New super strong ropes find their way from extreme duty in the World’s worst sea conditions to replacing traditional rigging wire on a cruising trimaran.

By Jack Molan -San Carlos, Sonora - Mexico

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 none.

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 specs.
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 Joy!

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!

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And finally, the supplier and engineer behind the fittings.





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