Official Luthiers Forum!

It’s been a long time since I’ve posted here (hijacked into making furniture by my wife). I’ve only built 13 guitar-shaped-objects, over 12 years since the last one, so I hope you will bear with me…I’m hoping for guidance on a 12-fret 000 guitar ( #7) I built 16 years ago that has problems probably caused by me thinking I knew what I was doing by then.

It was given to a brother-in-law who has cared for it meticulously but recently mentioned it now has a small “bump” on the back of the the neck from the nut to second fret, and has become “a little harder to play” [action is now 7.5 and 9.5 (64ths)]. Rather than reply “tough it out whiner” or “so take up slide”, I foolishly said “let me take a look”.

Problem 1: action
Solution?
I made this an adjustable neck (a variation off of Mike Doolin’s first design (before he moved the adjustment bolt’s access to the back of the heel).
I should be able to adjust (increase the neck angle, and so lower the strings over the fretboard) to a normal action with a turn of the adjustment grub screw controlling neck angle.
I will have to remove the neck and shave about 0.025 off the face of the heel that contacts the body, to allow it to move deeper into the neck block after adjustment (I didn’t stop to think of someday needing to actually adjust an adjustable neck).
That also should be easy, unscrew the bolt attaching the neck to the body and have at it. I may cut a new saddle and nut as well, if I can’t fine tune adequately with the neck adjustment.

Problem 2: The real problem – Neck has bulging of maple skunk stripe from just ahead of the nut to the 2nd fret [see pix 1 & 2] with a sharp edge on either side of the bulge.

I believe the bulging out of the ¼” skunk stripe of maple is the result of my (not thinking ahead) making the center maple strip the same width as the subsequent trough for the truss rod, in combination with using epoxy for gluing up the neck blank.

The shift in the maple strip seems exactly where the truss rod would bear on it. I don’t know why on earth I would have set the truss rod as if I needed to create some back bow, as the neck has 2 carbon fiber stiffeners, was dead flat when built, and I’m pretty sure relief, action, etc were good at completion of the build because I was always pretty anal-retentive about that stuff.

The only thing I can think of is that: the Doolin adjustable neck design was so much fun to play around with, being adjustable in all three dimensions. I remember I did spend several months just playing around with this guitar before finally letting him have it - different settings and doing experiments (it allowed true A-B comparisons as A and B were exactly the same instrument). Maybe I set the truss rod to push as if a back bow for some experiment, and forgot to take it back to neutral?

At any rate, I think that is what has caused the bulge – pressure from the truss rod on what is a very thin remaining thickness of maple (after cutting the truss rod trough), only secured to the rest of the neck by the remaining epoxy. Essentially, I think I created a focused stress riser concentrated exactly on what is a very small area of only epoxy bond. Over the subsequent 6 years I think that was just asking for cold creep at that spot.

Does this seem to be a reasonable explanation?

Solution?
1. Ease off the truss rod to remove further pressure.
2. Sand bulge down to flush
3. Re-finish neck (French polish) no problem, FP a neck was one of the pure joys I remember from those days.
4. Don’t use truss rod in future. Already has CF, back bow unlikely(?), and truss rod intentionally inaccessible to player to prevent them thinking that’s how to adjust action. (have to remove neck [easy] to reach truss rod adjustment).

Looking for advice / criticism before diving into this.
Thanks in advance for any help you can give.

Interesting. Wondering if you ease off the truss rod if the bump will "retract". This might indicate whether a glue creep, glue starvation or failure of the joint. More analysis of the root cause in in order.

Note that your first attachment is so big that it expands the reading window of your post so it goes off the screen- not so easy to read the post.

_________________
Measure Twice,

Karl Borum

I’ll be interested in hearing what real experts have to say. To some extent, my inherent dislike of laminated necks like this is driven not by the visual aesthetic (which is beautiful) but rather by what you said at some point: it was just begging for cold creep to happen. If you are going to laminate necks, I think it is really important to use a glue that won’t creep, because the thing is going to be under some kind of stress, one direction or another (or both directions at once). I won’t speculate on the right fix; again, I defer to the experts. But I would be uneasy about going without a truss rod, just in general. Good luck with the fix.

I built the same neck but if you do it again the heel should go into a recess in the body

I had the same problem with the truss rod. The StewMac Hotrod is too tall. I removed the fretboard and put in more wood in the bottom of the channel then used a less tall Blanchard rod. I also have CF in the neck but would not want to not be able to use the truss rod.

You can see where I repaired it. Was 10+ years ago. I did not sand it flush (wouldn’t recommend that) but just pushed it back in and reglued it.

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Steve Smith
"Music is what feelings sound like"

I will just point out that if you sand the bump flush, there will be even less material behind the truss rod.

Sometime you just have to recognize that by trying to be fancy, you’ve baked in a full on problem, and not all problems can be solved.

Is it possible that the truss rod has been over tightened to try to bring down the string action height, even though you tried to make the adjustment inaccessible?

Hey RNR welcome back I remember you. I hope you are doing well beyond the guitar issues.

For everyone reading this once again an old style StewMac Hot Rod truss rod tried to come out the back of the neck.... There was another thread about this a few weeks ago here and many threads over time on the OLF on this very topic.

I would have to see it to really understand what your neck design on what you called and made me laugh by the way and I needed to laugh to thank you. I would need to better understand your neck joint since it is non standard. Rick Turner RIP called our guitars back then GLOs for guitar like object.

Regarding the bulge I would be inclined to remove the fretboard which is a HIGHLY invasive thing that repair luthiers rarely do and rip out that hot rod rod and replace it with a modern truss rod that is not as tall.

Once this is done you also gain more room under the rod to install a hardwood or even aircraft plywood stiffener in the floor of the truss rod channel. We've done this before on a nice Luthier made instrument that the SM truss rod came out the back of the neck.

The newer SM rods are less high and there are also many newer rods these days double action should be your choice that would work. Reinstall the fret board and then sand and refinish the neck.

You didn't say where the action was measured we measure at the 12th so you're right it needs a neck reset. You did state it in a manner that Dave and I use to describe action in our shop good going and thank you. Anyway at the 12th the action should be about 4 and 5.5 (64th" for everyone else). 4 is the high e 5.5 the low e again at the 12th.

This is all repairable although it is a large project. I think I understand what you intend to do to the neck joint but I do not fully understand the Doolin method. He stopped building though like you did and like I did. We move on don't we.

Let me know if I can help I would be happy to and again welcome back.

I didn't read the other replies so forgive me please if I am redundant short of time here.

The Doolin joint is a good design with only a few drawbacks. When done properly one can easily adjust the strings to be flat on the neck or a 1/4" high in increments as low as 0.002" if the adjusting screw is a 10/32, for example. I have a plan to fix the issues I've identified (after playing this guitar for over 10 years), make the drawings and see if I can get Andy to make up a few for me. As a serious player It is very nice to be able to tweak the action during string changes, especially as the seasons change and especially if you like it low like I do.

RN, if you replace the truss rod as I advised you can make the filler strip of maple (or any wood that is stiff and strong) and I recommend you extend the rout at the nut end so the filler strip goes about 1/4" past the break area, basically out under the nut but not into the headstock area. That will help to better support the end of the truss rod.

_________________
Steve Smith
"Music is what feelings sound like"

I have not work with epoxy in guitar making. So take this as just an idea.
Why not slightly heat/warm the neck in the problem area ( I have read that most epoxies will soften around 100-130F) and clamp with a caul to make it creep back to where it should be. This may involve blowing warm air on the jig/clamp for several hours as you do not want to go too high in temperature. If the fretboard was glued also with epoxy this may be a problem.
Again just brainstorming here.

Alain, unfortunately just regluing the joint is not going to fix the problem. Real issue is the tall Hot Rod required thin area in the neck under the truss rod. When adjusting the rod it just created too much pressure, compounded by the CF reinforcement, and caused the failure.

_________________
Steve Smith
"Music is what feelings sound like"

Sorry about the picture size- I don’t know how to change it now.

Don: I believe I was concerned about the added moisture from what was 6 total glue lines and so used epoxy for that and the fretboard. Live and learn.

Steve: Your repair was so good I don’t have a clue where it is in your picture. “just pushed it back in and reglued it.” – could you share specifics – how pushed back in, how long, reglued from surface or once fretboard was off? Oh, and the neck does sit in a recess. I modified Mikes design to make it a 1 bolt neck, but the rest is the same idea.
If I get back into the guitars, I think I probably go with his newer design -adjust from back of the heel like an old Stauffer. You might want to look at that. (Are you the same Steve Smith from back when on the old MIMF? Feeling like old home week!)

Hesh: here’s the neck on the problem guitar.

https://www.mimf.com/library/Randy_Robe ... -2008.html

Ed: Thanks for the reminder. I don’t think the owner would have messed with the truss rod, I think I own this.

To all: Thanks a ton for the advice so far. I’m really, really averse to removing the fretboard to replace the truss rod. It’s got a fair amount of paua inlay, and see that option as a very very last resort.

https://www.mimf.com/library/Randy_Robe ... -2008.html

If it’s possible, any ideas that could avoid fretboard removal would be especially welcome, even if not the “best" fix.

Ignorant question, but would it seem likely that I would find myself needing to induce back bow down the road since this has been 16 years of pulling the neck forward? And, if I needed to increase relief with the current truss rod, would I be free from my current problem since it should be pushing up on the fretboard instead of down on the neck back?

Hey RN, I'm the same guy from the MIMF, good to see you still around!

Understand you did the recess just a 1 bolt solution. If I build another one it will adjust from the outside of the heel like a Stauffer although I made a custom hex drive on a small 1/4" ratchet and can adjust through the sound hole with strings on.

In my repair I removed the fret board, pushed the break back in glued and clamped it then cleaned up the inside and glued in a maple strip to make the channel shallower for the Blanchard rod. That made the neck thick enough under the rod to take the stress of adjusting the new truss rod.

Sorry, I don't have a photo of the maple reinforcement I put in the bottom of the channel.

The original break



Just clamped it with a delrin caul



Here you can see the difference in the original Hot Rod and the replacement Blanchard truss rods.

_________________
Steve Smith
"Music is what feelings sound like"

What Steve said and nothing will stop the instrument from reverting to the bulge. We see epoxies slipping more around 145F which will also soften and slip other glue joints.

In my experience a number of "slipping" operations that have been done in the past don't last and slip back. From neck pressing to slipping a neck block these operations can be problematic and not always, always permanent.

RN you really need a functional truss rod and the only real fix here that is going to be both functional and last is to replace the problem, the StewMac original hotrod rod. The only way to do that without making a new neck is to access the rod with the board being removed. Inlays can be removed and reinstalled.

I'll add that a proper fret dress at a minimum will be required as we will be changing the level set of the fret board. I personally would be inclined to refret it so we have a shot at leveling the board too.

Lots of work I know. This is not a quick fix problem it's a major structural issue caused by a rod that was dimensionally unsuitable for the reality of the neck thicknesses that people use on our instruments. Sucks I know.

Opinions:
To avoid this problem, what is the thinnest layer of wood to be left below a 2-way truss rod, in a 1 piece mahogany neck?

I've always read that 1/8" is the minimum. I prefer to leave at least 3/16" if possible.

dang I used a couple of those SM rods. By sorting one problem, not having mass removed from under the nut area to prevent possible Gibson style headstock breakage it looks like those early rods created a much larger problem over time.

I also used several although only 1 turned out to be problem but 1 was more than enough

_________________
Steve Smith
"Music is what feelings sound like"

Yeah they suck (the original taller ones) we have seen heart break from them a number of times in person and I've read about here perhaps a dozen times over the years.

Truss rods are also a form of insurance. So it's like purchasing insurance for your home and somehow the insurance burns down you home....

Again, thank you all for the wise counsel. I completely understand the only true “fix” is, as Hesh describes and Steve has demonstrated – replace the truss rod.

However, after thoroughly explaining the process to the owner and referring him to the above posts, he has decided he is not comfortable with that extensive an assault on his guitar (my gut feeling also, at least if attempted by me).
So (above all, do no harm) I would like your opinions of the following approach, which I believe still leaves a correct true “fix” possible down the road if necessary:

1. Induce relief partially with truss rod and string tension.

a. Fortunately requires front bow, not back bow, so:
i. truss rod end no longer pressing on blow out “bump” and now pressing on fretboard.
ii. Pressure from truss rod on back of neck is now mid-shaft around (6th fret), where wood and bond is thicker. (This does risk extending the “blow out” farther on up the neck over time if this area doesn’t hold.)

[Result so far – Neck off and truss rod in “neutral” the fret tops are dead flat 1-12 (beyond 12th drop off will be induced when tongue re-glued to top). Gradual ½ turn counter-clockwise induced a 0.004” relief at frets 5,6,7, unchanged after 3 days to settle in.]

b. Restring to tune to see if adequate additional relief is induced to end up with 0.010-0.015.

2. Adjust (increase) neck angle to bring action down to desired 4 and 5.5 (64ths).

a. Will require shaving up to 0.025 “ off some of the faces of the heel that abut the neck block cavity to allow heel to sit deeper into the pocket to allow this
adjustment. (original build miscalculation. again, why would it ever occur to me that someday you might adjust an adjustable neck??)

3. Nut likely OK as is. New nut if needed

4. New saddle if needed.

a. Change of nut to saddle distance and speaking length of fretted notes should be insignificant (though not unchanged) when neck is adjusted, as pivot point of
neck at 12 fret remains unchanged. (Can also be grossly adjusted with adjustable neck if needed to bring string length within saddle adjustment range).

5. clamp " bump" back in (ala Steve)

6. Thin superglue on edges of back of neck Bump out to eliminate any gap created for finishing, even if it's not likely to create much of a bond between the bump faces since the old epoxy is still in there.

7. Light sand just to knock down any edges and re-FP.

8. Move 2 states farther away from current location…

For Sale:
5 old style SM double action truss rods. Just found while sorting through boxes. Makes a great X-mas gift for the Ex.

Seems like a lot of work to got through without doing the full repair but after all it's up to you and the owner. You could get lucky and what you propose will be stable and never cause another problem ,,, or not. Good luck with it.

_________________
Steve Smith
"Music is what feelings sound like"

If it were me in this situation, I would replace the neck. Building a better neck would be preferable to trying to work around the shortcomings of the existing one.

Sounds like a well thought out plan RN and I specifically like that you considered that all of this is reversible and the whole-nine-yards new neck fix can still be done at a later date if someone wants to.

No one should ever attempt anything related to Lutherie that they are not completely comfortable with. I've seen the outcomes of this and it's not pretty and everyone loses.

People bring us stuff that they messed up and often it's the case that we will not rescue them. Poor prior work can be much more involved than taking it to a pro in the first place.

Couple of things that may assist you:

1). You can creatively level frets to increase or decrease a neck angle even though the neck angle does not change. We do this from time to time when a neck reset is warranted and the instrument does not deserve the investment.

2). String gauge changes can make a different too including if you can't get the action where you want it.

Good luck