Re: ACMO rigging - unusual failure


Bill Kinney
 

Craig,

Your description of the amount of tension on your backstays sounds perfect...  so much for my theory...  The construction of the swage certainly looks good mechanically.  The photo is not detailed enough, but the broken ends of the wire, either in  the swage, or at the end of the cable... they look quite rusty and brown.  A sudden catastrophic failure from work hardening would leave the ends of the wire that came apart bright and shiny, but grainy looking.  What I THINK I see is evidence of slow stress corrosion cracking of the inner strands of the wire.  We had a failure of that type on one of our jib cars.  The photos there might give you an idea what I am trying to describe...  

https://fetchinketch.net/2019/07/26/failure-analysis/

I'm a bit surprised at the comment that stainless steel "can not rust."  That certainly isn't my experience either in industrial or nautical situations.  On our old ACMO rig we would polish off the surface rust off the swages and lower foot or two of wire every six months or so, and it would come back. More slowly if we waxed it, but still inevitably. I doubt the swages were still oozing assembly grease a decade after they were made.

Bill Kinney
SM160, Harmonie
Hollywood, FL, USA

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