Yet another math question

[Dave Bagwill]

FWIW, here is something from the Fishman site:
_____________________________________________________
5 - 8 DEGREES: What about these few degrees? Well, we
think you should tilt the saddle back by this amount when-
ever you cut a saddle slot. Here's why:
a.
The backwards tilting saddle will be much better at resist-
ing the tendency of the center strings to bow to the saddle for-
ward and create a long "D" shaped saddle slot and its accom-
panying space between the back of the saddle and the back of
the slot.
b.
The pickup will "see" more downbearing force and will
sound better.
c.
As a result of better force distribution between the saddle
and bridge, the bridge will remain more stable, resist distortion
and bending, and sound more solid. (Remember Objective II?)
Even though it's more trouble and it ain't historic, etc., we're
convinced that it does really improve the pickup installation
and often, the acoustic response. Further, it's not so much
angle that it looks objectionable.
As a bonus, this technique often helps us move the string
take off point a little further back on the bridge, when needed
to help correct "folding-up-sharp" intonation.
a - ROUTING A SLOT
You will need a small plunge router to do the job. Make a
base for the router with a 5-8° angle to achieve an angled slot.
Make a routing jig to fit on top of the guitar. Cover the bottom
of the jig with a cork or rubber gasket. The jig bottom should
clamp to the guitar's edges only, and not tend to squeeze out
the belly shape in the top, thus accommodate the aforemen-
tioned screw jack. The guide for the router base must fit pre-
cisely to avoid slop in the cut. Make adjustable endstops for to

[Dave Bagwill]

Here is a jig for cutting the tilted saddle slots. I've just glanced at it, but it seems to make sense.

http://www.anzlf.com/viewtopic.php?f=24&t=1741

[Dave Bagwill]

I have not forgotten about this project, and it is one of my goals to build a fixture that allows me to tune a top to a given set of strings, in the next year.

[Dave Bagwill]

I think it was John Parchem that mentioned an approach that may have some merit for part of this.

I have a nice 000-12 cedar/mahogany that is built for fingerstyle.

Step 1 - I have sets of strings of known pull (from the D'Addario calculator page).\
Then set the instrument into a holding jig with a suspended gauge touching the top.
Start tuning the guitar incrementally and notice when the first deflection begins.
Make a note of the pitch of each string and use the calculator to determine what the total pull is at that first deflection point.
Does it deflect at the standard tuning? If so, that string set is probably just about right.
If it starts deflecting below pitch, or above pitch, calculate the string pull and then check the website for a string set that matches that pull.

That is all step 1.
Step 2 - Slacken the strings so they are not providing any pull. Begin to incrementally add weight to the bridge or wherever deflection was measured in step 1. Add weight until the first deflection point .

Think about whether the pull of the strings and the weight can be correlated. That will be the key. If I can get some kind of correlation, that will generalize for other tops that are in process, I can tune the tops by starting with the given set of strings, which has been my goal all along.

Stop me if I'm crazy!!

[John Parchem]

Sounds worth trying. Both the deflection from the strings and the deflection of the weight will follow the stiffness of the top. If you get enough information I think it gets you in the ball park for a defection test based on tuning and string tension.