I decided to rig Satori with synthetic high-modulus polyethylene rope. Its a heat treated and stretched, then given the designation SK-75. On the street err…pier, it’s called Dux. Here’s some fun facts.
Colligo Dux rigging is sized for stretch, not breaking strength. Compared to wire, SK-75 has more material stretch in relation to breaking strength. This means that if 1 mm wire breaks at 1000 pounds (which it doesn’t) and creeps 1mm per year, then 1/4 mm dux with the same 1000 pound breaking load will have 3mm of creep per year.
For this reason, synthetic rigging is sized for material stretch (creep) rather than breaking strength. To put it in context, on my project I used 9mm dux with a breaking load of about 24,000 pounds which is only slightly larger diameter than the 5/16 wire it replaced, yet just about 2 times as strong!
Synthetic rigging weighs very little. I was able to hold the entire rig (less the forestays) in one hand. The weight reduction aloft will hopefully do great things for the responsiveness of the boat while under sail. It also makes the rigging process much less of a pain in the ass. No wires dragging all over your topsides and you can build all of this on your living room floor!
You can splice it. Before this project I had never spliced anything. Ever. Now I’m a splicing fool. Not only is it easier than dealing with mechanical fittings, it’s simpler and fully inspectable at all times. Even underway. In fact the entire rig is now fully inspectable, even down to the bronze chainplates.
It’s more susceptible to chafe. I haven’t used the boat yet but I’m going to have to adopt a whole new attitude while underway from now on. Hopefully a zero tolerance policy toward chafe will make the boat even safer. The nice thing is any chafe that does occur will be extremely visible. This goes back to my point above: every critical connection on this rig can be visibly inspected or can easily be taken apart.
There is something completely zen and rewarding about building and working with rope. In addition to splicing, I learned how to parcel and serve when building the uppers. This additional protection was required on the spreader tips. Brian Toss’s book “The Riggers Apprentice” proved helpful when trying to adapt these old world rigging techniques to super modern SK-75.
Due to a number of factors, I decided to run lashings in tandem with bronze turnbuckles. Originally unsure if this dual adjustment setup would look hacked up, I can now recommend it with confidence. I get all the saltyness of the lashings yet I don’t have to go through the nightmare that goes with tensioning a rig this size using only lashings.
Right now I’m extremely pleased with the uniqueness of the rig, the ease of working with this rigging and the margin of safety gained. I’ll report back once I get the boat sailing on what my mechanical stretch is turning out to be and further thoughts on sailing the boat.