Issues with synthetic rigging?

[Mark Johnson]

Can any of you guys with years of experience using synthetic rigging, fill me in on the following?

The comparison that I would like to see between Dux and 316 SS wire, is @ 18 or 20 years old. Of the countless thousands of boats in our area, (Eastern NC), there has only been one dismasting in the last 5 years to my knowledge, and it was a new racing boat under extreem conditions. If one removes from the conversation the < 5% who are cruising all over the world, or live full time in the tropics... The other 95% around here spend winters in the Bahamas, are daysailors & local cruisers, or make a couple of one or two year Caribbean cruises... still spending the majority of their years in our moderate lattitudes, and brackish water. Of this 95% of cruisers, almost all go over 18 or 20 years before changing out their rigging, some even go to 30 years, (admittedly at their own risk)! Has your accelerated UV testing made a compairison to wire at this 18 + year life span, under the above circumstances?

Another point I am curious about... I have switched to some DUX synthetic rigging 6 months back, they are for my running backstays, and DUX seems like a perfect application here. I normally leave them "made up" and fairly snug, to use as a handhold when boarding the boat. When using the staysail, I will put 4 more turns on the "quick adjust" handle turnbuckles, but so far, haven't given them the acid test.
I go to the boat daily, and have noticed that @ 75 degrees F, the runners are quite snug, but @ 40 degrees F, perhaps that same morning, they hang completely limp. Since solid materials expand when heated, and contract when cooled, it can't be that the DUX has gotten longer on a cool morning. I assume that the metal mast has contracted at a rate vastly higher than the DUX, creating loose runners in the morning. Presumably with wooden or composite spars this is less of a problem,. My wire rigging has never done this "changing tune with temperature", and I imagine that it's because the wire expands and contracts at a rate somewhat similar to the metal mast.

With aluminum mast that are long & skinny, (like mine), and dependant on consistant shroud tension to keep the mast in column, wouldn't this become a problem if I tune the rig in the summer, then go sailing on a cool fall day? Has anyone else noticed this characteristic? I have done a LOT of reading on synthetics, and have yet to see this subject brought up...

Best regards, Mark