Replies to This Discussion

Permalink Reply by Tom T on January 9, 2022 at 2:12pm

The need for a truss rod (adjustable or not) really depends on the build.
If you build three and four stringers with Maple or Mahogany necks, the strength of the wood pretty much exceeds the ability of the stings to pull a bow in the neck. That's assuming a reasonable selection in string sizes. Strings that have a tuned-tension of around 16~18 lbs do not exert a lot of pull on the neck. If you are using softer wood for the neck, then all bets are off regarding no truss rod. Oak may be okay but Poplar is usually too weak when shaped to a good playable shape.

If you are building 5~6 stringers, the need for neck reinforcement begins to come into play depending on the neck wood and neck shaping. I've built 5 stringers with mahogany and maple necks and no truss rod (and not problem). With six stringers I install an adjustable truss rod just to be safe.

I'm sure there are more opinions on this matter and I hope people share them.

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Permalink Reply by Oscar Stern on August 13, 2023 at 10:26am

Yeah an Adjustable Truss Rod would also be great for if you're converting 3 or 4 string Cigar Box Guitars into versions w/ 5, 6, or more strings.

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Permalink Reply by Taffy Evans on January 9, 2022 at 3:05pm

Hi I G, my take on this is based on my experience of using different types of neck reinforcement over close to 45  years or so.

I found that a straight round steel rod, the length of a neck, that can be bent between my thumbs will most likely also bend under string tension or timber movement. If it is stiff enough to resist bending it may be too large for the job.

I have always suggested that a flat bar is far more resistant against bending when fitted into the same width channel in the neck. EG: a bar 1/4"x 1/2" has more resistance to bending up than a 1/4" diameter rod. In fact an Aluminium bar 1/8" x 9/16" offers more resistance when fitted tightly in its channel.

My early 1970-80 steel-string guitars had steel bars [key steel] of the size mentioned above. I still have two of them] and the necks still have perfect alignment and action. Although I will mention a bit neck-heavy. The T section reinforcement allowed for the stiffness to remain while a lot of the weight was lost.

The heaviness/mass in the necks contributed to great sustain when played. Now I combine adjustable truss rods and carbon fiber bars.

To use a round rod it is best if it is adjustable, fixed one end with a nut adjusting from the other. In effect trying to shorten the rod when tightened.  However, this will not have the desired effect of countering the pull of the strings or the bowing of the neck.

The rod needs to be bowed in its channel in a way that as the rod nut is tightened the bow in the rod is "flattened" out, taking the neck with it in the desired direction. This can be seen in cheap reinforcing systems that use a U channel with a round rod running through it. The rod does not sit flat but has a small steel riser in the middle of the U channel creating a bow in the round rod.

These only work one way, pulling down against the pull of the strings.

A two-way version is shown that I make myself. as the adjusting nut is tightened or loosened the truss rod [which is bar-shaped] bends up or down.

I know, I know more info than you needed......

Cheers Taff

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Permalink Reply by Taffy Evans on January 10, 2022 at 5:08pm

Hi again. Tom T is correct and his answer addresses your opening question, "are truss rods needed"?  My answer was directed at the second question, "does it reinforce"?

Cheers Taff

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Permalink Reply by Carl Floyd on January 12, 2022 at 5:24am

"I have always suggested that a flat bar is far more resistant against bending when fitted into the same width channel in the neck. EG: a bar 1/4"x 1/2" has more resistance to bending up than a 1/4" diameter rod. In fact an Aluminium bar 1/8" x 9/16" offers more resistance when fitted tightly in its channel."

Great idea that make a lot sense for a CBG.  Thanks, Taff!

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Permalink Reply by BrianQ. on January 12, 2022 at 8:48am

Like Tom said, most 3-4 stringers don’t need it if using maple, Seagull has been making the 4 string Merlin with maple necks without truss rods with great success? I like two-way truss rods strictly because of the setup aspect, trying to adjust relief without it is quite a lot of work. You’d be surprised of how many beginners that know nothing about relief or how affects their playing, but I say, if that’s how you do it & it works for you, then keep doing it, it’s your thing? 

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Permalink Reply by ILL GREEN on January 16, 2022 at 10:38pm

Thank you guys!!

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Permalink Reply by ILL GREEN on January 16, 2022 at 10:43pm

Thank you Tom T, Taffy Evans, Carl Floyd and Brian Q!

Great awesome tips, I was trying to reply last week but nothing worked not even the HTML trick.  Though I did find another way to post while in Visual Mode; just type up what you're gonna post, now copy your entire posts, tap "Add Reply". Your post will appear but will be in blank.  Simply hit "Edit" and paste your post and tap "Save".  And viola, your posts are on the air

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Permalink Reply by ILL GREEN on January 17, 2022 at 7:31am

 Sorry, I can't quote a post either.

"The need for a truss rod (adjustable or not) really depends on the build.
If you build three and four stringers with Maple or Mahogany necks, the strength of the wood pretty much exceeds the ability of the stings to pull a bow in the neck. That's assuming a reasonable selection in string sizes. Strings that have a tuned-tension of around 16~18 lbs do not exert a lot of pull on the neck. If you are using softer wood for the neck, then all bets are off regarding no truss rod. Oak may be okay but Poplar is usually too weak when shaped to a good playable shape.

If you are building 5~6 stringers, the need for neck reinforcement begins to come into play depending on the neck wood and neck shaping. I've built 5 stringers with mahogany and maple necks and no truss rod (and not problem). With six stringers I install an adjustable truss rod just to be safe.

I'm sure there are more opinions on this matter and I hope people share them."

• Yes, I like 4 stringers (easy for me to play though I play 6 string acoustic). Didn't know that about poplar necks. I have made 2 necks of poplar for 4 string electric and they are still holding.  I did received them with a green tint but I left them in a shed for 3 months that was 100° F inside all the time.  They became a bit brownish, I am no woodsmith, but I figured it to be sturdy.  This build is cherry wood though. 

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Permalink Reply by Tom T on January 17, 2022 at 11:35am

Popular isn't necessarily a bad wood for necks, but is more apt to bow than the harder woods I mentioned. It yours is holding up, don't worry about it. Just keep building.

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Permalink Reply by Carl Floyd on January 18, 2022 at 3:25am

I am currently carving a Poplar neck with a Red Oak fretboard for a 3 string CBG without a truss rod.  I expect it will be just fine, especially since it will be tuned down to E B E.

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Permalink Reply by ILL GREEN on January 22, 2022 at 11:50am

Hi I G, my take on this is based on my experience of using different types of neck reinforcement over close to 45  years or so.

I found that a straight round steel rod, the length of a neck, that can be bent between my thumbs will most likely also bend under string tension or timber movement. If it is stiff enough to resist bending it may be too large for the job.

I have always suggested that a flat bar is far more resistant against bending when fitted into the same width channel in the neck. EG: a bar 1/4"x 1/2" has more resistance to bending up than a 1/4" diameter rod. In fact an Aluminium bar 1/8" x 9/16" offers more resistance when fitted tightly in its channel.

My early 1970-80 steel-string guitars had steel bars [key steel] of the size mentioned above. I still have two of them] and the necks still have perfect alignment and action. Although I will mention a bit neck-heavy. The T section reinforcement allowed for the stiffness to remain while a lot of the weight was lost.

The heaviness/mass in the necks contributed to great sustain when played. Now I combine adjustable truss rods and carbon fiber bars.

To use a round rod it is best if it is adjustable, fixed one end with a nut adjusting from the other. In effect trying to shorten the rod when tightened.  However, this will not have the desired effect of countering the pull of the strings or the bowing of the neck.

The rod needs to be bowed in its channel in a way that as the rod nut is tightened the bow in the rod is "flattened" out, taking the neck with it in the desired direction. This can be seen in cheap reinforcing systems that use a U channel with a round rod running through it. The rod does not sit flat but has a small steel riser in the middle of the U channel creating a bow in the round rod.

These only work one way, pulling down against the pull of the strings.

A two-way version is shown that I make myself. as the adjusting nut is tightened or loosened the truss rod [which is bar-shaped] bends up or down.

I know, I know more info than you needed......

Taffy

All info from you is well appreciated Taff, thanks for chiming in!

Thanks for confirming an idea I had of bowing the truss rod a tidbit. But I like your diy design! Is there a thread on diy truss rods? I'm not at that level but a good thread can cook into my mind and after a while I can do it.

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