I’ve seen several videos where builders have set up the action, on their cbgs using a long straight metal edge resting on the nut, several thicknesses of coins, low down the neck, to determine the height of the bridge. However this is done before the strings are added. I’m left wondering how do they take into account the bending of the neck when the string tension is applied? I’ve built 4 instruments and they’ve all bowed, under tension, and the thickest neck is 35mm.
Do you tune high or maybe you need reinforcement? Really the moment you cut out the section that goes under the lid, you create an opportunity for bowing. If you reinforce this area from the bottom, you won’t have so much bowing?
Hi, you are correct about setting the action height, movement of the neck and the top are considerations when setting action. So it’s best to do the final setup with the strings on and up to pitch.
I use a straightedge to get an idea of where things will sit whilst building, but do the final set up as described above.
If a neck 35mm thick bends with 3 or 4 strings, I would looking at certain things that contribute to a weak neck. Some things to look at….
- Where does the neck bend, is it as Brian Q suggests, or between nut and 12 fret.
- What is the timber used for the neck
-is a fingerboard used
- are frets used
- string gauge and tension
All these effect the stability of the neck.
There is usually a slight bow in guitar necks, this called relief, it aids in string clearance over frets. But is only a few thousands of an inch, measured over the 7th fret
Neck reinforcement? Well that another subject.
It’s best to post some pictures so we can see what’s going on?
I don’t have a particular problem as most of my builds are fretless. However I’m reviewing one of my builds and replacing the neck with a fretted one. I’m simply commenting on something I’ve seen in videos.
I thought you wrote that you had 4 necks that bowed. Sorry.
They have to some extent, but as they are fretless it hasn’t been detrimental. Before stringing I would use a straight edge between nut and bridge and the distance, along the neck would be fairly uniform. However after stringing the distances, especially from fret 15 would be increased. I simply used a lower bridge. My builds are all through necks and therefore I don’t have a break angle.
Michael, have you tried using back angle, a lot better action, especially on fretted necks? Cheers :)