[pianotech] Downbearing

[Gene Nelson]

>
> It's very mystic. Get yourself some Henbane, a small round rock, and a 
> toad... No, wait, that's something else. Ok, here's the deal. A bridge 
> with the top parallel to the bottom, strangely as if it had passed through 
> a planer, sitting more or less centered on a line of crowned ribs, will 
> make the bridge top close to parallel to a line from agraffe to hitch, 
> which will get you positive bearing on both front and back of the bridge. 
> Where the comparison of these angles ends up depends on the final net 
> downbearing angle, and how much it has deflected the board.
> Ron N
I am curious about how you would apply this reasoning in the treble section 
of a RC board.
If your bridge is set to the apex of the radius cut into the rib, I have 
found that it is not possible to get the bridge to align with the apex of 
the radius cut into the top few ribs starting in the upper tenor 
section(that is unless you want to change this apex rib line dramatically). 
The bridge will not move straight down when load is applied - moves more at 
an angle toward the capo .
Is a bit of guess work needed here to avoid loosing front bearing?
Is is safe enough to plane the bridge in this area based on the sample 
notches cut when setting bearing (same as the other sections of the piano 
where this is not an issue) and always end up with positive front bearing?
Gene