Fretless fingerboard issue...

[esa372]

I have a four-string fretless Jazz bass, and I have discovered something odd with the fingerboard.

Under the E-, A-, and D-strings, the relief is ~.25 - .30 mm at the 8th fret, but the relief under the G-string is practically zero... noticeably less (visually and tactilely) than the other three strings.

As a result, I'm am getting much more (and better) "mwah" from the G-string that I get from the other three. If I tighten the truss rod (even an eighth of a turn) to lessen the relief, the E, A, and D, create more "mwah", but the G-string chokes on the fingerboard.

So, wonderful TB community, what steps should I take to get this fingerboard straightened out? My thought is that I should remove the neck, set the truss rod so that the board is perfectly flat under the E-, A-, and D-strings, and sand down the G-string side to be level and even with the rest.

Is this the right way to go, or does TB know of another way to address this?

Thanks!

~esa

 

[lz4005]

Make sure the problem isn't that the neck is twisting first. If it's really that the board is uneven then your plan is good.

 

[esa372]

Thanks, lz4005! How would I check for twisting?

 

[Precision101]

Thanks, lz4005! How would I check for twisting?

Look down your neck at the headstock and it will look like a "staircase" it will Move one side slightly to the other

 

[esa372]

Look down your neck at the headstock and it will look like a "staircase" it will Move one side slightly to the other

Thanks, Precision101. There is no visible twist in the neck, thankfully...

It looks like sanding is the way to go. I'll wait a few days, though, in case there are some other suggestions from TB.

Thanks, guys!

 

[esa372]

Just a follow-up...

I did the sanding today; started with 150 grit, and worked up to 12,000 grit. When I put it all back together, the problem was solved - all the strings are equidistant from the fingerboard. Now I just have to file the nut a little to compensate for the (slightly) lower fingerboard.

Thanks for the help and suggestions!

 

[jamro217]

Luthier's corner had a great answer to your question as well as an education in fingerboard shapes in general. Bruce Johnson is the guy to ask.