Inner reference models
Section 10.4 presented three outer models as coordinates for composite near the surface. Here the same is due for composite near the core. The two models that follow share a manufacturer — Butterfly — and share a position — inner — but use different fibres, and that difference is enough to cover the two extremes of the inner spectrum as section 10.3 described it.
Butterfly Innerforce Layer ZLC. Five wooden plies with two sheets of ZLC — zylon-carbon, the fibre described in 10.2 — in inner position, beside the core. Zylon contributes stiffness and speed, but being separated from the rubber by two plies of natural wood, its effect arrives filtered. The ball does not leave with the immediacy of a Viscaria; there is a fraction of time more in which the blade yields, the rubber works and the player perceives the contact. That margin is small, but it changes the experience: where the outer blade pushes, the Innerforce Layer ZLC accompanies and then pushes.
The speed is high — comparable to many outer ALC blades — but the acceleration profile is different. On soft and medium strokes, the blade responds with a gradation outer blades do not offer: there is a perceptible difference between a touch and a drive, between a drive and a loaded loop. On hard strokes, the stiffness of the zylon comes into play and the bat accelerates decisively. It is that double personality — sensitive at the bottom, powerful at the top — that has made it one of the most widely used inner blades on the professional circuit and in the advanced club game.
Its natural combination is with tensor rubbers of medium to high hardness, where the elasticity of the sponge rests on a base that neither holds it back nor sets it off. The rubber-blade interaction, which governs the result more than either of the two separately, is developed in chapter 11. The modern allround bat profile with an inner base and a soft tensor is detailed in 12.7.
Butterfly Innerforce Layer ALC. The same inner position, the same constructional logic, but with ALC — arylate-carbon — instead of ZLC. As explained in 10.2, arylate is less stiff than zylon, and that difference, already appreciable in outer position, is amplified in inner position. With two plies of wood damping the impact before it reaches a fibre that is itself more flexible, the result is the softest version of composite with a name of its own: a blade many players describe as the frontier between all-wood and composite.
The dwell time is the longest of the four reference fibre blades covered between 10.4 and this section — longer than the Viscaria, than the Timo Boll ALC, than the Innerforce Layer ZLC. The vibration is generous for a composite blade: it reaches the hand with enough richness to inform about the quality of the impact, something outer blades compress. The speed, by contrast, is the most contained of the group. It is not a slow blade — it is still faster than most all-wood five-ply blades — but it does not seek to compete in raw power with the outer blades or with the Innerforce ZLC. What it seeks is a point of balance that lets the player move across from all-wood without losing at a stroke the tactile feedback described in 9.1.
Its natural audience is the player who wants somewhat more speed and consistency than an all-wood blade but is not prepared to give up graduated feeling. It is also the habitual basis of the modern allround bat outlined in 12.7: inner ALC with a soft or medium tensor, an assembly that offers speed enough for attacking club play without the hardness that demands refined technique.
What separates the two is, at bottom, the same thing that separates ZLC from ALC in any position: the stiffness of the fibre. The Innerforce Layer ZLC is faster and somewhat drier; the Innerforce Layer ALC is more sensitive and somewhat slower. But both share the essential of inner position: a touch closer to all-wood than any outer blade of the same fibre, and a response curve that distinguishes between intensities of stroke instead of flattening them. The choice between them depends on how much speed the player needs and how much tactile information they are prepared to give up. The following section places both options — and the whole family of composite blades — in a wider context: the debate over whether modern equipment has gone too far in the pursuit of speed.