Normally, I burst in on the graphite discussions earlier, but have been swamped lately!
As some of you long-time viewers already know, I'm a big Modulus fan and have been close friends with Geoff Gould who developed the original Modulus neck in conjunction with Alembic for many years now. So, we've chattered about why things were done the way they were many times in the past.
The interesting thing about building things out of composite materials is that you can engineer the characteristics of the final piece fairly precisely and repeatably. You'd have a hard time building a one piece wood neck that had specific stiffness or resonant frequency. You can get closer by laminating the neck, since the layers in opposition can counteract some of the natural irregularities in the wood. With something like a graphite neck, you can build in a very specific stiffness and you can control where the stiffness is directed. You see this to a greater extent in composite stuff like bike frames or golf club shafts, where they can engineer flex in in one direction and stiffness in a different direction.
When Geoff first got the idea of building a graphite bass neck, he was working at Ford Aerospace in Palo Alto, CA as a technician and composites fabricator. He was making satellite parts, totally cutting edge stuff at the time. These sorts of applications are totally weight-conscious - lifting a payload was monumentally expensive and very limited, so if you couldn't hit a weight target, you just couldn't do that mission. The strength of engineered graphite vs. steel, aluminum, or titanium was so much greater that they could use a lot less material for the same strength.
This is where the idea for the Modulus neck came from. Geoff saw Phil Lesh battling neck dive at a Dead show and thought that a lighter-weight graphite neck would solve the problem. He ended up talking with Alembic who built the first instruments with graphite necks, and the rest was history.
The lack of a trussrod in the original Modulus design was intentional on Geoff's part. From a purist's standpoint, he wanted the entire tension of the string, from end to end, to be borne only by graphite. The graphite material he used was exactly the same stuff that he was buiding satellite parts and Indy car tubs from, a graphite fabric that was impregnated with epoxy resin. Sheets of the pre-preg were cut and laid in a mold which was then cooked under heat and pressure in a giant autoclave until the resin cured and locked the graphite fibers into a solid matrix. The pre-preg fabric is unidirectional - the fibers all run parallel to each other - so you can engineer the performance of the parts by adjusting the direction that the grain of the graphite fibers and overlapping them in different directions. The material is thermoset, which means that the heat changes the material. The fabric is flexible before it's cooked, but after the curing reaction it is pretty impervious to heat and humidity. This is different than a thermoplastic material which is molded to a shape under heat, but will change again if you re-heat it later.
Even today, Modulus and Status necks are built using this process (Vigier was like this too back when they had graphite necks). Modulus necks are multi-piece assemblies which are laid up in molds. Status instruments are made by wrapping the pre-preg around a styrofoam core, basically the same process that you use to make surfboards. The Steinberger and Moses necks are made with a different process, where the neck is poured from a liquid resin around a graphite backbone. The latter necks gain strength and stiffness from the backbone, but the structural characteristics aren't as controllable as the monocoque structure of Modulus necks (of course, the Steinberger and Moses necks are poured from a uniform material, so there is less variation than wood).
The resulting neck in a Modulus is really strong and stiff relative to wood, but still flexes under string tension, which it was intended to do. You can make a super-strong neck that doesn't flex or deflect at all under string tension, but this requires use of a stronger and more expensive pre-preg fabric. If you handled a Modulus or Steinberger, you'll immediately notice that, if anything, it's heavier than a wood neck rather than lighter. That's because the neck could be engineered to flex to the proper position under tension using less exotic materials which were heavier.
The earliest Modulus necks were made of these super-strong fabrics. A couple of years ago, a very old six-string Quantum through-body appeared on eBay. It turned out that this instrument, the second or third Modulus-logo'ed bass had been stolen from Geoff's office years before. The seller (who had purchased the instrument at a pawn shop) returned the instrument to Geoff, who was surprised to find that this BEADGC bass had it's regular low-B strings on it but was tuned up a fourth like a guitar! It was actually still playable, although I would insist on safety goggles and a full face shield before I'd touch it myself. There's no way that a wood neck could handle that sort of tension. And yes, these very old Modulus necks defintitely have a different tone than the regular production.
If there's a sonic advantage to no trussrod, there's certainly a physical disadvantage which is that you can't easily fine tune the action for your playing style and desired strings. As has been mentioned above, if you want to modify the relief, it needs to be done via a very expert fret milling. Ultimately, this is why all the makers of composite necks today have trussrods. The latitude of change in these necks is much less than the trussrod would yield in a wood neck, but sufficient to tune for different strings and desired action.
This helps make the instruments more produceable as well. In the case of Modulus, the secret recipe of the materials and construction is carefully tuned so that the fretboard can be planed to dead level and frets installed dead level under no tension, then will pull into the desired target relief when strung up. Over time as the materials change, they need to adjust the fabrication instructions to compensate, and this slowed down production because transitional instruments needed to have additional fretwork before they could go out the door.
Incidentally, the fingerboard on Modulus, Status, and original Steinberger is phenolic, the very first composite material. The graphite is way too hard to be shaped into a playing surface (it will quickly dull regular tools). Geoff considered a wood fingerboard but was concerned that it might not be stable since wood can be very subject to expansion with humidity and heat. He ended up selecting phenolic because it's easy to work (pretty much the same as wood) and aesthetically he wanted the neck not to have any wood in it.
The graphite in a Modulus neck is fabricated in two pieces - a main molded U-shaped part that has the shape of the back of a guitar neck and a thick flat plate that it bonded on to the top of the U. Together they form a monocoque tube which structurally is stronger than a solid neck (and saves on expensive materials as well). The phenolic fingerboard is epoxied on top of the flat piece.
The individual pieces are REALLY strong and stable. If properly constructed they won't bend, twist, or warp over time. It turns out that that's actually the Achilles heel of the Modulus neck. The curved main part is cooked in a mold, then the open side of the U is milled with a carbide tool to be dead flat and the flat piece is bonded on top of that. The problem arises when the milling doesn't done properly. This can leave an internal tension in the neck assembly where the parts want to spring apart with only the epoxy bond holding them together. Ultimately, a neck like this can fail and split along the bond line. This is the dreaded delamination which is largely fatal for Modulus necks as it requires the neck to be completely disassembled, remilled, reassembled, refretted, etc. Even with perfectly machined parts, the epoxy bond line is actually not that strong relative to the neck pieces and can be compromised by heat or when an instrument takes a dive off the stand. I think most of the reports of warped necks are actually delaminations (actually, it is a warp that's causing this).
I don't think you can find a better sounding instrument that a Series bass with Modulus neck. But it's got to be a nightmare for both Alembic and Modulus. Unlike regular Modulus production (which is mostly bolt-ons), graphite Alembics were very rare, so there was much less opportunity to tune the neck recipe for easy setup. The threat of a delamination is bad enough on a bolt-on where you have to scrap the neck, but a nightmare on a through-body where it could potentially lead to a non-repairable instrument. For these rare instruments (by all accounts much less than 100 total), there was also some jockeying around about exactly how they were made - Modulus always fabricated the parts, but in some cases the neck assembly was done at Alembic (where they had less experience but could maintain more control) and some at Modulus (where they had more assembly experience but no insight into how the neck would be mated to the body).
I was fortunate to have a Series II graphite neck made back around 1987, probably one of the last. I have no issues with stability although the action was never quite to my liking out of the factory (insufficent relief). Years later, I had this corrected in a very expensive fret mill by the builder who did most of Modulus' custom shop work, but even with his level of experience, it was hard to convince him to take on the job as he was concerned about disturbing the side LEDs in the event that he had to remove a fret. He didn't have to and it all worked out OK for my bass in the end though.
The fab process of graphite necks is so radically different than the woodworking that goes into a wood-necked Alembic, that it's not suprising that it's not offered anymore. Not only is it hard to manufacture, but you lose the ability to customize profile, scale length, and more.
David Fung
