Why do we need crown?

[Erwinspiano at aol.com]

Howdy Mr. Bill:


Seems to me that the only reason we're worrying about  adequate  
downbearing support against the string load or a board  panel which is  
flat to begin with, is the fear that the downbearing  of the strings  
(being borne up into by the bridge height) would push  the panel  
through flat into a negative crown. But wouldn't  the string plane  
only push the board until the string plane itself  flattened out?.
  Yes ! Of course



I'm guessing that negative crown with negative bearing would  produce  
the same pair of opposing springs (board panel plus string  plane)  
that we all grew up calling home, with positive crown and  positive  
downbearing. You'd enjoy the same mechanical advantage  either way.  
(You'd just have to toss out bridge pins as a coupling  mechanism.)
  Seems right


Ladies and Gentlemen, over in this corner, wearing the purple   
shorts, we have...." a no crown no bearing piano that works, but   
still sounds somewhat different than we're used to, which isn't   
necessarily bad........

.........but not something I'd bet on when  it goes up against  the  
reigning champ, a crowned board  ("Spring'o'Spruce™") with appropriate  
bearing.
  Yes I agree.  I once tuned a miserable 9 ft  kawai that never really had 
any fire in the tone .  Then one day, when I  had time to kill ,I checked the 
bearing with a lowell gage .  ZIp, nada  nothing.  I used a crown string to look 
at bearing.. Massive Crown.   No bearing.  Moral of story.  The car looks 
good but there is no gas  in the tank .  The same is true of springy spruce with 
no bearing.   Looks good but it doesn't go very far.
  Dale





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