HEAD to HEAD:
WEEZLE EXTREME V C BEAR TR200 TRICORE
More technology goes into the modern undersuit than went into the old woolly bear, but would a bulky Weezle out-insulate a deceptively slim C Bear? John Bantin tries them both out
KEEPING WARM IS A SCIENCE tempered by the personal requirements of the individual. We metabolise food to make energy, and this is dissipated in the form of work or heat, or both. CBear 01566 777636, www.c-bear.co.uk; Weezle Diving Services 01535 655380, www.weezle.co.uk
Whether we get cold or not depends on how much energy we make and how much of that heat is lost. It's a question of insulation.
But insulating a person is far more complex than lagging a hotwater tank. Each of us seems to require varying degrees of insulation.
For example, we were in the office, discussing how we should go about comparing undersuits, and I noticed that Steve was sitting comfortably in a T-shirt whereas I was equally comfortable in a T-shirt plus a thick sweater. We needed different levels of insulation for the same effect.
Also, it is not the insulation material that keeps heat in but the air that stays trapped in its fibres. Water conducts away heat 25 times faster than air, so once you get under water it's a good idea to try to maintain a layer of air between you and that rapidly cooling environment.
For this reason, in the colder conditions that we encounter in Northern Europe we try to stay dry with a drysuit. But with the human body inside a watertight container, which essentially describes a drysuit, insulation gets even more complicated. Our skin needs to breathe, to sweat, and to dry off, cooling down through the effects of the evaporation of that all-important sweat. So how can we achieve that function while keeping ourselves from becoming too cool?
The days when divers simply wore a heavy sweater and woolly underwear beneath their drysuits are gone. Science has taken a hand in designing materials for this specialist application. A good undersuit should maintain a layer or air between you and the outer wall of your drysuit by filling the space with some inert material that allows this layer to form.
There should be few heat-bridges, which is a good reason to avoid any quilting effect. Wherever the material is drawn together by stitching, heat can pass across, and that is heat from your body, heat that is energy.
You also need the moisture that forms from your perspiration to be drawn away. That's called "wicking" in the trade. The moisture is drawn away in the same manner as the paraffin of an oil-lamp is drawn up by its wick. The undersuit designer needs to select a material for the inner side of the undersuit that comes into contact with your skin, that is good at drawing away the moisture and keeping your skin dry and comfortable.
A cotton T-shirt might work well air-side but it doesn't wick well. Once enclosed in a drysuit you will notice that sweaty feeling only too soon.
Many undersuit manufacturers now offer additional layers or "base" layer suits. Any material in contact with your skin under a drysuit must have good wicking properties.
Because we tend to go on wearing our undersuits once we have climbed out of our drysuits, the outer layer needs to repel water and dirt, and to be reasonably windproof too.
Some manufacturers add mesh areas around the wrists so that there is no danger of a cuff dump being obstructed. Alas, this is one area where your blood supply is near the surface, and therefore you will lose a lot of heat through it.
How do you go about choosing between the undersuits on offer? Two of the most popular makes are C Bear in Cornwall and Weezle in Yorkshire.
The C Bear Tricore TR200 Undersuit is claimed by its maker to be "the most thermally efficient with reduced bulk Thinsulate undersuit available". It is made from a Tricore fabric, composed of a double-laminated breathable water-resistant material called Ree-Tech, a water-resistant 200gm type C Thinsulate and a wicking fleece on the inner side. Laminating avoids the effect of heat-bridging caused by stitching.
It's an all-in-one suit with a two-way zipper that can be very convenient for gentlemen; an elasticated back for a snug fit; a top-fastened breast pocket; a hand-warming hip pocket; a vent in the left sleeve, presumably to help with a cuff dump; woolly elastic cuffs; and elastic thumb-loops and foot-straps to keep everything in place as you climb into your drysuit.
Optional extras with this C Bear include a lumbar pad, a leg patch for use with a pee-valve, separate or attached socks, and a made-to-measure service.
3M Thinsulate has almost become a generic name for drysuit undersuits, such is its popularity as a thermal-insulation material. The idea is that its reduced bulk makes it more manoeuvr-able and, because there is less bulk, the diver needs less lead to compensate. So far so good.
Not a diver but someone who obviously has faith in the insulating properties of this suit, Curtis Rivers intends to wear one during his Operation Goliath Guinness World-Record attempt to undertake the longest abseil in history. He plans to descend 2500 feet from a balloon flying 12,000ft high.
The Weezle Microdive Extreme Plus looks very different. It appears bulky, though it is very light in weight. It is so compressible that it squeezes down into a tiny pack. Put it on and you'll feel you're ready to walk across the Poles.
Its secret is in the down-like micro-fibres it uses. These swell to fill the available space and trap heat-insulating air. They are also hydrophobic Ð they refuse to get wet!
The micro-fibres used in the Weezle are a Swiss invention and are claimed to conserve heat even when wet.
I have experienced a damp dive with a Weezle with no apparent discomfort, discovering the wet patch on the outside of the undersuit only when I got changed, but of course the air is the insulator, so a total flood will certainly deprive you of much of the insulating effect.
Walking about in the Weezle Extreme Plus, like a sparrow fluffed up against a winter's chill wind, does not reflect what happens once it is between you and the walls of your drysuit and you are under water. It compresses down.
The pressure of depth and the fit of your drysuit contrive to push all those micro-fibres together. In fact, if you could see it at this time, it would look very much like the otherwise much slimmer C Bear offering. But by filling all the available space, it makes your drysuit seem to fit you perfectly.
Neither does it need to be used with a lot of lead, because under water it loses much of that bulkiness. It is only as bulky as your suit, and the air you feed into it, allows it to be.
The shell of outer material is called Pertex. It "lets perspiration through but keeps water out", claims its maker. This hi-tech material has a very precise thread spacing that makes for this one-way traffic. It feels like parachute silk.
Inside, it has a lining of suede-like polyester. This gives it a fine nap pile on one side, which is what makes for the wicking property of this material. Moisture will always move from the nap to the smoother surface. It draws moisture from the inside to the outside and spreads it over the maximum area so that it has the best chance to evaporate.
The Weezle suit has a two-way zipper and elasticated cuffs but makes no concession to alleviating any problem of trapped air when using a cuff dump. But then, there seems to be no heat-loss at that important point, either.
So which undersuit is better? Well, it really is quite difficult to decide.
The TR200 looks harder-wearing and comes with the 3M Thinsulate pedigree. The Weezle looks much warmer when worn without a drysuit and it certainly weighs less.
It feels soft and comfortable, and even warm to the touch.
As to bulk, I found that I needed to use exactly the same amount of weight with my drysuit when using either undersuit.
I'm sure both manufacturers would claim to have the ultimate product and I'm sure either will keep you warm. If you do still get cold, add another layer, a properly wicking base layer, underneath.
The CBear TR200 Tricore undersuit costs £180 in standard form and comes in seven men's sizes, XS-XXL, and five for women, 10 to 18. The Weezle Microdive Extreme Plus costs £140 and comes in four sizes, combined with three body lengths, complete with matching long undersuit boots.