"NotPony" wrote in message
news:LrEuf.1732$Pe6.483@trnddc08...
Wouldn't it make sense to talk to a rigger about
rigging?
S.

In the martix, no.

John Cairns


"Capt. Rob" wrote in message
oups.com...
:
:
: In my research for my book I interviewed 5
surveyors in NY, PA and FL
: who specialized in sailboats. ALL prefered rod
rigging over traditional
: wire. ALL felt that it's virtually impervious to
failure, so long as
: the fittings were updated and NONE had seen a
failure and only two had
: even heard of rod rigging rigs failing and in
both cases it was
: actually the chainplate that had failed! ALL had
inspected rod rigged
: boats from the early 80's that were found to be
in excellent condition.
: Of course my boat is not very old and her
rigging is like new with
: terminals updated in 2004.
: Bob, it's best to actually do some real research
instead of posting
: superficial info from Sailnet that you coppied
and pasted.
:
: RB
: 35s5
: NY
:

have a hard time believing that rod rigging fails less than wire.


As Gary pointed out, rigging failure is rare compared to a fitting or
chainplate cracking. That said, rod rigging is stronger and virtually
impossible to break, where wire does and has parted under sail. I'll
take the rod rigging every time thank you, especially on a boat in the
fine condition that mine is in. I also had rod on the C&C 32 and it was
bullet proof...really.

RB
35s5
NY

It's not necessary for the material to be ferrous to do magnetic testing.
All it has to be is conductive. You can induce currents into the metal by
means of an electric field (and yes, it can have circulation ie it is
magnetic). The discontinuities in the induced current (due to cracks) will
cause a net increase in the responsive magnetic field (even though it is not
magnetic material - think - copper wire produces magnetic fields but it is
non ferrous) or changes in the E field on the surface of the metal. There
are films responsive to E fields, these can be used on the metal surface or
you can use small electric field probes.

You can even use the old standby of iron filings if you know what to look
for. I prefer RCS measurements to look for cracks.

Amen!



wrote in message
ps.com...
The cracks shown in that link are exactly like the ones I found in my
20 yr old rigging. The cracks in mine were very difficult to find
until I used fine sandpaper. They were all on the lower swaged end.
Most of the cracks were under small brown stains that were the result
of the stainless in the crack becoming non-stainless and rusting. They
required a 10X magnifier to find. At work, I ground the fittings away
to see how deep they went and they went through the entire fitting. I
even used dye penetrant with no luck. I replaced all the rigging and
lifelines last year.
NOW, although thefittings and wire and rod are stainless, stainless can
be slightly ferromagnetic and can be tested via flux leakage methods (I
used to do magnetic NDT research). Furthermore, the area around a
fatigue crack is less stainless and more ferromagnetic than the bulk
material. This may allow testing via mag particle inspection
(so-called magnafluxing). It is entirely that nobody has done this
because they simply assumed that teh stainless material wouldnt allow
this to work. Unfortunately, I threw the old rigging away so I cannot
try this.

http://www.mac-ndt.com/app.cfm?App=2






wrote in message
ps.com...
The cracks shown in that link are exactly like the ones I found in my
20 yr old rigging. The cracks in mine were very difficult to find
until I used fine sandpaper. They were all on the lower swaged end.
Most of the cracks were under small brown stains that were the result
of the stainless in the crack becoming non-stainless and rusting. They
required a 10X magnifier to find. At work, I ground the fittings away
to see how deep they went and they went through the entire fitting. I
even used dye penetrant with no luck. I replaced all the rigging and
lifelines last year.
NOW, although thefittings and wire and rod are stainless, stainless can
be slightly ferromagnetic and can be tested via flux leakage methods (I
used to do magnetic NDT research). Furthermore, the area around a
fatigue crack is less stainless and more ferromagnetic than the bulk
material. This may allow testing via mag particle inspection
(so-called magnafluxing). It is entirely that nobody has done this
because they simply assumed that teh stainless material wouldnt allow
this to work. Unfortunately, I threw the old rigging away so I cannot
try this.

http://www.ndtint.com/amigo.htm


wrote in message
ps.com...
The cracks shown in that link are exactly like the ones I found in my
20 yr old rigging. The cracks in mine were very difficult to find
until I used fine sandpaper. They were all on the lower swaged end.
Most of the cracks were under small brown stains that were the result
of the stainless in the crack becoming non-stainless and rusting. They
required a 10X magnifier to find. At work, I ground the fittings away
to see how deep they went and they went through the entire fitting. I
even used dye penetrant with no luck. I replaced all the rigging and
lifelines last year.
NOW, although thefittings and wire and rod are stainless, stainless can
be slightly ferromagnetic and can be tested via flux leakage methods (I
used to do magnetic NDT research). Furthermore, the area around a
fatigue crack is less stainless and more ferromagnetic than the bulk
material. This may allow testing via mag particle inspection
(so-called magnafluxing). It is entirely that nobody has done this
because they simply assumed that teh stainless material wouldnt allow
this to work. Unfortunately, I threw the old rigging away so I cannot
try this.

Bob:

Yes, that is eddy current testing. I have not yet considered it. I'd
prefer to use mag particles (iron filings) as this does not require
runing a probe along all possible surfaces.

How about sending an acoustic pulse along the rod rigging the same as a time
domain reflectometer works. The pulse speed is a property of material and
tension and the reflectance a function of acoustic impedance. Cracks would
raise the impedance. The cracks could be located along the length of the rod
by simply applying the pulse signal at one point.

http://www.tscm.com/riprcop.html




wrote in message
oups.com...
Bob:

Yes, that is eddy current testing. I have not yet considered it. I'd
prefer to use mag particles (iron filings) as this does not require
runing a probe along all possible surfaces.

Cracks would
raise the impedance. The cracks could be located along the length of
the rod
by simply applying the pulse signal at one point.

Seems to me that for this to work well you'd need to remove the rod
from the boat and tension it is some sort of way, equally. Then you
might read cracks, but be unable to actually locate them, meaning a
small non-dangerous imperfection in the rod might give a false reading.
Seems like a tool that would get abused to sell a lot of uneeded
rigging..
Just about every rig failure I've ever heard of was wire. While I'm
sure rod has failed....I've never heard of it. Anyone know of a rod
rigging failure they can point to online? I'm too sleepy to google
today.

RB
35s5
NY

Bob Crantz wrote:

How about sending an acoustic pulse along the rod rigging the same as a time
domain reflectometer works. The pulse speed is a property of material and
tension and the reflectance a function of acoustic impedance. Cracks would
raise the impedance. The cracks could be located along the length of the rod
by simply applying the pulse signal at one point.

Sounds good to me, I don't belive tension (or compression) has anything
to with the speed of transmission in a solid.

Cheers
Marty

Rob:

You don't have to remove the rigging at all. On the TDR pulse you can easily
see the where the spreader touches to rod, you can run your hand up and down
the rod and see its location on the TDR. Since sound waves don't propagate
through cracks, the sound energy would be reflected back at the source and
the location of the crack could easily be identified.

All you need is a good piezo transducer that transmits and receives, a pulse
generator (a simple circuit) and some display like an oscilloscope. You can
even make a display on a laptop. With some signal processing you could
really do some great analysis of the rigging.

Think of a sonar with metal instead of water as the medium. One could even
spot cracks and corrosion in the end fittings. Also think of a musical
instrument. If the fret or neck on a guitar is damaged, it is easy to hear.
These same principals apply to the TDR.

Amen!

"Capt. Rob" wrote in message
oups.com...
Cracks would
raise the impedance. The cracks could be located along the length of
the rod
by simply applying the pulse signal at one point.

Seems to me that for this to work well you'd need to remove the rod
from the boat and tension it is some sort of way, equally. Then you
might read cracks, but be unable to actually locate them, meaning a
small non-dangerous imperfection in the rod might give a false reading.
Seems like a tool that would get abused to sell a lot of uneeded
rigging..
Just about every rig failure I've ever heard of was wire. While I'm
sure rod has failed....I've never heard of it. Anyone know of a rod
rigging failure they can point to online? I'm too sleepy to google
today.

RB
35s5
NY