Graphite (etc.) Rods for Neck

[spindlebox]

These things seem unreasonably expensive online, so as I do with most things, I try to find viable alternatives for just about everything.  I'm a Chef by trade, and I do this a lot in the kitchen as well.  It's just my nature.

Has anyone used different materials to do this, with the same results?  I'm just curious.  Especially if there's something that we can reclaim to do this.  I don't mind doing a little extra work to save money, and from keeping things out of the landfill.

Looking forward to your replies!

[ADFinlayson]

I bought some carbon fibre rods once, similar dimensions to what you've got pictured above and I noticed they actually had quite a lot of flex, so from then on I decided they were a waste of money. I might change my mind if ever I have a neck twist, but I'm also of the opinion that if it's going to, it will twist eventually with or without fibre rods. My other argument for not using them is that anything that stiffens the neck is making the job of the truss rod harder so it's more likely to snap or suffer a stripped nut.

As to your question re alternatives, a friend of mine is a classical builder and as a traditionalist doesn't believe in truss rods, but he uses a centre strip of ebony as neck reinforcement - Imagine routing a 1/4" truss rod channel and just glue in some ebony. It's slightly heavier but ebony is way strong and you could route a 3x6mm channel either side of your truss rod and glue in some quarter sawn ebony. I expect you could get 6-8 trips out of a single fretboard blank. 

[spindlebox]

7 minutes ago, ADFinlayson said:

I bought some carbon fibre rods once, similar dimensions to what you've got pictured above and I noticed they actually had quite a lot of flex, so from then on I decided they were a waste of money. I might change my mind if ever I have a neck twist, but I'm also of the opinion that if it's going to, it will twist eventually with or without fibre rods. My other argument for not using them is that anything that stiffens the neck is making the job of the truss rod harder so it's more likely to snap or suffer a stripped nut.

As to your question re alternatives, a friend of mine is a classical builder and as a traditionalist doesn't believe in truss rods, but he uses a centre strip of ebony as neck reinforcement - Imagine routing a 1/4" truss rod channel and just glue in some ebony. It's slightly heavier but ebony is way strong and you could route a 3x6mm channel either side of your truss rod and glue in some quarter sawn ebony. I expect you could get 6-8 trips out of a single fretboard blank. 

Man, that's a great idea.  I will consider that for sure!!!  I mean, you could also do a laminate neck with ebony too and that would look cool and do the same thing.

[ADFinlayson]

2 minutes ago, spindlebox said:

Man, that's a great idea.  I will consider that for sure!!!  I mean, you could also do a laminate neck with ebony too and that would look cool and do the same thing.

Totally, I was thinking about this entirely as hidden reinforcement, like fibre rods. I generally only make 1 piece necks these days because it's less work, less glue joints so I didn't consider multi lam, and IMO multi lam necks definitely don't need reinforcement. 

[curtisa]

Probably the more critical question that should be addressed is whether your neck needs reinforcement in the first place. I personally wouldn't add anything extra if the materials used or the stresses they'll be under don't require additional reinforcement. If you're making your neck from good quality, strong, stable materials and not subjecting them to unusual loads there shouldn't be a structural reason to add carbon fibre rods. That can apply to multi-lamination necks too.

Having gone through a phase of installing carbon fibre in necks that probably didn't need it, I actually found them counter-productive. In those necks they made the process of adjusting the trussrod to get the neck to provide some degree of relief for playability nearly impossible. The necks were simply too stiff.

If you feel you do want to experiment with it though, the key thing to look for in a reinforcement material is finding something that has more bend resistance in the same direction as the material you're removing from the neck to replace it with. Maybe some aluminium U channel from the hardware store, or two aluminium strips inserted either side of the truss rod with the skinny edges facing up? If the reinforcement material is lighter than the wood it's replacing it also makes sense, which is why carbon fibre is a popular material to use. Maybe you could go to a waste recovery centre or thrift shop and see if anyone has thrown away an old kite/RC helicopter/tent that you can harvest the carbon struts from?

[spindlebox]

28 minutes ago, curtisa said:

Probably the more critical question that should be addressed is whether your neck needs reinforcement in the first place. I personally wouldn't add anything extra if the materials used or the stresses they'll be under don't require additional reinforcement. If you're making your neck from good quality, strong, stable materials and not subjecting them to unusual loads there shouldn't be a structural reason to add carbon fibre rods. That can apply to multi-lamination necks too.

Having gone through a phase of installing carbon fibre in necks that probably didn't need it, I actually found them counter-productive. In those necks they made the process of adjusting the trussrod to get the neck to provide some degree of relief for playability nearly impossible. The necks were simply too stiff.

If you feel you do want to experiment with it though, the key thing to look for in a reinforcement material is finding something that has more bend resistance in the same direction as the material you're removing from the neck to replace it with. Maybe some aluminium U channel from the hardware store, or two aluminium strips inserted either side of the truss rod with the skinny edges facing up? If the reinforcement material is lighter than the wood it's replacing it also makes sense, which is why carbon fibre is a popular material to use. Maybe you could go to a waste recovery centre or thrift shop and see if anyone has thrown away an old kite/RC helicopter/tent that you can harvest the carbon struts from?

All great ideas.  Actually, I am getting some Aluminum Billets that I'm going to have to take 1/2" (12mm) off, (I'm making some Fretboard Slotting Templates with them for my Miter box), so maybe I'll try and use that!!  I'll see what it looks/feels like when I get here.  Like the idea for the tent materials too.  They usually use those graphite rods of some sort to put inside and those might serve well in this purpose too.  Yeah, those purpose made ones for sale - somebody's making a killing on 'em, and this is the first and last time from me!!!

Cheers everyone!!

[Bizman62]

It's funny how similar ideas we seem to have all around the globe!

My first thought after having read the question was to use wood instead of carbon fibre as a hidden laminate. There's some good wood species that are stiff and don't break easily. I took a look at the Wood Database and did some filtering to find lightweight woods with a high Modulus of Rupture and low Volumetric Shrinkage and found some relatively common woods there: https://www.wood-database.com/wood-filter/?fwp_average_dried_weight=49.80%2C59.80&fwp_modulus_of_rupture=20130.00%2C30970.00&fwp_shrinkage=7.20%2C12.80

[spindlebox]

4 hours ago, Bizman62 said:

It's funny how similar ideas we seem to have all around the globe!

My first thought after having read the question was to use wood instead of carbon fibre as a hidden laminate. There's some good wood species that are stiff and don't break easily. I took a look at the Wood Database and did some filtering to find lightweight woods with a high Modulus of Rupture and low Volumetric Shrinkage and found some relatively common woods there: https://www.wood-database.com/wood-filter/?fwp_average_dried_weight=49.80%2C59.80&fwp_modulus_of_rupture=20130.00%2C30970.00&fwp_shrinkage=7.20%2C12.80

Yes!  I love this idea.  I was also thinking of BAMBOO - but other than SKEWERS it's a bit hard to find what I had in mind.  Maybe I'll grow it!!  HAHA.  

Definitely going to try getting some Ebony and cutting strips - but it's good to have these as viable alternatives too.  I think "JANKA" hardness is what we're looking for here?  Honestly, for this build, I'm using some Bloodwood for my fretboard, and I have a piece that's not QUITE long enough for a fretboard - I may cut a couple strips and inlay that for this guitar I'm building.  

Edited October 30, 2022 by spindlebox

[Invader Zim]

I'm curious why hardness is of a concern here when stiffness is more pertinent.

As I posted in your Wood ID thread, MOE and MOI are what should be of concern.

 

I would suggest Titanium reinforcement.

https://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641

[Bizman62]

2 hours ago, spindlebox said:

I think "JANKA" hardness is what we're looking for here? 

In my understanding not so much. Janka hardness tells how much pressure is needed to insert a steel ball into the wood, i.e. it tells how resistant the wood is against nicks and dents. MOR and MOE are more important as they tell how much the wood flexes and how easy it is to flex. This explains those pretty well: https://www.wood-database.com/wood-articles/bow-woods/  and this takes it further: https://www.wood-database.com/worlds-strongest-woods/

The bow index somewhat relates with necks as well as both should keep their shape although necks might benefit from a higher MOE value. If I've understood it correctly, carbon fibre has a way higher MOE than any wood but as has been told CF may be way too stiff.

One thing to consider wood rather than CF or metals is that with wood you can use wood glue which is less brittle than epoxy. Both glue types will add to the stiffness, though.

All that said, my previous filtering wasn't quite accurate. Something like this might give the extra stiffness, the upper half of MOR and the upper third of MOE: https://www.wood-database.com/wood-filter/?fwp_modulus_of_rupture=16280.00%2C30970.00&fwp_modulus_of_elasticity=3012000.00%2C4517000.00

 

 

[Invader Zim]

I'm trying to be helpful here because misusing and/or misunderstanding a term can lead one astray.

Hardness is confused with stiffness quite often and understandably so. Steel is a great example.

Moment Of Inertia and Modulus Of Elasticity of a material can be a helpful guide when designing

or building a beam. A neck is a beam. Think about resonance and how the construction of a neck

influences and causes changes in resonance. Look at how Warwick installs short bars at a strategic area

on their necks.

https://www.youtube.com/watch?v=ZZwjJSQB0z4

 

My problem with epoxy is it needs to be measured and mix properly for OPTIMAL results. I've also

experienced glue softening and shear failure on 20 year old work. I use it only when CA is impractical.

Use slow cure CA gel when gluing in graphite or Titanium neck reinforcements.

 

YMMV.

[Invader Zim]

Complete seat of the pants neck reinforcement engineering.  The graphite is layered with

strips of mahogany and sandwiched between strips of Formica.  Each step of the lamination

process  I placed the bars in a clamp at the 22.5% point and listened to the sound when I set them in motion.

These beams were quite lively and worked  wonderfully in an 11 string electric alto guitar/ lute.

I had misrouted the slots so it was a good time for something different.

CA gel was used for laminating and installation.