Re: [Paddlewise] How long would you wait - garbage bag

Pamvetdr_at_aol.com wrote:

> I'm fascinated to see garbage bags as an  alternative on your list. I
> have considered carrying a contractor  strength, large garbage bag in
> case of capsize of a person without a wetsuit or  dry suit (this was 
> precipitated by an incident a couple of years ago  where I had great
> trouble rescuing a friend who was much less competent  that they had
> portrayed themselves to be in doing rescues). It seemed to me that  if
> the person could open and get into the bag, even with a lot of water, it
> would greatly reduce the flow-by cooling effect of the water and even
> allow a constant layer of warmer water to stay by their skin.

Pam, two reasons this might not be so useful:

1. Mobility is compromised by a voluminous film such as a garbage bag.  to 
prevent ready eschange with surroundings, you'd have to strap it pretty 
tight, several places.

2. The water inside the GB will have to be warmed up by the person using 
it.  The heat capacity (aka specific heat) of water being enormously high 
(close to the body's), warming any substantial mass of water trapped inside 
would rob the body of a lot of heat.  If you trap a water mass equivalent 
to half your body mass (easy to do), warming it up will drop your body temp 
substantially.  If such a mass of water is initially at 60 F, at thermal 
equilibrium, heat exchange will warm it up to about 80 F as the body cools 
to the same temp.  At 80 F, you would be severely hypothermic and probably 
unresuscitatable.

Wet suits work by providing an insulating layer of air-filled neoprene (and 
a little water inside the WS) which reduces heat transfer substantially. 
The urban myth that it is the "layer of water trapped by the wet suit" 
which achieves the major insulating effect of a wet suit is probably the 
basis for the idea that a garbage bag with trapped water would help a 
person stave off hypothermia.

Fleece is a better choice for insulation; better yet, a wet suit; even 
better, a dry suit.

-- 
Dave Kruger
Astoria, OR
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