Tuesday, 30 May 2017

Immersion suits

For the crew of a multihull the disaster scenario is having to tackle the problem of survival and rescue on the unsinkable capsized hull


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Taking to a life raft is taking a huge (although sometimes unavoidable) risk. Life rafts float, but are terribly light and tiny and can get whisked away in a gale and tumbled over and over by wind and breaking waves. They have minimum equipment on board. Under most circumstances one is more likely to die in the raft than one would be on a stricken boat. Hence the advice "while it is still floating, the boat is the best life raft" and "only step UP into the life raft."

Immersion suit, Guy Cotten
Immersion suit, Guy Cotten

Survival on a multihull

As multis are substantially less likely to sink than are monohulls, the importance of a life raft as essential emergency equipment on a cat or a tri is somewhat diminished. For the  crew of a multihull the disaster scenario is having to tackle the problem of survival and rescue on the unsinkable capsized hull. The crew may be able to shelter in a hull by entering through a hatch or by sawing a hole, though the conditions inside my not be favourable through lack of air space and water sloshing around. If this happens, the crew might tether the life raft to the hull and await rescue inside, though there is danger of the raft being torn away from the boat by breaking waves, especially since rafts are not designed with multiple strong attachment points. Wherever the shelter is sought the chances of survival will be much greater, especially in colder waters, if the crew is wearing survival suits.

Survival suits (also called immersion or anti-exposure suits) are required safety equipment for oil rig workers, commercial fishermen, and other mariners. The standards for these in commercial uses are controlled by SOLAS (International Convention for Safety of Life at Sea). They are becoming increasingly used by yachtsman and particularly by multihull sailors. The Offshore Racing Council (ORC) of the ISAF (International Sailing Federation) recommend the carrying of immersion suits for Category 0 and 1 racing in latitudes above 30 degrees. Some yacht racing bodies allow immersion suits to substitute for the life raft in yachts under 12 meters Category 2 races. The rationale is that the unsinkable upturned hull is in fact the life raft. The only time a multihull sailor would be forced to use a life raft would be if there is a serious fire that destroys the boat.

Immersion suit, Viking
Immersion suit, Viking

Features of cold water immersion suits:

Insulated - prevents hypothermia in case of disaster at sea. Suits should ensure that the wearer's body core temperature does not fall more than 2C after a period of 6 hours immersion in calm circulating water at a temperature of between 0C and 2C. Typically a waterproof foam material like 5mm Neoprene is used. The insulation must work even if the suit is flooded.

Waterproof - normally with seal round the face, wrists and waterproof zip.

Whole body protection - the suit should cover the whole body except the face

Easy to get into - must be easily unpacked and donned - even when in the water.

Buoyant - foam insulation has inherent buoyancy, though probably insufficient to adequately support the body. Some suits have additional buoyancy which may be removable.

Fireproof - the suit should resist fire for a few seconds

Facilitate use of fingers - the suit should have gloves that keep the hands warm enough to perform basic tasks and accordingly allow the necessary freedom of movement

Stowage and storage - should be compact and resist degradation. Should also be stowed so it can be easily accessed when the boat is inverted.

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