Dynex Dux redux

[Gashmore]

I have finally started some quantitative testing on a sample of 9mm Dynex Dux that John at Colligo sent me. I have not completed the creep test but the dynamic stretch figures are in. I am getting a page together on my web site with all the gory details but I thought I would report the preliminary results here.

The purpose of my examination is to get some numbers to compare to 1x19 wire. I tried to follow the Cordage Institute's procedures but as the sample had only 28" clear of undisturbed rope I used an electronic positioning sensor called an LVDT capable of detecting .00005" movement. By adjusting for the specific weight of the rope I had estimated from Strong Ropes figure of .00055 in/in/1000lb for 11mm that 9mm should have an elongation of .00084, about equivalent to 5/16" 1x19. The tested figure (average of 20 pulls after 50 cycles to 20% of MBL was slightly better at .00078 in/in/10000lb. I have to attribute this to the possibility that the fiber is slightly more in line with the load in the smaller diameters.

One major difference I found was the hysteresis or rate of recovery after the load is removed. 1x19 will recover 90% or more of the elongation immediately and the rest over just a few seconds. Relaxed from 5,000lb to 2,000lb Dux only recovers about 60% immediately and another 30% over the next half hour to 45 minutes. It took almost 12 hours to recover all the elongation. What I think this means is that you shouldn't try to tune a rig immediately after it has been loaded heavily. If you dial in the tension before the shroud has fully recovered it will be to tight a few hours later. Also I think it is possible that the leeward shrouds might seem slightly slack immediately after a tack. I will have to examine this more closely.

The other interesting fact is the almost complete lack of torsional deformation. 1x19 will try to rotate as the lay straightens but braid remains in line. I don't think I would do away with cotter pins in the turn buckle though. :-)

Creep test begins next week and will take a couple of months.

[Brian Duff]

You Rock!


I mean it. Thanks for taking the time to suss this stuff out!

[Gashmore]

Well, after almost 2 months at 2,000 lb load at 80F on my 9mm sample I have almost nothing to report. .01" difference in the 24" gauge length. I just boosted it to 4,000 lb and will keep it there for another month but so far this is about as exciting as watching paint dry.

A further note on the slow recovery. I have received a couple of emails asking if the line stretches more if it is loaded again before it recovers. The answer is no. Loading fully recovered line from 2000 lb to 5000 lb the stress/strain curve is basically a straight line. Overlaying the curve from loading an unrecovered line there is a little variation as the load first increases until the slack is taken up. From that point on both are essentially equal.

[Jack]

Gashmore, As you know I have my entire cutter rigged trimaran in Dynex Dux. I recently had a sailmaker out for a sail. Tony Morrelli, he jumped around a lot and helped me tune the rig. He kept saying "this stuff acts just like wire" He would yank on a shroud or stay and become real enthused and kept saying, this is amazing, it acts just like wire.
He said changes that are this big don't just come along very often. Combine that with the fact it is not exotic, expensive and with in reach of the DIY guys....well he said he can understand why people are reluctant to trust it. This is just not a normal event.
He said he like the deadeyes like I do, but he felt regular sailors will want to use turnbuckles. Guess John better get a photo of the terminator attached to a turnbuckle.

[Joe Henderson]

Dear Gashmore, Jack and Brian,

It is gratifying to see the cause of Dynex Dux being taken up so enthusiastically in the Northern Hemisphere.

Down here at the bottom of the world, we have been aware for more than three years that this stuff behaves like wire, albeit with a slightly more elastic take-up period.
We have rigged more than 20 vessels ( Keelboats and dinghys, as well as multihulls) using this material and have nothing but respect for the way it deals with load cycling, chafe and U/V attack.

Of particular satisfaction is the way that this material responds to competent rigging skills.
The better job you make of the terminations, including the choice of tensioner ( Colligo, Pre Court, Custom Stainless, Lashing, lanyard or Turnbuckle) The better and more suited to the particular application the set of rigging will be.

One should not assume that Dynex Dux is a "one size fits all" super-material but rather treat it as a quantifiable, proven and documented extra resource that responds well to clear thinking and skilled manipulation.

All the numbers quoted in this and other threads are (surprise, surprise!) in pretty close agreement with the manufacturers figures that have been available for some time on the web, ( Strong Rope and Hampidgan to name the two foremost sites.)

Perhaps now the use of this stuff as direct replacement for 1X19 wire on mainstream criuising and racing yachts will be accepted. We have, as I say been specifying it for three years now.

The crucible that is the Bering Sea fishery has proved the toughness and durability of the gear, now the fashionable world of the "Universal French Plastic Yacht", among others, surely needs to embrace the technology.

While we are on the subject, and to address the spectre of twitchy new owners being suspicious of the material, I seem to remember Brion Toss writing a beautiful piece on how, in the old days, Hemp and Flax fibre rigging (to name but a few of the various natural fibres that were in common use for both standing and running rigging) was the norm and everybody was suspicious of this new fangled metal rigging!

"The more things change, the more thay stay the same" I can not remember who said that first, but it seems apt!

Regards,
Joe Henderson.

[Jack]

Joe, very cool posting. The written piece you are referring to I believe is:

http://www.briontoss.com/education/a...miscsept04.htm

To think that Brion wrote this is 2004. That seems like a long time ago in the short history of these ropes.

Am I dreaming, or did Herreshoff say (after being banned from racing his new fangled catamaran by the NY yacht club)

"In yachting, progress is fine, as long as there is not too much change"