Sailing Mid-Layers Compared: Sail Racing vs Zhik vs Gill

This is an objective comparison, not a hands-on test. Figures are the makers' published specs; full credit given where the others lead.

The mid-layer does two jobs that partly fight each other: trap still air, and let water vapour out before it condenses on the cold inside of your shell. How a garment resolves that tension — grid-knit active fleece versus synthetic fill, air-permeable versus wind-blocking, four-way stretch versus compression-resistant loft — is the whole comparison. This looks at how Sail Racing, Zhik and Gill build the insulating layer, where the fabric platforms genuinely diverge, and what actually matters under a shell on a Melges 40. See what to wear sailing for the system it sits in, between the base layer and the shell.

At a glance

The two archetypes, and why you carry both

Every "mid-layer" range splits into two fabric families that obey different physics. Get this distinction right and the rest of the comparison falls out of it.

Active grid fleece — Polartec Power Stretch and Power Grid, Gill's Thermogrid, Zhik's fleece line. A double-knit where one face is raised into a waffle of loft blocks and the reverse (or the recesses between blocks) stays flat. The loft squares hold air against the skin; the channels between them give the fabric high air permeability, so vapour vents freely while you work. It stretches four ways, recovers, and — being solid-fibre polyester with no membrane — never wets out or loses loft when damp. The cost is wind: a bare grid fleece is deliberately air-permeable, so it only insulates properly under a shell. That's fine — that's exactly where a mid-layer lives.

Synthetic fill — PrimaLoft Black Eco (Sail Racing), Zhik's Xeflex. Fine crimped microfibres, or a lofted non-woven batt, trapping far more dead air per gram than any knit. PrimaLoft Black Eco is comparable to roughly 350-fill-power down for warmth-to-weight, with the crucial marine advantage that the fibres are hydrophobic — it keeps most of its clo when wet, where down collapses. The trade-off is air permeability: fill is a static insulator with a tighter face fabric, so it blocks wind but also throttles vapour transport. Push hard in a fill jacket and you'll wet it out from the inside.

On a Melges 40 the implication is direct. The crew work — hoists, gybe-sets, grinding, hiking — spikes body heat and the waterproof shell traps that vapour against you. So the working mid-layer is almost always a grid fleece (vents while you graft), and the synthetic-fill piece is a thermal reserve: on for the tow-out, the pre-start park-up and the drift home, off (or unzipped) the moment the boat loads up. A serious campaign carries one of each. The comparison below runs both families.

The comparison

Fabric platform and warmth-to-weight

Sail Racing builds its stretch mid-layers on Polartec Power Stretch — a poly/elastane four-way-stretch knit with a brushed inner face and an abrasion-resistant nylon outer face (the "Pro" tier adds a tougher face still). The nylon face is the point: it survives hiking straps, non-skid and a shell's inner scrim far better than a bare fleece pile, and it lets the fabric double as an outer piece in the dinghy park. For static warmth Sail Racing runs PrimaLoft Black Eco at 100 g/m² fill in the Spray PrimaLoft — the maker quotes roughly 0.65 clo and ~350-fill-power-equivalent warmth, in a body of recycled nylon with a graphene liner claimed to spread and even out heat. That's a coherent two-piece story: a durable stretch fleece for working, a genuine down-alternative for parked warmth.

Zhik runs both families too. Its fleece line uses a hollow-core polyester fibre — the hollow bore traps additional air inside each filament, lifting warmth-to-weight over a solid-fibre knit of the same mass — plush brushed inner, smoother pill-resistant knit outer; Zhik also offers a straight Polartec zip fleece. Its headline piece, though, is Xeflex, which pairs a radiant-barrier layer (a metallised/reflective element that bounces back long-wave body heat conventional fibre insulation lets pass) with vertically-lapped insulation — fibres oriented perpendicular to the fabric plane so the batt resists wind-compression and keeps its loft under a shell and under load, where cross-lapped batting flattens and loses clo. That's a legitimately different mechanism from PrimaLoft's crimped-fibre loft, and the radiant-barrier angle targets the heat that fill alone doesn't catch.

Gill concentrates on the grid-fleece side with Thermogrid: a 92% polyester / 8% elastane four-way-stretch knit with a brushed waffle interior — the classic grid geometry, raised loft blocks for warmth, recessed channels for airflow and fast dry-time, and a smooth outer face specifically to slip under a shell. It's pill-resistant and, model-for-model, typically the keenest price on the grid. Gill's warmth ceiling in a single piece is a touch lower than a dedicated PrimaLoft jacket, but as the working mid-layer of a system the Thermogrid is squarely on-spec.

The engineering read: for the working layer, Power Stretch's nylon-faced durability is the standout and the reason it earns the premium; hollow-core and Thermogrid both deliver competent grid warmth-to-weight, with Gill the value play. For the thermal-reserve layer, PrimaLoft Black Eco and Zhik's radiant-barrier Xeflex are genuinely different bets — crimped-fibre down-mimicry versus reflect-plus-compression-resistant loft.

Breathability and moisture transport

This is where a mid-layer is won or lost, because the failure mode isn't "too cold" — it's condensation soaking the inside of your shell.

On the grid fleeces, the mechanism is shared and real. The bi-component knit pairs a hydrophobic yarn against the skin with a hydrophilic outer, so liquid sweat is driven off the skin and spread thin across the outer face to evaporate, while the open grid channels give air permeability far above solid fleece — Polartec's own high-loft fleece sits around ~240 CFM as a reference for how open this class of fabric is. Practically: a 150–200 gsm grid fleece moves vapour better than a 300 gsm solid fleece at the same output, which is the entire reason to buy one. Sail Racing adds mesh side panels to the Spray Polartec to vent the flanks under the arms; Gill's Thermogrid leans on channel airflow and the smooth outer; Zhik's fleece prioritises a high-wicking quick-drying outer face.

On the fill side, the picture flips and Zhik makes the sharper claim. Xeflex is marketed as a highly water-repellent composite with class-leading breathability for its warmth, explicitly designed so your base layer and waterproof/breathable shell function as intended — i.e. it won't become the vapour bottleneck in the stack, which is the standard sin of a warm fill jacket. Sail Racing's PrimaLoft piece relies on PrimaLoft's inherent air-through-fibre breathability plus fleece-lined vents; it breathes decently for fill, but any fill jacket is a step down in air permeability from a grid knit — which is exactly why it's the reserve layer, not the working one.

The engineering read: on breathability the whole grid-fleece class is close and all three are fit for hard crew work. Among the fill pieces, Xeflex's explicit "let the shell work" design gives Zhik the edge for a warm layer you might keep on longer.

Layering geometry, stretch and articulation

Fabric warmth is moot if the garment fights the shell over it. Three things decide that: girth, zip placement and cut.

Four-way stretch is table stakes here and all three deliver it in the fleece — Power Stretch, Thermogrid (8% elastane) and Zhik's knits all move with a smock, add negligible girth and don't tent when you reach for the vang. The fill pieces are where clashes appear, and the good ones engineer around it. Zhik Xeflex uses an asymmetric front zip deliberately offset from the centreline so its zip stack doesn't pile up under a shell's centre zip, a slim offshore map, water-resistant stretch cuffs and a Reziseal-compatible collar that mates cleanly with a Zhik shell's neck seal. Sail Racing plays the coordination card hardest: its mid-layers are cut on the same slim block as its shells and salopettes, so the shoulders, sleeve length and hem stack without the girth clashes you get mixing brands — a real, if unglamorous, advantage when you're buying a full kit. Gill covers the mobility basics well — raglan sleeves for unrestricted arm travel, an offset internal wind guard behind the zip and thumb loops to lock the cuffs and kill the sleeve-ride-up that lets water in at the wrist.

The engineering read: in the fleece, layering geometry is a wash — everyone's four-way stretch. In the fill layer, Sail Racing's system-coordinated block and Zhik's offset-zip/Reziseal detailing both solve the real problem (zip-stack and neck clashes under a shell); Gill's raglan-and-thumb-loop execution is sound and value-priced.

Construction, hardware and durability details

The details that survive a season of salt and grinding:

• Zips — Gill specifies full-length YKK with an inner wind guard, the reliable choice. Sail Racing and Zhik use quality coil zips; Zhik's asymmetric routing is the smarter layering call, Gill's YKK the surer long-term bet on the component itself.
• Face durability — Sail Racing's nylon-faced Power Stretch is the most abrasion-resistant fleece face here (hiking straps, non-skid, the shell's inner scrim); all three use pill-resistant outer knits so the fleece doesn't fuzz where a harness or PFD rubs.
• Water shedding — Sail Racing uses a PFC-free DWR on the PrimaLoft shell (regulatory-durable and the responsible chemistry); Zhik's Xeflex leans on a highly water-repellent composite so spray beads rather than wets the fill.
• Insulation stability — Zhik's vertically-lapped batt is engineered specifically to not lose loft under wind pressure or a tight shell, a genuine edge over conventional batting that flattens. PrimaLoft Black Eco's hydrophobic microfibres are the hedge against the marine reality that everything gets damp — it holds most of its clo wet, where down would collapse.
• Thermal detailing — fleece-lined hand pockets (all three), mesh pocket bags (Gill, to drain and vent), high wind-blocking collars, elasticated hems to stop the bellows effect that pumps cold air up the torso on every hike.

The engineering read: Gill's YKK and mesh-drained pockets are the value-durability standout; Sail Racing's nylon face and PFC-free chemistry lead on the fleece and the responsible build; Zhik's vertically-lapped, loft-stable fill is the cleverest solution to the compression problem that quietly robs warm layers of their rating.

Our pick

For a coordinated Grand Prix system, Sail Racing is our pick — but on specifics, not slogans. The nylon-faced Polartec Power Stretch is the most durable working-fleece face here and survives the abrasion a race boat inflicts; the PrimaLoft Black Eco (100 g, ~0.65 clo, hydrophobic, PFC-free DWR) is a genuine down-alternative reserve layer that holds warmth wet; and the slim block, cut to match its shells and salopettes, removes the zip-stack and girth clashes that plague mixed-brand kits. That combination — durable active fleece, credible fill, geometry that just works under the shell — makes it the most complete insulating layer of a full system.

Zhik is the sharper choice if your priority is a warm reserve layer: Xeflex's radiant barrier plus vertically-lapped, compression-resistant insulation is a legitimately different and clever mechanism, and its "let the base and shell work as intended" breathability is exactly what you want in a fill piece you might keep on. Gill wins the grid-fleece value argument outright — Thermogrid's 92/8 four-way-stretch waffle, full-length YKK, raglan sleeves and thumb loops cover every functional base for the working mid-layer at the keenest price. All three are genuinely good; the differences are real and mechanical, not marketing.

Who each is best for

• Sail Racing — crews building a coordinated system who want a durable nylon-faced working fleece and a credible PrimaLoft reserve that stack cleanly under matched shells. (Our pick.)
• Zhik — sailors who want the warmest reserve layer per gram and rate the radiant-barrier, loft-stable Xeflex mechanism and offset-zip layering.
• Gill — anyone specc'ing the working grid fleece on value — Thermogrid delivers the full grid-and-YKK feature set for less.

The takeaway

A mid-layer is a two-part problem: an air-permeable grid fleece that vents while you work, plus a synthetic-fill reserve that traps still air (and keeps its warmth wet) for the parked-up moments — and how a garment resolves the breathe-versus-insulate tension is the whole comparison. Our pick: Sail Racing for a coordinated Grand Prix system — nylon-faced Power Stretch, PrimaLoft Black Eco fill, PFC-free DWR and a block that stacks under its own shells. Choose Zhik if a warm, loft-stable, radiant-barrier reserve layer is the priority, or Gill if you want the full grid-fleece feature set at the keenest price. Field notes to follow. See the base layers and salopettes comparisons for the rest of the system.