Acoustic Guitar Construction

Wondering what neck thickness people aim for when carving a steel string guitar? I’ve built 4 guitars following the Compiano book, but find the necks a bit thick and hefty. He draws a pencil centre line down the back of the neck and then carves the profile leaving the line alone. On my last build I followed OBrian’s YouTube video where he rasps a groove at the first fret to a neck thickness of 21mm then another at the 10th fret to 24mm, he then carves the neck down to theses reference points. To my shock, when I did this, I broke into the bottom of the truss rod slot at the first fret and had to scrap the neck! How much wood should I safely leave from the bottom of the truss rod slot, without ending up with a chunky neck? Thanks in advance.

My necks are 20=21 mm at the 1st fret. So 14-15 mm of wood and 6 mm of fretboard. My truss rods are 9.5 mm. I install the truss rods flush, So even with 20 mm I still have 4.5 mm of neck wood. I have not had any problem with these truss rods.

If you sunk your truss rod too deep or had a thick fretboard you could get into trouble.

Thanks for the reply John, useful information and much appreciated. Could I ask, if the truss rod is installed flush without a spline to hold it down, do you use any glue or sealant in the slot to stop any potential rattling or movement?

I use a dab of silicon glue on each end. When I say flush I mean flush, so the fretboard holds it down. I use the LMI 2 way truss rods which are squarish. I slightly under route and work with a chisel until it is just flush. Proud is really bad as the fretboard will not glue on. I would use a spline if I routed too deep, but it may end up less than 1 mm.

I have found that just engaging the truss rod tightening until the rod is under tension but not bending the wood keeps the rod from rattling.

Thanks again John, I’m about to install a truss rod so I’ll give it a go.