Compression ridges was :Do you dry the ribs, along with the board, prior to gluing ?

[Dean May]

>>Where's the analog in a piano if the bass 
soundboard is stiff?

The analog is either the tapering of the panel near the edges, tapering the
ribs near the rim, routing a groove around the perimeter, or floating it, or
perhaps some other yet unknown process.


Dean

Dean May             cell 812.239.3359 

PianoRebuilders.com   812.235.5272 

Terre Haute IN  47802

 


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Saturday, February 02, 2008 10:47 PM
To: Pianotech List
Subject: Re: Compression ridges was :Do you dry the ribs, along with the
board,prior to gluing ?



> If I consider a woofer speaker, it is designed to be very rigid/stiff to
> produce a large area pressure pulse without deflecting/deforming the cone,
> otherwise the pressure pulse would disintegrate. The cone is also very low
> mass so that it can accelerate quickly back and forth with large
amplitudes.
> It is very flexible around the edges but not the cone. 

The cone is stiff, so it won't deform into chaos, but it's 
perimeter is pleated so the entire cone can move easily at 
large amplitude. Where's the analog in a piano if the bass 
soundboard is stiff? The bridge cantilever is a feeble attempt 
that doesn't really work, where floating the tail is a fair 
comparison.


> This is what I would like to see a little clarification on. You and others
> speak of the need for increased flexibility in the bass section. When you
> say you need increased flexibility in the bass for amplitude of movement,
> aren't you really saying you need the flexibility around the edges, or
even
> a floated edge? The panel itself needs to remain rigid or stiff, but for
it
> to move it has to be able to give around the perimeter. 

Of course. You don't have much choice on whether the panel is 
stiff or not. It'll be fairly stiff (along the grain) whatever 
you do. In a big board, the bridge is far enough from the tail 
that the panel has adequate flexibility. In a small piano, 
separating the panel from the rim in the tail supplies it. 
Cross grain, the ribs will be designed to accommodate the 
differences and supply a balance of support and flexibility as 
is needed and possible.
Ron N