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Dynex Dux rigging on the yawl Arcturus

Dec 28, 2010

To the editor: Aided by my fiancé Mia Karlsson, I am in the process of making our 35-foot yawl Arcturus seaworthy enough to tackle the North Atlantic. We originally intended to re-rig with wire and STA-LOKs, pretty much standard fare for cruising boats, but at last year’s U.S. Sailboat Show in Annapolis, Md., I met John Franta of Colligo Marine, and he convinced me otherwise.

John, in conjunction with Mike Meer of Southbound Cruising Services (a local yacht rigger in Annapolis for whom I would serendipitously later work), was exhibiting a 1970s-era Westsail 32 cutter, and she was rigged in the traditional way. Spliced rope hung from her spars, tensioned with deadeyes and lashings and served partway up with tarred marline.

John explained that the rope, called Dynex Dux, was in fact quite high-tech. The commercial fishing and logging industries began using the stuff in the late 1990s, replacing the wire on their winches and making fishing nets from it. Jack Molan, an Alaskan fisherman himself, explained to me firsthand how it has revolutionized the industry, replacing heavy wire with super-light, non-stretch, highly durable rope. John (an engineer by trade) and Jack, each multi-hull sailors, got the idea to adapt it for sailboat rigging — and they’ve had it rigged on their boats, which they keep in the Sea of Cortez, for nearly a decade.

What intrigued me was the notion that a sailboat could be rigged in the traditional way, yet be done so by using cutting-edge technology and modern materials. Sailboat rigging, over the course of history, had truly come full circle.

John and Mike were clever enough to recruit Brion Toss, author of The Complete Rigger’s Apprentice, and the accepted guru of yacht rigging, to come speak during last year’s show. He was an early-adopter of Dux, and said simply, “Dux will change sailing — wire rigging will be a 150-year anomaly in the history of yacht rigging.” I was convinced.

Dynex Dux starts as the more commonly known Dyneema, a super-strong, low-stretch braided synthetic rope, used mostly as high-tech running rigging on racing boats and performance cruisers. The Icelandic company Hampidjan then treats the Dyneema in a special steam oven, simultaneously heating and stretching the rope. What results is Dux — the treatment work hardens the fibers, increasing its abrasion resistance, reducing stretch to virtually zero (less than wire, incredibly), and making for a smooth yet extremely strong braided rope.

After getting to know John at Colligo, who designs and makes all of the fittings for rigging a boat with Dux (deadeyes, thimbles, lashing blocks, etc., all made from lightweight aluminum), we ordered a spool for Arcturus and got to work learning how to splice. Dynex Dux marks a paradigm shift in rig design — where wire size is designed around breaking strength, Dux is designed around creep. Unlike stretch, which is elastic and reversible — like a rubber band — creep is permanent and irreversible — it’s the fibers themselves literally getting longer over time while under a static load. Taking this into account, we sized the Dux based on the boat’s righting moment, which when expressed as foot-pounds, represents the strain the rig will incur, plus a safety factor. With this number in mind, we consulted Colligo’s data charts and determined that 9mm was an appropriate size, and would not, in fact, creep under our rigging loads. The slightly larger diameter (we would have used 7mm or 9/32-inch wire) results in an inherently stronger shroud, between two to five times that of wire depending on the boat.

Cost was certainly a consideration, given the fact that Mia and I do all our own work and are operating on a minuscule budget. And yet where super hi-tech fiber rigging such as PBO and carbon systems can cost many times that of wire, Dux comes in at +/- 10 percent, depending on the boat. The line itself is more expensive per foot, but as a complete system, including end fittings, the cost of a re-rig is remarkably in line with that of wire. Which was ultimately the catalyst that allowed us to consider it in the first place.

Splicing the line is child’s play, making Dux an ideal material for do-it-yourself refits (and, more important, emergency repairs offshore). We used what’s called a ‘modified brummel eye-splice,’ inserting a Colligo end fitting on both the upper and lower ends of each shroud. These end fittings are one-piece, solid anodized aluminum, and have a pre-drilled hole for attachment to clevis tangs on the mast, plus four radiused lashing holes for the deadeyes at deck level. I did all the work on the boat, going aloft to remove one shroud at a time, measuring each as we went.

The most challenging aspect of the re-rig was measuring the Dux. After its steam treatment, the 12-strand braid becomes very stiff, and must be worked open with a fid in order to splice it. This creates the slightest slack in the line at the splice, which must be re-tensioned on a winch prior to fitting aloft. By burying the tail during the splice, the line also shrinks slightly. The shrinking (we lost four inches per splice…) and resetting of the braid (…and then got two inches back) results in a net two-inch loss for each splice, for the 9mm line we used. By using deadeyes, any mis-measurement can be hidden by adjusting the length of the lashing line (one-quarter-inch standard Dyneema), but the relatively small travel on most turnbuckles requires very careful measuring indeed, if turnbuckles will be used to tension the rig.

Once setup, tuning the rig was very straightforward. The idea was first to get the mast in column — by sighting up the sail track — and then to tighten everything down symmetrically. We tied each lashing off to a halyard and used the winch to get enough tension. After a static tune at the dock, we went sailing in a moderate breeze, tacking back and forth upwind and sail-tuning the rig once underway, again making sure to keep the mast straight and in column. We then tightened the lee shrouds just enough to keep them from going slack.

Though the process was tedious at times (being a yawl, we had a total of 14 shrouds to replace — removing, measuring, splicing and re-stretching each), it was easy and enjoyable. I did most of the work in Arcturus’ cockpit, using only a sharp knife, two fids, a magic marker, a stout bosun’s chair and Mia’s help to go aloft.

Arcturus’ 30-year-old wire rig is now at the bottom of a recycling center in Florida, and we are $6.00 the richer for it. We managed to reduce the weight off the rig by more than 50 pounds, making Arcturus noticeably stiffer when heeled and easier on the helm. She is and always will be a tender boat, designed to heel quickly to lengthen her waterline, yet she’ll stand up in the puffs much more readily than she would before. It’s rare that we’ll put the rail under anymore with the proper sail combination. We chose Dux not for its light weight or performance gains (which are measurable), but because it was simple, traditional and easily repaired at sea. It’s definitely higher maintenance than wire — we had to apply tarred nylon service where it bends around the spreader tips, and we are always on the lookout for chafe — but to quote Toss again, “with the privilege of having rigging back in the hands of the sailor, comes the responsibility of understanding how it works.”

Andy Schell is a professional captain and freelance writer. He and Mia live aboard Arcturus, a 1966 Allied Seabreeze, which they are currently fitting out to sail trans-Atlantic to Sweden. Contact them at andy@fathersonsailing.com.