I've got a lot of Modulus basses (Modulus built the graphite neck on your Alembic) and I've probably experienced most of the problems that these necks have. I would agree that the problem you had is dominated by by the phenolic fingerboard.
The graphite neck is made in 3 pieces. There's a molded section that has the shape of the back of the neck, headstock, and continues into the body up to the bridge. It has a U-shaped cross section (the neck is hollow). There's a thick flat piece (Modulus calls this the underlayment)that is bonded on top of the U-shaped neck section and is under the fingerboard. Finally, there's a phenolic fingerboard bonded onto the underlayment. You can see all these pieces if you look at the edge of the neck.
The main neck piece and the underlayment are really, really structurally strong. They are largely impervious to temperature, humidity, and other environmental factors. The phenolic fingerboard material is a special kind of paper that's been saturated with a resin. It's actually fairly sensitive to humidity and temperature, I think more so than a traditional fingerboard wood like ebony.
The main piece and underlayment are bonded together using epoxy and this forms a hollow tube (or monocoque) which is an extremely strong structure. Even then, it will still flex under string tension or even from the tension of the fingerboard. Under extreme temperature conditions that you had by accident, you were probably seeing the force that the fingerboard can exert against the graphite neck structure.
The big difference in thermal expansion between the neck and fingerboard is actually a pretty deal and it exacerbated by the way the neck is fabricated. The problem here is that the graphite neck components are really strong, but the epoxy that's holding it together is much less so. In a perfect world, the epoxy has perfect mating surfaces and is equally strong as the epoxy in the neck pieces, but mixtures can be wrong, the chemicals can vary, as does the prep and conditions during assembly. Modulus builds the neck out of many sheets of graphite fabric which are hand laid into a mold and cooked at high temperature and pressure. The underlayment is a regular plate so it's always flat, but the neck piece has to be milled when it comes out of the mold so that it has a dead flat surface. In most cases, this all works out fine, but if there is any bow in the main neck piece, forward or back, then you have two very strong pieces trying to separate each other and only the glue holding them together.
With the sun exposure you had, the fingerboard is stressing the underlayment. This is particularly bad because the bonding area between the main neck piece and the underlayment is two thin lines at the sides of the neck (remember, it's U-shaped). The fingerboard is bonded across the entire surface of the underlayment so it actually has an enormous amount of strength to pull on the weaker joint. The most serious problem that you can have with a Modulus neck is a separation of the main piece and underlayment (they call it a delamination) which is potentially fatal.
All these necks are built up by hand and there weren't a lot of Alembic necks at all (I think it's around 50 but only Alembic would know for sure). In regular production at Modulus, the fabricators have a recipe of how much material needs to be placed in the neck and where, but for special stuff like the Alembics, it's a little more chancey, so the Modulus folks often overbuilt these necks to make sure that they were solid and stable, but this might affect the relief in the completed neck which is an extra hassle for setup at Alembic (no truss rod here, so relief needs to be manually cut into the fingerboard and frets).
I think you actually want to be pretty careful about heat and temperature with these necks (which really means treat them like a wood neck). High and low heat can affect the glue joint as would impact if you drop the instrument.
I have had 3 delaminated necks, two of which I've had repaired. One was due to a significant bow in the main piece and too narrow of a gluing area. The other was a failure from a drop (sadly, this was a BassStar through-body). I have the original fingerboard+underlayment from that one which had to be completely disassembled, remilled, and reassembled. It has a concave bow of nearly 1.5 (the phenolic is the short side here). It's physically quite hard to bend, even though the underlayment is only about 1/8 so you can imagine the amount of tension that the glue joint and main neck piece was bearing.
Finally, there has been some evolution of the neck materials over the years. The earliest necks have a finish that looks like tiny crystals, then there was a wavy-patterned fabric, then checkerboard, then the large polygons/chunks that you see today. These finishes are actually all cosmetic material that's placed in the mold for appearances and past that cosmetic layer, the construction is pretty similiar. But I would definitely agree that there are differences in stiffness, stability and tone between the different generations. The oldest ones sound best to me and feel the stiffest, as Mica mentions. However, it's been my experience that the older ones are a lot more likely to have fabrication problems than the polygon necks that comprise most of the ones out there. By the time Modulus was doing the polygon necks, they had much better equipment and had refined the build techniques significantly. All three of my failed necks are old ones - two checkerboards and one wavy.
In case you're wondering, I'm close friends with Geoff Gould who founded and ran Modulus for many years and, in addition to owning a lot of Modulus basses (and a 1987 Series II graphite neck), we've spend countless hours talking about how this stuff was put together.
David Fung
