Replacing a truss rod - A sanity check

[SamIAm]

Sorta, actually replacing a truss rod that is in perfect working order with a shorter one to allow the removal of the headstock and portion of the neck to turn a long scale neck into a short scale headless neck - a sanity check. (But that was a bit wordy for the title!)

 

Why would I want to do this I can hear you shout ...

 

To end up with the headless 5 string short scale neck I desire, I seem to have a number of options:

1. Buy one off the shelf (I'm struggling to find one suitable)
2. Get one made for me (expensive)
3. Self build (A huge amount of work)
4. Mod one (Not quire as much work)

 

It occurs to me that with option 4 (Modding one) the work required is less than for a self build.

 

Modding (As I understand it) a neck requires the removal of the existing fingerboard (using the application of heat and very very gently prying apart), cleanup of the surfaces of the neck and fretboard, removal of the existing truss rod (Non-trivial but it appears doable from what I seen on youtube), cleaning of the existing truss rod channel and possible enlargement or reduction to suit the new truss rod, cutting the neck and fingerboard to the new scale length taking into account the headless string mounting unit, gluing the fingerboard back on and then the tidy up and hardware attachment.  If done carefully I would hope to avoid having to do any significant refinishing of wither the neck or fingerboard.

 

Compared to a self build I would not have to shape the neck, heel or fingerboard, fret the fingerboard, route a completely new truss rod channel and hopefully I can avoid most of the finishing of the neck/fingerboard; it would come with the additional work of removal of the fingerboard and trussrod, cleaning away the old glue and the shortening of the neck.  Overall it seems to me that the total effort would be considerably less (Assuming I don't screw things up!)

 

Lopping off the top 3 frets of a neck would result in a slightly wider nut, but that is likely to suit my purposes.

 

As this is something I have never tried before I wanted to fly the idea up the BC flagpole and see if anyone had any cautionary tales/warnings or advice that I've not considered?

 

S'manth x

 

Edited January 1, 2023 by Smanth

[Maude]

My brain can't work it out at the mo but would the fret spacing work to the scale length?

If the first three frets went, then the old 15th fret would become the new 12th, would this be halfway between the new nut and the bridge?

It might well be, say if 4" was chopped off but the space between 12th and 15th was 2" then all would be good, wouldn't it? 🤔

 

[PaulThePlug]

^ fretless...

 

So shortening a long scale 4 to make a short scale 5?

[SamIAm]

36 minutes ago, Maude said:

My brain can't work it out at the mo but would the fret spacing work to the scale length?

If the first three frets went, then the old 15th fret would become the new 12th, would this be halfway between the new nut and the bridge?

It might well be, say if 4" was chopped off but the space between 12th and 15th was 2" then all would be good, wouldn't it? 🤔

 

Intuitively it struck me that the fret spacing would be OK as it is basically the same as playing with a capo.

However, to achieve a more informed position, I went onto one of those fret position web calculator sites, produced a layout for 34 inch and for 28.6 inch (Which is where fret 3 lies on a 34 inch ... OK so it's 28.59)

 

Comparing a few points in a spreadsheet it seems that they are near as dammit the same spacings so I think the maths adds up.  On a shortened neck, I would use the original 3rd fret as a new 0 fret.

 

 

S'manth x

Edited January 1, 2023 by Smanth

[SamIAm]

28 minutes ago, PaulThePlug said:

^ fretless...

 

So shortening a long scale 4 to make a short scale 5?

If I go ahead with this I suspect my first attempt will be on a fretless neck ... but I believe it should work on fretted necks also.

 

S'manth x

Edited January 1, 2023 by Smanth

[tauzero]

The frets would correspond if the bridge saddles stayed in the same place. Assuming you did the chop at fret 3, that would become fret zero or the nut, and fret 15 would become the octave fret. Easy to confirm that that's the case by measuring fret 3 to fret 15 and fret 15 to the bridge, which would be the same, or putting a capo on fret 3 and checking the octave harmonic is at fret 15.

[itu]

As you already know, the roundings make the numbers look slightly different from each other. If you took the side markers away and used a capo, the neck could be shortened as much as you like, as long as there are frets or fretboard.

[3below]

AFAI can think at this time of night... it will work.  One factor to consider is the side and face dots.  These will be in the wrong places and will have to be drilled and plugged (straightforward enough) and new ones inserted as required.  With a fretless neck, think long and hard about where you want dots at:  1,3,5,7,9 12 etc or between 2-3, 4-5, 6-7, 8-9 and 11-12 etc.  I know where I like my dots lol.

Edited January 1, 2023 by 3below

[SamIAm]

5 minutes ago, 3below said:

I know where I like my dots lol.

Me too  currently it has side markers at the exact fingering positions (and I popped on some pencil marks for the intervening positions) ... I would go for that approach again.

 

S'manth x

[Woodinblack]

1 hour ago, Smanth said:

Intuitively it struck me that the fret spacing would be OK as it is basically the same as playing with a capo.

However, to achieve a more informed position, I went onto one of those fret position web calculator sites, produced a layout for 34 inch and for 28.6 inch (Which is where fret 3 lies on a 34 inch ... OK so it's 28.59)

 

Comparing a few points in a spreadsheet it seems that they are near as dammit the same spacings so I think the maths adds up.  On a shortened neck, I would use the original 3rd fret as a new 0 fret.

 

They will be the same apart from maybe rounding. one fret up has to be the same proportional distance from the previous one, regardless of the original scale, ie, the 15th fret will always be the 12th fret from the point of view of the 3rd fret, as it will always be half the length of the remaining scale.

 

Distance from bridge = total scale / (2 ^ (fret / 12)))

 

As far as I can see that is the easy but. But how do you put a shorter truss rod in a bass modifying the original holes, and to do so isn't that more work than just building a new neck in the first place?

[tauzero]

I think you'd have to wait until you'd got the fingerboard off before working out the length of truss rod you'd need. I would guess at 460mm - https://www.blackdogmusic.co.uk/product/double-action-truss-rod-360mm400mm420mm-440mm-460mm-or-620mm/ has a variety of lengths (not many of which are ins tock).

[AndyTravis]

Would this not be a decent starting point?

 

Ibanez Mikro 5 string?

[SamIAm]

12 hours ago, Woodinblack said:

But how do you put a shorter truss rod in a bass modifying the original holes, and to do so isn't that more work than just building a new neck in the first place?

I’ve seen a couple of “how to replace a broken truss rod” videos online (hardly a. Through education tho).

I listed what I think are the steps in my OP, I think the mod will be less work overall, especially with shaping and finishing.

[SamIAm]

@AndyTravis, indeed the GSRM25 is in the space of what I want. I’ve failed to locate one used and have one on backorder from Thomann, but it’s a 9-12 week wait.

The 25 does not appear suitable for a headless conversion tho as the bridge saddle points seem too close to the end of the body to accommodate headless tuners; I really want to go headless, I like the look and balance but the better tuning stability is attractive but key is that with a bit of work (crimping and superglue) at the nut end, I can cut down any length of string to fit … 28.6 inch strings are not at all common.

 

S’manth x

[tauzero]

39 minutes ago, Smanth said:

@AndyTravis, indeed the GSRM25 is in the space of what I want. I’ve failed to locate one used and have one on backorder from Thomann, but it’s a 9-12 week wait.

The 25 does not appear suitable for a headless conversion tho as the bridge saddle points seem too close to the end of the body to accommodate headless tuners; I really want to go headless, I like the look and balance but the better tuning stability is attractive but key is that with a bit of work (crimping and superglue) at the nut end, I can cut down any length of string to fit … 28.6 inch strings are not at all common.

 

S’manth x

 

I would have thought you'd be able to fit the tuners onto the body if using Guykers - they might overhang a bit though. From front to rear fixing screw hole is 45.5mm.

 

[SamIAm]

Nods @tauzero.

 

Doing a rough analysis,on the GSRM25 the B string saddle position to end of body is a touch less than the width of the 22nd fret, which Ibanez say is 67mm.

All of the headless tuners I can find are longer than this (From the Guyker diagram I'd say they are about 67mm + the size of the tuner serrated head bit).

I really really do not want them to extend beyond the body, I'd hope to put in a recess like this example

 

S'manth x

 

Edited January 2, 2023 by Smanth

[3below]

Further left field thought:

 

Rout a pocket at the bridge end and inset a block to extend the body by a few cm as needed. Merge this block into the body with suitable curves and then rout the inset for your tuners as needed. You are effectively extending the body a few cm.  This will require a refinish.  At this point it I think it would probably be easier to make a new GSRM25  body that is slightly elongated and has the recess that you want.

[SamIAm]

@3belowindeed ... the GSRM25 I have on backorder is not intended for modification (as much as I'd like a headless) ... well, not major body/neck changing mods at least!

 

I've my eye on a bass I already own for the neck shortening ... and I will be able to shift the headless tuner positions up along the body enough to allow for no overhang.

 

S'manth x