Soundboard Evaluation

[Farrell]

I quackulate just about 1.5 mm. I guess this would all work out. If the board had 1.5 mm of crown in the middle (or perhaps a bit more assuming they dried the board down a bit prior to ribbing - so maybe 2 or even 3 mm or so), then perhaps it had 1 or 1.5 mm of crown after stringing and had the positive bearing indicated below, and now it has sagged down a bit. I realize we cannot say with any certainty what exactly has happened, but this would seem logical???

Is that what Baldwin used - 72-foot radius ribs over the whole soundboard? Did they dry the board down pretty far to get a fair bit of compression crown?

Thanks very much for your input on this Ron.

Terry Farrell
  
----- Original Message ----- 
From: "Ron Nossaman" <RNossaman@KSCABLE.com>
To: <pianotech@ptg.org>
Sent: Sunday, June 02, 2002 12:19 AM
Subject: Re: Soundboard Evaluation


>Well, let's push the board up 1mm. At note E4, the back scale would go from 
>a  -2/3° angle to a +2/3° angle, and the front angle would go from a +1/6° 
>angle to about +1/4° (I'm just guessing at a 2-inch back scale and a 20-inch 
>front scale). I hope I have done my math correctly (I actually had quite a 
>bit of advanced math in college, but, well, er, a, some of it has slipped on 
>by). 
>That seems like a lot of change for a tiny bit of soundboard movement. 
>But I do see your point. It doesn't have to roll to produce negative back 
>bearing with positive front bearing. Interesting. Thanks.
>
>Terry Farrell

That looks pretty close. And yes, the stuff does evaporate out of old brain
cells. All of them, near as I can tell, but then how could I tell? It does
seem like a lot of angular change for a small vertical movement, but how
far does a 72' (22M) radius crowned rib of 508mm (20") have to be pushed
down to be flat on top?


Ron N