Elevated fretboard geometry

[KingCavalier]

Hi all,

I’m trying to understand the geometry of the elevated fretboard. Below is a sketch I did with three possible scenarios. The top sketch is based on a standard steel string acoustic where the body depth at the neck and end block is measured from the top. The center drawing shows the body depth is split equally from a center line. The bottom shows the body depth reversed from standard where the depth is measured from the back. I didn’t include the scenario where the top is angled down in the upper bout like Thomas Humphrey, I wanted to start here first.

The neck angle (or lack thereof) is parallel to the red reference line in all three drawings. That line is also parallel to the top, center or back respective to each drawing and 90 degrees to the sides.

Hope this makes sense.

Any help would be greatly appreciated.

SA

[Frankieabbott]

Hello King Cavalier. Fretboard geometry. Important issues going on here. As long as the guitar plays well on the first 5 frets...up to the 12th fret..or further. Take your pick. Neck angle. Hardly anyone measures it but it's a vital component to a guitars overall ease of playing. Or, at the worst case scenario, being unplayable. I like all things neck break angle related.......but can I suggest that you visit The Tundra Man Workshop for all things necks and angles.

[Howard Klepper]

It took me a minute to get what you are talking about, since the body depth is the same whether you measure it top to back or back to top.

You are talking about whether the top or back is perpendicular to the sides in #1 and #3, while neither are in #2. Another way of talking about this is which side--top or back--has the body taper.

I build as in #3, with all the taper on the top side. Then I set the neck square to the body. The thickness of the neck extension is the drop in thickness from the bridge to the neck plus about 1/8", so that with a 1/4" fretboard, the fret tops are pointing at the top of a 3/8" bridge.

You could do it the other ways, but you would have to give the neck a negative set relative to the sides in #1, and probably also in #2, although that could work with a very small elevation of the fretboard extension. If you set the neck parallel to the red line in #1, you would need too tall a bridge. Same with #2, if you had a tall rise in the fretboard extension. Think standard bridge thickness when you do this. A lot of people refer to the neck set as relative to the top, in which case anytime you elevate the fretboard extension you have a negative neck set. For my own thinking, I find it easier to use the sides at the block as my reference for what is positive or negative set, since that will tell me how to cut the joining face at the heel.

Hope this helps. It's a fairly complex thing to visualize.