[C38] Life-lines

[Les]

Oxygen is required to make stainless "stainless".  It is an oxide the
insulates the metal from corrosion.  I believe that the crevice issue
comes from the addition of salt in small quantities in the crevice.  the
chlorine binds more easily with the oxygen, removing the insulating
oxidation, permitting the "bad stuff" to reach the steel.  In addition,
the chlorine itself forms several acidic compounds, none of which are
good for the metal.  In any event, the result of a small amount of salt
water being bound into contact with stainless will cause corrosion.

	I don't know the reason that people don't like the plastic coating on
the lifelines, other than the fact that they can't see the stainless.
Modern techniques make the plastic bind very tightly to the wire.  We
insulate all the copper wiring with plastic for both isolation and
corrosion prevention.  Why not life lines.  The general point of failure
for life lines is the point of the junction, which can be penetrated
with saltwater, and produce the dreaded crevice corrosion at that point.

	In my experience, the wire seldom fails at a mid-point, but rather at
one of the junctions.  Of course I have only seen coated stainless wire
that failed 2 times in my life, and both times that was at the joint.
Both times the piece in question was not cleaned or had anything done to
it, and both pieces were many years old.  Now scientifically that is a
statistically insignificant sample, called anecdotal evidence, but I
have been on the water a long time, not all of it on sail boats, so I
think I have seen lots of cable.  

	At the same time, the stainless netting used on ships failed at the
junctions.  The junctions were generally formed by a crimp connection
around the wire where two pieces ran parallel, then were crimped to
periodically with alternate strands, so when it was expanded it made a
net.  It failed at the crimps, not at the point where it hung from the
rails that supported it.  The rail connections were just eyes with an
opening for the netting.  And even though the netting chaffed at the
eyes, the first failures were at the junctions.

	At least that was my experience.  

	That said, the lines in discussion are "lifelines".  so you pays your
dime and you takes your chances.  Do what you can to discover the truth
and act accordingly.  I don't know the answer.

Regards,
Les H
On Sat, 2010-07-10 at 12:07 -0600, S Orton wrote:

> I was going to replace my life lines as recommended by the CC, but on
> detailed inspection, I declined.  My reasoning:
> 1.  Where there was rust at the swaged end fitting, I cut away the
> plastic, cleaned up the wire with a "fine" wire brush rotary tool,
> bent the wire back and forth, and observed no failed strands.
> 2.  As far as know Catalina still uses coated wire and West Marine
> still sells the stuff.
> 3.  I don't understand this oxygen deprived corrosion.  When you think
> about the roller swaging of the end fittings on all our rigging, there
> isn't much oxygen moving into the fittings.  It has to be rather
> stagnate inside the fittings.
> 4.  My surveyor told me this was a "recommended" not a "mandatory"
> requirement and it didn't affect my insurance.
> 5.  I'm not a metallurgist by training, but in my previous life, I
> worked as a ME in aerospace for 40 years, working with corrosion
> resistant materials and never coming across the term "oxygen deprived
> corrosion" in SS.  If some body has some factual engineering info on
> the subject I would love to read it.
> With that said I inspected every inch of the life lines, looking for
> rust marks, cutting away the plastic, and found no broken stands of
> wire (fish hooks).  Now I did replace my rigging (25 yrs old) at a
> material cost of $1700.
>  
> Cheers, Steve O (Santa Susanna- #304)  
> > From: 1derful at comcast.net
> > To: Listserve at catalina38.org
> > Date: Thu, 8 Jul 2010 19:49:45 -0700
> > Subject: [C38] Life-lines
> > 
> > Someone suggested I replace my life-lines because they are coated in
> plastic 
> > so I can tell if they are fraying. They advised stainless steel.
> Seems 
> > like an expensive retro-fit.. I can't remember every really using
> the life 
> > line to prevent falling overboard.
> > 
> > Also does anyone know the height of our Catalina 38's? I've been
> going 
> > under some bridges lately and from the cockpit it looks as though I
> am gonna 
> > lose my mast. Hasn't happened yet.
> > 
> > Patrick
> > Blue eyes
> > S F Bay 
> > 
> > 
> > _______________________________________________
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> > Listserve at catalina38.org
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> 
> 
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