Killer Octave Question

[Bill Ballard]

At 10:06 PM -0400 4/10/03, A440A@aol.com wrote:
>   I know that someone has done the math on this.  How much "spread" is
>required of a rib that is 20 inches long, curved on a radius of say 40' to
>allow the center to drop .020"???  It has been too long since I dragged my
>kids through high school geometry to remember arc and such, but I know
>somebody out there has the answer at hand.

I seem to  remember that ten years ago, Chris Robinson did this on a 
large piano  rim, not a piece of paper. He had a fresh board, not yet 
strung, with 1/8" of crown, and placed a jack between the two sides 
of the inner rim. He spread the rim and watch with a dial indicator 
as the crown got pulled flat.

If I remember rightly, the rim didn't need to spread more than 0.01" 
to flatten the crown. 1/100" might make on worry the soundboard 
crowns were riding on very thin ice, but that's before 18 tons of 
string tension starts pulling in the other direction.  Hopefully his 
Alzheimer's isn't as advanced as mine, and someone can get the answer 
out of him.

Bill Ballard RPT
NH Chapter, P.T.G.

"When writing a mental note, first procure a mental piece of paper"
     ............mental graffitti
+++++++++++++++++++++