Truss Rod & D-Tube

[GarrettS]

The long body headless guitar design progresses! 

It'll be a 24 fret neck-through with a slim, asymmetrical neck. I'm thinking 9-piece flame maple neck with ebony and holly stripes, and one massive flamed purpleheart or bloodwood spine. Something like the below.

How can I lighten the weight of the truss rod? Will a D-Tube alone suffice?  If not, how can I lighten the truss rod?

This is not my guitar, it's a Barlow Guitars guitar.

https://dragonplate.com/carbon-fiber-d-tube

 

 

 

Edited February 7, 2022 by GarrettS
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[Bizman62]

5 hours ago, GarrettS said:

How can I lighten the weight of the truss rod?

Will a D-Tube alone suffice? 

If not, how can I lighten the truss rod?

Start by answering these questions: How much does a truss rod weigh? Is that weight too much for me to handle?

As I didn't know I weighed a bass size cheap dual action truss rod - 22½" (572mm) long, 180 grams. For a guitar some 16-18" would be long enough and would weigh about 150 gr.

A D-tube alone might suffice BUT there's no adjustability. A player I know told that he has to adjust the truss rod of his Strat during outdoor gigs. The riverside stand can get quite cool after sunset but the halogen spotlights can be pretty hot so your back is freezing while your front is roasted. One sided thermal expansion can be that tricky!

If you can't guarantee that a) you'll get the neck right on the first try and b) you'll always play in a controlled climate, I'd suggest a truss rod. There's several types and materials available. These weigh less than half of the cheap one mentioned in the beginning of my post: https://www.philadelphialuthiertools.com/truss-rods-washers-and-nuts/two-way-truss-rod-full-titanium-extremely-lightweight/

[ADFinlayson]

I looked in to d-tubes and and decided against them for 3 reasons:

1. They're woefully expensive
2. They're much wider than a truss rod so there is less glueing surface for the truss rod - wood glue will not bond the rod to the fretboard 
3. No adjustability which will possibly be an issue with tuning and/or string gauge changes.

Is it actually necessary? Being a headless guitar, you've got no headstock and no tuners which is not only reducing weight but also weight leverage. You could reduce that leverage further by using a wheel truss rod so the truss rod nut is at the neck/body joint. 

[GarrettS]

20 hours ago, ADFinlayson said:

I looked in to d-tubes and and decided against them for 3 reasons:

1. They're woefully expensive
2. They're much wider than a truss rod so there is less glueing surface for the truss rod - wood glue will not bond the rod to the fretboard 
3. No adjustability which will possibly be an issue with tuning and/or string gauge changes.

Is it actually necessary? Being a headless guitar, you've got no headstock and no tuners which is not only reducing weight but also weight leverage. You could reduce that leverage further by using a wheel truss rod so the truss rod nut is at the neck/body joint. 

1. It's about $50 more than the truss rod. Not much, considering what's going into this baby.

2. Were you thinking of using a D-Tube and a truss rod?

3. To balance the guitar, the proportion of weight from the neck to bridge must increase. The body is chambered, the neck and fretboard will use heavy woods. the neck at the lower frets uses extra jumbo frets. The decided strap button position also affects the balance.

Reducing the neck weight with D-Tube would solve that problem. It's 50 grams and weighs less than the wood it replaces (especially true for the heavy woods I've chosen).

Truss rods add weight in the neck all the way to the "headstock" (which in my case is just a tiny piece of wood useful for a guitar hanger).

D-Tube not being adjustable seems like it might be an issue.  If we could see large numbers of builds using D-Tube that were 5-10 years old and working great, that would really improve my confidence in them. It's unproven and not without risk. 

[Bizman62]

54 minutes ago, GarrettS said:

Reducing the neck weight with D-Tube would solve that problem. It's 50 grams

You're not telling the length, but for comparison the Full Titanium two way rods linked above weigh 56 (14.2") or 72 (18,1") grams depending on the length.

[ADFinlayson]

11 hours ago, GarrettS said:

1. It's about $50 more than the truss rod. Not much, considering what's going into this baby.

2. Were you thinking of using a D-Tube and a truss rod?

3. To balance the guitar, the proportion of weight from the neck to bridge must increase. The body is chambered, the neck and fretboard will use heavy woods. the neck at the lower frets uses extra jumbo frets. The decided strap button position also affects the balance.

Reducing the neck weight with D-Tube would solve that problem. It's 50 grams and weighs less than the wood it replaces (especially true for the heavy woods I've chosen).

Truss rods add weight in the neck all the way to the "headstock" (which in my case is just a tiny piece of wood useful for a guitar hanger).

D-Tube not being adjustable seems like it might be an issue.  If we could see large numbers of builds using D-Tube that were 5-10 years old and working great, that would really improve my confidence in them. It's unproven and not without risk. 

No, I'm in UK and a decent 2 way truss rod will cost me £10-15. Those carbon D tubes I've seen come from USA at $75-100 which translates to £120-150+ by the time I've paid shipping and import duty. I wasn't suggesting a d-tube and a truss rod. The rods I use are 1/4" wide but those d-tubes are 1/2" - 3/4" which leave less glueing surface for the fretboard unless the fretboard is going to be epoxied on. I mostly build guitars for others so keeping the margins in mind is important and also the adjustability from a truss rod for someone else's playing style is important to me. If you're building your dream guitar and don't want the adjustability of a truss rod then fair play. But on the other hand, if you've stuck £800 into exotic wood for this guitar, having a neck that you can't adjust to that sweet sport might also be a real problem. 

I think you're on to something with strap button position, going back leverage, you're going to save much more "weight" having your strap button in the right place than the few grams you're saving using a d-tube instead of a truss rod, which IMO is not worth the loss of adjustability. The point I was trying to make about your guitar being headless and leverage is that your neck is going to not weigh very much without tuners at the end of a headstock, even if you are using fairly heavy woods. I've made a few heavily chambered guitars now and never had an issue with neck dive. 

[Andyjr1515]

I'm in a slightly different place, @ADFinlayson & @Bizman62

I do agree that the weight difference is not likely to be the make-or-break for balance.  With the leverage, then relatively small weight differences at the headstock can indeed make that kind of difference, but that impact fast diminishes if the weight is distributed along the whole neck.

However - the need for a trussrod to counter temperature and humidity changes is a bit of a myth if the neck is rigid enough.  Take Vigier and others that have no truss rod.

So I can accept that the wide D section in carbon might make the neck sufficiently rigid.  Also, because the neck then isn't going to flex, the glue area for the fretboard would be quite sufficient.

But it will sound different to an equivalent instrument with a conventional truss-rodded neck.  Not saying it will sound better or worse, just that it will be different.