"noexpert" wrote in message
...
Are solid stainless steel rods any less vulnerable?
What alloy is used for major standing rigging; there must be some less
prone to chloride/stress attack, or?
I worked with some higher than 316 plus extra titanium alloy(32?) for
seawater boiler; it was a much better choice than regular 316.
I am not sure if this alloy is being offered in steel rope shape.
Any one knows more about it?
thanks


Navtec rod rigging uses an alloy they call "Nitronic". It is supposed to be
much more resistant to corrosion than the alloys commonly used in wire
rigging and turnbuckles.

I remember the collapse of a public pool ceiling killing a number of peoples
in switzerland some years ago.
The hang up ceiling was supported by hidden 304 type (18-8) S-hooks behind
and out of sight for inspection.
I recall the report stating that the chloride laden pool air and humidity
exposed the hooks causing this intercristaline corrosion leading to sudden
failure to support loads.
As I understand the engineering world in Europe took note and better suited
s/s alloys are utilised now.

If rigging for ocean going boats is still made from 304, I think it amounts
to criminal negligence to continue to equip boots with these essential
structural members in a maritime environment where plenty of chloride (salt)
are present.

Having worked with both 304 , 316 and others the price difference of those
different alloys were not really the mainconcern but mainly to get the right
stock for the task on hand.

I am not clear what the nitronic s/s alloy is made of, but if it is more
suitable why bother with 304 at all.

GBM wrote:

"cavelamb" wrote

Just a suspicion, but it seems to me that the problem here is a result of
the swaging process itself.

When the swage is squeezed, there should be uneven compression which would
cause the material to yield unevenly - leading to rather high localized

stress

concentrations. In-service vibration, over time, should lead to exactly

the

kind of cracks described by GBM.

FWIW, for highly stressed aircraft cables, the terminals (ends) are

*Rolled*

rather than squoze...

Richard


Could be, but experience shows that this type of failure does not occur in
fresh water. The experts advise that it is the presence of chlorides in
crevices with an oxygen deficient atmosphere and stress that cause the
failure. The whole swage and the wire strands are stressed to various
degrees.

GBM



Capillary action would draw water up the wires and into the fittings.

Sea water there would be a bad thing (tm) that would aggressively attack the
small surface fractures in the fitting.

Your point about sealing the swedged fitting with epoxy should reduce the
susceptibility quite nicely just by sealing the open end of the wire and
fitting.

Keep the nasty old sea water out of those tender places...


Richard

"GBM" writes:

"Chris" wrote in message
oups.com...

So how does this dye test work?


Chris - You don't seem to be getting an answer to your question. Cracks in
welds etc are often better seen after treatment with a dye penetrant. This
is sometimes sprayed on. have a look at this Magnaflux web site then do your
own search. http://www.magnaflux.com/index.asp

I worked as a yacht rigger for many years. I consulted with metallurgical
snip

Hope this helps!

Great post.

Anyone on the expected life span and inspectability of the synthetic
rigging now adapted by racers?

--
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Martin Schöön

"Problems worthy of attack
prove their worth by hitting back"
Piet Hein
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