304 vs. 316

[pgillihan]

I have a 36 foot corsair catamaran. Upon a return trip from Bermuda I discovered severe breakage of the capshrouds just as they entered the swage on the mast t terminal. Both cap shrouds had breakage and I noticed at least one of the wire strands had broken several feet away from the swage fitting on one of the shrouds. The rigging is 3/8 and the boat displaces 11 to 12 thousand all up. The cat routinley hits 9 and 10 knots and you can feel it load up . We made it to Bermuda in just over three days with steady 18 knots at 60 degrees apparent. Sometimes with a reef in the main, sometimes not, just at the break point for a reef. The boat carries a lot of sail especially the main , and is fractionally rigged. The caps and forestay terminate several feet below the masthead.

There seemed to be no problem with allignment of the shrouds and the t terminal, but i did change the top fitting to a noresman. My rigger convinced me 316 was the way to go for corrosion resitance, and that strength or resitance to shock load will be ok with 316. ( he thought the wire was poor quality and /or the swage was incorrectly done) Now I think i should have gone to 304 for the increased strength. Upsizing the wire is just too expensive. I still have the forestay to replace ( i dont know if its broken i cant get enough slack in the furler system to inspect the swage) and if i have to take the furler off i might as well replace it, although this wire was apparently replaced at a different time with prehaps different wire than the cap shrouds. None of the wire is over 5 years old.

Should i have gone with 304 in the caps and should i go to 304 in the forestay. I guess its a matter of corrosion resitance vs. strength , but how bad is the corrosion in a tropical climate. I do a lot of single handed sailing and i have lost one rig in my days which is enough.