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Off Center Truss Rod


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I don't think it would have a substantial effect if the guitar was finished well and if the truss rod was not too far off center. If it was really off center I am not even sure that much would happen. Having talked to a very experienced woodworker (does not build guitars) his opion was that the least warping and twisting would happen if the truss rod were diagonal across the fretboard.

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I wasn't quite sure I read your post correctly wohzah, was your buddy saying that the best method for installing a truss rod would be diagonal? In not being a luthier I don't know that one could offer such a suggestion without any experience in guitars, I know it is a form of woodworking, but such things don't always translate, ya know? Anyway, I'm not even sure if thats what you were saying, just checking to see. Having the truss rod off to one side too far would likely throw some twist into the neck. Just like having two truss rods side by side, if they aren't turned equally, you can add twist into the neck. I would imagine that having one truss rod off to one side would be in effect, the same as the pressure on one side would be different than the other, thus inducing twist. How much off it would need to be, I would have no idea, but I wouldn't really be happy or comfortable with a neck unless it was very, very close to center at least.

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I wasn't quite sure I read your post correctly wohzah, was your buddy saying that the best method for installing a truss rod would be diagonal? In not being a luthier I don't know that one could offer such a suggestion without any experience in guitars, I know it is a form of woodworking, but such things don't always translate, ya know? Anyway, I'm not even sure if thats what you were saying, just checking to see. Having the truss rod off to one side too far would likely throw some twist into the neck. Just like having two truss rods side by side, if they aren't turned equally, you can add twist into the neck. I would imagine that having one truss rod off to one side would be in effect, the same as the pressure on one side would be different than the other, thus inducing twist. How much off it would need to be, I would have no idea, but I wouldn't really be happy or comfortable with a neck unless it was very, very close to center at least.

now, im with you on the 'truss rod in the center' thing;

to me ,thats just the way it is

but diagonal supporst and bracing in a 'x' fashion is a great way to strengthen structures; so id assume thats what this guy was pulling out of his a$$;

but if i could add to this discussion for s#!ts and giggles;

why should the rod not be placed closer to the bass side of the neck; there is far more tension present from the thikcer strings, if the rod is completly in the middle and the strain is coming uneven from side to side ,is that not enough to twist the neck on the 'corners' while only retaining straightness thru the middle?

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I wasn't quite sure I read your post correctly wohzah, was your buddy saying that the best method for installing a truss rod would be diagonal? In not being a luthier I don't know that one could offer such a suggestion without any experience in guitars, I know it is a form of woodworking, but such things don't always translate, ya know? Anyway, I'm not even sure if thats what you were saying, just checking to see. Having the truss rod off to one side too far would likely throw some twist into the neck. Just like having two truss rods side by side, if they aren't turned equally, you can add twist into the neck. I would imagine that having one truss rod off to one side would be in effect, the same as the pressure on one side would be different than the other, thus inducing twist. How much off it would need to be, I would have no idea, but I wouldn't really be happy or comfortable with a neck unless it was very, very close to center at least.

The guy who told me this used it as a suggestion, I have yet to try it, not wanting to foul up an expensive and or well thougt out project. I may throw it into a cigar box guitar or something. I agree it would have to be very exact and people have little trouble with truss rods. Also it would have to be a non adjustable truss rod, which are few and far between in modern guitar building.

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I understand how a woodworker could come to the diagonal idea or the x brace style idea, but as I said, while it is woodworking the concepts don't always translate and offering such suggestions without having knowledge of building guitars could be harmful to people that would look upto someone with so much experience. I only wish I had prior woodworking experience and I really appreciate the advice and knowledge of those who do in luthiery.

My dad is a talented engineer and he is always trying to offer ideas when I discuss what I am working on (guitar), and his ideas are very cool and seem to fit, but they would honestly not work for building guitars or maybe some would, but there are much better ways. Here and there methods are improved, but I think the standard build process and structure is fairly well keyed in at this point.

As for the truss rod ideas, I just don't think you can move the truss much without adding the possibility of twist into the neck. Keeping it centered and in using the recommended cut of wood go a long way to prevent problems with the neck, in changing the direction and position of pressure and adjustment I think you're more likely to create a problem vs. prevent a problem. I just used a 2way adjustable truss and 2 carbon fiber rods which pretty much covers it support wise . The cf rods follow the taper of the neck, so support is fairly equal around the entire neck while still allowing minor adjustments if ever needed. If I were to experiment with anything it would be the positioning of the cf rods, outside of that I think current setups work. Regardless, I'm always curious of everyones opinions and points on such subjects. J

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Consider this: The truss rod should be on center within reason. In reality, a hair one way or the other is not going to be a show stopper.

With the truss rod off center too much, the whole neck may bend unpredictably if a lot of tension was applied.

Double action truss rods work to bend the neck and are sort of "stand alone" in the way they work. If your accuracy is less than perfect, then this type of rod would provide some useful 'fudge-factor'. If your neck is accurately made, then the truss rod will have little to no tension after the guitar has been strung.

-Doug

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Besides, it's really not difficult at all getting the truss rod perfectly centered. Just use the edge guide with your router, a bit of measurement, a little planning, that's all it takes. It's really hard to justify screwing this one up. It's definitely not the most difficult part of a build. And a new neck blank doesn't cost that much.

So while in theory it might be okay, in practice, it makes no sense at all.

A friend of mine is an excellent woodworker. He's been transforming himself into an excellent luthier too. But he's had to do a lot of studying and research in order to get there.

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Something that hasn't been mentioned is the issues that could arise when carving the neck.

There have been plenty of stories of people carving into their truss rod channel.

And this is where the neck is the thickest!

Imagine the issues you will face if it's off-center....

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Something that hasn't been mentioned is the issues that could arise when carving the neck.

There have been plenty of stories of people carving into their truss rod channel.

And this is where the neck is the thickest!

Imagine the issues you will face if it's off-center....

Thats actually an excellent point. So even if this idea would work theoretically, you wouldn't be able to implement it with any standard sized neck thickness, its best to just stick with the standard processes with truss rods.

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why should the rod not be placed closer to the bass side of the neck; there is far more tension present from the thikcer strings, if the rod is completly in the middle and the strain is coming uneven from side to side ,is that not enough to twist the neck on the 'corners' while only retaining straightness thru the middle?

I think if you are really **** about uneven string tension resulting in neck warping, you would use string gauges that resulted in more even tension across the different strings. I believe a lot of people do make up their own sets from singles to get more consistent tension.

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why should the rod not be placed closer to the bass side of the neck; there is far more tension present from the thikcer strings, if the rod is completly in the middle and the strain is coming uneven from side to side ,is that not enough to twist the neck on the 'corners' while only retaining straightness thru the middle?

I think if you are really **** about uneven string tension resulting in neck warping, you would use string gauges that resulted in more even tension across the different strings. I believe a lot of people do make up their own sets from singles to get more consistent tension.

Found this thread on a search because I'm still working on my first full sized build, realized my truss rod is off center to the bass side by about 1/32" at the headstock, and the thought that it might actually be helpful did occur to me. So I did a search and found this.

Clearly it's not off by a lot, and there are 4 carbon rods in there so I doubt it'll twist, but it also wasn't intentional. If I'd were worried about the bass string tension I'd shape the neck a touch thicker on the bass side :D

Todd

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String tension will be very close across the set of strings, at least if you are using a set of modern strings. They are built with this in mind. You can have a look at the specs (tension to pitch, gauge and such) on the Daddario web site. They also have information on how strings work, are built etc... It is worth while to go do some research, as strings are such a huge part of your instruments.

Peace,Rich

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Good point Rich,

If you ignore the G and the D as they're so close to midline, then per that site, the two top strings are around 37.4# total on a medium set, and the two bottom strings add to about 47.6# tension. So only around a 25% increase. And as the neck isn't very wide, and the vectors aren't 10# difference at 90 degrees, I doubt that 10# higher tension on the bass side is going to twist the neck. The numbers are here: http://www.daddario.com/DADProdDetail.aspx...&Class=AACA

But I can still pretend my 1/32" oops will help offset that 7-10# difference in tension, can't I? :D ;-)

Todd

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Good point Rich,

If you ignore the G and the D as they're so close to midline, then per that site, the two top strings are around 37.4# total on a medium set, and the two bottom strings add to about 47.6# tension. So only around a 25% increase. And as the neck isn't very wide, and the vectors aren't 10# difference at 90 degrees, I doubt that 10# higher tension on the bass side is going to twist the neck. The numbers are here: http://www.daddario.com/DADProdDetail.aspx...&Class=AACA

But I can still pretend my 1/32" oops will help offset that 7-10# difference in tension, can't I? :D ;-)

Todd

They offer many "off the rack sets" some will be closer than others. They are making up the sets to fit a customer wants, not best balanced set. This page has more info on what they make and how to calculate what your tension will be based on the scale you are using. link

You can select strings that are very close to equal in tension, and that is a very cool byproduct of how good string manufacturers are today.

Rich

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Rich,

I looked at that page too, but realistically, why bother trying to balance better than a 10# difference. The 10# difference is mostly compressive. The component of it that would actually induce a twist in the neck is so minimal that it's probably not worth considering unless the neck is very thin, or a very flexible wood. In that case, you'd have other issues to worry about, like my friends mahogany tele neck that we had to add carbon rods to, to give the guitar some tuning stability during bends.

Todd

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Rich,

I looked at that page too, but realistically, why bother trying to balance better than a 10# difference. The 10# difference is mostly compressive. The component of it that would actually induce a twist in the neck is so minimal that it's probably not worth considering unless the neck is very thin, or a very flexible wood. In that case, you'd have other issues to worry about, like my friends mahogany tele neck that we had to add carbon rods to, to give the guitar some tuning stability during bends.

Todd

Todd,

I didn't want to imply you had to use or not use one set over another. I was just wanting to point out that you can get or make up sets that are very close to balanced across the neck. Some sets that are offered are not put together based on a well balanced set, but for the wants or preferences of certain players. As far as the concept of balancing the string tension, it is a good thing obviously. I can't say for sure if a heavily out of balance set would or would not distort a neck over time, but I suppose there would be a greater chance of it happening (although reasonably close would certainly not seem likely to cause a problem). It is a good oportunity to look over string construction, scale, tension, density, elasticity, intonation. At least if you had never had a chance to do so.

Rich

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Hey Rich,

I hadn't taken your response to mean that, sorry if it sounded like I had. I agree with you that highly unequal tension might have an adverse effect on the neck, especially over years of use. That makes intuitive sense even if I've never seen it. And that site you pointed us to is great info.

I'm probably too lazy to ever experiment with equal tension sets enough to find what I like best, but it's nice to know that I can check to see how off kilter the tension might be on a stock set, and it's probably a good idea to avoid the worst offenders.

Regards,

Todd

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  • 13 years later...

I was searching for answers to this and this thread came up in my search. I realize it's very old. I am attempting putting a new fretboard on a Chinese neck. When I pulled the attached fretboard off I noticed the truss rod route was not exactly centered. By the nut it is but it gradually goes off-center that by the end of the truss route I'm guessing it's about 1.5mm off center. That's one point five millimeters. It's doesn't seem like much but you can tell immediately that it's off-center when viewing it from a distance.

I thought about widening the truss channel a bit and adding some spacers on one side but it's a lot of extra work for something that might not matter.  I'm posting this for any opinions.

IMG_1405.JPG

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It almost looks like they've aligned the channel along the bass side of the neck but that would be about 5 mm off... Anyhow, as the channel is at an angle fixing it would require filling the entire length with a slice of veneer at least as thick as the offset is and then realigning and rerouting the channel. Not too much of an effort if you have the tools, jigs  and materials at hand. Trying to fix that with individual small pieces is not worth the hassle and it can even make things worse.

Then again, you never know about wood. What if the wood is stiffer by nature on one half? In that case an offset might be a valid option, Or, if you carve the neck asymmetric? Wouldn't that change the behaviour of the truss rod as well? Plus the thickness of the strings... There's already many unknown variables so adding one more may not make any difference.

So it's doable, actually getting the fretboard off may have been the hardest part of the process. But would you have noticed that had you left the original fretboard on is another question.

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