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Thread: Truss Rods vs Carbon Fiber?

  1. #1
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    Default Truss Rods vs Carbon Fiber?

    Which do you prefer and why?

    I used a carbon fiber rod in my first build and it was super easy, but I've noticed that Truss Rods are on average about $10 less cost wise (ie LMI) and DO off an additional level of adjustment. If this is your preference, which style do you prefer? LMI offers something nice looking for $18 (https://www.lmii.com/truss-rods/3272...875-x-316.html), Stewmac's looks a little more basic for $14 (https://www.stewmac.com/luthier-tool...truss-rod.html)... or is there something else?

    Carbon fiber is just a little easier to use but as I shop around I find its a little difficult to find the exact dimensions I want (1/4" x 3/8") at a reasonable price. Someone recommended Dragon Plate but they only have 1/8" x 3/8" (for a really good price) ... so is it acceptable to embed the 2 pieces together rather than 1 solid 1/4" x 3/8" piece?

    So I ask again, which do you prefer and why?
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    Registered User sunburst's Avatar
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    Default Re: Truss Rods vs Carbon Fiber?

    We've been over this several times around here but I don't know if you can easily find discussions using the search feature.
    It comes down to adjustability. CF is not adjustable, an adjustable truss rod is.
    (My opinion to follow: )
    If you want a one-size-fits-all solution to maintaining neck shape, CF is a good method.
    If you want to be able to adjust for different strings, different players, different musical situations and so forth, install an adjustable rod.

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  4. #3

    Default Re: Truss Rods vs Carbon Fiber?

    On the second question; one rail or two, if the function is keeping the neck from bending up, not sideways, two pieces is just as good as one.

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    Registered User Glassweb's Avatar
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    Default Re: Truss Rods vs Carbon Fiber?

    after 50 years of playing the mandolin my motto (one of many I guess) is this... if it doesn't have a functional truss rod, I ain't buyin' it.

  7. #5

    Default Re: Truss Rods vs Carbon Fiber?

    All of my personal builds got single action truss rods, but they are minimally engaged for now. Down the road, who knows?

    However, I just worked on an older Rigel that had no truss rod (they were just CF) and the neck was badly bowed. I had to flatten the fingerboard from both ends, guesstimating at how much relief string tension would provide, then refret it. I've seen this in older instruments quite a bit. With a truss rod, you can set the neck to flat before leveling the frets. If string tension puts too much relief in the neck, you can dial it back with the truss rod. So my vote is go old school, the truss rod is a repairman's friend.

  8. #6
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    Default Re: Truss Rods vs Carbon Fiber?

    Ok, so what's your preference within the links above, or is there any difference?... LMI's truss rod has a coating that supposedly minimizes vibration, the SM version seems pretty basic.... and what is the difference between single action and double action truss rods?

    One more question... Is a truss rod embedded in epoxy or just held in place by the slot and hole that the end piece fits in?
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  9. #7
    Registered User sunburst's Avatar
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    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by soliver View Post
    Ok, so what's your preference within the links above, or is there any difference?... LMI's truss rod has a coating that supposedly minimizes vibration, the SM version seems pretty basic.... and what is the difference between single action and double action truss rods?

    One more question... Is a truss rod embedded in epoxy or just held in place by the slot and hole that the end piece fits in?
    I make my own (or have them made for me) so I have no particular preference between the linked ones. The two are very similar and functionally equivalent. They are also similar to mine, but mine are lighter in weight.
    For mandolin necks I see no need for a two-way rod. The neck is short and stiff relative to guitar/banjo/other necks, and I do not recall ever seeing a back-bowed mandolin neck. The extra weight of a two-way rod is simply extra mass IMO, and a single action rod is all that is needed.
    The rod must be free to move in order to work, and epoxying an adjustable rod into the neck will render it useless. The rod must, however, be fit snugly under a filler stick so that it cannot rattle or buzz.

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  11. #8

    Default Re: Truss Rods vs Carbon Fiber?

    After building three mandolins with graphite bars, I'm thinking I'll try a single action truss rod on my next one. A couple of years ago I followed a discussion about how the bent Gibson rods worked, which revealed lots of interesting installation techniques. Is there any consensus about how well a truss rod just below the finger board works compared to those that go down toward the heel, whether bent or straight? I seem to recall someone saying they had built truss rod necks with all the common installation techniques, and they all worked. Is it worth exploring this further or just go with one parallel to the fingerboard?

  12. #9
    Registered User sunburst's Avatar
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    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by Parker135 View Post
    ...I seem to recall someone saying they had built truss rod necks with all the common installation techniques, and they all worked. Is it worth exploring this further or just go with one parallel to the fingerboard?
    James Condino.
    IMO, it is not worth experimenting, it's all been done. We can save time and effort by learning from others' experience.
    "Single action" truss rods must be installed below the neutral axis of the neck shaft to be effective, and theoretically the function improves the deeper they are set. Fortunately, due to neck shape and construction, the neutral axis is not far below the fingerboard.

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    Default Re: Truss Rods vs Carbon Fiber?

    I had a Gibson a few years ago with a truss rod that would not straighten the neck. Removed the fingerboard and deepened the truss rod in the neck and it works perfectly now. As was said earlier, deeper works better.
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    Default Re: Truss Rods vs Carbon Fiber?

    I owned several truss rod mandolins over the years and never had problems with any of them.

    Several years ago, against my better judgement, I bought a mandolin with CF. It was so pretty and the tone was amazing. The action always felt stiff, and the strings above the 7th fret didn't have quite enough clearance, which affected the tone. I thought I could raise the bridge and fix the problem. However to fix the problem I had to raise the action to the point where it was difficult to play. I've had good luthiers look at it and try to tweak it, but it is beyond fixing.

    I would never consider carbon fiber neck reinforcement again!

  15. #12

    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by sunburst View Post
    James Condino.
    IMO, it is not worth experimenting, it's all been done. We can save time and effort by learning from others' experience.
    "Single action" truss rods must be installed below the neutral axis of the neck shaft to be effective, and theoretically the function improves the deeper they are set. Fortunately, due to neck shape and construction, the neutral axis is not far below the fingerboard.
    Okay, deeper it is! I must have remembered incorrectly. Thanks, John.

  16. #13

    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by sunburst View Post
    James Condino.
    IMO, it is not worth experimenting, it's all been done. We can save time and effort by learning from others' experience.
    "Single action" truss rods must be installed below the neutral axis of the neck shaft to be effective, and theoretically the function improves the deeper they are set. Fortunately, due to neck shape and construction, the neutral axis is not far below the fingerboard.
    Okay, deeper it is! I must have remembered incorrectly. Thanks, John.

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    Default Re: Truss Rods vs Carbon Fiber?

    As John says, we have been over and over this again and again. Everyone always comes up with some example where a carbon fiber rod has failed, but seldom any examples where a truss rodded neck has failed. My experience is zero failure of carbon fiber, and 0.75% with enough bend to justify a refret. The refrets fixed the problem permanently. I have seen plenty of bent necks with a truss rod, or a truss rod so tight it can't adjusted to fix a bow in the neck so failures are much more than zero. Also truss rods weaken the neck at the nut so breakages are more likely. My bet is with the "failed" carbon fiber necks, the carbon fiber rod was not big enough, so it is not the fault of the carbon fiber method it is the fault of the builder for not installing enough carbon fiber! If you use a 1/2 inch x 1/4 inch carbon fiber rod then it is very reliable, not adjustable, but will never need to be adjusted ever. No complaints so far after 26 years, and for those who know it all and absolutely insist on a truss rod then bully for them, go elsewhere, I already have a big backlog of work, they won't be missed. I do use a two way adjustable truss rod for octave mandolins and guitars, so I am not against using them.
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    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by peter.coombe View Post
    ...My bet is with the "failed" carbon fiber necks ... is not the fault of the carbon fiber method it is the fault of the builder for not installing enough carbon fiber! ...
    My bet would be that the majority of failures of either system are the fault of the builder.

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    Default Re: Truss Rods vs Carbon Fiber?

    My bet would be that the majority of failures of either system are the fault of the builder.
    Yep, but with truss rods it can also be the fault of the manufacturer of the truss rod. Of the truss rods I have used, one had to be replaced because a faulty weld snapped (lucky I did not install another I found with the same faulty weld), and I have another guitar with a different truss rod that I am fairly certain has a snapped weld as well. Not confirmed yet because I need to take the neck off to confirm, and I have not had the time to do it. I guess one can make them yourself, and one way mandolin truss rods are easy, but two way guitar rods are more involved and I hate metalwork.
    Last edited by peter.coombe; Jan-06-2021 at 6:00pm.
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  23. #17
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    Default Re: Truss Rods vs Carbon Fiber?

    This is great information... thanks so much everyone.

    In the hunting I have done, one annoying anecdote I can share with anyone else looking: when it comes to Carbon fiber, the term "rod" only applies to ROUND profiles ... anything with a square or rectangular profile Is referred to as a carbon fiber STRIP. So if you are searching sites of manufacturers rather Luthier Supply companies, search for "1/4" x 3/8" carbon fiber strip" and you are more likely to find what you are looking for.

    My second mandolin which I am starting will be for myself and I don't foresee the need of having that adjustment as all of my other mandos have CF reinforced necks, so I will forego the truss rod this time 'round. Dragon Plate has a minimum order of $30 so there would only be a savings if I were in more of a production mode. Amazon was out of stock of a 6mm x 10mm x 400mm CF so I found a 6mm x 10mm x 600mm CF on eBay for approximately $18 with free shipping. That may be enough for 2 instruments but I'm not 100% certain. We shall see.
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    Registered User j. condino's Avatar
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    Default Re: Truss Rods vs Carbon Fiber?

    Yes, about 8 years ago I asked ten of the best mandolin builders in the world some serious truss rod questions. I got about 17 different answers, so....

    I made up ten identical necks, with ten different truss rod designs. They all worked so close that there was virtually no difference. Pick the one you like and go with it.

    There are thousands of old Gibsons with no adjustable or carbon rods inside the neck that have worked fine for 100 years. A well designed and made neck is very stable on its own just as much as a poor neck build will represent a lifetime of frustration no matter how much internal additions you put in.

    I make all of my own adjustable rods out of titanium & I also use carbon fiber rods. It usually comes down to whatever the person commissioning the build has obsessed about over the internet for too long.....

    As someone who also has done extensive repair and restoration work for 40+ years, 99% of the messed up necks I've seen have been instruments WITH an adjustable truss rod that was abused by someone who did not understand how they worked. I always find it interesting that small scale instruments like the mandolin do fine without adjustable rods and giant instruments like the double bass never have them, but the mid sized instruments in the mandola- octave-mandolin to guitar range seem to need a lot more neck adjustments.

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  26. #19

    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by j. condino View Post
    There are thousands of old Gibsons with no adjustable or carbon rods inside the neck that have worked fine for 100 years. A well designed and made neck is very stable on its own just as much as a poor neck build will represent a lifetime of frustration no matter how much internal additions you put in.
    23 A Jr as evidence. Bought from the family of the original owner. Original bridge (not adjustable) and ebony nut. Strings were so old when I got it they disintegrated upon contact. Refret, set-up and clean Bill of health by Sunburst circa 2017. Only issue is the nut on the pickguard clamp likes to loosen itself up and rattle at the worst possible times. Plays like a dream. My buddy. This mandolin actually hung out at the Workshop de Condino for a few days several moons ago.

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    Default Re: Truss Rods vs Carbon Fiber?

    double post.
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  29. #21

    Default Re: Truss Rods vs Carbon Fiber?

    I've only ever had to adjust truss rods on customer's mandolins if the customer (or someone in the past) messed with it or broke it.
    So I build mine with carbon fiber. Same reason I use a zero fret -- less for someone who doesn't know what they're doing to mess up, ruining the player's experience of the instrument I made.

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  31. #22

    Default Re: Truss Rods vs Carbon Fiber?

    My building experience with a grand total of three mandolins includes one with a single eighth-inch aluminum bar and two with single eighth-inch carbon bars. For those using two carbon bars, do you install them in individual groves set slightly apart to help reduce twisting, or fit both within a single, wider groove?

  32. #23
    Registered User Tom Haywood's Avatar
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    Default Re: Truss Rods vs Carbon Fiber?

    Old discussion; new examples.

    A 1920 version of the Gibson A Jr. shown in the above post came into my shop yesterday for repair to the back pulling loose. The first thing I noticed was how perfect the neck is after 100 years with no truss rod. Last week, a mid range classical guitar came in for - wait for it - truss rod repair. A truss rod in a classical guitar was a red flag that the manufacturer isn't choosing the right pieces of wood for the necks. First thing I noticed was that with zero tension on the rod, the neck was bowed like a boat. Further inspection showed that the rod had been bent where the adjusting nut goes, the nut was off and the threads in it were all boogered up, and the plastic "washer" that the nut pushes against was basically destroyed. The cost of repair exceeds the used value of the guitar.

    I discovered a while back that it all boils down to the piece or pieces of wood used in the neck. The right piece of wood will hold the tension without warping. The problem is how do you consistently find the right piece of wood, and how do you trust it for years to come.

    I use a 1/4" round straight non-adjustable steel rod in some of my mandolins, such as the campfire model. I don't think it is needed, but I feel more comfortable. Carbon fiber accomplishes the same thing but costs more, so I haven't used it. In my more expensive models, I use a single action adjustable truss rod - usually the SM version, . The reason is that sometimes slight adjustments to the action are needed as the weather changes throughout the year, and the truss rod adjustment is an available tool to get it perfect.

    FWIW, I discovered this week that models of a very nice upright bass sold by a high end violin/cello/bass dealer now have truss rods so that minor adjustments can be made when the weather changes.
    Tom

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  34. #24
    Adrian Minarovic
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    Default Re: Truss Rods vs Carbon Fiber?

    I've been using simple adjustable rods from my first build and don't think I'm going to change that. I still have my first mandolin and never needed to touch the truss rod. But if the time comes I know it is there to help.
    Often good piece of wood is not enough. I believe well chosen wood with straight grain can be trusted for a century or so at least, but I've seen my share of mistreated instruments that spent time in wet basements, hot attics or other hostile places and those often show bends under tension of strings. Carbon fiber would not help with these, sometimes it would be nearly impossible CF reinforced neck that bowed in such conditions. Most truss rod fitted necks can be brought back to life just by adjusting the nut.
    BTW, I use 4mm metric threaded rod for truss rods with brass nuts on both ends similar to old Gibson, though my curve is not as smooth as theirs but almost straight copying bottom of neck and then abrupt ~15 degree angle towards center of heel. I use shrink tube on them. All you need is a metal saw and a file.
    The S-M and other commercially available rods for mandolins seem awfully heavy to me. Old Gibsons used even thinner rods than I do.
    Adrian

  35. #25
    Adrian Minarovic
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    Default Re: Truss Rods vs Carbon Fiber?

    Quote Originally Posted by Tom Haywood View Post
    FWIW, I discovered this week that models of a very nice upright bass sold by a high end violin/cello/bass dealer now have truss rods so that minor adjustments can be made when the weather changes.
    There is definitely some movement in traditional building techniques of violin making especially in cello and bass areas where necks are very suspectible and reinforcement of some kind has already shown it's role. Besides neck reinforcements some makers use also neck heel reinforcement as the shape is suspectible to slow bending right at the L shaped area of heel thus lowering the neck angle which is considered very critical in classical luthiery.
    Adrian

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