Compound Fretboard Raduis

[westhemann]

That's what I was thinking when I was reading it...banjos and classical guitars.I don't know that they have flat bridges,but I figured they might.

[westhemann]

Looks flat

[Ken Bennett]

Very flat indeed, Wes.

I did some drawing, and measuring, and calculating. This is pretty interesting.

It turns out that my guess about the 10" radius nut going to a 20" radius bridge was close enough. The fretboard would go from 10" to about 17.5" (16" would probably be just fine). And this would be conical. The rate of change in the radius is linear. Checking at 5 equally spaced points along the scale, the radius changes by the same amount from point to point. See column A below.

In the case of a 12" radius at the nut going to a flat bridge such as the banjo I'm about to inlay, I estimate that the radius does not change by the same amount from point to point. The change is less near the nut and gets greater and greater as you move toward the bridge. See column B:

-----------------A-----------------B

nut................10"..................12"

5th fret..........12.5"...............18"

12th fret........15"..................32"

24th fret........17.5"...............72"

saddle...........20...................infinite(flat)

When the banjo neck arrives it will be interesting to see if the Nechville is radiused anywhere near like the numbers I came up with in column B.

Edited November 16, 2010 by Ken Bennett