Soundboard thoughts / questions

[Stéphane Collin]

Hi Ric.

I am now working on a 1853 Pleyel which ressembles what you say, apart from 
the laminated board.
The soundboard grain runs roughly perpendicular to the bridge.
The bridge is in one piece, with a huge cantilever in the bass.
There are 8 ribs running roughly 30° to the grain of the board, thinner in 
bass side and in trebble side, thicker in medium scale.
Interesting, there is one cutoff bar in the usual position and fixed to the 
rim, and one more rib parallel to that cutoff bar, not fixed to the rim, and 
forming an X shape with the other ribs, positionned half way from the cutoff 
bar to the foot of the cantilever of the bridge.
Floating bass.
The belly is arched so to form a crown.
The scaling is low tensionned.  Overall tension not above 11.000 kg.
Tapping the board shows that it clearly sounds best where the bridge foot 
lies.
The piano sounds great.
One more bizarre thing : it has a pure pythagorean scaling from D3 up to A8, 
with octaves length in a true 2 ratio.  Never seen this elsewhere.

Do you want to get the grain perpendicular to bridge desing back ?

Best regards.

Stéphane Collin.

----- Original Message ----- 
From: "Ric Brekne" <ricbrek at broadpark.no>
To: "pianotech" <pianotech at ptg.org>
Sent: Sunday, April 02, 2006 6:29 PM
Subject: Soundboard thoughts / questions


> Hi folks.
>
> Please correct my thinking where dead wrong.
> -- Load support for soundboards needs to run (roughly) perpendicular to 
> the bridges.
>
> -- Given a low enough tensioned scale,  this could be accomplished by 
> running the grain of the soundboard (roughly) perpendicular to the 
> bridges. Especially if that soundboard was laminated crowned in that 
> direction.
>
> Questions relating to the above:
>
> -- How do you calculate load bearing strength of such a laminated board ? 
> Any straight forward formulas ?
>
> -- What would be the needs and purposes for ribbing this kind of board 
> across the grain ?
>
> Perhaps this all sounds a bit off the wall... but I would apreciate any 
> thoughtfull answers.
>
> Thanks
> RicB
>
>
>
>
>