Untapered Soundboard Ribs

[Ron Nossaman]

>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 board is held more than adequately to the rim either way. Not a 
practical issue. Morticing the ribs in does add a little stiffness, raising 
impedance, but just making the ribs a little taller will do that. You do 
get a better diaphragm effect (or at least more flexibility at the panel 
perimeter) with floating ribs, with the possibility of panel cracks at the 
inside curve where the panel joins the rim. Unless, of course, you have a 
laminated panel.


>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

While I'm not even a little bit convinced that fitting notches to the ribs 
is nearly as important acoustically as is generally assumed, they do make a 
nice tooling index for getting the soundboard back where you had it when 
you located the bridges. That can be done other ways though, with less 
trouble than morticing the rim..




>>Hi Dale,
>>
>>This is another one of those "please explain" threads with no proven answers.
>>
>>Whilst I was in China I went to a City called Yenti ?. there was a piano 
>>manufacturer there that was making upright pianos based on the Kawai 
>>piano. Now these pianos had soundboards with tapered ribs but,  the ribs 
>>ended about 1" before the rim and was terminated by a screw through the 
>>soundboard, rib and into a holding block of wood.

It's not that unusual, though the screw and backing block shouldn't be 
necessary if the glue works.


>>This meant that the board was fixed at its outer edge only by the board 
>>itself.

Yep.


>>To me this is getting into the radio speaker method with a freer edge to 
>>allow the board to be more sympathetic to the strings vibrations.

That's the idea, less internal friction loss compared to the clamped end ribs.


>>All my work in China was done through interpreters so I may have some 
>>miss information but I saw the soundboard with my own eyes.
>>
>>Regards
>>
>>Tony


Ron N