Soundboard contruction methods

[Ron Nossaman]

> I don't know how you would "bend a curve" into a rib except by steaming 
> it and thus straining the structure and I can't imagine anyone going 
> about it that way, so I have little doubt that Hamburgs ribs are planed 
> to a crown just as most people's if Hartwig is to be taken at his word.

I've had people describe flat ribs being pressed into a curved 
caul with the panel on assembly as being curved ribs. It is my 
understanding that the Hamburg Steinways have crowned, not 
bent, ribs.


>> Yes. Panel compression is also commonly achieved or increased by 
>> pressing the assembly into a curved caul as the ribs are glued on.
> 
> Well, that is not the compression that is most significant!  

No, it's not, but pressing the assembly into a caul more 
deeply dished than the rib will, when it's taken out, result 
in panel compression levels greater than expected from just 
the MC difference. A compression supported board can be built 
with little to no drying of the panel by this means if the 
ribs can be forced into a tight enough radius caul.


> Now to use the local neologism of "rib-crowned" for such an assembly, no 
> matter how it may have caught on, strikes me as either misleading or 
> just plain meaningless.  

It didn't "catch on". It's descriptive of the process.


>The term suggests that the board is crowned by 
> the ribs, which is not the case at all, 

It is precisely the case.


>and the contrasting of "RC" with 
> "CC" leads one to suppose that compression is not present in a 
> "rib-crowned" board, when in fact compression is the principal factor in 
> the development and maintenance of the crown and the crowning of the 
> ribs is carried out simply to prevent the ribs from straining to pull 
> down the naturally-formed crown to no purpose.

Only if you can't conceive of a board crowned without panel 
compression. A rib crowned board relies on panel compression 
to some degree support crown, but crown would be formed with 
no panel compression at all by the crown in the rib. Read the 
definitions again.


> I understand.  Now, while my own personal hobby-horse is that all that 
> matters in a soundboard is the ratio of stiffness to mass; 

And spring recovery rate. Yes, as far as initial performance 
goes. What we're trying to do with RC&S is to build boards 
that work now, and won't fail structurally later in adverse 
climate conditions like the high compression boards do.


> That is not to say that either compression or crown are necessary for a 
> good soundboard -- 

There's no good reason I've seen that both can't be dispensed 
with, given an alternative to the required stiffness and 
spring rate. This is a different subject.


>but for a board without either, spruce is not the 
> right stuff.

Which is an entirely different subject.
Ron N