Fandrich
> <pianobuilders@olynet.com> wrote:
>
>
> 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.)
>
> -----
> Isn't it true that on the SD-10 (and perhaps on the SF-10 - I'm not as
> familiar with it) the ribs aren't let-in to the rim in the traditional
sense.

Depends on what you mean by 'traditional.' It's been a long time since I've
seen rib ends actually fitted to a notch in an inner rim. This includes the
Baldwin grands. The notch is routed deeper than the rib end is thick.


>
> There is a kind of routed or milled recess or channel in the area where
the
> rib ends.  The rib does not touch the rim either on its bottom face or on
its
> side faces.  There is considerable clearance all around.  I can see that
this
> prevents a dropoff in stiffness at the rim.  Does it also prevent this
> cracking problem that you mention?

Yes.


>
> There is no reason to inlet the ribs of a laminated
> soundboard to the inner rim. There are many reasons to not do so.
>
> Del
>
> ------
> Some of which are?  I don't see what difference it makes whether the panel
is
> laminated or not.  It seems to me that if there is a desire for stiffness
at
> the rim then the ribs need to extend all the way to the rim whether the
> soundboard panel is solid or laminated.  I didn't think the point of a
> laminated board was to get more panel stiffness than you get with a solid
> board.  I assumed you would shoot for equivalent stiffness to a solid
board
> and would get the assembly stiffness the same way you do with a solid
board,
> with the ribs.

Laminated soundboards are considerably stiffer across-grain. The rib
extending into the inner rib adds to the overall stiffness. If this is
desired, all is well and good. However, most (if not all) laminated
soundboard panels found in pianos today are used as direct replacements for
so-called 'solid' boards. Generally the laminated soundboard panel ends up
overly stiff around the parameter. Since there is not need to protect them
from cracking there is no practical benifit to extending the rib into a
notch in the inner rim.

Del