[pianotech] rcs design considerations

[Dale Erwin]

Gene
  Here's a clue...I known that when I thin Yamaha boards (ie C-7s .390 ish) at there perimeters the sound becomes more lively, more sustain and a brighter spectrum. These have a mahogany rim. Softer than maple denser than some other woods known to be used.
  Those thick tight grain boards can really make them stingy so reducing the board mass helps them sing more freely.  I've done this a few times and witnessed the improvement. I believe the thick board is part of the... I can ship them any where, to any climate and they will hold up strategy. They are coated in thick Polyu. too

 

 

Dale S. Erwin
www.Erwinspiano.com
Ronsen Piano hammers
Sales,custom prep and tech support
209-577-8397
209-985-0990

 

 

-----Original Message-----
From: Gene Nelson <nelsong at intune88.com>
To: pianotech at ptg.org
Sent: Fri, Aug 6, 2010 9:51 pm
Subject: Re: [pianotech] rcs design considerations


Thanks so much for the replies. Yes Dale, I am a bit confused. 
The piano is an 1880's Hallet and Davis 8'9" 
The belly bracing is substantial with several beams crossing eachother as they go in two directions. I do not think stiffness is an issue within the limits of the softwood it is made with so low mass or low impedence would be the issue. 
It sounds like if I increase the rim impedence then a board design can lean toward the typical board desing that I am familiar with. If I do not then a thicker board and shallower grain angle relative to the belly rail would be reasonable? 
The thicker board is always counterintuitive to me for this reason: Strings displace the board assembly and it is the ribs that respond by returning to their original position. If a board is thicker it is more massive and would cause the assembly to return slower, making the lower firquencies more predominate. But we tend to thin the board in the bass. 
The 12 foot piano in southern california has a 12.5mm board and David has a difficult time getting higher partials. 
My scale is yet to be determined and I will be making a new bridge so I just do not know where the tension will be yet. 
Gene 
----- Original Message ----- From: "Ron Nossaman" <rnossaman at cox.net> 
To: <pianotech at ptg.org> 
Sent: Thursday, August 05, 2010 8:49 AM 
Subject: Re: [pianotech] rcs design considerations 
 
David Love wrote: 
>  Ron mentioned beefing up the rim which in effect then changes the rim > mass in order to be able to use what would be the same basic design. 
 
Both mass and stiffness. This is most critical in the top half 
of the scale, where the higher frequencies produced need a 
high impedance boundary. By the time you've added a big cutoff 
bar, a fish, and belly rail bracing and mass, you've 
essentially replaced the top half of the soundboard perimeter 
with high impedance material and can design accordingly 
without needing new sets of rules. 
 
> That’s another approach.  I think the question though is given a soft wood > rim without altering the mass what changes must be made to accommodate the > difference. 
 
Mass wasn't mentioned in the original question, but building 
with a lower density softer material will also decrease mass. 
 
Ron N 
 
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