Re: [Paddlewise] Hypothermia Table

From: "Ulli Hoeger" <uhoeger_at_hotmail.com>

> >From: "Michael Daly" <michaeldaly_at_rogers.com>
> >Too many variable to determine easily.  A good dry suit will allow 
> >indefinite exposure, as will a heavy wetsuit.
> 
> I have a problem with this statement, and I assume we all still talking 
> paddling clothing here. Don't get a wrong impression of safety. Wearing a 
> dry suit while paddling will still leaves the possiblity of hypothermia. 
> Don't get or give people a false sense of security.
> 
> A "good"(?) dry suit will definitley NOT give you indefinite exposure time!

I was talking in terms of scuba gear, but nonetheless, a good dry suit _will_
give you indefinite exposure time.  This assumes that you have the correct 
level of insulation under the dry suit.  Even the neoprene dry suits that
divers wear require insulation inside for ice diving.  A single layer
of 7mm neoprene will not keep you warm at 0C.

The big difference between a dry suit and a wet suit for a diver is comfort,
not warmth.  Both can be made to insulate sufficiently, but almost everyone
who tries a drysuit prefers them.  

It is true that there are fools out there that wear dry suits without
insulation even where it is warranted (and suffer the consequences - I 
believe someone on Paddlewise reported such an incedent off the US 
Atlantic coast a year or two ago).  I think that Shawn's table is trying
to stress the importance of insulation in dealing with water temperatures.

If we want to get picky about indefinite exposure times, the table that
Shawn presented (based on the source he gave) showed indefinite exposure
for water above 80F.  This is not correct, strictly speaking.  It assumes
that you are fit and fed enough to continue to generate heat.  In fact,
you can suffer from hypothermia at 80F - this is only 2F above the body
core temperature at which that vast majority of us would die.  I 
wouldn't want to be stuck in the water so long that that would happen -
we're talking days here (consider the time spent in water by tropical
shipwreck survivors - famous case of a US Navy WWII sinking).

Let's assume that we will be referring to reasonable uses of gear and 
temperature.  Shawn's table does show insulation requirements and 
the intent should be to be conservative.  Perhaps he could extend his
footnote to include comments that insulation levels are personal and
some may need more than others for the same level of comfort/survivability.

For example, unlike Dave, who is comfortable in 70-80F water, I wear a 
3mm FJ in the pool during the winter sessions.  I find it a tad cool for 
a couple of hours of rolling and rescue practice - YMMV.


Mike





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