Technical sailing shirts are generally worn on warm to hot sunny days without any other layers. They are intended to provide:
- Sun protection
- Prevent overheating
- Manage moisture
Unlike other activates which might take place in low humidity, in shade, or inside an air-conditioned gym, sailing takes place in direct sunlight, in a humid marine environment, in warm to hot conditions.
For sailing conditions technical shirts should have these characteristics to provide the most performance:
- Highly breathable
- Loose fitting to –
- Shade the body
- Provide airspace & air movement to accelerate evaporation
- Reduce direct shirt contact with skin so the sun heated material does not transfer this heat to the body
- Moisture-wicking to maximize evaporation and keep you dry.
- Have a high UPF rating and cover as much of the torso, arms and neck as possible for UV protection
- Made of light color fabrics to reduce heat absorption from the sun
The following explains the factors involved in choosing the best technical shirt for sailing, and may further guide you in choosing your next sailing shirt.
UV Blocking Fabrics – Protecting your skin from the sun damaging rays is the top priority of any good sailing shirt as sailors are exposed to direct sunlight, and reflected sunlight from the water and decks of boats. Sailing is considered one of the most sun-intense sports you can participate in. Shirts protect you from the sun in two ways: UV blocking fabrics and by how much of our bodies this fabric covers.
Sunblock or sunscreen’s ability to block the sun’s ultraviolet B (UVB) rays is expressed as its Sun Protection Factor (SPF) rating, which does not include ultraviolet A (UVA) rays. Fabrics that are tested and certified will be given an Ultraviolet Protection Factor (UPF) rating. UPF ratings cover both UVA &UVB. The higher the UPF rating the garment has the more UV is blocked.
The American Society for Testing and Materials (ASTM) established the standard for material testing and it is accepted worldwide.
UPF Rating Protection Category % of UV Radiation
UPF 15-24 Good 93.3 – 95.9
UPF 25 – 39 Very Good 96.0 – 97.4
UPF 40 – 50+ Excellent 97.5 – 98+
As a point of comparison to everyday clothing, a thin white cotton T-shirt has a UPF of around 5.
UPF Rated clothing will be labeled 15, 20, 25 for Good; 25, 30 or 35 for Very Good; and 40, 45 or 50+ for Excellent.
Tip: The higher the UPF rating the better
The more of your body your shirt covers the more protection you are provided. Choose long sleeves over short. Consider a shirt with a mock turtleneck for greater coverage. ¼ zip shirts will be long sleeve and have the highest collars. Some tops are available as hoodies for even more coverage during less strenuous activities. Consider adding a Buff for comprehensive neck and face coverage. Remember to apply and reapply sunblock thought out the day to uncovered skin.
Tip: Cover as much of your skin as your activities will allow.
Moisture Management Materials
Most all, if not all, technical sailing shirts are made from Polyester. The fabric is durable, fast drying, and does not absorb moisture. Most importantly Polyester will wick moisture away from your skin (capillary action), moving it outward to where it can evaporate from the surface of the material.
Weave can affect the speed of wicking and the speed of evaporation.
‘Waffle’ or ‘Honeycomb’ woven fabric moves moisture away from the skin most effectively and provides the most surface area for moisture to wick to and also more airflow such that evaporation is increased. Because of the less dense weave, these materials may have a lower UPF rating or use a chemical treatment during manufacture to increase the UPF rating.
Plain woven fabrics will be a denser weave with a flat silky finish. It does not allow as much airflow or surface area as a waffle woven fabric but still does a good job of wicking moisture to a wide area and promoting evaporation. The fabrics generally have a high UPF factor without chemical treatment.
Polyester fabrics are hydrophobic (non-water attracting) so they do not absorb moisture, but they are excellent at wicking moisture along their fibers by capillary action. One drawback is that as sweat is being wicked along the fibers, body oils carried in sweat can be separated and bond to the polyester permanently. After repeated wearing, the buildup of these oils may begin to make the shirt smell like body odor, and will eventually need to be discarded.
Note: For sailing do not wear any cotton clothing. It will absorb and hold moisture and leave you uncomfortable.
Tip: Purchase shirts made of polyester, and those with a ‘waffle’ knit for the highest performance.
What cools you, or at least warms you the least in hot weather when sailing? If you would like to know more about the technical reasons that determine the best features in a technical sailing shirt, the following section will provide valuable information.
Evaporative Heat Loss
The evaporation of water (sweat) from the surface of your skin. It takes a lot of energy to evaporate water, whether it is boiling hot or at room temperature. When liquid water does evaporate it uses stored heat to vaporize (escape into the air), and cools the surface it left. The evaporative cooling effect takes place right where the water turns to vapor. As water evaporates from the surface of your skin it cools your body. When it is evaporating from a tight fitting shirt it is cooling you, albeit not as efficiently as with bare skin. Water evaporating from a loose fitting shirt provides the body no direct cooling benefit.
Low Relative Humidity
Speeding up the evaporative process increases the amount of cooling received. The lower the air’s relative humidity expresses as a percentage, the faster water will evaporate. In a desert climate there is little moisture in the air (low relative humidity) and water freely and quickly evaporates and cools. In marine climates with high relative humidity, water evaporates less quickly and cools less; and requires a highly wicking material to move moisture off your skin.
Tip: This will seem counter-intuitive, but in the high humidity climate you sail in, evaporation is slower, so you will want a loose-fitting technical shirt (keep reading)…
The larger the surface area a liquid is distributed on, the higher the evaporation rate, and the more it cooling if creates. A bead of sweat on your skin takes much time to evaporate in and of itself. If that bead of sweat is pulled away into the material of a shirt and distributed by capillary action out to a wider area of fibers it is exposed to more air, evaporates more quickly and created more cooling (and the drier you will stay). Technical moisture wicking shirts are made with either flat or ‘waffle’ woven fabrics. The advantage of ‘waffle’ woven fabrics is that they offer more surface area for water to evaporate from thus accelerating the evaporative process.
Tip: Wear shirts made of synthetic wicking fabric
Wind – Flow Rate of Air
Convective heat transfer – transferring body heat directly away from your skin (or tightly fitting clothing) to cooler air passing over. High airflow increases this transfer. If the air is warmer than your body temperature, obviously, this works to your disadvantage and heats the body.
Boundary Layer – If the air around a liquid is still and not moving, the air surrounding the liquid will reach high relative humidity and the evaporative process will slow or almost stop. If there is ‘fresh’ air moving across the surface of the water (evaporative boundary layer) the evaporative process will not be slowed by stagnating ‘wet’ air. Higher air velocity (wind speed) increases the amount of water that will evaporate.
Tip: Keeping yourself in direct airflow will keep you cooler and drier.
Shade from Sunlight
Thermal radiation – The radiant energy from the direct sun heating your skin or tight-fitting clothing. Shade is the protection from direct sunlight in a manner that allows for airspace and air movement (ventilation). Tight fitting clothing heated by sunlight will directly transfer that heat to your body. Loose fitting clothing that has been heated by the sun has space for air between the fabric and your skin and therefore transfers less heat. A loose fitting shirt creates shade for your body.
Tip: Technical shirts should be loose fitting when sailing
Darker colors absorb more heat from the sun than do lighter ones. White absorbs the least around of thermal radiation from the sun and is the least hot (coolest).
Tip: In hot weather, sailing shirts should be white or light in color, and in warm weather darker colors can also be worn.