Stiff, stable neck...stiffening rods?

[goodchicken]

I've heard people give yay and nay opinions on using stiffening/stabilizing rods like steel, graphite, or carbon fiber. Some say if done right they should help a neck stay stiff and prevent any unwanted movement. Others say if the wood wants to move, you probably can't stop it over time.

I have a flat sawn birdseye maple neck blank (and matching fingerboard blank) that I want to make the best neck from w/o laminations. So I'm entertaining to rod ideas again, and since it's been quite awhile since I've seen those discussions, thought I'd ask...think it's worth it?

Now the bonus point question would be what material to use. Neck dive is not something I'm worrying about if the answer is steel like what rods Warmoth sells. I'd lik to hear other opinions on tone, sustain, etc affects when adding rods, but that would be secondary to me to gaining stability.

Thanks!

 

[Bruce Johnson]

Hello goodchicken;

As long as you aren't badchicken, we'll be glad to help. We have a few long detailed threads here in Luthier's Corner all about this subject of stiffening necks; how and why. Here are a couple that I can immediately find:

Neck reinforcement rods vs truss rod

Less expensive carbon fiber reinforcement

Carbon fiber option

Aluminum reinforcement rods? Maybe?

DIY Carbon Fiber reinforcement?

 

[Gilmourisgod]

@Bruce Johnson has done some convincing work using carbon fiber TOW strands embedded in epoxy to prevent the the backstrap of the neck wood from "stretching" over time. I have yet to try it myself, but I have done three basses with 1/4" x 3/8" pultruded CF bars either side of a single DA trussrod, all are fully adjustable and seem quite stable. I cant say how much of that stability is due to laminated multi-piece neck construction and careful grain orientation vs the benefit of the rods, but.....so far/so good.

 

[Bruce Johnson]

Here's my mandatory introductory lecture:

I'll say it again: Stiffness and stability are two different things.

If you build the neck correctly, you won't have a problem with stability. It won't warp or twist over time (long term stability) and it won't move much with changes in the weather (short term stability). The neck can be built to be stiff or to be soft. If it's built carefully, it will be stable.

Reinforcing rods or bars of graphite, steel, whatever, add stiffness to the neck. That is, it will take more pounds of force to bend it the same amount. So, if you built the neck poorly and the wood tries to warp or bend with the weather, the graphite rods will resist against that bending. The rods can't completely stop the bending, but they will reduce the amount.

The truss rod is an adjustable stiffener. It can add no stiffness, if it's loose, or a lot of stiffness, if it's tight. Tightening it adds stiffness and forces the neck to bend backwards. A double-acting truss rod can force the neck to bend backwards or forwards.

The truss rod only has a limited amount of force that it can apply. The stiffer the neck is overall, the less range of movement you can get from tightening the truss rod. If the neck is really stiff, the truss rod is useless. If a really stiff neck warps, you are out of luck. The truss rod can't help it.

If the neck is built well, and doesn't have a stability problem, then the reinforcing rods aren't necessary. They are just added weight and stiffness, and they are restricting the capability of the truss rod.

How stiff or soft you decide to build the neck will have an effect on the overall sound of the bass. That's a complicated subject by itself, but in general, a stiff neck makes the bass colder, clearer, with a flatter attack curve and minimal background coloration. A softer neck makes the bass warmer sounding, more percussive, and with more background coloration. But there are many overlaps and other factors in there. So, you may want to build the neck really stiff, or not. It depends what kind of bass you are building.

Building a neck correctly, so it doesn't have stability problems, is also a big topic by itself, but it comes down to three things:

1.) Making sure that the wood is properly dried and free of internal stresses.
2.) Cutting the wood and any lamination strips to put the growth rings and grain lines in the best orientation along the neck axis.
3.) Sealing up the wood, so that moisture from the air doesn't soak in and out as the humidity changes.

I hope this answers your question? When you get into the details, building a "good" bass neck is more complicated than it appears. There isn't any single best way; there are tradeoffs and many different approaches.​

 

[Beej]

I agree with everything above - since you're talking about a one-piece birdseye neck blank, how long have you had it? How long has it been seasoning and in what kind of environment? For context, I don't put any board into a neck that has been in my possession for less than two years, and most of them have been aging much longer in my wood racks, and came to me kiln dried and seasoned as well. A dry, seasoned board will be more stable generally speaking.

 

[byacey]

Birdseye maple is actually a poor choice for a good neck, as the birdesye figure is only seen on slab cut stock. It's not as stiff as quarter sawn stock.

 

[Bruce Johnson]

Here's a long thread where we talk all about quartersawn, flatsawn and laminate necks, how and why:

About That Quartersawn Maple.....

 

[goodchicken]

Yes I guess stability is the better choice of words for what I'm after, so essentially going for less chance of unwanted movement.

I've heard that a birdseye neck not being quartersawn and also not laminating would likely go against what I'm after, but I also want to retain the vanity of the look I want! lol

I have had this blank for maybe 4 years I think. It and the fingerboard are flat and square.

 

[dwizum]

Birdseye can be fine if it's a good piece (no runout, no other defects) and is treated properly.

Bruce has already said anything else I would have added to the thread. To put his comments in context, birdseye generally tends to be both less stiff and less stable than straight grained maple. Both of those deficits can be overcome though.

My personal approach when using figured maple is to use it as-is with no reinforcements if I'm using an especially stiff fretboard (most ebony species, or purpleheart) but to add stiffening reinforcements if using a less stiff fretboard (most rosewoods, maple, etc).

 

[Gilmourisgod]

I bought a nice piece of maple birdseye a few years ago, and luckily it started warping before i tried to make it into a neck. I think like everyone else here, I've had the surprise of what was a straight and stable piece of wood Ive had for a while go whonky on me in the act of cutting it, sometimes immediately, sometimes after sitting around for a couple days. I can see the appeal of a one piece figured neck, but from my limited experience, laminated necks are less problematic. You might get lucky and get a perfect neck....or not. My G&L L2k was built in 1983 and is the most stable wood neck ive ever owned, so go figure, Leo knew his stuff. Personally, i like the the aesthetics of a lamination, working some more decorative wood into a maple sandwich, and knowing that those glue joints and grain orientation will strengthen the whole assembly. Now i gotta re-read all Bruce's articles on neck building.....

 

[dwizum]

One piece figured necks are definitely a crapshoot. I've had some craaazy changes in shape as blanks were cut down. Basically, you have to be ready to either fix the change in shape if it's very minor, or discard the neck, at each step.

 

[RichterScale]

One piece figured necks are definitely a crapshoot. I've had some craaazy changes in shape as blanks were cut down. Basically, you have to be ready to either fix the change in shape if it's very minor, or discard the neck, at each step.

This would've been my answer. Wood is wood. You could build 10 necks from the same species, same cut, etc and 5 hold forever and 5 turn into bananas.
That's why I chose to just do laminated necks out of the gate.
And they don't always have to be exotic, extreme contrast laminates.

 

[tpaul]

 

[micguy]

I'll say it again: Stiffness and stability are two different things.

If the neck is built well, and doesn't have a stability problem, then the reinforcing rods aren't necessary. They are just added weight and stiffness, and they are restricting the capability of the truss rod.
​

Yep - you can absolutely make a stable neck without reinforcing rods. You can make it stiffer or less stiff by changing the cross section (or changing the length0, but given a fixed cross section of a given wood, reinforcing rods will stiffen it a bit more. This does change how the neck performs.

The necks on my basses are all roasted maple, which reduces the weight some and adds stiffness. They have graphite reinforcements (more stiffening), and light tuners on the headstock - added stiffness and reduced mass are things that drive the resonant frequency of a neck upwards. That moves the "area of reduced sustain" (all necks have this, and if it's bad enough, we call it a "dead spot") up the neck, where it tends to be less problematic. Most Fender necks have this thing going on on the G string, frets 4 to 7. Mine are all fret 8 or 9 and less noticeable than most.

 

[Turnaround]

Birdseye maple is actually a poor choice for a good neck, as the birdesye figure is only seen on slab cut stock. It's not as stiff as quarter sawn stock.

There is actually very little if any difference in stiffness between flatsawn and quartersawn boards. They easiest way to demonstrate this is with a piece of dowel - in one orientation it is effectively flatsawn and at 90 degrees it is quartersawn. Put one end in a vise, end grain running parallel to the floor, suspend a weight at the other end, and measure the deflection. Then re-orient the dowel by rotating it 90 degrees in the vise so the end grain is perpendicular to the floor, and see what the deflection is like with the same weight at the same place on the dowel.

 

[Bajo Clarkko]

This is my ‘91 Warmoth Jazz Bass with a Birdseye Maple neck. It has the standard Warmoth stiffening rods. I’ve adjusted it only once in the last 31 years, and that’s only because I went from medium tension strings, to a lighter gauge set of strings. No problems.

 

[roller]

+1

All the birdseye necks I've owned have moved around more to my liking.

I prefer classic flatsawn maple with graphite or carbon bars/strips... not really for the stability, but the bars tend to even out the notes on the neck (not as many hot or dead spots). Graphite and carbon will bend under pressure and yes, will change with alterations to humidity.

Additionally, I like maple necks with a separate maple fretboard (i.e., not a neck that is all one piece). I believe a separate fretboard adds to the overall stability of a neck.

Birdseye maple is actually a poor choice for a good neck, as the birdesye figure is only seen on slab cut stock. It's not as stiff as quarter sawn stock.

 

[stringthrough]

I've had non-rodded necks that remained stable and straight from season to season and I've had rodded necks that needed adjustments at least twice a year.

I don't understand why this is the case but it suggests to me that these rods are mostly hype.

 

[byacey]

There is actually very little if any difference in stiffness between flatsawn and quartersawn boards. They easiest way to demonstrate this is with a piece of dowel - in one orientation it is effectively flatsawn and at 90 degrees it is quartersawn. Put one end in a vise, end grain running parallel to the floor, suspend a weight at the other end, and measure the deflection. Then re-orient the dowel by rotating it 90 degrees in the vise so the end grain is perpendicular to the floor, and see what the deflection is like with the same weight at the same place on the dowel.

In the violin world centuries ago, it was discovered quarter sawn wood for the neck, bellies and back stood up much better than other cuts against warping, sunken arching, necks twisting, etc. If it's good enough for them, it's good enough for a bass. it's also no accident that violin family bridges are all quarter sawn, too.

 

[Turnaround]

Quartersawn wood shrinks mostly in thickness, not so much in width. Flat sawn shrinks more in width than thickness. So for violin backs and tops it is best to use quartersawn wood since any shrinkage in width would open the seams. The same is true for necks - any shrinkage across the width would jeopardize the neck joint, especially on cellos and double basses. But the choice of quartersawn for necks comes at a price - the neck is more likely to twist. In the decades that I serviced the violin family of instruments, most neck problems were related to twist.

For that matter, the same is true for violin bridges. They are closely fitted to the curve of the top plate. And shrinkage in width will cause the bridge foot to lose proper contact with the plate.