The Offshore Voyaging Reference Site

Dynice Dux, Part 1: Practical Low-Stretch Rope Rigging For Offshore Sailboats

Since writing about the three refits I’ve done for offshore voyaging, the most comments I’ve received are from people interested in the synthetic Colligo Dux rigging we fitted on Arcturus. That rigging project was the funnest part of the entire refit and, six years later, Arcturus is still sailing strong with her synthetic shrouds and lifelines.

But Dux is not for everyone, nor is it suitable for every use. So here’s a look at what it is, where it’s great, where it’s not so good, and why it can be considered to have already passed John’s 20-year field test.


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Richard Dykiel

Looking forward to your part #2. Meanwhile a couple questions regarding the lifeline application. I just redid my life lines with standard dyneema. The only splice I know to do in that application is brummel lock splice:

– Do you have an example about splicing dyneema around a thimble? Could not fund an easy one to follow on the net.

– Are you sure about using dyneema for the lashing? Isn’t it too slippery for this application? I used a small diameter spectra line (I was even ready to use tarred seine 🙂

Thanks

John Harries

Hi Richard,

Just to clarify, I’m pretty sure that Dynema and Spectra are the same materials, just different brand names. They both have the problem of slipping though knots. That said I have used Spectra lashings for years without issues. The secret is a lot of half hitches (at least 20) around the lashing and then, if your as anal retentive as I am, sew the end down.

Richard Dykiel

OK the multiple names are confusing. But the spectra line felt definitely less slippery than the 1/4″ Amsteel I used for the life lines. I agree on the half hitches frenzy.

Andy

Some of the different companies dye the line different colors, and this can add a sort of ‘stickiness’ to it. In some cases this is good, in others it’s bad – for example, the slipperiness of the line actually allows for easier tensioning when you’re doing a lashing. Tie it off right and it won’t slip at all, and this becomes an advantage. The stickier, dyed lines are harder to tension properly.

John Harries

Hi Andy,

I never thought of that, but I can confirm it’s true. Just bought some blue Spectra and it is indeed harder to get a lashing tight with it, as against the natural colour stuff. Great tip.

Adam

I installed dyneema lifelines on my previous boat. For the lashings I used double braid with a dyneema core and polyester cover. No trouble with slipping or making half-hitches.

Marc Dacey

Andy, how is Dux different from PBO, which was being touted as the way forward in “soft” standing rigging about a decade ago? I find some of these trade names/generic names somewhat confusing, particularly in the Spectra/Dyneema/Amsteel realms. I certainly agree they are great products when used selectively: I went to four Dyneema-core, Dacron covered halyards last season (6mm core, 1/2″ cover) and am very pleased with the results. (By the way, this stuff is far cheaper by the 500 foot reel and you’ll use what you have left over). I haven’t, however, felt the need to change my mainsheet tackle, staysail halyards or sheets, where lack of creep is less critical and is sometimes desirable.

John Harries

Hi Marc,

PBO is a completely different material than Spectra/Dynema/Ansteel, which are all the same thing. The really scary thing about PBO is, as I understand it from a professional rigger, it loses a lot of it’s strength when wet! That’s why PBO shrouds are always covered in a plastic shell. Also, PBO can’t be spliced, it is wound to length.

Marc Dacey

Ugh! No interest, then, as it sounds very limiting and, frankly, unsuitable. Thanks for the warning.

PaddyB

Interesting article, thanks. Like the backstay idea.
Another use for dyneema never mentioned is for temporary repairs – if you mix dyneema fibres in with some epoxy it can make a really strong joint. My Aries windvane connecting rod is probably stronger than new 🙂

JCFlander

Hi, that idea of synthetic backstay antenna is neat.

Just that it might require a bit of further attention to work on all condtions.
There’s two possible issues:
– How performance is affected when the stay is wet, and there’s no additional insulation bits between deck and lower end or mast top.
– How to make sure that insulation is sufficient to avoid it to arc to crew members from backstay.

With 150W HF set, probable highest voltages on feedpoint end might be something like 1000V. That’s too much for regular 600V wire insulation, so arcing might happen along wet backstay – or to head of the helmsman, if almost touching the stay.
And, yes, 150W of RF doesn’t kill, it’s more of a nuisance, so this thing is not a life-or-death issue. (Except, perhaps, antenna performance on emergency, usually during a storm.)
Also, the whole wire from antenna tuner below to mast top is part of a radiating antenna. So, wire exiting from deck should have extra insulation.

Personally, I would use high-voltage tested wire as antenna wire, e.g Huber+Suhner Radox 125, that is tested with 3500 volts on delivery and is tinned. Though it has an insulation that resembles more of a bicycle brake bit than PVC, so it might be a real nuisance to get into the rope. Perhaps better to attach it externally. Shouldn’t be much of additional windage.
That way, wire insulation takes care of RF insulation.
If HV tested wire is not readily available, adding heat shrink to whole wire might improve insulation sufficiently.
Sorry for a long-ish post…

JCFlander

Now, it migt be a bit heavy-handed to dismiss 600V cable as unsuitable, since it seems that the test voltage for a cable that has 600V continuous rating is about twice of that. Exact data is on UL and IEC test standards, that are not readily available. Thus, e.g. regular Ancor 14AWG marine cable or similar, or EN H07 2,5mm2 that is rated to 750V continuous, could have sufficient insulation.

So – If cable has extra shielding (heat shrink) below head height and cable rating is at least 600V, it seems that it would work okay.

Andy

Thanks for the comments gang, sorry for my absence. Just dropped anchor in Portsmouth, VA after a gorgeous overnight sail down the Bay – the last time Isbjorn will sail the Chesapeake for at least 3 years! I’m back ashore now and look forward to commenting on this and the next in the series about Dux!