Here is the question. (Excluding the the obvious like visible damage,
fish hooks, etc.):" When do you decide to replace old standing rigging?"
I'm hoping for helpful hints, like what to look for. I do not believe
in fixing what ain't broke just because it is old.
This is a very tough question to answer. I've worked as a rigger and had this conversation with labs that to testing.
The service life remaining in the wire cannot be tested with certainty without destroying the wire. That's fine if you have 50-100 cables on a bridge. Test one to failure every year starting at 5 years and you get to a pattern for wire under those conditions. Not really an option if you are looking at 8-6 wires on a boat.
The corrosion and cracks are one thing and easy to spot. The unknown is how many stress cycles the wire has gone through and the magnitude of those cycles. Standing rigging acts just like a big spring. Depending on what loads are applied the service life can be near infinite or can be limited severely.
30,000 miles. Is a good yard stick. That is 6000 hours at 5 knots.
How long does it take to spend 6000 hours sailing your boat? 20 weekends at 10 hours a day is 200 hours, ad a 10 day cruise and you get 300 hours a year for a 20 year service life. The rig is stressed all the time it is in the boat, every passing wake that rolls the boat is "using up" the rigging.
Bottom line I don't trust wire more than 10 years old unless I know it has been off the boat and stored properly in the off season. For year around boats I suggest the mast comes out every 5 years for a complete inspection and the rigging replaced at 10 years if there are NO warning signs at 5.
Ask anyone that has lost a mast ... it ruins your day. Many people think that rigging is a forever thing, do they never service their cars? Wire is a machine, it wears out just like any other machine.
Maine Sail's 10-14 years is a decent range. Particularly for NE boats that are laid up in winter. I'm always amazed at how "new" a boat from that area looks compare to one from the west coast.
Randy