Does my mandolin need a truss rod?

[mboursnell]

The neck of my mandolin is mahogany, with two rosewood strips layered into it. I was thinking of glueing a carbon-fibre truss rod down the center using epoxy-resin based glue. Do you think I need a truss rod? Any views?

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92151

The fingerboard is ebony.

[sunburst]

A truss rod is adjustable, If you want adjustability, you need a truss rod.
A CF rod is a stiffener, is not adjustable, and is not what I would call a truss rod. I don't know (and can't know) if the neck is stiff enough as is, but if it is, no you don't need a CF rod. If it is not stiff enough a CF rod would be a good thing (assuming you don't want it adjustable). If it is stiff enough and you add CF anyway, there is no harm.

[mboursnell]

Hmm. Thanks. So the question is: how to decide if it's stiff enough....

[Pete Jenner]

Go on be a devil - put the bar in. I see you have already bought it so why not use it?

[sunburst]

Hmm. Thanks. So the question is: how to decide if it's stiff enough....

At the risk of sounding like a bit of a smartass, string it up for a few years and if it bows too much, it wasn't stiff enough. That's the best way to tell.

[Lefty Luthier]

I recently had a mandolin that I built in 1962 in for a refret job. It has a walnut neck that had no truss rod or other type of stiffener. That neck was as straight as when delivered after being under constant tension for 50 years. I do believe that it is advisible to use either an adjustable truss rod or CF spline in all instruments and I am certain that on a guitar it is essential.

[mirwa]

A truss rod is adjustable, If you want adjustability, you need a truss rod.
A CF rod is a stiffener, is not adjustable, and is not what I would call a truss rod.

Without wanting to dish you, I respectfully disagree.

A truss rod is an insert placed into a neck to ""truss"" the neck, the truss is simply a definition of a supportive structure.

Many instruments come out with ""non"" adjustable truss rods.

To the original op, if you have it, then fit it, you can only improve the strength and reduce the risk of long term bow.

[JEStanek]

When I think Truss Rod or see them spec'ed onto a mandolin, I assume it is an adjustable rod accesible through the headstock or the soundhole. A CF stiffener does just that, and it needs to be properly installed and of the right size for the neck. I don't view then as necessary on all mandolins, especially short necked (12 frets to body), made of good, well seasoned, hard woods. I think many people expect them to be there, even if they aren't really necessary.

Jamie

[Goodin]

At the risk of sounding like a bit of a smartass, string it up for a few years and if it bows too much, it wasn't stiff enough. That's the best way to tell.

John I always enjoy reading your posts. very informative and sometimes funny.

What did Gibson use on their mandolins pre-1922 (pre adjustable truss rods)? I've owned and played many and don't recall any of them having a bowed neck.

[sunburst]

What did Gibson use on their mandolins pre-1922 (pre adjustable truss rods)? I've owned and played many and don't recall any of them having a bowed neck.

Gibson used triangular hard maple (some say they were cherry, but all I've seen were maple) inserts that ran the length of the neck, and were so big that they were the bulk of the neck. Sometimes they put them in guitar necks too, and the only pics I can find right now are of a later (40s) guitar. Apparently the 'war shortages' of metal prompted them to revisit the old method of inserting the maple stiffener. The end of the maple piece often shows through the peghead overlay, and can be seen a the end of the neck heel. Maple is a very stiff wood that was easily available and inexpensive for Gibson.
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BTW, some of the pre-22 necks did bow. Perhaps as a player, you don't see those as often as I, as a repairman, do.

[Goodin]

Thanks John. Yes I was surprised with how stiff maple is the first time I cut it on the band saw. As hard or harder to cut than ebony. What do you do to straighten out those old no truss rod necks?

[sunburst]

Depends. As it happens, I just did one in several steps:

First step, I removed the fingerboard and "heat set" the neck. That is, I clamped it on a heat bar with shims to give it a slight back bow. Heat the neck as hot as possible with no finish damage then let it cool clamped into a back bow. That took care of some of it.
Next step was to mill the fingerboard surface of the neck to flatten it more, but you can't go too far and still reglue the fingerboard without major finish touch up.
Next step was to re-glue the fingerboard with hot hide glue and a clamping caul that forced the neck into a slight back bow until the glue fully cured.
Next step, mill the fingerboard perfectly flat, with a slight drop-off past the 10th fret or so.
Next step, new frets followed by a mill and re-crown.
At that point, string tension pulled just the right amount of bow into the neck for good fingerboard relief, and the extender part of the 'board was no longer too high and causing buzzes.

All in all, it's a little more work than tightening an adjustable truss rod.

[Goodin]

All in all, it's a little more work than tightening an adjustable truss rod.

Yes, SLIGHTLY more work than adjusting a truss rod. ;)

[Big Joe]

I checked out a really good mandolin by a fairly new builder last week. Everythin was excellent, but it did not have a truss rod. It had a CA rod. It was plenty stiff, but the fretboard has a bit too much relief to give good playability and perfect intonation. The only fix for this is to pull the frets, plane the board, and then refret. That is a LOT of work and expense to take care of what an adustable truss rod would acomplish in a few moments with no repairs to the instrument. Only a few can actually build an instrument with no truss rod and get it perfect. As far as rigidity, it is great. However, for adjustability it does not function well at all.

[lonewolf]

The key word is adjustable. As a full time repairman of over 40 years, if I didn't learn anything else, it's that players do not all want the same thing. They use different string gauges, tune to different pitches some times, and definitely play differently. The only way to accommodate all of them, is through adjustability.

Many companies over the years, have tried various types of non-adjustable stiffeners in stringed instrument necks, and so far all have failed, when measured over the long life of most instruments. The most famous I guess would have to be the Martin guitar company, who tried more than one design of neck inserts, before finally giving up in recent years, and installing adjustable truss rods in their guitars. I could name many other makers as well.

Yes a mandolin neck is very short, but the string tension is also very high! Sorry but my vote is for an adjustable truss rod ,or even two (that's right) in some cases.
Gene Warner
retired repairman

[almeriastrings]

Many companies over the years, have tried various types of non-adjustable stiffeners in stringed instrument necks, and so far all have failed, when measured over the long life of most instruments. The most famous I guess would have to be the Martin guitar company, who tried more than one design of neck inserts, before finally giving up in recent years, and installing adjustable truss rods in their guitars.

Not quite.

For the record, my original early '39 D-18 still has perfect neck relief. So, interestingly, do the two war-time Martins I own, both with ebony reinforcements. Same with my '50 D-28 and other 50's to early 60's examples I have acquired over the years. I was picking Bill Clifton's old D-35 just last night... neck relief on that is still as good as the day it left the factory.

C F Martin have also not "given up" on non-adjustable necks. The D-18 and D-28 "Authentic" and "Museum" series still use non-adjustable T-bars.

I'd just add, that in my experience, THE big problem with adjustable rods is that people who don't have a clue what they are doing 'adjust' them! Out comes the hex key to "lower the action", etc... I've seen so many stripped threads and rattling truss rods it's ridiculous. I am not suggesting there is anything wrong at all with an adjustable rod (provided it is made right and installed right), but simply that unfortunately, it does give people who know nothing something else to mess with.... done right, and used correctly, they're fine.

[mirwa]

That makes no sense. A guitar built in 1939 with no truss rod still has perfect neck relief. Either You mis-understand what is correct relief or the guitar has been levelled and refretted in its life

You should have 0.002" relief at the 8th fret, the rest of the board should be almost dead flat. I do not believe this is possible on an original untouched non truss rod neck.

Martin, bless there souls at least tried many options over the years to try and minimise the impact strings have on necks, through there risks and innovations we today can experiment safely.

Ive repair hundreds if not in the thousands of D-18's and D-28's, and yes I am a authorised Martin repair centre, manufacturers warranty and non warranty work.

In the older days working out the thickness of a neck was hit and miss, its not like today where we have computers and calculators that can measure force per sq area against applied loads, add this in and you can achieve a safe cross sectional area that will work, even then it still does not always work, becuase you also have to deal with grain and grain runout.

Truss rods are the best thing in the world, I do believe carbon fibre non adjustable units are the next best option as they seem to give a slightly warmer sound, all of course IMO.

[Jim Baker]

My Stewmac campfire kit came with a steel stiffener which has worked out very well. However, I built an octave mandolin and used carbon fiber. After a few months the action gradually changed so I rebuilt the neck with a truss rod. No change since. My next build is a mandolin. I plan to try carbon fiber in it.

[almeriastrings]

You should have 0.002" relief at the 8th fret, the rest of the board should be almost dead flat.

You seem to be suggesting that there is a single, universal amount of neck relief that suits any guitar, any player, playing any style, using any strings.

Is that so in your opinion?

Just like to clarify that.

[mirwa]

Relief is different to action height, action height is set to suit the players style. Relief - dependant on the type of guitar classical / acoustic / electric / bass then yes there is a universally accepted amount per style of guitar

[almeriastrings]

I am fully aware it is different to action height, I am simply trying to clarify whether you are claiming that 0.002" relief at the 8th fret is suitable and appropriate for the instruments mentioned, namely, vintage Martin dreadnoughts, and that such relief is "correct" regardless of string gauge, or playing style.

I also confess to being slightly surprised, that as an authorised C F Martin warranty repair centre, you claimed that Martin no longer used non-adjustable neck reinforcements, when this is completely untrue, and these continue to be used on their high-end guitars to this day.

[mirwa]

I also confess to being slightly surprised, that as an authorised C F Martin warranty repair centre, you claimed that Martin no longer used non-adjustable neck reinforcements, when this is completely untrue, and these continue to be used on their high-end guitars to this day.

Did not realise I had said that, can you cut and paste where I had made that statement.


I am simply trying to clarify whether you are claiming that 0.002" relief at the 8th fret is suitable and appropriate for the instruments mentioned, namely, vintage Martin dreadnoughts, and that such relief is "correct" regardless of string gauge, or playing style. .

Yes, it is irrespective of string gauge or playing style, if you were for example to do something like a drop C tune and wanted to run a 60 thou string on your bass side, this would be about the only exception.

For info, we are an authorsed warranty repair centre for Martin, Taylor, Gibson, Tanglewood, Dean, Yamaha, Music Man, Cort, Sterling, Luna, Johnson, Jose Ferrer, Kayne, Walden, Valencia, Hagstrom, Lag, Gypsy rose, Mahalo, to name but a few.

The point, I do this for a living.

That being said it does not detract from my original statement, I do believe if your neck has perfect relief almost dead straight at this juncture in its life (that is it was made 73 yrs ago) then its had the board planed to perfection and had a refret, or you may not understand what the relief for your guitar should be.

[almeriastrings]

Sorry, that was another poster who said that. Apologies for confusion.

You have not answered the direct question I put, however.

I am fully aware it is different to action height, I am simply trying to clarify whether you are claiming that 0.002" relief at the 8th fret is suitable and appropriate for the instruments mentioned, namely, vintage Martin dreadnoughts, and that such relief is "correct" regardless of string gauge, or playing style.

Could you address that, please?