Repairing necks with nonadjustable trussrod

[Tim Logan]

I am not a luthier - just a player. I have a mandolin (which I absolutely love) that has a nonadjustable trussrod. I would like to know if or how the neck can be repaired or adjusted if it ever gets a slight bow and throws the intonation off. Thank you in advance for any input.
Tim

[multidon]

I don't claim to be a luthier either but I have studied the subject quite a bit, and have done some projects, with varying results!

There are two ways to go in such a case as you describe. Both involve re-frets. The first is to pull out the frets, then plane the fret board to flatness, then re-fret, level frets, crown, and dress. This leaves the fret board a little thinner at the two ends, but usually not a big deal. The other way is to do a compression re-fret. You replace the frets with new frets that have a thicker than normal tang. The collective additional compression of the new fret tangs forces the neck back towards straightness.

Sometimes, simply leveling the frets is enough if the curvature is very minor. This leaves the neck bowed but the frets level, which often makes no difference to the player since you don't press the string all the way to the fret board anyway.

You will hear some advocate for "heat pressing" a neck. This used to be the standard procedure back before there were truss rods, and still is used on classical guitars. The problem with heat pressing is it is seldom permanent. Once wood has a set to it, it often wants to return to that state.

[pops1]

You can also remove the fingerboard and level the neck, then replace the fingerboard. You won'n necessarily have to thin both ends if you don't remove the fingerboard, but you will have to thin the end at the nut from maybe the 5th fret to the nut. Compression fretting may work depending how deep your neck is. I wouldn't worry about it until you need to many teens Gibson's are still fine and don't have a non adjustable truss rod.

[Tim Logan]

Hi Don and pops1 -
Thank you very much for your input. It relieves me to know that there are options. This is a great sounding vintage mandolin and i wouldn't want to lose it to an unsolvable neck problem. I really appreciate your responses.
Regards,
Tim

[Steve Sorensen]

Not too complicated to have a luthier pop off the fingerboard, cut out the carbon fiber rod(s) and replace with an adjustable truss rod. Of course, there will need to be a way to access the new truss rod for adjustment.

At the root of the issue is the reality that fixed CF trusses are not adjustable. So, depending on the neck wood, temperature and humidity fluctuations, string gauges, action height from the bridge, etc., these necks only drift in one direction over time . . . adding more and more "relief" which makes the instrument feel harder and harder to play.

When I first started building, I thought CF rods were the modern solution -- "Keeps the neck straight as an arrow." Sadly, this is not always true.

I've talked to a few other builders who also have been forced to do this surgery on their CF reinforced necks. Bummer. At this point, I've had to replace about half of the CF rods from my early builds with adjustable truss rods. I expect more will need the fix over time. Seems like only the chunkier, really hard sugar maple necks have the inherent stiffness to avoid this problem.

Sadder but wiser . . .

The good news is, once you get the neck issue fixed, the mandolin will likely feel like a dream to play. It is hard to emphasize how often I see players befuddled by increasing loss of "ease of play", slowly, like the frog boiling story. They have no idea that the neck of instrument is at the root of the problem.

Steve

[Tim Logan]

Thank you Steve!!
Tim

[fatt-dad]

my 1920 Gibson A3 was stored in an attic, prior to my purchase. The neck bowed. It doesn't have an adjustable truss rod. Dude removed the fretboard, steam-pressed the neck to flat, returned the fretboard and voilla! It's remained stable since then, c. 1985 and I still play it. . . A lot!

f-d

[jmkatcher]

I bought a used instrument - apparently with a carbon fiber stiffener - but with no adjustable truss rod. The neck & intonation were off requiring the frets pulled and the board replaned. The repair person thought that because the instrument wasn't old or abused in any way, that it had simply not been constructed right to begin with (by maker with good rep too, not slave children somewhere). It was fixed well and the new fret job was better than the original but I had a bad feeling about the whole expensive experience. I'll never buy another non-adjustable instrument again.

[amowry]

I have to say I've had the opposite experience-- I've had to repair a number of trussrod necks from various builders that didn't have the stiffness to hold up over time, but I've only had to re-flatten one carbon-reinforced neck, which is easy to do as part of a refret. I think a key element is that the fretboard has to be glued on with hide glue so that it won't creep over time, because the fretboard is essential to the stiffness of any neck.

[peter.coombe]

I will back up Andrew. I have been using carbon fibre in necks for maybe 20 years, built around 200 mandolins and mandolas and have only needed to re-flatten one as part of a re-fret. With the other posts, I suspect if the neck bowed then the carbon fibre rod used was probably not big enough. I have always used 1/2" deep x 1/4" wide carbon fibre and have no intention to change because in practice it has been very reliable. I have seen plenty of bowed up necks with truss rods.

[Marty Jacobson]

I've had to fix many mandolin necks with truss rods. 90% of the time, it was due to someone messing with the truss rod without knowing what they were doing. Sometimes in doing so, they mess up the nut, threads, or both. So far I haven't had to do anything to one of my mandolins, or someone else's, with a CF stiffener.

[Max Girouard]

I'm with Andrew, Peter and Marty on this one. We've installed carbon fiber rods (beams) in over 100 instruments and found them to be very reliable. We also use a 1/2" deep and 1/4 " wide beam set deep in the neck with a slow cure epoxy. We get to see over a dozen instruments every March at the March Mandolin Festival, and so far all the necks have stayed just about dead flat.

We have however switched over to a truss rod as a standard offering, only because we found it easier to sell an instrument equipped with a truss rod. Many of our custom instruments are still made with carbon fiber per customer requests and our recommendation.

[pops1]

I had to deepen a truss rod in a Gibson because it was not able to keep the neck flat. It was in wrong, a year later now and still works well. I have seen bow in both, but I don't think I could say there is an advantage to either done right.

[Scott L]

I owned a beautiful, great-sounding mandolin by a respected builder that had CF neck reinforcement without an adjustable truss rod. I loved everything about the mandolin except for the presence of excessive relief (slight bow) making the action above about the 7th fret too high. I looked into fixes, but decided I would just sell the mandolin rather than investing the money. I found out that it is indeed possible to fix this problem, and it may be relatively straightforward to repair from a luthier's perspective, but it is a costly repair from a consumer perspective. I've been hesitant since that time to consider buying any mandolin without a truss rod. That being said, I have a 1921 Gibson A-4 without an adjustable truss rod, and its neck is straight and a joy to play.

[fatt-dad]

I guess I should add, my 5 year Cohen has been very stable. It has a CF rod in it.

f-d

[HoGo]

I've had to fix many mandolin necks with truss rods. 90% of the time, it was due to someone messing with the truss rod without knowing what they were doing. Sometimes in doing so, they mess up the nut, threads, or both. So far I haven't had to do anything to one of my mandolins, or someone else's, with a CF stiffener.

99% of mandolins (or other plucked instruments) have adjustable trussrod so these problems will occur frequently and are not sign of flawed concept. The only such repair I did was failed square steel tube in neck. Epoxy failed and the neck bent. I filled the slot with new wood and installed standard compression rod.
IMO, if PROPERLY executed both systems are valid, but on longer necks (f-hole mandolins or banjars, guitars) I would prefer adjustable as need for relief changes upon owner and playing style etc. On shorter necks like oval A's nonadjustable is OK as very unlikely it will need adjustnment.
I personally use light thin (4mm diameter) compression trussrod, I hate those heavy double rods in mandolin, it throws the balance out of window...

[peter.coombe]

I don't think any of us are saying that a truss rod is a flawed concept. I use a double action truss rod on all my guitars and longer scale length mandola so horses for courses. It is just that what was posted about carbon fibre rods being unreliable in mandolins is not our experience.

[Tim Logan]

Hmmm....I just discovered something interesting. The Mandolin in question is a 1994 Bruce Weber signed Flatiron A5-Jr. the Flatiron catalog lists NON-adjustable truss rod under the specs. However, on a whim I just took off the trust rod plate. There is a nut on the end of the trust rod - which I assume means it is adjustable. Is that an incorrect assumption? Thanks in advance. Regards, Tim

[pops1]

A nonadjustable rod would have no need for a cover so I would say yes, it is adjustable.

[rudy44]

The mando I play (shown as my avitar photo) has a 2024-T4 aluminum bar I embedded within the neck. I built in a tiny forward bow and it has remained exactly as built for 25 years, so a non-adjustable neck isn't doomed to failure...

[gtani7]

another thing to consider: I've heard of refrets where the tangs were too wide for the slots and this forced a properly relieved neck to be flat or even backbowed. I suppose if you have too much relief, this could be used to correct for that.

[pops1]

another thing to consider: I've heard of refrets where the tangs were too wide for the slots and this forced a properly relieved neck to be flat or even backbowed. I suppose if you have too much relief, this could be used to correct for that.

The old Martin bar frets were made in different thickness frets just for that purpose. I have used that to success in the past.

[Ron McMillan]

my 1920 Gibson A3 was stored in an attic, prior to my purchase. The neck bowed. It doesn't have an adjustable truss rod. Dude removed the fretboard, steam-pressed the neck to flat, returned the fretboard and voilla! It's remained stable since then, c. 1985 and I still play it. . . A lot!

f-d

That's great to hear. My 1920 Gibson A2 needs precisely that done to make it playable again. Now, all I need to find is a Thai luthier who understands the job at hand

EDIT:

Though it appears that not all experts agree that steam is the way to go. Cafe member Paul doesn't appear to use it any more.