Buttressed Arch. Question for Ron N.

[Ron Nossaman]

> Yes, better, thank you. As one guy building soundboards, I'm not sure how to
> use this info. but it helps me to understand the system. 

That's what the information is for - understanding what is, 
and more important in this case, what is not. How are you 
crowning boards, incidentally?


>IS there a force
> pushing the rim out, 

No, there is not. There is some rotational force on the belly 
rail from string downbearing because it's cantilevered, but it 
has no affect on crown.



>and is there any advantage to trying to make that rim
> immoveable, 

Absolutely. I routinely add bracing to the straight side, and 
particularly to the belly rail (mass too, here). It doesn't do 
the slightest thing for crown, but it raises the impedance of 
the rim and belly rail so it absorbs less of the soundboard's 
energy, improving tone and sustain.


>and is there a consequence to it moving with respect to the
> soundboard?

Yes, it absorbs energy that should ideally stay in the soundboard.
Ron N