The Catamaran Adventures of Noel and Ceu

Dyneema Dynex Dux Synthetic Standing Rigging on a Catamaran

Life everyone else, we used to have stainless steel rigging.

But when it came time for the 10-yearly scheduled replacement, we decided to go with synthetic rather than stainless again. Why did we do this? There are several problems with stainless that are overcome by using synthetics:

1) Stainless steel is subject to crevice corrosion. That means that water gets trapped in tiny cracks and eats away at the stainless. The trouble is, you can’t see this happening until BANG! suddenly your rig falls overboard without any apparent warning. Over the past year I was regularly up the mast checking things, and yet look what happened despite that. Fortunately these cracks were spotted in time, and nothing dangerous happened. But that is too close a call for my liking.

2) Apart from corrosion, there is quite a high failure of swaged terminals, even well before the 10 year replacement cycle, caused by improper fitting. Again, totally invisible. Sta-Lok, Norseman, and Castlok compression fittings get around this problem, but the corrosion issue remains.

3) Stainless is heavy. Who needs all that weight up there?

4) If your rig does fall overboard, you need to cast it loose in a hurry, before your mast puts a hole in your boat. But how are you going to cut that steel cable?

So, how does Dynex Dux overcome these problems?

1) It is sized by stretch and creep, not by breaking strength. I.e. you use a size that provides almost no creep over a 10 year life. This sizing, which turns out to be marginally fatter than the steel cable, provides for a breaking strength that is 2 to 5 times stronger than your existing stainless cable.

2) Dynex Dux is extremely UV and abrasion resistant – but even if either of these occur, the damage is on the OUTSIDE – which means you can SEE it. And remember, you have a 2-5 times margin of safety.

3) it is a 1/4 to 1/5 the weight of steel rigging – which means a stiffer righting moment for monohulls, and less pounding upwind for all boats. (The goal is always to keep weight as close to the center of the boat as possible).

So what exactly is Dynex Dux?

Dyneema (also sold as Spectra and Amsteel)  is ultra high molecular weight polyethylene. This is essentially the same stuff as your shopping carrier  bags, except that the molecules are way, way bigger and longer. The are aligned in the same direction, which is what provides all the strength. To produce Dynex Dux, this is then factory stretched under high tension and temperature which work-hardens it, producing even more strength and abrasion resistance.

We ordered our Dynex from John Franta at Colligo Marine. John is very helpful and does everything he can to make things work. However, we did have some challenges with getting the right lengths and also the correct sizes for the end fittings that slot into the mast. Once we got those sorted out, we were good to go.

The good thing is that if you mess up your lengths, you can redo the splices and correct for that!

A year down the road, everything is still looking good. You can see pictures of our installation here: dynex dux rigging on a catamaran

Leave a Reply