BYO: Neck Angle, Bridge Height, FC Plan

Jeff Moore

The reason I'd like to get one is because I have figured out a completely different neck joint but I cannot and do not want to build guitars.
So these guitars built with what may be permanent neck joint problems present an opportunity for me.

Also it isn't really the 12 fret option I'm after, but the wider nut width that is associated with the 12 fret guitars. So if one of these troubled guitars has a wide nut, that would be equally usefull project for me. I'm talking 47mm or 1-13/16" or greater.

Craig Bumgarner

UPDATE: After all my whining about my screwing up the neck angle on this guitar, I ended up playing and giggin' it for two years as is. I liked the sound well enough but the 4.5mm action was getting in the way at times and I was curious whether a proper bridge height would improve the tone, so I finally worked up the nerve to do what had to be done.

• Pulled the frets and took the fretboard off with heat
• Cut the heel off
• Drilled down from the top around the neck tenon to release the neck from the head block
• Repaired the drilling damage to the head block
• Glued on a new heel, shaped it.
• Adjusted the neck angle
• Reinstalled the neck & fingerboard
• Refretted the fingerboard
• Touched up the finish

I choose to cut the heel off and chop the neck out instead of trying a more standard steam release because I was concerned there were just too many other glue joints in the vicinity. Cutting might have been more work, but safer and more predictable.

One question I had going in was whether the difference in bridge height would make much difference to tone. I thought it would. Originally the bridge was pretty short at 14.5mm. After the neck angle change it was 19mm, right on Selmer spec. This is a fairly substantial change to the break angle of the strings over the bridge and the downward force of the strings on the top, but frankly, the tone didn't change much, maybe a little richer and louder, but nothing dramatic. I was surprised. It does play much better now with 3.2mm action.

The change also allows my Peche a la Mouche pickup to fit which is a nice plus.

I've used this guitar as a test bed in other ways recently. I thinned the top down to a consistent 2.2m from the rather inconsistent 2.3-2.6mm. This increased the volume and bass response some, but at the expense of some clarity in the mids and highs. Also added a sound port to the upper side which makes it louder and bassier for me, the player, though not much different for the listener. I notice this same effect with D hole guitars and I'm speculating it is because more sound gets out of the D hole which the player hears. What the audience hears however is mostly what is being produced by the vibrations of the top itself, not the hole(s).

CB

Bones

Hey Craig,

What neck angle did you end up with? Is that the same angle you still use?

thanks

Craig Bumgarner

Hey Bones, actually, I don't think in terms of neck angle at all any more. To me, neck angle is just a means of getting the right break angle of the strings over the bridge. The geometry of my tops is pretty consistent, so different break angles are achieved with different height bridges and I now just think in terms of bridge height.

The way I do it is empirical, set the neck up so I get the bridge height I want and whatever neck angle is what it is. I don't measure it. I use a long blade on a bevel gauge to measure the angle between the side at the head block and the top. I add the thickness of the fingerboard (usually 7.5mm), the frets (1.2mm) and double the desired action on the low E at the 12th fret ( say 5.2mm). These numbers total 13.9mm. So if I want a 19mm bridge, I need ~ 5mm gap in my bevel gauge at the bridge point. If I want a 17mm bridge, then a 3mm gap. 14mm, no gap at all. I should probably adjust a little for compression of the top once strung up, but I don't and it works out.

With these guitars, it is common to add a wedge under the fingerboard from the body join to the end where it overlays the top. I don't try to build this angle into the top geometry. My top geometry is a cylinder from head block to the bridge and who knows what south of the pliage.

Bones

Ok yeah that makes sense. Thanks!

Bones

I'm thinking I need like a 1-1.5 degree tapered shim to go under the fingerboard extension to get like 17-18mm bridge height. Anyone have an idea how to make that (I'm guessing on my thickness sander double stick taped to a thicker board)?

What type of wood?

Thanks

Bones

PS- Does the shim typically taper to zero thickness at the egde of the guitar body or is it left a mm or 2 thick there?

thanks

Craig Bumgarner

The way I do it is glue black maple veneers to the underside of the fingerboard. I found cutting a wedge that actually fits is pretty tough. The veneer idea works much better unless the size of the wedge is really big.

With the neck w/ fingerboard in place on the body, I use a stack of veneers at the the end of the fingerboard extension to see how many it will take. Say it will take three (1.5mm). The first I make full length, the next two thirds, the last one thirds. I glue them to the under side of the fingerboard extension, the longest on first, then the next longest and so on. I use super glue and accelerator to minimize hydration and to get it done quick. Make the veneers a little wider than need be and trim them down to the edge of fingerboard once the glue kicks.

Use a scraper, a thumb plane and/or a small sanding board to level out the steps. Important to keep trying the fit as the top is seldom a perfectly in-line plane.

The black veneers I use are maple, dyed black, get them in a five pack about 8" x10" from Amazon (the same veneer makes great shims too, life time supply for you and your friends).

Bones

Cool thanks Craig. So does the shim typically sand down to zero thickness right at the heel of the neck or do you leave some thickness there?

Craig Bumgarner

Bones wrote: »

Cool thanks Craig. So does the shim typically sand down to zero thickness right at the heel of the neck or do you leave some thickness there?

I don't leave any thickness of wedge at the heel. Sometimes, the zero point starts 10-15mm from the heel. You have to look at it and test fit. Also, the top is seldom perfectly in plane, so you have to test fit a lot while taking the stepped veneers down. But if you do, you can get a very good fit.