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14th fret hump and a rubber neck
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10137&t=50885		 Page 1 of 1
Author:  Conor_Searl [ Thu Aug 09, 2018 12:14 pm ]
Post subject:  14th fret hump and a rubber neck
First the hump at the 14th fret. I recently reset the neck on this D-28 clone I've had hanging around for months. Because of the new neck angle a hump has developed at the 14th fret. I had removed a portion of the fret board because I couldn't find the pocket when trying to take the neck off, and roughed a saddle in without having re-glued the fretboard extension so didn't realize the hump would be as pronounced as it is. My action at the 12th fret with the roughed in saddle is about 3/64 on the bass side, and 2/64 on the treble so there is room for a higher saddle to mitigate some of the interference and buzzing I'm getting from the hump. But the frets are on their last legs of this guitar as well, so I'm wondering would the appropriate fix for this be pulling the frets and milling the fretboard plane flat?

Which brings me to my rubber neck. This guitar has no truss rod. Under tension the relief is about .021, without tension it settles into about .009. Is this swing normal or is that a lot? It seems like a lot. So if I were to pull the frets for a re-fret it seems to me that some compression fretwire would be in order to add a little stiffness to the neck and remove some of that relief.

Do my assumptions seem reasonable?
Author:  DanKirkland [ Thu Aug 09, 2018 2:43 pm ]
Post subject:  Re: 14th fret hump and a rubber neck
It happens. You have some options.

Depending on how bad the hump is (pic?) you could get away with a fret level and have the fret plane be flat.

You could also do a full refret like you said and level out the board.

On every single neck reset I do a level regardless if there are any issues or not. It just insures that everything is trued up and ready to do once it's all back together.

Considering what you've already mentioned with the hump being really bad, I'd opt for a full refret and level down the board if there's sufficient thickness to do so.
Author:  Freeman [ Thu Aug 09, 2018 3:36 pm ]
Post subject:  Re: 14th fret hump and a rubber neck
What Dan says. However a couple of things

First, if it is a D28 clone it probably has a metal truss rod, just not adjustable. Old Martins had several different kinds of bars, their necks are remarkably stable (my '74 has about 10 thou of relief, my '80 D12-28 about 12. Not bad for 50 years old). Yours pulling 12 thou of relief seems like a lot but that is a good number to remember.

Second, did you get the geometry correct? I remember all sorts of drama with this guitar - you sawed the f/b off, couldn't get the dovetail seated. Are you happy with the way you reattached the f/b extension?

If the geometry is correct then my first thought would be to just level the frets and see what you've got. You know your are going to get 12 thou of relief, thats the high side but probably acceptable on a bluegrass D28.

If you don't like that, and you probably won't, then pull the frets, level the board (making sure you don't screw up the geometry) and refret it. Level the frets and you should be good to go. Remember you are going to end up with 12 thou of relief.

I have never done a compression refret but I know that when I use standard wire and 0.020 slots I get a tiny bit of compression backbow (I can see it when I fret a board off the neck). Most of the time if I start out with a perfectly level board and the t/r at neutral my strings will pull less than 10 thou of relief. Thats why I'm thinking that if you just start with a flat board and new frets you will be OK.

Third choice, pull the fretboard and start over.
Author:  Conor_Searl [ Thu Aug 09, 2018 3:56 pm ]
Post subject:  Re: 14th fret hump and a rubber neck
DanKirkland wrote:
Depending on how bad the hump is (pic?) you could get away with a fret level and have the fret plane be flat.


In the excitement of actually getting this done, I didn't even think to level and dress the frets. That's done now, and has helped quite a bit. I had pulled two frets, one at the body joint in search of the dovetail pocket and one at the 12th where I ultimately sawed the fret board off. I fixed up the fret board and just reinstalled the frets. So, duh .

I think I'll still recommend to my friend that we do the re-fret down the road, levelling the fretboard. But I figure it probably wouldn't hurt to at least let this guitar settle into it's new existence.
Author:  Conor_Searl [ Thu Aug 09, 2018 4:04 pm ]
Post subject:  Re: 14th fret hump and a rubber neck
Freeman wrote:
First, if it is a D28 clone it probably has a metal truss rod, just not adjustable. Old Martins had several different kinds of bars, their necks are remarkably stable (my '74 has about 10 thou of relief, my '80 D12-28 about 12. Not bad for 50 years old). Yours pulling 12 thou of relief seems like a lot but that is a good number to remember.


You're right, it is a metal rod. That makes sense about just doing a normal re-fret, at the very least once its done, with the fretboard levelled if I still need to get rid of some relief I can introduce one fret at a time and watch what happens.

Freeman wrote:
Second, did you get the geometry correct? I remember all sorts of drama with this guitar - you sawed the f/b off, couldn't get the dovetail seated. Are you happy with the way you reattached the f/b extension?


You're right this guitar has been the source of many questions over the past few months. There seems like there are about a hundred things I'd do differently next time, but I think it's actually pretty good for my first try. I'd definitely shim the fret board extension in the future, the fall away from the body to the sound hole looks quite dramatic. And is probably making the hump look worse.
Author:  Conor_Searl [ Thu Aug 09, 2018 4:19 pm ]
Post subject:  Re: 14th fret hump and a rubber neck
Here it is. Thanks for all the help everyone!
Author:  DanKirkland [ Thu Aug 09, 2018 6:59 pm ]
Post subject:  Re: 14th fret hump and a rubber neck
Conor_Searl wrote:

You're right this guitar has been the source of many questions over the past few months. There seems like there are about a hundred things I'd do differently next time, but I think it's actually pretty good for my first try. I'd definitely shim the fret board extension in the future, the fall away from the body to the sound hole looks quite dramatic. And is probably making the hump look worse.


I recall a wise old man telling me one time "Everyone has to learn everything at some point". He meant that nobody has everything figured out the first time around.

So if you have to ask a hundred questions, then ask a hundred questions. I know that alot of the old mindset is "if you have to ask you don't need to know" but that's stupid. If you don't know, then ask until you get it figured out.

I say good on you for asking alot of questions on the topic. If nobody ever asked, how would anyone know anything?
Author:  SteveSmith [ Fri Aug 10, 2018 9:48 am ]
Post subject:  Re: 14th fret hump and a rubber neck
If you want to put in a few frets as in a compression fret to address the relief then do them in pairs around the center. Which pairs and where the center is will be determined by careful measurement of the relief under tension, for example you might decide that 5 and 9 are where you want to start. After each pair put the neck back in tension and remeasure everything to figure out which ones are next. It's time consuming but not as difficult as it sounds.
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