Thursday, 14 January 2016

Dynema Shackles; Then & Now

As cruising sailors we can find ourselves a little behind the bleeding edge when it comes to changes in sailing technology. In a way I'm comfortable with that, happy to let the racing guys figure out what works and then adopt it some time later, when it costs much less.

So, we're now very happy to be using "hi-tech" Dynema (or UHMwPE) soft shackles, as in the image at right, in several applications on board Crystal Blues.  However yesterday we were taught a very clear lesson in just how far these new line technologies have moved ahead.

We visited the Southern Ropes manufacturing facility here in Cape Town, on a mission to analyze the remaining strength in some of our older lines (more on that later).  While there we noticed two HUGE soft shackles made of UHMwPE being checked.

Rated at over 76 tonnes, these shackles are made from 28mm UHMwPE line that has been heat treated and coated to improve the strength and life of the shackle.  This one is destined for the mining industry.  Interesting to note that the sailing market is only around 5% of Southern Ropes total business base.

Southern Ropes showed us the heat treatment facility where these lines are effectively baked under controlled tension to minimise the "creep" or elongation characteristic that is the one down side of UHMpWE or Dynema in longer term use.

The production line includes baths to die the fiber to desired colors and other stages that apply coatings to enhance the line strength by retaining the fiber alignment as it comes off the hot tension rig.

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