Killer Octave Question

[Ron Nossaman]

>>Solid, why?
>
>I just wasn't used to hearing that a long bridge of maple was that floppy, 
>and thought that the difference in stiffness between vertically laminated 
>and solid might account for your testimony.

Well, I see I've failed again to get the point across. The bridge isn't 
floppy. It's curved. Like Terry's illustration of a piece of flat cardboard 
with a hole cut in it and placed over a basketball. The curved edge of the 
hole in the flat cardboard touches the domed basketball all the way around. 
The cardboard doesn't have to be crowned, and a curved bridge doesn't 
either - nor droopy, to fit a crowned board. It fits because it's curved. 
Not floppy, not crowned - curved.


>>Dozens, not hundreds.
>
>I'll take your word for it. My condolences to the owners (if they've notice).

Most don't, and still have no clue.


>On the surface this was a joke.

That's how I took it. I almost asked how many times it had happened to you, 
and were you able to fix it, but I stopped just in time.


>The rest of the paragraph did confirm that you've run into good Steinways 
>as well.

Of course. How could I not? When they're nice, they can be very nice. And 
so many more of them could be very nice if only...


>The Steinways at the dealer just up the river from me aren't very 
>compelling to me or my customers. I've always assumed that whatever could 
>be made of these pianos would be "after-market voicing", but I certainly 
>would have learned a great deal, as you did, checking bearing at various 
>points on these boards.

You very likely would, as well as the futility of trying to voice those 
boards that were concave and that bearing that was negative, into the piano 
of your customers' dreams.


>Don't mind me. I've just had to run another sacred cow through the meat 
>grinder. I going to have to turn the bulk of it into patties and go 
>through it, burger by burger, over the month six months. Regardless of 
>Terry's bald dome sticking through his topless hat, the only curvature 
>which the ribs provide is perpendicular to the board and bridges. Any 
>curvature in the board parallel to the grain and bridges would seem only 
>to come from a special shaping of the belly rail and the rasten. That 
>shaping that would seem to be an even trickier piece of wood-working (its 
>pattern having come from the intersection of a paper "doughnut, whose hole 
>was shaped more like a piano rim than a circle).

Don't put the grinder away just yet, and get another package of buns out of 
the freezer. Question: How is it physically possible to have crown in all 
the ribs perpendicular (or thereabouts) to the panel grain, with the  board 
glued to what is nominally a plane surface around the perimeter, without 
forming crown along the grain? Answer: I can't imagine how it would be. If 
the center of the board is higher then the edges across the grain, it 
pretty much has to be higher in the middle along the grain too. Installing 
a ribbed soundboard, you have to MAKE the left rear and right front of the 
board go down on the rim and belly bar. They resist this procedure, and 
forcing them down will slightly reduce the cross grain crown. But that's 
how it works.


>It would seem to me that the ribs, and the crown they provided, would be 
>all the support for the string load the board would need. Any crown 
>parallel to the board grain and bridges, with the panel out of the rim, 
>would seem to be spurious and inconsequential, all the more so because at 
>the end of the day, crown in that direction has nothing to do with any 
>belly work, but simply the shape of the rim.

Nope, it's simply the shape of crown formed by the ribs. It's a 
consequence, not a design feature. And you're right, it's the ribs, or 
panel compression cross grain in compression crowned boards, that support 
bearing. That is, if anything does. And as long as there's positive crown 
along the ribs, there will be crown along the panel grain.


>So apparently it doesn't matter that when a poorly mated bridge bottom and 
>soundboard top are glued together, the resultant joint will have an 
>inherent stress. (The stronger of the two springs will bend the other.) 
>But this is nothing which crowned ribs aren't doing to the board 
>perpendicular to the grain. And it if did matter, correcting it would 
>require that extra step of fitting not just the bridge to the board, but 
>the rasten to the resultant board curvature around its perimeter. In both 
>cases, not just extra hours, but stock removal which cut put the rest of 
>the belly process at risk.

That will get it, except that a flat bridge and crowned soundboard aren't 
particularly poorly mated. They're a lot closer than you're probably 
picturing. Oh, and all the much feared stressing is accommodated by the 
spruce very quickly and becomes no stress of any consequence.


>Let me know if i have to write something on the board 100 times, but don't 
>ask me to eat more that ten burgers a day. <g>
>
>Bill Ballard RPT

Uh-oh, too late. Got milk?

Ron N