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January 5th

Synthetic Rigging: Not just for racers anymore?

Posted by // January 5, 2012 // COMMENT (0 Comments)

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From day one this project has been a lighthearted battle of wills between my father and I. On the one hand (as anyone familiar with his articles is likely to have noticed) he seems to extract some sort of deep-seated joy out of tinkering with the cutting edge of technology. On the other, I experience a similar feeling when I manage to repair some thirty-five year old bit of the boat that seemed destined for the scrapheap. Minor skirmishes -such as the tossing out and subsequent retrieval of used screws- are a daily occurrence. Then there are the grand engagements. The rigging was one of these. As you can see from the photo, it didn’t go in my favor, though in all honesty it was conceded without much of a battle. I’m actually rather excited to play with this stuff!

What I’m holding on one finger (it’s much lighter than it looks in the photo) is the entirety of our standing rigging, which is Dynex Dux braided fiber rope from Colligo Marine. It’s one of the hot new technologies on the market and the first synthetic rigging which has any relevancy to the average cruising sailor. My father and a number of well-respected riggers think it will be a game-changer in the rigging industry and while I’m a bit skeptical I do think it’s quite interesting stuff.

Dynex Dux is a synthetic rope made by an Icelandic company called Hamipidjan. It’s made by heating and stretching synthetic SK-75 rope, a process which actually makes the material stronger and more stable. At about twice the strength of same diameter stainless steel and only a fraction of the weight Dux has proven its  integrity in a number of heavy-duty industries including logging and commercial fishing. Not surprisingly, this caught the interest of a few riggers who like playing with cutting-edge tech. Also not surprisingly, it took them quite a lot of fiddling to make it work on sailboats!

What people found when they started trying to use it for standing rigging is that although the stuff is just as strong as it claims to be, it’s also quite difficult to work with. Fortunately folks like John Franta at Colligo Marine, Mike Strong in Australia, and Brion Toss spent quite a bit of time and money playing with it until they figured out a few key techniques that make it work for sailboats.
Dux is slippery enough that it won’t chafe through when loggers use it unprotected to haul trees through the forest but this also makes it very difficult to knot or splice. One of the early issues they found was that cycles of slack and tension would pull out many splices so folks did plenty of destructive testing until they settled on ones that work. The Brummel Long Splice seems to be the most used.
Then there was the issue of stretch. Dux stretches in a number of ways that stainless wire doesn’t, a property that is responsible for most of the modest number of negative reviews it has suffered. The  heating and stretching during manufacture makes it less susceptible to stretch then standard SK 75 but its increased slipperiness makes for a great deal of constructional stretch when the splices are first tensioned. Some riggers, especially the DIY sort, underestimated this only to find that their rig was stretching once tensioned. This was often blamed on rope stretch or creep when it was really just due to the elongation of splices. To compound the problem Dux also has a greater degree of creep than stainless wire of the same strength. Thus if you use breaking strength as the limiting factor when sizing a rig (as you would with stainless wire) you will end up with a great deal of creep. Instead you must size a Dux rig for stretch and creep which are its limiting factors. You need to keep static loads to a small percentage of the breaking strength (around 20%) to minimize creep, resulting in a rig which would seem greatly overbuilt when compared to stainless wire but is still much lighter. Lets look at my rig for an example:

The wire rope on there was 1/4″ for the lower shrouds and 5/16″ for the upper shrouds, giving breaking strengths of 6,900lbs and 10,600lbs. The Dynex Dux we’re replacing it with is a uniform 7mm, even for the lowers, which has a breaking strength of 16,500lbs! This should result in not only an increased safety factor but also a minimum of creep (Colligo claims a maximum 0.1 inches/year). To top it off, this entire ‘overbuilt’ rig is a fraction of the weight of my stainless rig. I’ll get back to you with the numbers when I track down a scale.

The old 5/16″ backstay compared to the 7mm Dynex Dux.  
Quite a difference!

So in every respect we’ve looked at this Dynex Dux stuff seems to match or surpass stainless wire – it is much lighter, stronger and resistant to chafe, and when properly sized and installed stretch and creep stay within reasonable limits. This is supported by real-world application. In 5+ years many boats have been rigged with Dux with very few problems other than those which can be traced to an incomplete understanding of how to work with this new material. It is a revolutionary material and there is little doubt in my mind that within a few years it will be the rig of choice for racing sailboats, mega yachts, and any boat where minimizing weight aloft is a priority. However (and this is a big one) there are two very important numbers I haven’t brought up yet which just so happen to be the most important numbers to ninety percent of cruisers: cost and life expectancy.
 These numbers are the make-or-break which will decide whether this new material revolutionizes the entire sailboat rigging industry or just those sectors of it with deep pockets. Fortunately, things in this department look pretty good and are likely to keep getting better.

First let’s take a look at cost. Pricing a rigging system is inherently difficult because there are so many factors to consider but the oft-quoted figure with Dux is that it is ‘only marginally more costly than stainless rigging’. This is possible because unlike any other synthetic Dynex Dux is cheap. Actually it is cheaper by the foot than stainless wire! From West Marine 5/16″ 1×19 stainless wire is $4.63 (304SS) or $6.44(316SS) per foot. Dynex Dux from Colligo Marine is only $2.99 per foot in the 7mm size which replaces 5/16″ standing rigging. If anything this price is likely to go down since Dux is still a relatively new material.
Then there is the cost of fittings, and labor. Unlike easily fitted stainless Dux must be hand-spliced which adds up if you don’t want to do it yourself. Dux also needs special fitting because bending must occur over a quite large radius in order to keep the strength off the material. The cost of these fittings is comparable to stainless turnbuckles if you’re willing to rig with the very interesting system of traditional dead-eyes and lanyards that Colligo Marine often uses (more on this at Charlie Doane’s blog).

Photo from  Colligo Marine

This is what we opted for with my rig, but it is supposed to be a bit more of a pain to use than standard turnbuckles (though I love the look!). I’ll report back once we step the mast. If you’re not wanting this ‘traditional’ system it is possible to use Dux with standard turnbuckles but you’ll need to purchase these in addition to the dead-eyes, driving up your costs.

Photo from Colligo Marine

Once again, the cost of fittings for Dux is likely to decrease as it comes into wider use, especially because  these fittings are mechanically much simpler than those used with stainless wire. So this all looks pretty good, right? Well except that many people in the market for a new rig have perfectly serviceable fittings and just need new wire (or rope). In this case you’re certainly looking at greatly increased costs to go with Dux. Still to some people this is worth it in order to save a bunch of weight aloft.

Then there is the issue of life expectancy, which is directly related to the lifetime costs, an all-important figure for most cruisers! Dynex Dux is actually such a new material that no one really knows what the life expectancy is.  The issue here is that the limiting factor in Dux’s service life is almost certain to be UV degradation but very little data is available on this because up until quite recently the material has been almost exclusively used in low-UV situations such as logging or commercial fishing in Alaska. The figure given by Colligo is replacement after five years but this is a conservative number which they expect to go up as they continue UV testing in very sunny Southern Mexico. They compare this number to a recommended eight-year lifespan on stainless wire but  that is a very conservative number (as Charlie points out in the post I linked to above). If it turns out that Colligo’s five years is equally conservative then we’ll really be talking but having spent years in the tropics watching various plastics melt, crack, craze, and shatter I have a hard time believing Dux will be so much different, no matter how future-tech it is! I also think it’s important to know how apparent this UV degradation will be- even if Dux lasts a long time I don’t think it will find its way onto many cruising boats if it tends to fail without warning. Fortunately synthetics tend to give plenty warning before they fail so I doubt this will be an issue.
On the other hand, the raw material is half the cost of the 316SS that you really should have for tropical cruising so once you have the fittings if you’re willing to learn (or pay for) the splicing you could rig the boat twice for a similar cost and have all the benefits of strong, light fiber rigging. The life expectancy of the mechanically simple dead-eyes should be much greater than turnbuckles which helps to bring down the lifetime cost of a Dux rig. No one expects this material to last as long as steel but it is an improvement over stainless in enough other respects that it won’t have to last as long in order to take over the market. At this point a 7-10 year lifespan seems within the range of possibility and if this proves true I expect we’ll be seeing a lot of cruising boats out there with Dux rigging. If it doesn’t, I for one will be re-rigging with classic stainless!

Dux is a very new material on sailboats but in the past few years it has thoroughly broken the mold of synthetic rigging, proving itself to be a strong, reliable, and affordable alternative to wire. In my mind there are still a number of questions which need be answered before it becomes viable for the budget-conscious cruising sailor but if it can jump a last couple hurdles I think Dux, or something like it, will be the new standard within a decade. This is why we have decided to rig with it. On the face of it Dynex Dux doesn’t make a lot of sense for a refit like mine -the weight-saving benefits aren’t going to make a big difference on my small, heavy boat and there was no need to replace all the hardware on my standing rig so it was a bit silly to redo the entire thing. But we did it because in this case the cutting edge of technology seems likely to become the future standard and we want to find out firsthand if this stuff is all it’s cracked up to be. It was one of the few times when my dad’s enthusiasm for new technology fit in with my desire to keep things (relatively) simple, and I do love the idea of traditional dead-eyes! I’ll be keeping you posted on how it goes up and performs but so far I’m impressed.

There was a bit of a blip there as I’ve been busy during the two weeks of 8-12 hour workdays while my folks were here helping out but I’ll have lots of photos coming up as I recount the massive amount of work we did on the boat. Things are really coming together!

This article was syndicated from Safe At Harbour But Meant For The Sea: DIY Sailing with Paul Calder

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