Curve on Bridge Bottom

[Farrell]

Ok, now for a serious response, aside from thinking clamps   ;-).  

Align your rib clamps on a table, with all the centers along a line. You can put your board in there and glue on your ribs as is.

An alternative is to look at that and say, yeah, but my bridge line squiggles. So to compensate, you move a few of the clamps this way and that way so that the lowest point (ribs/panel put into clamps up-side-down) in the cauls now follows the horizontal long bridge line. Yes! This will make for a better bridge-to-crown-apex alignment!

Maybe not.

Glue in your ribs with this clamp arrangement, and glue on your bridge. Picture what you have done to the ribs that are in the area of the tenor/treble break - they go from the curved side of the case to the forward bass corner. You would have moved these clamps toward the forward bass corner of the board, and that would leave that rib end up a little higher - great! That way the rib end will set on the inner rim more willingly. But I suspect what will actually happen is that when you take the clamp off, the panel will simply cause the rib to rotate end-to-end. The rib end at the forward bass corner will go down and the rib end against the middle of the curved treble area would rotate up. I think you will end up with the board just the same as if you had left the clamps in a straight line.

Now when you go to put the board in the piano you will find that as you squish the board onto the inner rim, you will note that the forward bass rib ends need to go up, and the ends along the curved side of the rim need to go down.

I'm writing this and curves and rotations and moving clamps are swirling all through my head. I don't know that anything I have said makes any sense or has any merit. Too much bending wood here. I have sent this post however, perhaps just as a statement of how complex trying to understand all the dynamics of curved ribs and flat panels and bent panels and curved bridge bottoms and curved inner rims, rotating bridges, rotating ribs, etc., etc., are. Yikes! I think I need to finish my clamps and get some spruce and start cutting and gluing and observing!

Maybe the bottom line is: Do it! Shut up! Don't worry about it! And see how it turns out. If it is bad, do something different next time.

Maybe I got too much think in my clamp.  :-)

Terry Farrell
  
----- Original Message ----- 
From: "Greg Newell" <gnewell@ameritech.net>
To: <pianotech@ptg.org>
Sent: Sunday, May 05, 2002 2:30 AM
Subject: Re: Curve on Bridge Bottom


> 
> Terry,
>          Could you please explain this a little more. I can't visualize 
> what you mean.
> 
> Greg
> 
> 
> At 09:29 PM 5/4/2002, you wrote:
> >"wouldn't all the ribs just rotate end-to-end and even out after you take 
> >the think out of clamps"
> 
>