Posted: Jul 04, 2011 - 06:02 AM
The marine eye is a hydraulically swaged fitting, stronger than nico press/thimble. The rigger I use said they are done in a 20,000lb press.
As Dave said, they are very strong, very few people,(none that I know) use a back up. In essence what happens is the walls of the marine eye are pressed so tightly into the cable that they deform,into the strands of wire. If you look closely at the wire you will see that it is spiral wound, sort of like really coarse threads on a bolt. Once the marine eye gets formed into these "threads" the only way for it to come apart is to break the wire, break the eye, or shear off all the "threads" that are now formed inside the barrel of the fitting. The eye is stainless steel of a quality that exhibits high resistance to shear loads, making it very strong.
The only way to provide redundancy would be to run an entire second set of shrouds to a second set of chainplates in the hull, & a second masthound. Murphys Law says that if you added a short length of wire from just above the eye to another hole/pin on the chainplate, it would fail up at the hound, or the chainplate would pull out of the boat.
Replace them all if old, any broken strands, or even kinks, then sail. I run a backup for my forestay, but only because the connection is line, (via a Portuguese turnbuckle). I have mostly inexperienced crew helping me, & the second line is to tension/detension the rig, the first is taped to prevent inadvertent release.
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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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