Crew Tech Tees and Caps: What We Look For

This is a research note, not a rated review. We have not yet worn a full season in these tees ourselves, so what follows is how the category is engineered to work and what we would assess — written in "is designed to" terms, not "we tested".

A crew technical tee is a moisture-transport and UV-barrier problem worn eight hours a day on a wet, high-UV, high-output platform — so the fibre chemistry, weave, verified UPF and seam mechanics matter far more than the logo on the chest. Team branding turns the garment into crew identity and a sponsor surface, but that is downstream of whether it keeps eight people thermally comfortable and sun-safe through a long salty day. Here is how the category actually works at material level.

The fabric is the whole decision — and it is a physics problem

Everything else on a tech tee is detail; the knit is the product, and the mechanism is capillary transport. A textile capillary is the space between adjacent fibres and filaments in the yarn; the driving pressure is the Laplace capillary pressure, which scales with liquid surface tension and inversely with the effective pore radius. Fine, closely-packed filaments generate higher capillary pressure and pull liquid further and faster — practical wicking channels sit in the tens of microns. The point of a performance knit is to make that pressure gradient carry sweat and spray from the skin face to the outer face, where the large exposed surface area lets it evaporate.

Engineered polyester — including branded fibres such as Coolmax — is hydrophobic, with moisture regain under about 0.5%, so essentially no water enters the fibre itself. It works structurally, not absorptively. The classic Coolmax filament uses a flattened cruciform (tetrachannel) cross-section: four longitudinal grooves that raise the fibre's specific surface area by roughly 20% over a round filament of the same denier, giving it more capillary channels and more evaporative area per gram. That is why a good synthetic tee dries back to comfort in minutes while cotton stays wet all day. Polyester is also cheaper, tougher and holds a sublimated print well. Its weakness is not moisture but odour: because it holds little water it also holds little of the sweat, but it presents a clean surface that skin bacteria colonise readily, so a hard-worked synthetic tee turns ripe within a wear or two even with an anti-microbial finish.

Merino wool — usually a 150-200 gsm knit — solves the same problem by the opposite route: it is a hygroscopic vapour manager, not a liquid wick. The fibre is bicomponent. A hydrophilic keratin cortex buffers water vapour into its structure (standard moisture regain about 17%, and it can hold up to roughly a third of its dry weight in moisture before feeling wet), while an ultra-thin covalently-bound lipid layer — 18-methyleicosanoic acid, the "18-MEA" cuticle — keeps the outer surface water-shedding. Sorbing vapour is also mildly exothermic, which is why merino feels warm as you start to sweat and buffers temperature across a wider range. Its odour resistance is chemical, not marketing: the keratin side chains bind acidic, basic and sulphurous odour compounds and lock them in the cortex until the garment is washed, so it can be worn for days between washes — decisive on a multi-day regatta with no laundry. Independent olfactory panels have measured markedly lower retained odour intensity for wool than polyester after equivalent wear. The cost is drying time (that same water-holding cortex sheds slowly) and price. Merino-synthetic blends — merino spun with nylon or polyester for durability and elastane for stretch — are the pragmatic middle ground, and increasingly what experienced crews actually buy: most of the odour and thermal behaviour of wool with better abrasion life and faster dry-back.

Fabric weight is the other lever, and it trades breathability against warmth. Warm-weather tees sit around 120-160 gsm for maximum air permeability and drying speed; cooler-climate base tops run 190-220 gsm for a little insulation without becoming a mid-layer. A crew running events across seasons will hold both.

Why cotton fails twice: the thermal maths

Cotton is not merely "less good" — it fails on two separate physical axes, and both matter on the water.

Thermally, cellulose has about 8% moisture regain but wets out completely, so a soaked cotton tee holds water in direct contact with the skin. Still air is the actual insulator in any clothing system; water conducts heat roughly 23-25 times faster than that trapped air (about 0.6 versus 0.025 W/m·K). Once water displaces the air in the knit, the garment's clo value collapses and it becomes a conductor bleeding body heat straight to wind and spray. On top of that runs evaporative cooling: the latent heat of vaporisation of sweat is about 2.4 MJ per kilogram, so every gram evaporating off a wet cotton tee pulls roughly 2.4 kJ out of the crew — welcome when you are overheating and hiking flat out, dangerous when the breeze is up and you are sitting still between races. A technical knit moves the liquid off the skin to the outer face so evaporation happens away from the body, not against it; that is the entire mechanism that keeps the layering system working.

UPF: what the number means, and why "wet and dry" is the whole point

Sun exposure is a genuine occupational hazard here — hours on the water with UV reflected off the sea adding to direct sun — and in Australia it is not a footnote. This is where the tee earns its keep beyond comfort.

UPF (Ultraviolet Protection Factor) is defined as the erythemally-weighted UV irradiance reaching a detector with no specimen, divided by the value with the fabric in the beam. In practice it is close to 100 divided by the percent UV transmittance: block 98% (transmit 2%) and you get UPF 50; transmit about 3.3% and you get UPF 30; transmit about 6.7% and you get UPF 15. UPF 50+ is the top labelled rating (at least 98% blocked). Critically, UPF integrates across both UVA and UVB weighted by the erythema action spectrum, whereas the SPF number on a sunscreen bottle only characterises UVB. For a race crew, only 50+ is worth specifying.

The number is a proxy for physics. UV attenuation through a textile is governed by the cover factor and porosity — UPF rises with cover factor and falls sharply as porosity increases; for high protection, open area between yarns needs to be well under a couple of per cent. Dark and high-chroma dyes add absorption, and many technical fabrics carry inorganic UV blockers (titanium dioxide or zinc oxide micro/nanoparticles) that scatter and absorb UV; TiO2 is also the standard polyester delustrant, which is partly why dense synthetics test well. The UPF value encodes all of that, but weave tightness, colour and finish are the physical reasons behind it.

Now the sailing-specific detail: the test standard, and the state of the fabric when tested. The Australian and New Zealand standard AS/NZS 4399 and the US method AATCC 183 measure spectral transmittance on a spectrophotometer; the base AS/NZS rating is taken on new, dry, unstretched fabric against the Melbourne summer solar spectrum. But a sailing tee is wet most of the day, and wet behaviour splits by fibre in a way that is easy to get wrong:

• Cotton gets dramatically worse wet. The fibres swell and force the weave open, and the water film reduces internal scattering by matching the fibre's refractive index — both effects raise transmission. Documented drops take white cotton from around UPF 5 dry to UPF 1-2 wet, transmitting well over half the incident UV. A wet cotton "sun shirt" is close to no shirt.
• Dense synthetics generally hold, or even improve, wet. Polyester barely swells; the water largely fills inter-yarn voids and, with the fibre already near the water's refractive index, saturation can nudge measured UPF up rather than down.

So "UPF 50+" on the swing tag is necessary but not sufficient. Verify the claim is to AS/NZS 4399 (or AATCC 183), and prefer fabrics whose protection is characterised wet as well as dry — a rating quoted dry-only on a loose, pale knit is not a safe assumption over the transom. A tight synthetic or wool knit in a darker colour is doing real optical work; a thin pale one is not.

For the full picture on sun cover across the kit, see our foul-weather gear explained guide and the sailing sunglasses guide — eyes and skin are the same exposure problem.

Fit and chafe: the failure mode nobody photographs

A tee can have perfect fabric and a verified wet UPF and still injure a crew if the seams and fit are wrong. This is the single most under-rated attribute because it only appears under load, over hours.

The base top is worn under a smock and often a buoyancy aid or pack — see lifejackets vs buoyancy aids. Every seam is a candidate hot-spot where salt crystals, sweat and repeated relative motion abrade skin. A conventional plain seam leaves a folded seam allowance proud on the inside face; that ridge is the friction source — thousands of load cycles of fabric against skin under a strap turn it into a chafe burn. Good tech tees use flatlock or bonded seams. A flatlock (the interlock/coverstitch family, ISO 4915 class 600 stitches) butts the two fabric edges and interlocks them with looper threads so the join lies flush on both faces, with no allowance to rub; bonded (welded or taped) seams remove stitch thread from the skin side entirely. Just as important is seam routing: the seams should sit off the shoulder yoke, the scapulae and the rib lines where harness webbing and pack straps concentrate pressure. A raglan or well-articulated set-in sleeve lets the arm go fully overhead to grind or trim without dragging the hem up, and a slightly longer back hem keeps the tee tucked when you bend and hike.

What good looks like: the tee stays put through a full pit sequence, no seam is felt under a strap, and the fabric tracks the shoulder rather than binding it. What bad looks like: the hem creeping up under a smock, a shoulder seam raw by the second race, or a tee so tight it restricts the arm — or so loose it bunches and holds water against the skin. Under salt, seam chafe is a genuine skin injury that compounds daily across a regatta, not a comfort quibble.

Layering: the tee is the foundation, not the whole answer

The crew tee is layer one, and its job changes with conditions. In the cold it sits under an insulating mid-layer and a smock and must keep the skin dry so the insulation above it can trap still air; in the heat it is the only layer, doing sun cover and sweat management alone. A synthetic base moves liquid outward into the next layer so it never pools at the skin — the mechanism that keeps the whole stack functioning. This is exactly why the base must be synthetic or wool and never cotton: a cotton base traps water at the bottom of the system, collapses its own insulation and defeats everything above it. Long-sleeve versions extend UPF cover to the arms and are the sensible default for a full sun day, with short-sleeve tees kept for cooler or lower-exposure sailing.

Team kit and branding: get it right, but keep it second

Matching team tees and caps do real work beyond performance: they make the crew instantly identifiable on the dock and on camera, reinforce team discipline, and carry sponsor marks into every regatta photo and broadcast. The engineering constraints are consistent. A sublimated print dyes the graphic into the fabric as a gas-phase disperse dye, so it adds no coating, does not crack or peel, and — unlike a heavy screen print or heat-transfer panel — leaves the knit's air permeability, wicking and UPF intact; a solid printed panel is effectively a non-breathable, non-wicking dead zone laid over the fabric. Order a full graded size run early, because getting eight crew into correctly-fitting kit is a harder logistics problem than ordering a single tee. And a cap needs the same discipline as the tee: a UPF-rated crown and brim fabric, a brim stiff enough to actually shade the eyes, and ideally a dark under-brim to kill upward glare off the deck and water plus a retention clip; a cotton cap is the same mistake as a cotton tee, wet-through and sun-transparent by mid-morning.

How we would evaluate

When we have worn these across a season, we would assess: wicking and dry-back time after a genuine soaking; whether the UPF rating is credible and holds wet, not just dry; seam comfort under a harness and pack over a long day; fit and range of movement grinding and hiking; odour after multiple wears without laundering; and how the print and fabric survive repeated salt exposure and washing. Until then, this is a research note — honest findings once we have used them. For the wider kit picture, see the Labs index and our race sailing jackets comparison, which sits over the top of whatever base tee a crew chooses.