How do I fix this?

[seangil]

I'm attaching a bolt on neck for a new guitar and found that I have a slight gap between the fretboard and the body. The cause is that the top slopes down in the inch before it hits the binding by a little less than 1/32". As a result, there is not a straight plane for the fretboard to make full contact with the body. So I have to either deal with a gap or eliminate the gap, but then have to bend the fretboard down to the body. I have one other guitar in progress where I have the same problem.

Two questions....

1) Any idea what I could have done wrong to end up with this slight dip in that last inch of body lenght?

2) What are the options for filling it?

I have tried using veneer to make a shim, which can close that gap, but then creates another one right behind the shim.

Photo can be seen here:

https://www.flickr.com/photos/199153562@N07

Thanks for the help.

Terb

[Fathand]

What is preventing the neck/fretboard from moving down to the guitar top?

Was the heel not cut at the correct corresponding angle to the top, usually 1-2 degrees off square. Is the tenon bottoming out or the holes in the neck block in the wrong position? Some combination of these?

I have shimmed under a fretboard but usually the other direction, getting thicker towards the soundhole. Shim would be tapered and the full length of the gap or the fretboard extension. In your case you run the risk of too high action. Have you tried the straight edge test from fretboard to bridge.

Options

Adjust the heel angle, basically a neck reset.

Can you enlarge or move the holes in the neck block so the neck/fretboard sit lower?

Shave the bottom of the tenon?

[seangil]

Thanks for your response. I did cut the heel a bit off-square and the tenon is not bottoming out. The neck position is actually giving me the right height over the bridge location at the moment. The problem is that the top is not in an even plane from the edge of the soundhole to the binding. So if I put a straightedge on the top starting from the soundhole, it makes even contact with the top until about one inch for the binding and then the top arcs downwards. So given the geometry of the top, I have to either:

a) lower the neck so that the fretboard makes contact at the binding, but then bend the fretboard down to make contact with the top near the soundhole (which might mess up the fretboard/bridge geometry); or

b) fill that gap somehow.

But, for a reason that I need to figure out to correct in future builds, I do not have a perfectly flat top on the centerlline from the binding to the soundhole.

Any further thoughts?

[runamuck]

It looks to me that you sanded more off the top close to the edge causing the gap.

You could resand the top with a block if you feel you will have enough structural thickness there or remove material from the underside of the fretboard extension to match the top. The second option will be more difficult.

[phavriluk]

I think the answer isn't binary. Do as much flattening the angle of the soundboard as is possible and then make up the difference with tapering the bottom of the fingerboard. Easy for me to say...

If you need to find 1/32" so the fingerboard sits flat. that's 1/64" each off the fingerboard and soundboard, as I'm trying to visualize what I infer. A thick pencil line.

I understand that more often than we like we go through periods of imitating the Sorcerer's Apprentice.

[Fathand]

If all your neck geometry is to your liking, I would be loathe to change it and would go for the cosmetic repair.

Make a shim out of fret board scraps the width of the fretboard. Taper it to match the gap, notch it or cut it in half to go around the tenon. Use a tiny piece of 2 sided tape to hold it in place while test fitting. When happy with the fit, glue permanently and sand flush with the fretboard sides.

As for what went wrong? I had a similar problem when I tried increasing (decreasing?) the radius on the brace above the soundhole once putting more curve in the top there. Or as previously mentioned, a sanding error.

[Alan Carruth]

I dome the top, including the upper transverse brace. I feel this helps the top resist cracking in the low indoor winter humidity here in New England. If I set the neck so that the fingerboard lies down flat on the top the projection at the bridge is 'way too high, so I end up with some 'overstand' of the neck at the body joint; usually 2-3 mm. The fingerboard touches the top at the sound hole edge. I could lower the neck to eliminate the over stand, but the end the fingerboard would have to be thinned out from the bottom to fit, and could get quite thin. Instead I use a wedge of the same material as the neck under the end of the fingerboard, and taper that to fit the top.

The point here is that there are several 'right' ways to do things, depending on your design choices. Many people do make the UTB flat, as, I believe, does Martin, but that's not a Commandment from Heaven. My violin making teacher said that what matters is whether whatever you did can be justified, and looks as though you meant it.

[Rudy4]

If it was me I'd opt to assemble the guitar as is and fill the "gap" with a fill stick that matches the fretboard wood. You need to make sure the top is sealed first so you don't stain the top wood.

I'm not sure if you're familiar with Taylor's NT neck joint, but Taylor adds filler in the crack between the heel and the sides. It's a tiny gap, but most players will never realize there's a gap there. Your gap can end up being almost as hidden if you do it carefully.

I try my best to never remove wood to try and get something to fit up cosmetically. I do my own designs and figure I made it that way on purpose. It's like the old carpenter's joke, "I cut it off 4 times and it's STILL too short!"

There aren't that many small shop builders who don't have at least a tiny bit of fretboard fall-off between the body edge and sound hole, although you have the opposite problem. I cut and fit a long thin wedge of matching wood so the board stays in the same plane, although it wouldn't be a big deal to let the board pull down that small amount.

You can see the end of the taper under the end of the tenon here:

[DickHutchings]

Hey Rudy, what's going on here? The thing on the heel looks like a strap button but not? What what kind of mechanical connection is shown on the right and how is it attached.

[Rudy4]

Originally Posted by DickHutchings

Hey Rudy, what's going on here? The thing on the heel looks like a strap button but not? What what kind of mechanical connection is shown on the right and how is it attached?

I use Dunlop Straploks on the majority of my instruments. The system comes with "dual function" strap buttons that can use either the Straplok connector or a standard strap can be used.

They also can be used with an alternate flush attachment which you see in the photo. When a strap is used it looks like this:



The business end gets a matching recessed Straplok fitting and also has the output jack for a K&K Pure Mini pickup.



What you see under the center tongue of the fret board extension is a tee nut that is "JB Welded" into a recessed counterbore in the bottom of the fret board. It drops through the Popsicle brace where a small screw is inserted and tightened to hold the tongue down against the top plate. Here's an example of a home brew tool used to reach into the sound hole to snug down the retaining screw.



Looking in to see where the retaining screw will be go:



All the details for that guitar, as well as a complete CAD construction drawing can be found in this AGF topic:

Complete Small Body Slot Head 14 Fret Plan

[DickHutchings]

Thank you. I will use of this in a future build. The inset strap locks are brilliant 👏

[Rudy4]

Originally Posted by DickHutchings

Thank you. I will use of this in a future build. The inset strap locks are brilliant 👏

It's also possible to inset the standard "dual function" strap buttons. It requires a bit more care in fitting, but the results are worth the extra effort. You do have to be sure that you take a strap along that has the quick releases fitted. That's not a problem for me, as I usually leave the strap attached all the time.

Here's a recessed standard strap button:

[seangil]

Originally Posted by Rudy4

I use Dunlop Straploks on the majority of my instruments. The system comes with "dual function" strap buttons that can use either the Straplok connector or a standard strap can be used.

They also can be used with an alternate flush attachment which you see in the photo. When a strap is used it looks like this:



The business end gets a matching recessed Straplok fitting and also has the output jack for a K&K Pure Mini pickup.



What you see under the center tongue of the fret board extension is a tee nut that is "JB Welded" into a recessed counterbore in the bottom of the fret board. It drops through the Popsicle brace where a small screw is inserted and tightened to hold the tongue down against the top plate. Here's an example of a home brew tool used to reach into the sound hole to snug down the retaining screw.



Looking in to see where the retaining screw will be go:



All the details for that guitar, as well as a complete CAD construction drawing can be found in this AGF topic:

Complete Small Body Slot Head 14 Fret Plan

Hi Rudy,

I'm back looking at this again...Do you construct your guitars without using any glue under the fretboard? For a bolt-on neck, that seems far preferable to using glue for purposes of easy resets in the future. However, the person that I was learning from used glue, so I have been doing that with my subsequent builds.

Sean