Warmer wetsuits

NPL has performed tests for UK wetsuit manufacturer, Spartan, to help further their knowledge of how wetsuits keep people warm.

The Journey

In order to provide Spartan with the thermal performance data they needed, NPL decided to perform some initial laboratory-based tests on wetsuit samples, followed by some field-testing of wetsuits during proper use.

The laboratory tests involved measuring the thermal resistance of 4 samples of neoprene cut from a Spartan wetsuit. The four samples were different thicknesses, and their surface finish was either single or doubled lined. NPL’s specialised equipment, a piece of kit called a single-sided 305mm guarded hot plate, was used to measure the samples’ thermal resistance. This equipment holds the sample of neoprene horizontally inside a chamber, which is then heated from underneath. A detector at the top of the chamber, above the sample, measures how much heat has passed through the sample – this is the sample’s thermal resistance value. The results showed that the wetsuits’ surface finish had no bearing on how good an insulator it was.

Following the laboratory tests, the team performed some field tests in Clacton, on the Essex coast, far from the controlled laboratory environment of NPL’s Teddington site. Instead of using the lab-based guarded hot plate facility, the team used portable wireless sensors and a thermal camera.

Spartan’s Mark Minter and John Morgan, and pro-windsurfer Chris Murray donned their wetsuits and joined NPL’s Dr Richard Dudley and Dr Rob Simpson on a chilly day in March 2010 to test the wetsuits in their natural habitat – in the sea and on the beach.

Richard and Rob monitored Mark, John and Chris’ body temperatures throughout the trial using wireless temperature sensors taped under their right armpits.

The thermal camera was used to measure each man’s temperature, in his dry wetsuit, before entering the sea. The three men then spent up to two minutes in the sea, to simulate the short spells of time windsurfers typically spend in the sea, before being measured by the thermal camera again. The men then spent ~10 minutes exercising in the sea, to simulate the longer periods of time surfers and swimmers endure in the water. The fourth and final measurement of the day was taken of the men after they had been standing in their (wet) wetsuits in the cold breeze for ~10 minutes.

What was interesting about the difference between the laboratory and field tests was that, in the lab the wetsuits’ surface finish made no difference to how well it insulated against heat loss. But, in the field tests the surface finish had a measurable effect on how well the wetsuit kept its user warm. This difference is caused by wind wicking moisture (and therefore heat) away from the surface of the wetsuit via convection – or ‘wind chill’. The effect of wind chill has been recognised for some time, but measuring it in this way increases our understanding of it, and can help wetsuit manufacturers mitigate its effects.

The Impact

The potential impact of this collaborative research is wide-reaching.

In the short term, Spartan will be able to make better wetsuits, more efficiently. Which in turn will hopefully lead to improved customer-satisfaction.

In the longer term, if this work is extended to other wetsuit manufacturers and neoprene suppliers, it could have a huge social impact. Millions of people in the UK spend their leisure time enjoying activities that require wetsuits to brave the often chilly UK waters (such as surfers, scuba-divers, swimmers, tri-athletes, wind-surfers, sailors, kite-surfers etc). Improved wetsuit materials and construction could have a positive impact on these people, allowing them to spend more time in the water, and giving them the freedom to do their sport of choice in much colder conditions than they are currently comfortable doing.

Find out more about NPL’s thermal (link: http://www.npl.co.uk/engineering-measurements/thermal/) or materials (link: http://www.npl.co.uk/advanced-materials/) research