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304 vs 316
Rod Rigging. Nitronic 50!
"Keith Hughes" wrote in message ... Nigel wrote: "Howard" wrote in message ervers.com... Something to ponder while watching the snow. I have a 20 year old steel cutter with original wire rigging. Ted Brewer design. The orignal owner fitted it out with all 1/4" 316 standing rigging. I'm thinking of changing out part of the rigging, the back stay and fore stay. It all looks good but just because............. Anyway two questions: 1. Supposed I change out the wire, these are the two longest, and then save the used wire as emergency wire. The wire fails at the bottom connection so wack off 6" and the rest is good! No? New bottles etc. of course. The wire fails at the bottom for a couple of reasons. One, when using compression fittings, the metal hardens from compression (i.e. work hardening) reducing ductibility at the wire/fitting interface which makes this area more succeptible to cracks. And two, from corrosion due to salt water wicking into the fittings and pitting the wire - especially true when any micro-cracks are present presenting a less-passive surface. 316 s/s is about 20 times more resistant to salt pitting and corrosion than 304, and thus will last significantly longer under sea spray conditions. 2. Ted Brewer recently wrote in Good Old Boat about standing rigging and is apparently partial to 304 vs 316. That does not seem to be conventional wisdom, yet consider the source. So what say you, 304 does have more strength for the same weight and windage. What are the detractors and how severe? 304 has slightly more tensile strength (5-10%), *for any given level of cold worked temper* than does 316. However, you need to make sure you're comparing apples to apples, since the tensile strength of each will double for fully hard temper vs 1/4 hard temper (ASTM A 666, Standard Specification for Austenitic Stainless Steel, Sheet, Strip, Plate & Flat Bar). So fully hardened 1/4" 316 wire has almost twice the tensile strength of 1/4 hardened 1/4" 304 wire. Thus you need to make sure of the temper when you're comparing the two (or purchasing). Whether the longevity of 316 will pay for the additional cost, in your situation, I don't know. IMO, if you sail often, and sail hard, use 304 and replace more often. If you spend more time in the bay, or marina, use 316 and replace less often. Keith Hughes |
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