Sea survival suggestion - would it work?

[Guest]

When a person falls into the seas around the UK, wearing a lifejacket, survival time is obviously going to be very limited because of the onset of hypothermia.

Obviously, part of the problem is cold sea water circulating through clothing and carrying away heat - the circulation of the water itself reduces body warmth fast. Wet suits are of course designed to combat this by creating a layer of water that is held next to the skin that is heated by the body and is not washed away by colder water.

Which brought me to the thought - if a MOB wearing a lifejacket were to have attached perhaps to the waistband of his lifejacket, or perhaps in a pouch of his oilies, a large 6' long plastic bag, along the lines of a tough/reinforced dustbin liner bag, then he could hold it under the water, pull over the whole body, and pull tight at the neck, this would create a layer of insulating water that might keep the MOB alive for considerably longer.

Has anything like this ever been tried/considered? Obviously it would need some tweaking - probably a sprayhood necessary for the lifejacket, and it would restrict or prevent the ability to kick and paddle with arms and legs - but maybe that would not be a bad thing in terms of preserving energy. I can see it would be tricky to get into while in the water, but maybe not impossible, and maybe good design could help.

A bit like a very crude survival suit without arms legs, or other holes except for head - a bit like a plastic sleeping bag with no air in it, only water, creating a pocket of warmer water.

Is it a dumb idea?

 

[BrendanS]

I just wear a dry suit with optional wooly bear fleece underlayer, when things are wet and cold.

 

[Guest]

That sounds sensible, but I was thinking about something that was built into oilies or whatever for those occasions when one falls overboard without putting on dry suit first /forums/images/graemlins/wink.gif

 

[Mirelle]

It has been tried - by the Norwegian Maritime Directorate, no less...

...when they were running comparison tests for commercial "survival suits", which are now mandatory aboard merchant ships, around 1995, as I recall.

The conclusion was that two black plastic bin liners were just as good as some very expensive commercial ones.

So well done - you are thinking along just the same lines as one of the most admired bodies in the field of safety at sea!

 

[BrendanS]

Fair enough, though I suspect that it would be hugely difficult to actually get into in real circumstances unless well trained.

 

[Guest]

Re: It has been tried - by the Norwegian Maritime Directorate, no less...

Glad to hear it's not necessarily a crazy idea. Maybe yachties need a (lightweight)solution along those lines too? A couple of bin liners wouldn't occupy much space or weight in personal body gear - even better if joined together into one king-sized one. Make it dayglo orange, and Bob's your uncle.
Maybe.

 

[Guest]

Sure it wouldn't be especially easy, but not necessarily impossible either. If it was completely immersed in water with no air, once the aperture is got over the feet - there would be pretty strong motivation to get it on, given the alternative!

 

[BrendanS]

It would work, maybe, with trained and motivated individuals. I'm trying to get my head around explaining how to crew who don't understand the concept, and struggle to unravel a bin bag in a kitchen in the warm, and get it successfully deployed in a bin. Would need to be tougher, and hence more bulky, than a typical bin bag or feet would go through it. It makes sense though, and will probably tuck a few in life jackets.

 

[Guest]

Having spent a considerable time once involuntarily ditched in the Channel, I well remember the desire to keep the warmer water next to the skin. I was lucky enough to be wearing a wetsuit, but even then the warmed water flowed out of it toooo easily. Brrrr...

I reckon that even with a standard thickish bin bag it should be possible to wear it without kicking holes in it - one would certainly have plenty of motivation to preserve it's integrity. But I haven't tried wearing one in the sea.

Then again it could be made of rip-stop material - maybe something like spinnaker sail cloth(how waterproof is it?)? If this were too bulky it could even be built into the design of oilies - sewn into some part of the lining from where it could be accessible to be ripped out, or built into part of the lifejacket harness somehow... Even used as padding in the lifejacket waistband... or whatever

 

[BrendanS]

Still think it will help trained motivated and educated, more than normal man overboard.

I've been voluntary mob

 

[cliff]

Wet suits work on TWO principles - The first is to minimise the flow of cold water over the skin and the SECOND is to provide an insulating layer over the body i.e expanded neoprene. Drysuits work by keeping the user dry and are used with an insulating under garment i.e a "wooly bear" or "baby-gro" The idea of climbing into a couple of "bin bags" is IMHO of little merit as the bin bags have very little in the way of insulation properties. As the cold water between you and the bag warms up the heat will pass through the bin bag to the sea. Any "bag" would need to possess good thermal insulation properties to have any chance of being effective.
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[Sixpence]

a builders type rubble bag ( much thicker ) would get over the risk of kick damage , and easier to open too

 

[Woodlouse]

You could customise your binbag with a silver foil lining. /forums/images/graemlins/grin.gif

 

[Cruiser2B]

Expanding on Cliff's point - with a wetsuit, the inner water layer is very thin, whereas a loose "bag" even if insulated, would contain too much water which would cool your body excessively. UVIC did a study on cold-water survival in the 70s, which led to the development of the Mustang survival jacket. It uses a deployable neoprene flap to cover the crotch and a hood stowed in the collar - the greatest heat-loss comes from the crotch, armpits and head. One of these and using the HELP (Heat Escape Lessening Position) is your best defence against the cold water.

 

[FWB]

The emergency 'space blankets' which I carry are actually large bags. They would be perfect for your idea.

 

[Solitaire]

There are already such things - TPA's (thermal protection aids). And there is even an Emergency Survival Bag

 

[sarabande]

I have considerable reservations about the thermal retention properties of any bag which is not insulated by something such as neoprene.

In a straightforward plastic bag, whether or not with a laminate of silver foil or similar, the inner volume of water is in intimate contact with the sea outside, and the surface area of the bag would provide more than enough contact to transmit any heat generated inside to the sea outside.

A human being works at something like between 125 and 250 watts, depending on the activity, and has a surface area of between 1.6 m2 (women) to 2.0 m2 (men). A survival bag will have a surface area of approximately 3 m2. It therefore looks as if any heat generated by a human being will be transferred pretty efficiently from the body via the inner water, through the plastic bag to the sea outside .

Now, if you could have two layers of plastic and blow air in between them, you would have a floating insulated bag, aka a mini liferaft....

 

[guernseyman]

A yottie once told me that if you ditch in windy conditions you slowly drown as your lungs fill up with inhaled spray.

If that is true then should hoods have some sort of zippable front panel with allowance for ventilation and vision?

 

[BrendanS]

spray hoods are available and have frequently been advised as necessary on the forums

 

[RIMCOas01]

Something like this maybe suitably adapted:

http://www.needlesports.com/acatalog/blizzard.gif
http://www.sailgb.com/pi/Lifemargue/Thermal-Bag.jpg

But I am sure I have actually seen these for marine use ... someplace !

M