Buttressed Arch. Question for Ron N.

[Fenton Murray]

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. IS there a force
pushing the rim out, and is there any advantage to trying to make that rim
immoveable, and is there a consequence to it moving with respect to the
soundboard?
----- Original Message ----- 
From: "Ron Nossaman" <rnossaman at cox.net>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Friday, April 14, 2006 9:28 AM
Subject: Re: Buttressed Arch. Question for Ron N.


>
> > I don't KNOW, Ron. But if you keep talking I'll shut up and listen. If
my
> > brain were as flexible as Sitka, I'd be fine.
> > Thanks,
> > Fenton
>
>
> When you bend a piece of wood (rib), the fibers on the convex
> outside of the bend are stretched, and the fibers on the
> concave inside of the bend are compressed. So if you glue an
> expanding panel on one side of that piece of wood (rib), it
> will stretch the rib's fibers at the glue joint as it expands,
> bending the rib. Bending the rib stretches the fibers on the
> outside of the curve (top), and stretching the fibers on the
> top face of the rib causes the rib to bend and increase crown.
> It's that simple, and has not a thing to do with an arch. The
> panel will still rise and fall with humidity swings because
> the compression level in the panel changes with it's moisture
> content, and the resulting degree to which it stretches the
> top side of the rib changes with it, changing the crown rise
> as a result. Still no arch involved, it's a self contained
> leverage that works without end buttresses.
>
> Better?
> Ron N
>
>