Back to the future with Dynex Dux
fiber ropes, eliminating all wire!
Why would I say something like back to the future? A hundred years
ago boats were rigged with rope rigging. It was replaced with
iron and eventually steel. The last forty years (or so) has seen
stainless steel wire as the rig of choice for yachts. On each
change of material, there was a huge amount of doubt and miss-trust.
After all, we need what we know to be the “right stuff”.
All the more so when you are subjecting your stuff going to sea.
That is all changing now.
This new, extremely strong and lightweight rope is replacing the
stainless steel wire. And doing it at 1/9th the weight and double
the strength. All at a cost similar to wire.
||It is rigging that is lightweight, durable,
do it yourself and comparable in cost to wire. It is one third
the cost of exotic PBO or carbon fiber rigs. All of this is
now available to the sailor. What is this stuff? How is this
possible? By using Dynex Dux synthetic fiber ropes to replace
stainless steel wire.
My own experience with synthetic ropes goes back eight or ten
years. I am a Captain on a 125’ Bering Sea Trawler. Our
range of work consists of deploying huge nets and retrieving them
with huge loads of fish. If you have seen the “Deadliest
Catch” Program you know what kind of conditions we work
in. We are right along side all the crab boats, winter and summer
24-7. When they are swinging 700 pound Crab pots in horrible conditions,
we are pulling 150 ton bags of fish in one haul! Our line of work
requires the best equipment in the world and as Captain it is
my responsibility to be very vigilant and keep the crew safe.
We must operate in a safe and prudent manner. We search the world
over for the best possible equipment. We deploy nets that are
1100 Sq. meters opening (the size of a football field stood up
at the mouth) and use 1” wire (now Dux) that is 800 fathoms
long (4800 feet) The Bering Sea Pollock fisheries is one of the
healthiest in the world. It is a high volume year round fishery.
Our deck operation requires us to use wire in all our many different
applications. Cranes, haulback winches, gilson and pullmaster
winches are used. It is heavy equipment operation out at sea.
All of these winches required wire of one size or another.
We were introduced to new fiber ropes that would replace our
beloved wire a while back. Naturally, as traditional fishermen,
we were skeptical at first. We have some very heavy duty applications
for wire fishing year round in the Bering Sea. We were in no
hurry to get rid of our well-known and tested wire.
We started out with the first generation Dynex SK-75 in an area
that had the least amount of duty. We made sure it had nothing
to rub on, no heavy loads and no one would get hurt if it failed
in anyway. We did not trust this new “miracle rope”
over wire. After some time, we came to realize it was holding
up just fine. As we moved on to other applications on deck, it
continued to perform extremely well. We finally worked up to the
big one - a fifty ton Pullmaster winch. This is the main winch
that makes the initial lift of 150 tons bag of fish up the ramp
in, quite often, huge seas. The loads are unimaginable at times
when you get the boat out of sync with the seas. The winch line
will go slack then “SNAP” back on a shock load that
shudder the boat and crew. I once had a tug boat operator tell
me we were crazy. When I asked him why, he said: “you guys
load your cargo out at sea”. We had a newer new material
called Dynex Dux for this job. The makers were claiming it had
twice the strength of wire and it was the same size!
We kept a sharp eye on the Dynex Dux line on this big winch.
We watched for chaffing issues (none), we inspected the splice
for any sign of failure (none) and we watched for any nicks, cuts
or anything that would indicate a failure was coming on this all
important piece of equipment. Any sign of it breaking? There was
As it turned out, there were no problems at all. At least none
we had anticipated. After one particularly wicked trip in the
winter, we found the winch drum had cracked! A fifty ton heavy-duty
steel drum, the size of a refrigerator, had cracked where the
Dynex Dux was attached. All of our concerns about the line, the
splice and the covering of the rope were unfounded, but the winch
drum cracked! We had wire on this winch for fifthteen years and
we never cracked a drum! This brought home just how strong and
non-stretchy this new stuff was. I was convinced we were not only
safe, but we were safer than before. Wire would stretch or crush
under a load, but the rope just stayed tight and strong. It was
proving to be much stronger than wire for the same size and we
found many advantages on deck as it lightened up the crew load.
It allowed us to do more with less effort. It seemed these rope
guys were on to something good. As fishermen we also started to
see the ropes were outlasting the wires by a three to one margin.
In other words, the Dynex Dux would last three times as long as
wire in the application. Our resistance to the higher costs of
ropes over the galvanized trawler wire, quickly faded. It made
good business sense also.
As I began rigging my trimaran, I learned that sailors are just
a reluctant to change as fishermen. There is a healthy dose of
“show me” anytime I show my new Dynex Dux cutter rig
to sailors. So, how did I get from a work boat in the Bering
Sea to rigging my 34’ Trimaran?
First, a few definitions. SK-75 rope was introduced under the
name of Spectra, Dyneema, Amsteel and others. Each company has
it’s own name for the same basic rope SK-75, 12 strand.
There is also SK-60 (not as strong, but less cost). All the same
fibers start out as UHMWPE (Ultra high molecular weight polyethylene).
It is manufactured in only two places in the world: DSM of the
Netherlands or Honeywell in the USA. Yes, the SK-75 regular Dynex
was as strong as wire for the same size, but I found out it was
not going to work in a static situation like rigging. The reason
was “creep”. One of the properties you have to factor
in for rigging with synthetics is the “creep” factor.
Being a plastic, if you subject SK-75 to a constant high load,
at elevated temps, the rope will creep. This is different than
stretch. I knew it did not stretch after my experience with the
fifty ton winch cracking. This stuff is stiff! Creep is when the
rope elongates and does not return. Like something that stretches
out, but does not snap back. This fact was not a big deal to the
F-boat guys who use three wire rigs with rotating masts. They
were already using SK-75.
An Icelandic Net and rope company named Hamipidjan had the new
material they gave us to try on the fish boat. This was the same
basic twelve strand SK-75 rope, but it had been heated and stretched.
They made some pretty amazing claims as to how strong it was.
They called it Dynex Dux. The stuff was rated twice as strong
as wire cable for the same diameter! Now we were really looking
at some amazing changes in how to handle loads and jobs out at
sea. As a fisherman and sailor, I started to wonder how could
I incorporate this into my sailboat? Dynex Dux was a different
animal altogether! Hampidjan takes the twelve strand Dynex and,
with a propritery process, they heat and stretch it. By doing
this, the properties change dramatically over the normal SK-75
Dynex both in strength and creep.
For example, regular 5mm (3/16) Dynex has a breaking strength
of 7,000 lbs. (enough to lift a Suburban truck) but the same 5mm,
when it is converted to Dynex Dux, has a breaking strength of
10,400 lbs. This is a huge 48% increase in strength, without increasing
the diameter of the rope. Creep can be factored out of the rope
because of this huge strength.
I had to change all the Stainless Wire on the rig of my 34’
Searunner “Corazon’ Located in San Carlos Mexico.
The boat is a double spreader cutter rig built in 1979 with the
original wires and turnbuckles. I had lots of wires to change
out and I started to look into how we could substitute Dynex Dux
for the wire I had on my boat. My 34’ Searunner originally
had 7/32” and ¼” wire sizes. Looking up the
tables I could see that wire in 316 1x19 Stainless ¼”
size will have a breaking strength of 7,481 lbs and 7/32”
316 1x19 comes in at 5,728 lbs breaking strength. A similar size
rope is 7mm Dynex Dux which has a breaking strength of 15,000
lbs! I could see all this and I knew I was onto something here,
but I needed the help of a good engineer.
||Enter My friend John Franta in San Carlos Mexico
who has a 38’ Trimaran. He was very interested in what
I was attempting to do. Together we identified some of the
things we needed to address to be able to use the Dux rope
to replace the wire. One of the unique things about Dux is
the need to keep the bending radius large enough to meet Hampidjans
||In a static load situation like standing rigging,
Hampidjan insists on a five to one minimum so that is a radius
five times larger than the ropes diameter. We could not use
normal thimbles. In fact, we got reports of those stainless
thimbles elongating and deforming when used with Dynex Dux
in New Zealand (remember the cracked drum?) This led John
to design the “Terminator”.
||It has a nice radius and deep groove to hold
the Dux in place and it gives us a way to secure it to the
boat and mast. The “Terminators” are unique in
that you can use a pin to attach it like you would normally
to the mast. While using the same “terminator”
fitting on deck you can use it as a “deadeye”
with lashings to the “distributor” fitting or
you can use the same turnbuckles you already have.
They were all built with marine grade aluminum and anodized
to protect the alloy - very good stuff! He designed all the fittings
to make made sure we had the dimensions needed for Dynex Dux.
It is important not to bend this rope to tight. Hampidjan recommends
five to one as a minimum for static ratios and ten to one for
dynamic loads like blocks and halyards. This means the radius
you bend this rope around a fitting cannot be less than five times
the lines diameter.
With the new Colligo fittings available and the rope, I went
to work. The rope is a hollow twelve braid making splicing much
easier than most yacht ropes. I used a locking brummel splice
with a tail buried 72 times the line diameter. The tail length
was determined by break tests run by both John at Colligo and
Brion Toss. The rope is very slippery and will not hold a knot.
They just slip out under load if they are knotted. Brian has a
story of a rigger who tied this stuff up for going aloft. Tragically
the knot slipped and he fell to his death. A long tail on the
bury will insure that I would get the rated strength of the rope.
Tests by John at Colligo and Brion Toss showed if you use a shorter
tail, the rope will break below its rated strength at the apex
where the splice starts.
I had 26 splices in all and I managed to make up my entire rig
in two sessions that covered 11 hours total. As time went on I
got faster at the splicing. I gathered my entire boat’s
rope and fittings needed to rig my cutter. They all weighed in
at 15 lbs!
||This is a shot of me holding all of the new
rig out in one hand.
After I had the old wires off , I weighed them in at 55 lbs.
I took 40 lbs. off my mast up high where it really makes a difference.
The bigger the boat, the bigger the savings. I have a report of
a 66’ schooner taking 600 lbs. off his rig!
John at Colligo has fittings for larger vessels also. The fittings
and Dux have been successfully rigged on a 46’ Cat, and
the previously mentioned 56’ Monohull Schooner. As well,
John reports over 200 boats have now made the switch. The advantages
to synthetic rope over stainless steel wire is many. With the
Terminators and distributors there are no more worries about stress
cracking and corrosion and you can see the entire rope and inspect
for any chaff. It is really nice to hang onto.
A word about chaff. Dynex Dux is extremely hard to cut. The
SK-75 Dynex is used for butchers gloves! Loggers are using it
now for dragging logs across the ground. And I have see horrible
abuse in Alaska in down right ugly conditions. We have switched
every wire on the Alaska Trawler over to Dynex and Dynex Dux.
The stuff is extremely tough. If it were not durable, we would
never use it in the dark of an Alaska winter in the Bering Sea.
It is hard to imagine something like this working. It is hard
to get your head around it. It is a big shift in our thinking
to see a 3/16 piece of rope that will hold 10,000 lbs. Or two
pickup trucks! We are accustom to seeing wire do this, but not
rope! After I had rigged my entire boat with Dynex Dux, I had
a sail maker on board who went out for a sea trial. All day he
kept mumbling to himself and then yelling with a smile “this
stuff acts just like wire” as he yanked and tuned the rig.
As he departed the boat he said, “This kind of advancement
does not happen in the yachting world. It is always the high tech,
expensive and exotic boats that have this kind of advancement.
Here you have super light weight rigging which is much stronger,
something a person can do themselves and it cost no more than
stainless steel wire” (maybe even less).
One of the concerns I have heard as people have looked at the
rig are UV? How does UV effect it? Dynex Dux is rated “best”
amongst the synthetic ropes (certified by Lloyds and other insurance
companies) John at Colligo is conducting tests by taking a rope
each year that has been exposed to 350 days of intense Mexico
sun. The first years break test showed 20% reduction in ultimate
strength. A study conducted on Dux and UV at the University of
Auckland said there is not a big change after the first year.
There is a degradation of the outer coat, but the inside of the
rope is not as effected. Time will tell. I have running backstay’s
that are three years old and I do not see any visible change in
the rope. So far the word is “at least 5 years” but
we need to have it out there for that long to find out.
Covered Dux is available. It is a factory weave applied very
tight over the Dynex Dux. It will increase the diameter only slightly.
This option should remove any doubt about UV or chaff concerns.
By the time I was rigged, Colligo came up with “softies”
which are soft hanks, made from 5mm Dynex. They can be used for
hanks as well as any place you have shackles. I use them now for
attaching all my sails at the tack and the halyards.
My first series of sea trials were a real eye opener. We started
out with very light air and flat sea. The boat ghosted right along,
and as the wind built, we tack back and forth to tighten up the
lee shrouds. Using the dead eye configuration proved to be easy
to adjust the tension. I could do it by hand on the leeward side.
If I needed to tighten up something that was already under a load,
I could attach a halyard and get all the tension I needed. The
boat came alive! I could see the diffrence right off. In light
air there was no more dipping and hobby horsing with the accompanying
reaction back and forth. The energy went to forward drive. The
boat was rock steady and just slipping through the water. Pure
I have recommended to anyone interested in the new synthetics,
(and perhaps a little shy) to give it a try on lifelines.
If you tell someone you want to use synthetics, they will often
say you can’t do that! They will most often be referring
to regular SK-75 (Dynex, Spectra, Amsteel) and tell you that you
cannot use this for standing rigging. They are right! But they
are not referring to Dynex Dux.
The critical factor is sizing the rope to the size of the load.
You have to factor in the constant loads you expect. You size
it so that it is below 15% of the breaking strength. You may end
up with a rope twice as strong as wire, but this will eliminate
creep. This is the constant load, not the occasional peak loads.
I had a well know multihull designer recently tell me it will
not be too long before he stops designing boats with wire!
Read some comments in forums:
And finally, the supplier and engineer behind the fittings.