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Truss Rod Positioning?


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I'm thinking about starting work on another guitar, and something occurred to me that I hadn't thought of; I don't know how much it actually matters, but how far back do you position your trussrod in the neck? I use the LMI flat-topped double-action trussrods The last two builds I did, I simply moved it back enough that that hex-key nut on the end would lie under the plane of the headplate so it could be easily covered by a truss rod cover. This ended up putting the end of the flat rod under the guitar's nut on one of them, and just before it on the other one. Should I be backing these more down the neck towards the bridge? Should the end of that hex-key nut be under the guitar nut? That would put the end of the flat rod towards the first or second fret. Does this even matter, as long as the thing is in there?

Also, on the subject of neck-reinforcement, I'm looking at putting those carbon fiber rod things in there - looking at the stewmac diagrams, I'm assuming you space them out evenly on either side of the rod, but do you follow a straight path equi-distant from the trussrod their whole length, or do you follow the taper of the neck?

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I'm thinking about starting work on another guitar, and something occurred to me that I hadn't thought of; I don't know how much it actually matters, but how far back do you position your trussrod in the neck? I use the LMI flat-topped double-action trussrods The last two builds I did, I simply moved it back enough that that hex-key nut on the end would lie under the plane of the headplate so it could be easily covered by a truss rod cover. This ended up putting the end of the flat rod under the guitar's nut on one of them, and just before it on the other one. Should I be backing these more down the neck towards the bridge? Should the end of that hex-key nut be under the guitar nut? That would put the end of the flat rod towards the first or second fret. Does this even matter, as long as the thing is in there?

Also, on the subject of neck-reinforcement, I'm looking at putting those carbon fiber rod things in there - looking at the stewmac diagrams, I'm assuming you space them out evenly on either side of the rod, but do you follow a straight path equi-distant from the trussrod their whole length, or do you follow the taper of the neck?

Edited by Supernova9
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Leaving 3/8" under a double action rod is way overkill. With a 1/4" fretboard and lmii's 3/8" double acting truss rod(add 1/16" if you're using stewmac's), you'd end up w/ a 1" thick neck. 1/8" is fine, especially if you're reinforcing the with cf rods(only because the cf rods insure that the truss rod shouldn't have to do as much work as if they were not there). As for where the rods apply their force, take a look at this quick and dirty diagram(this shows the forces on the neck as the rod applies back bow):

frontbow2.jpg

**not to scale**

As you can see, a standard truss rod and a double action truss rod exert their forces in two very different places. If you want to go for a really thin neck and not worry about having your truss rod come out the back, a traditional truss rod and some small cf rods are the way to go. I say small cf rods because you don't want to make the neck so stiff that it will require front bow to be added, because you cannot do that with a traditional truss rod. However, you can get away with a 3/4" neck and an lmii truss rod though if you're carefull; I did it on my last build which has a black limba neck and no cf rods, and it's in great shape.

peace,

russ

EDIT: As for where the blocks of the double action truss rod should be, I would not worry about part of one block sitting below the nut. Since the blocks are normally about 3/4" long, it would still have room under the fretboard to apply pressure if you needed to add front bow. You main concern should be the amount of wood under the ends of the rod, no so much the amount on top of them.

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  • 1 month later...

I say small cf rods because you don't want to make the neck so stiff that it will require front bow to be added, because you cannot do that with a traditional truss rod. However, you can get away with a 3/4" neck and an lmii truss rod though if you're carefull; I did it on my last build which has a black limba neck and no cf rods, and it's in great shape.

Instead of starting a new topic, I'll bring this one back up, since it's related to my questions...how do you know if adding CF rods are going to make the neck TOO stiff?

I'm using hollow tube kite rods, as Myka does --the tube is about 1/4" (6 mm) thick, so that corresponds to StewMac's 4403 rods (0.200" x 1/4" x 18" length).

I'll also be using a double-action truss rod. It's a low-profile trussrod --3/8" (depth) by 1/4" (width)-- because the neck I plan to make will be thin and narrow ...I want to try 40 mm or so at the nut.

I could also use the thinner kite rods --but they're pretty flexible at this length, so I don't think they'd add any stiffness at all?

Or does the simple fact of adding carbon fiber in there add to the stiffness of the neck?

Oh yeah, and as long as I'm asking --it seems like routing three channels at the end of neck like that will be a pretty hairy experience --I'm worried that the wall between the channels will cave in or tear away.

Are you supposed to route the rods along the entire length of the truss rod, or can you start the CF rod channels farther down the neck--say after the first fret or so?

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Instead of starting a new topic, I'll bring this one back up, since it's related to my questions...how do you know if adding CF rods are going to make the neck TOO stiff?

Short of measuring deflection on your necks, taking notes, and/or doing a bunch of math...you don't. I've made one neck where the CF made it too stiff for the strings to pull in the right amount of relief, but a touch of truss rod tweaking took care of that. And that neck, frankly, was huge, very deep 'V' shape. Honestly, even with a pair of 1/8" x 3/8" rods and a nicely quartered Honduran mahogany neck blank, or honduran laminated with wenge for a baritone, a set of 10-52's still pulled excessive releif into the neck.

If you're making big, fat laminated maple necks, things get a little less clear-cut, methinks.

I'm using hollow tube kite rods, as Myka does --the tube is about 1/4" (6 mm) thick, so that corresponds to StewMac's 4403 rods (0.200" x 1/4" x 18" length).

I'll also be using a double-action truss rod. It's a low-profile trussrod --3/8" (depth) by 1/4" (width)-- because the neck I plan to make will be thin and narrow ...I want to try 40 mm or so at the nut.

I could also use the thinner kite rods --but they're pretty flexible at this length, so I don't think they'd add any stiffness at all?

Or does the simple fact of adding carbon fiber in there add to the stiffness of the neck?

Oh yeah, and as long as I'm asking --it seems like routing three channels at the end of neck like that will be a pretty hairy experience --I'm worried that the wall between the channels will cave in or tear away.

Are you supposed to route the rods along the entire length of the truss rod, or can you start the CF rod channels farther down the neck--say after the first fret or so?

Yeow, 40mm wide? That's pretty darn tiny. Anyway, hollow tubes will add a lot less stiffness than solid rectangular sections. They'll add more for their weight, but quite a bit less in absolut terms. IIRC, David doesn't use the round sections for stiffness so much as to even out the response/remove dead spots. Not to make the necks ramrod stiff. Those rods are probably stiffer than the wood they remove, which is the point. It'll add some stiffness, but I'd be incredibly surprised if you ended up with a neck that's too stiff, even if you were using rectangular section CF.

Also, I wouldn't worry too much about walls 'caving'; on necks with headplates/angled headstocks, I tend to run the CF rods all the way into the headstock, stiffening that area up as well. I'd run them the length of the fingerboard if possible. If you're worried about bits blowing out (really, with sharp bits, it shouldn't happen; I've never had problems, leaving at least 1/8" clearance between slots), just route and glue in the CF rods first, and then do the truss rod slot. Once the rods are glued in place (I like polyurethane for this, some people like Rick Turner use medium to thick CA glue for truss rod gluing; epoxy's a touch too messy), your neck's as good as 'solid' again.

Edited by mattia
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Honestly, even with a pair of 1/8" x 3/8" rods and a nicely quartered Honduran mahogany neck blank, or honduran laminated with wenge for a baritone, a set of 10-52's still pulled excessive releif into the neck.

Yeah, I have zero experience at this...

Yeow, 40mm wide? That's pretty darn tiny.

I'm trying to get close to the neck on my Melody Maker -- can't buy skinny necks like that, at least not on a longhorn body :D . I measured it today, it comes out at just a hair under 40 mm --so I'll probably go for 41 mm or so. That should be a good middle ground.

The main problem with the MM is it's not stable --I can't take it to practice or onstage, because it's just too sensitive...if I leave it in the house it stays in tune for weeks, literally. As soon as it leaves the house...I have to retune every five minutes. Not to mention it needs a complete refret after all these years...

So I figure I'll try to build a more stable neck that will still give me the same feel -- I'm using two pieces of wood for it, and adding the CF tubes.

I like the idea of the tubes because the rods just seem like overkill. But I think that using the laminated construction, instead of the MM's one-piece mahogany, should already get me pretty close to my goal. The CF tubes are just icing...and if they end up evening things out, so much the better!

just route and glue in the CF rods first, and then do the truss rod slot. Once the rods are glued in place (I like polyurethane for this, some people like Rick Turner use medium to thick CA glue for truss rod gluing; epoxy's a touch too messy), your neck's as good as 'solid' again.

Makes perfect sense!

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Mattia has you on the right path, routing the CF slots, gluing them in place with epoxy, then later routing the truss rod slot. The tubes like you are talking about are good, but like was already pointed out, they are hollow, which means that they might only be slightly stronger than the wood your removing to place them. I'd definitely go with a solid CF rod, they might be more expensive, but they add better stability to the neck. Just my own thoughts on it though.

I have a method I like to use to install CF rods and keep them closer to center to avoid a situation where you might carve to them by accident. I've seen it done before, so I know.. lol I just route out a 1/2" slot, so that the two CF rods and truss rod will fit perfectly. I then glue the two CF rods on each side with epoxy, using the truss rod with wax paper wrapped around it pushed into the slot, to press hold them in place.

new01.jpg

So far it's worked great on the last two guitars I've built. You don't have to try it, just giving you more options to decide from.

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Here's the quote from Myka that had me go for the tubes instead of the rods:

The necks are constructed using a two-way adjustable truss with 1/4" graphite tubes flanking the truss rod on either side. I find that the graphite adds stability and stiffness to the neck while minimizing dead spots on the fingerboard. The graphite accomplishes this due to its high velocity of sound as compared to wood, allowing for string vibrations to travel quickly and evenly through the neck.

I was wary about going for the rods, since I don't think I've every played a guitar equipped with one...the tubes are pretty stiff --they're difficult to bend--although obviously not as resistant as the rods. But maybe the tubes act like laminations in the wood anyway, which helps to solidify the neck too?

I like the idea that the CF tubes do double duty, although I imagine the rods act in the same way, regarding vibrations.

Of course there's nothing to stop me from going for the rods on the next neck! Somehow, I don't think this will be my last guitar... :D

I like your routing idea though--nice and neat, and no fuss... I'm thinking if I go this way I can use my round bottom bearing bit to route the walls of the route--that should nestle the CF tubes quite nicely, and the truss rod will fit into the flat bottom part of the route...I'll make a practice run first, of course. Thanks for the idea!

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Several of us build all our guitars with CF in the necks, you see very few reports of people going 'DRAT! TOO STIFF!', and my necks, anyway, aren't wizard-thin or narrow or anything.

I don't feel laminating wood adds much stiffness in and of itself; it adds stability, because grain directions are reversed and counteract the propensity to twist, and some stiffness because, again, of opposed grain directions, but the inherent strength is based on the inherent strength of the pieces of wood used. 'trapping' them in a laminated neck setup does let them 'use' that strength more effectively, methinks, but I wouldn't expect dramatic stiffness increases from taking a neck blank, ripping it into three pieces, flipping the middle, and gluing it back up.

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Stability is the key word for me...I really hate having to worry about tuning up my guitar while I'm trying to sing, that's all.

Luckily, my strat's a great player, it's rock solid, never goes out of tune. And the Rocket I built is pretty good that way too (haven't tested it under combat conditions yet though).

So I have plenty of freedom to experiment with this building guitars thing.

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By stability I don't necessarily mean in-tuned-ness, but rather that it won't twist or warp. A comment I got on what I felt was my floppiest neck to date (the one on the red guitar with naked girl on; long, thin, mahogany neck with CF/dual action rod, join at 22nd fret, meant quite a bit of flexibility) from a strat player - who never had tuning problems with his guitar - is how stiff the neck felt. He was used to his strat's flatsawn maple neck bending when he pulled on it, and implemented that in his playing style.

So both necks were stable, but one neck was stronger/stiffer.

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may i ask what truss rod your using there? i was gonna order one from allied, but they said it's gonna be a few months till they get there supply back in stock.

The one I used in the picture above was from Allied, so you was correct about that. I'm suprised they are out of stock though. I think they are really good truss rods and for a good price, I still have a couple left luckily.. lol

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yeah, i did some digging and found your thread on that guitar. man, you wouldnt wanna sell one of the ones you have, would you? even for a little more than you payed. :D

if not, do you know if the ones that LMII sell are as good a quality as the ones from allied? of if possibly i could buy a bass length from allied and cut it down? im just not sure about cutting one down becuase of the reverse threads, and how i would go about doing it. i know i can figure it out if i had one in my hands, but i dont wanna spend the money if its not gonna work.

Edited by adrock1740
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I have another truss rod related question -- I took off the fingerboards of two necks the other day, and the truss rods in both were wrapped (or shrinkwrapped) in some kind of thin black plastic housing.

Is that the way I'm supposed to do it too (the truss rods I bought aren't wrapped)?

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I have another truss rod related question -- I took off the fingerboards of two necks the other day, and the truss rods in both were wrapped (or shrinkwrapped) in some kind of thin black plastic housing.

Is that the way I'm supposed to do it too (the truss rods I bought aren't wrapped)?

It's not required, no. Doesn't really affect the function. I think it's more about keeping glue off the moving parts.

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I have another truss rod related question -- I took off the fingerboards of two necks the other day, and the truss rods in both were wrapped (or shrinkwrapped) in some kind of thin black plastic housing.

Is that the way I'm supposed to do it too (the truss rods I bought aren't wrapped)?

Wrapping is mainly to reduce chances of the truss rod rattling or buzzing inside the slot. It's probably good insurance to wrap your truss rod but on my steel strings I dont bother.

Edited by kiwigeo
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