Truss rods

[putnamm]

As this is my first-ever mandolin build, I am following Siminoff's book as much to the letter as I can. You may know that he recommends using a piece of welding rod, the peghead end threaded and the body end bent at an angle so as to seat in to the heel of the neck.

In reviewing more modern references (primarily websites and social media like Instagram) I see a lot of people using the carbon fiber rods. These seem to be straight, no bend, no thread for a nut to be placed.

My question is: Are the carbon fiber rods just easier, and that's why people use them? Does the absence of a nut sacrifice anything such as stability, tuning, etc.?

I have to admit, making and fitting that welding iron truss rod was one of the more painful and frustrating parts of this build!

Thanks for your feedback.

-Mark

[billhay4]

Carbon fiber rods are not really truss rods in that they are not adjustable. The function of a truss rod is to give some adjustment to the neck bow. Carbon fiber is to stiffen the entire neck, but they have no adjusting mechanism.
Some builders use both.
Bill

[Br1ck]

You can buy truss rods. It's nice to have double action rods.

My A-1 has survived 105 years without one, but the neck is short and stout.

[mirwa]

My question is: Are the carbon fiber rods just easier, and that's why people use them? Does the absence of a nut sacrifice anything such as stability, tuning, etc.?

A truss rod creates strength between two points, just like building a bridge and having trusses fitted.

An adjustable truss rod allows us to manipulate the curvature of a fingerboardif it is lesss than desirable.

Carbon fibre rods, steel box ones like Martins, aluminium channels these are all typically non adjustable truss rods.

You then have single action and dual action truss rods, single action only adjusts in one direction, dual actions adjust both ways.

At times I have fitted to “”12 string guitars” 2 carbon fibre truss rods and a dual action truss rod in the centre, makes for a beautiful thin neck with a smooth low action.

Steve

[LuthieroftheDesertLoon]

Any truss rod better than the other?
I know again this will be most likely choice
but what's the thought on who makes a better one.

[CES]

One of the advantages of CF that I've seen touted is it's weight reduction compared to a truss rod...

[Mandoplumb]

Is weight reduction in the neck an advantage? Some claime a heavy peghead add to the mandolin. Enquiring minds want to know.

[mirwa]

Any truss rod better than the other?
I know again this will be most likely choice
but what's the thought on who makes a better one.

I make my own
http://www.mirwa.com.au/HTS_Dual_Acting_Trussrod.html

Steve

[sunburst]

Is weight reduction in the neck an advantage?

I think so for a couple of reasons.

-Mandolins with F5 neck length have a serious tendency to be neck-heavy, hang awkwardly on a strap, and require the player to control the position of the instrument while playing. Lighter necks help with that. A mandolin with good balance in the hands feels better to many players, a that can contribute to improved enjoyment if not improved playing.

-All other things being equal, a lighter instrument is more likely to be responsive and have good loudness. Sound is subjective, so whether or not a more responsive, louder mandolin sounds "better" is a matter of opinion, but as long as "tone" (also subjective) is there, my opinion is that lighter sounds better.

Mandolin necks are so short and sturdy, having to support the tension of 8 steel strings, that they nearly never show a back bow, so IMO, two-way truss rods are not needed. Since two way rods are generally heavier than standard rods, that is a source of weight saving in the instrument and in the neck. To me, both of those things are more important than having a rod that may be able to correct the very rare back bow of a mandolin neck.
I no longer make my own rods, but instead have them made for me by a machinist, but they are basically a standard tension rod, but they weigh in at about 23 grams. That is lighter than most steel tension rods.

Carbon fiber neck reinforcement can weigh even less than that, but I prefer to have the option of adjusting neck relief rather than having a one-size-fits-all predetermined neck relief supported by a stiffener.

[LuthieroftheDesertLoon]

Thanks everyone, much appreciated
Good feed back

[HoGo]

I'm using 4mm threaded rod for truss rod (as the closest metric equivalent to vintage Loar size). Close to 20g weight, that is comparable to medium-sized CF rod used by many mandolin makers.

[sunburst]

...Close to 20g weight...

Does that include a washer and adjuster nut? Seems kind of light if it does.

[j. condino]

I most often use carbon fiber for mandolin necks, but when requested, I make all of my adjustable truss rods out of titanium. It is a bit more difficult to work with, but the weight difference is significant and there is something about the spring rate that is difficult to describe. Compare a plain steel rod to titanium and the ti is much lighter but it is has a very "snappy" and quick spring response that appeals to me.

About six years ago, I contacted about ten of the best builders in the world about truss rod advice; the heavy hitters that are worshiped around here. I was hoping for some continuity among them, but I got about 15 very conflicting answers. One way, two way, curve up, curve down,....blah, blah, blah...So, what to do? I answered my own questions and I made up six different necks with six different truss rod systems. Guess what- they all worked almost identical. That made the choice easy- I use a material that I like and picked the design that is the simplest to manufacture.

Here are a few from recent batch of 'dreads...

j.

[j. condino]

It is your first mandolin. Just pick something simple and go with it. Don't overthink things....

Worry about the bigger things for build number 2. The most important thing you can do is just make everything as simple as possible and finish this first instrument.

[HoGo]

Does that include a washer and adjuster nut? Seems kind of light if it does.

The rod itself is closer to 17 grams (never weighed it but according to my calculations it is below 18g) and I use rather small steel nuts on hidden side and also small brass ones in the pocket. Loar rods were also thinner than what most makers use today. I don't get the double action rods that have that mass of 3/16 rod even doubled. I didn't like the Waverly tuners because they added so much weigth to the neck.

[HoGo]

I most often use carbon fiber for mandolin necks, but when requested, I make all of my adjustable truss rods out of titanium. It is a bit more difficult to work with, but the weight difference is significant and there is something about the spring rate that is difficult to describe. Compare a plain steel rod to titanium and the ti is much lighter but it is has a very "snappy" and quick spring response that appeals to me.

About six years ago, I contacted about ten of the best builders in the world about truss rod advice; the heavy hitters that are worshiped around here. I was hoping for some continuity among them, but I got about 15 very conflicting answers. One way, two way, curve up, curve down,....blah, blah, blah...So, what to do? I answered my own questions and I made up six different necks with six different truss rod systems. Guess what- they all worked almost identical. That made the choice easy- I use a material that I like and picked the design that is the simplest to manufacture.

Here are a few from recent batch of 'dreads...

j.

I still have a set of bridge posts made of titanium and thumbwheels of aluminum. I think that's the place where the weight saving may help a bit more.

[sunburst]

The rod itself is closer to 17 grams...

My rods are 3/16" steel, but nearly half is milled away. No anchor nut, just a short "L" bend, small SS washer and 1/4" brass adjuster nut. I'm struggling with how they can be heavier than your 4mm rods. Perhaps I should weigh another one and see if I've made a mistake. (I just happen to have the balance set up to weigh a couple of mandolin backs, so...)
I agree on the Waverly tuners, but customers sometimes request them.
I calculated the weight difference for one customer who wanted to swap his tuners for Waverlys and the difference came out to about the weight of a pencil. We strapped a pencil to his peghead and he was fine with the extra weight, so now he used Waverly tuners.

[sunburst]

I weighed another truss rod, with nut and washer, 22.5 grams.

[Br1ck]

IVe had to use both directions of a double truss rod exactly once, when a guitar I bought shipped from a hot humid location to my mild climate. But over six weeks, I adjusted it back to where it started, so patience would have worked fine. Can't beat the peace of mind though.

[sunburst]

I used the reverse direction of two-way rods in guitar necks a couple of times, banjo necks many times (I use 2-way rods in banjos), but never in a mandolin. Length of neck and string tension have a lot to do with that.

[HoGo]

My rods are 3/16" steel, but nearly half is milled away. No anchor nut, just a short "L" bend, small SS washer and 1/4" brass adjuster nut. I'm struggling with how they can be heavier than your 4mm rods. Perhaps I should weigh another one and see if I've made a mistake. (I just happen to have the balance set up to weigh a couple of mandolin backs, so...)
I agree on the Waverly tuners, but customers sometimes request them.
I calculated the weight difference for one customer who wanted to swap his tuners for Waverlys and the difference came out to about the weight of a pencil. We strapped a pencil to his peghead and he was fine with the extra weight, so now he used Waverly tuners.

3/16 is 4.8mm so it is thicker than metric 4mm rod. Loars rods were even thinner at 3.9mm
I use allthread so if I discount for half depth of threads I have equivalent of 3.5mm diameter of solid steel rod 23cm long, calculation gives mass of 17.7grams (using 8g per ccm for steel). I use small nuts on both ends and regular steel washers. (a bit thicker one on headstock end)

[sunburst]

...I use allthread...

That explains it. When you said "threaded rod" before, I thought that meant rod that was threaded (at the ends).

[amowry]

I've been transitioning to adjustable trussrods on mandolins because a lot of customers seem to expect them, but I've put CF in more than 150 mandolins with no problems, and if I was going to build myself a mandolin I'd use CF. It makes for a stiffer neck (and lighter, obviously), with fewer things to go wrong. If the neck needs flattening 10 years down the road you can just do it when it's time for a refret, in fact that's part of a refret anyway. I'm not sure I'd say installing CF is easier, because it involves epoxy, for which I have a strong dislike . It takes time to mix, it's messy, and you have to let it cure overnight at a minimum.

[graham darden]

Dito to the CF.