attaching a neck on acoustic with an arched top

[jimbag]

I am building a steel string acoustic with a 50' radius arch in the top, and just realized that the angle where the fretboard and neck heel meets the body of the guitar is not going to be exactly 90 degrees because of the arch in the top. How is this dealt with in a build?

[redir]

Just set the angle in the heal of the neck so that it's the right height for your bridge height and saddle height. Typically the string height at the bridge is 1/2in so aim for that. A 3/8th inch bridge and 1/8th inch saddle is what you typically go for. Bear in mind that the top will distort up so you may want to aim for about 17/32in, about 1/32in higher then your target.

In setting the neck angle into the heal you may find that your fretboard extension is sticking up in the air. If it's not too great then you can just glue it down but if it's more then a 32nd or so then you will want to make a shim to fit it.

To determine this angle empirically, you mount the neck in place with the fretted fret board along with it and shoot a straight edge along the tops of the fret so that it hovers just about 1/32nd inch above the bridge where the saddle is. If you fret the instrument in a later stage like I do then just do the math.

[B. Howard]

I typically fit my dovetail with the FB off of the neck, makes the jount much easier to work. The angle is seldom 90 degrees to the rims because the bridge is typically thicker than the FB even with frets. I have found that .090"-.100" clearance from the plane of the neck shaft to the top at the saddle location in this manner yields perfect results every time with standard dimension parts.....

The easiest way to measure this is by taping a drill bit to the top at the addle location. I use a #95 machinists bit (.095"). then you can just lay a straight edge on the neck while you hold the joint and see what you need to do for angle.

[Bruce Sexauer]

I typically use a slightly tighter radius than 50’. My neck block is exactly square to the top, and my neck heel angle varies between 89.5 and 90.5 degrees, which variance I analyze before cutting the dovetail. An eighth inch of saddle height over the top makes a big difference in tonal character and I do try to get the tone each customer is after, but anywhere between 3/8” and 9/16” sounds great if everything else is done right.

[Skarsaune]

Originally Posted by B. Howard

I use a #95 machinists bit (.095"). then you can just lay a straight edge on the neck while you hold the joint and see what you need to do for angle.

Minor correction - a #95 drill bit is .0067". A #41 is .096".

I'm not a luthier but I am a machinist.

[jimbag]

Thanks guys

[B. Howard]

Originally Posted by Skarsaune

Minor correction - a #95 drill bit is .0067". A #41 is .096".

I'm not a luthier but I am a machinist.

Thanks.... Mis read the little chart on the screen. The big one is on the wall in the shop.