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Old 01 October 2008, 08:02   #21
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Originally Posted by codprawn View Post
One thing I have just thought of - whilst a jacket on it's own won't meet the ISO standard i would have thought it would still offer valuable protection as it is the core parts of the body that are most important for avoiding hypothermia.

When i used to do a lot of winter mountaineering and hiking I found that my legs were never cold - usually just wore normal trousers with a good jacket.

Obviously full protection is best but a jacket would be far from useless on it's own.
You must know that these arguements are flawed
If you end up in the water with just a jacket on one of the principle heat dissipation mechanisms will be your circulation. Your blood will carry the heat from your body core. With thermally unprotected legs much heat will be lost through them. Water is approximately 20 times better at heat conduction than air.
However, much heat will also be lost through your head; it does have a massive blood supply! So of you are serious about protecting yourself in case of a dunking, think about some head gear.
Winter mountaineering and hiking - your legs are working hard, dissipating a lot of heat from your hard working muscles, so of course they stay warm. Stop walking or hiking for a long enough period and they will get cold. Put them in water and the process would be significantly accelerated This happened to me in the French Alps once - but that is another story
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Old 01 October 2008, 08:21   #22
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The jackets have a hood. Keeping the head warm is essential.

In cases of hypothermia the body cuts blood supply to the extremities so hands and feet aren't so important - that's why so many people get frostbite.
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Old 01 October 2008, 09:14   #23
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Some interesting reading and comments…

All in all it depends on what you are doing, where you are going, sea state, weather and what performance you expect.

A 275N auto inflate life jacket complete with spray hood and crotch strap would always be my preferred option. In addition, an immersion dry suit with the correct level of underclothing, probably a thermal liner.

Two important factors to be considered:

Cold shock - the gasping reflex as a result of sudden immersion in cold water
Onset of Hypothermia

Maintaining body core temperature is vital, as stated the body will naturally shut down the extremities, hands, feet, arms, legs to make it happen. Insulating the back area around the kidneys is a key consideration

Slightly different angle, but consider the following:


CREW SURVIVAL SUITS – CALCULATING SURVIVAL TIME

JAR-OPS 3.827 Subpart K Section 2
(EXTRACT FROM JOINT AVIATION REGULATIONS – EUROPE)

1.0 Introduction

1.1 A person accidentally immersed in cold seas (typically offshore Northern Europe) will have a better chance of survival if he is wearing an effective survival suit in addition to a lifejacket. By wearing the survival suit, he can slow down the rate at which his body temperature falls and protect himself from the greater risk of drowning brought about by incapacitation due to hypothermia.

1.2 The complete survival suit system – suit, lifejacket and clothes worn under the suit – should be able to keep the wearer alive long enough for the rescue services to find and recover him.

In practice the limit is about three hours. If a group of persons in the water cannot be rescued within this time they are likely to have become so scattered and separated that location will be extremely difficult, especially in rough water typical of Northern Europe sea areas. If it is expected that in-water protection is required for periods greater than three hours, improvements should be sought in the search and rescue procedures rather than in the immersion suit protection.

2.0 Definitions

2.1 Clo. Value

The unit used by physiologists to define the value of clothing insulation. A typical business suit and the usual undergarments worn in an office have an in-air insulation value of 1 Clo. Clo. values are substantially reduced when clothing is compressed (as it is by hydrostatic compression under and immersion suit), or wet.

2.2 Tenth-Percentile Thin Man.
The tenth thinnest man in a sample of 100 men representing the offshore population. Thinness is measured by mean skinfold thickness.

3.0 Survival Times

3.1 The aim must be to ensure that a man in the water can survive long enough to be rescued, i.e. his survival time must be greater than the likely rescue time. The factors affecting both times are shown in Figure 1. The figure emphasises that survival time is influenced by many factors, physical and human. Some of the factors are relevant to survival in cold water; some are relevant in water at any temperature.


3.2 The relationship between water temperature, insulation of clothing and calm water survival is shown in Figure 2. The curves in Figure 2 are appropriate for the 10-percentile thin man and assume that his survival ends when his body core temperature drops to 34 deg C. At this temperature he is unlikely to die from hypothermia but he may be incapacitated by cold such that he will die from drowning. Fatter men with more body insulation can expect to survive longer than predicted by the curves.

The curves show that the survival suit and clothing worn underneath must have an in-water insulation value of about 0.5 Clo if the wearer is likely to survive for more than 2 hours when immersed in water. If he is wearing summer clothes beneath a leak-free survival suit, the 0.33 Clo line indicates that he will survive for less than 2 hours in water at 5 deg C and for less than 3 hours in water at 10 deg C.

3.3 The different solid lines in Figure 2 are defined in terms of actual clothing as follows:

0.06 Clo The immersed insulation of a man in lightweight summer clothing (overalls and underpants) without a survival suit.
0.33 Clo The immersed insulation of a man in summer clothing (as above) but with an effective survival suit on top.
0.50 Clo The immersed insulation of a man with a long sleeved and legged cotton underwear, a work overall, a thick woollen jersey, and an effective survival suit on top.
0.70 Clo The immersed insulation of a man with a long sleeved and legged cotton underwear, a pile fabric insulation garment, working overalls, and an effective survival suit on top.

3.4 The effects of water leakage and hydrostatic compression on the insulation quality of clothing are well recognised. In a nominally dry system the insulation is provided by still air trapped within the clothing fibres and between the layers of suit and clothes. It has been observed that many systems lose some of their insulative capacity either because the clothes under the ‘waterproof’ survival suit get wet to some extent or because of hydrostatic compression of the whole assembly. As a result of water leakage (or damping) and compression, survival times will be shortened: clothing of a greater dry and non-compressed Clo. Value must be worn to maintain survival time.

3.5 Whatever type of survival suit and other clothing is provided, it should not be forgotten that significant heat loss can occur from the head. A survival suit should have an insulated hood. Besides preventing heat loss, it will give the wearer some protection against accidental impact.


Estimated calm water survival times plotted against water temperature for thin individuals (approx. 10th percentile mean skinfold thickness) wearing various levels of immersed clothing insulation. The lowest curve is for lightweight summer clothing only. The other three assemblies including an immersion suit with increasing thickness of clothing worn beneath.
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Old 01 October 2008, 17:23   #24
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I am still trying to decide what to buy, the sizing is what is really stopping me as I have to do it mail order and the sizing given online for the Fladen suits is a bit non existent. The only guidance anywhere being it is "generous" what the h**l does that mean?
I'll prabably need to order one suit and us both try it on to see who it fits then buy the next size up or down depending on whether it fits me or her!
While I was looking around I came across these, may be handy as emergency suits at the price quoted £10.95. Not suitable for wearing normally as they are aluminised PVC but much cheaper than the ex RN suits going on ebay at two and three times the price almost identical.
I may get a couple to keep on the boat visitors or just in case.
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Old 01 October 2008, 17:31   #25
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I am still trying to decide what to buy, the sizing is what is really stopping me as I have to do it mail order and the sizing given online for the Fladen suits is a bit non existent.
Bruce if I remember correctly I am a "large" in Fladen size. I am 6 ft, and a 34-36" waist depending on recent beer and food intake!
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Old 01 October 2008, 17:33   #26
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Originally Posted by BruceB View Post
I am still trying to decide what to buy, the sizing is what is really stopping me as I have to do it mail order and the sizing given online for the Fladen suits is a bit non existent. The only guidance anywhere being it is "generous" what the h**l does that mean?
I'll prabably need to order one suit and us both try it on to see who it fits then buy the next size up or down depending on whether it fits me or her!
While I was looking around I came across these, may be handy as emergency suits at the price quoted £10.95. Not suitable for wearing normally as they are aluminised PVC but much cheaper than the ex RN suits going on ebay at two and three times the price almost identical.
I may get a couple to keep on the boat visitors or just in case.
BruceB, our crowd have the full range of Fladen sizes in use. If you PM your Vital Statistics (or height and waist even) I can confirm a real world fit for you. They are a generous fit. For the money, they're a class act.
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Old 01 October 2008, 17:33   #27
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Bruce if I remember correctly I am a "large" in Fladen size. I am 6 ft, and a 34-36" waist depending on recent beer and food intake!
Snap!
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Old 01 October 2008, 17:36   #28
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Bruce if I remember correctly I am a "large" in Fladen size. I am 6 ft, and a 34-36" waist depending on recent beer and food intake!
Damn, but you're in good shape!
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Old 01 October 2008, 17:44   #29
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Bruce if I remember correctly I am a "large" in Fladen size. I am 6 ft, and a 34-36" waist depending on recent beer and food intake!
Quote:
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Damn, but you're in good shape!
I think you have an admirer
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Old 01 October 2008, 18:04   #30
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I am 6'1" 36"waist, 42-44"chest
She who must be obeyed is 5' 71/2" and, to put it diplomatically, slightly thinner
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