Neck Angle Geometry

[Joey Herscovitch]

Hi Everybody
Just joined up & have enjoyed reading some of the posts & discussions on this site. They are very informative. Well I'm finally putting time into an acoustic guitar project that I started, would you believe, 29 years ago. Sort of tells you I'm a little older than 29. It's a little unusual in that the back & sides are flamed red oak (very pretty) that I started w/ a Luthier from the Vancouver, Washington area in 1979. It also has a shorter body length (I call it my Mini Dreadnought). It has a Sitka Spruce top & Black Walnut binding w/ Purple Heart purfling.
Right now I have finished the body & am ready to tackle the tricky task of fitting the neck to body joint. (I've read FF's article on checking neck angle at Frets.com.) I'll be using a traditional dovetail, & I have no trouble w/ the setup for that, BUT my concerns are regarding the neck setback angle. Specifically, when you cut a cavity into the body that is square to the top & a neck tenon at an angle less than 90 degrees, you end up w/ a fingerboard tongue that climbs away from the top. For example, by my layout, w/ the base of the neck cut at an 89 degree angle there will be a 1/16" gap between the end of the fingerboard tongue & the top. Smaller angle, more gap. While I realize that I can close this gap w/ clamping pressure when gluing, won't this cause either a dipping of the fingerboard after the 14th fret, or a lifting of the top in the same area, or both? Am I missing something or is this corrected by normal tensioning of the strings? Other than the Taylor system, on a glue joint would you ever consider relieving the fingerboard into the top at this angle to accomodate? Lots of questions.

[Ronnie Nichols]

I'm far from being an expert on this but my experiences with resetting necks in Martins has proven that the fingerboard indeed does dip after it joins the body (especially after you alter the neck angle). This is usually not a problem unless you are one of those pickers who plays on those frets. Most bluegrass pickers don't travel down there too often. I'm sure you could fabricate a shim to compensate for this if it is that much of a problem. If the fingerboard is bound, you could shim it prior to attaching the binding and it would be virtually invisible. If the brace in front of the sound hole is made correctly there shouldn't be any lifting of the top when you clamp the fingerboard to the top.
Ronnie Nichols

[Jim Bancroft]

When I install a neck I'm not concerned about what angle the neck comes off the body, but, where fingerboard with frets installed is in relationship to the bridge.

With a straightedge laying on top of the fret and projected to the bridge location, the straightedge should come to the top of the bridge or about 1/16" above.

If the bridge is installed this is fairly easy to do, but if the bridge is not installed, just make sure the straightedge is above the top the thickness of the bridge plus approx. 1/16". Bridge thicknesses vary some from about 3/8" to slightly less.

Jim

[Tim Mace]

I'm learner/beginner but so far(mandolins) I'm using 6 degrees....anybody get better results
with other angles?These angles affect neck relief & saddle tallness don't they? I'm trying to get the lowest action possible.

[Joey Herscovitch]

Thanks guys for your input. I guess as long as the angle isn't excessive the fingerboard dip shouldn't be too much to worry about. I'm just surprised cause I thought there should be no dip at all. Taylor's shim system is interesting in that regard as the whole fingerboard stays in a straight line relative to the neck angle.

[danove]

In my opinion, there should not be any dip.
Maybe acceptable on a cheap gear, but whith fine handcrafted ones
I think you should care for the entire playability.

Also the fingerboard is not supposed to be dead straight
- but this I've been on to in another thread :-)

[Tim Mace]

Ramirez had the bass side of the fingerboard lower near the sound hole ...probably to compensate for some of what you're concered with and to lower the bass string action more at the bridge.

[danove]

The other solution is to lift the basside a bit higher towards the nut side.
If my memory serves me well, Jim Olson has described this as
a slight twist of the neck.

[Joey Herscovitch]

I agree w/ you & that's what I would like to accomplish (no dip), but how do other builders deal w/ that discrepancy at the fingerboard extension?

[Tim Mace]

The best advice I've read was about taking those frets down so they are out of the
way since most players don't spend that much time up in extended fingerboardville.
I just carved a channel on a spruce top to level that area since it rests on a solid mahogany neckblock.It will look great when I mount the fretboard over it.

[danove]

I would shim that tongue to the top.

[Joey Herscovitch]

I probably will shim the tongue. I would have inset it into the top if I had I reinforced the underside w/ a pad instead of the upper transverse graft. Otherwise there's just not enough meat. Maybe on the next guitar. Thanks guys

[Doug T]

I use a 50' bowl form for my tops. I first glue the brace that is directly under the fingerboard completely flat (along with the bridgeplate) then the rest of the braces go in curved to the bowl. What I have found is that yields about 1.75 degrees up to 2 degrees. I sand the area completely flat where the fingerboard will sit, measure the angle and cut the mate to that angle on the heel of the neck. Thus, when the dovetail is created, I get a flat everything. That's easier than my first couple guitars which I shimmed under the fingerboard.