Staying with Synthetics

Discussion in 'Boat Design' started by jmolan, Sep 4, 2009.

  1. jmolan
    Joined: Dec 2008
    Posts: 66
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    Location: Mexico/Oregon/Alaska

    jmolan Junior Member

    From the Bearing Sea to a Searunner

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

    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 40 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.
    Lightweight, durable, do it yourself, and comparable costs to wire. 1/3 the cost of exotic PBO or carbon fiber rigs. All of this is now available to the multihull sailor. What is this stuff? How is this possible?

    Using Dynex Dux synthetic fiber ropes to replace stainless steel wire.

    My own experience with synthetic ropes goes back 8 or 10 years. I am Capt. on a 125’ Bearing Sea Trawler. Our range of work consists of deploying huge nets and retrieving them with huge loads of fish. If you have see 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 lb. 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 Capt. It is my responsibility to be very vigilant and keep the crew safe, and to 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 Bearing Sea Pollock fisheries is one of the healthiest in the world. It is 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. It is heavy equipment operation, out at sea. All of these winces required wire of one size or another.
    We were introduced to new fiber ropes to 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 Bearing 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. Nothing to rub on, no heavy loads, 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 50-ton Pullmaster winch. This is the main-winch that makes the initial lift of 150 tons bag of fish up the ramp in very frequent 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 ask him why, he said “you guys load your cargo out at sea”. We had a newer new material called Dynex Dux for this job. They were claiming twice the strength of wire 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), we watched for any nicks or cuts, anything that would indicate a failure was coming on this all important piece of equipment. Any sign of it breaking? 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 50-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, the covering etc. of the rope, were unfounded but the winch drum cracked! We had wire on this winch for 15 years and 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, we were safer than before. Wire would stretch or crush under a load, 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, and 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 3 to 1 margin. In other words the Dynex Dux would last 3 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 Bearing 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, less cost)
    All the same fibers start out as UHMWPE (Ultra high molecular weight polyethylene). Manufactured in only two places in the world. DSM of 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 50-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 3 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 12 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 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 12 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) the same 5mm, when it is converted to Dynex Dux has a breaking strength of 10,400 lbs. a huge 48% increase in strength without increasing the diameter of the rope. And 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 etc. Lots of wires to change out. 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 breaking strength A similar size rope is 7mm Dynex Dux which has a breaking strength of 15,000 lbs! I could see all this, I knew I was onto something here, but I needed the help of a good engineer.
    Enter John Franta. My friend John in San Carlos Mexico 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 5 to 1 minimum. So a radius 5 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 give 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 fittings to make made sure and have the dimensions needed for Dynex Dux. It is important not to bend this rope to tight. It looks like rope, and feels like rope, but is almost twice as strong as SS wire for the same size, and you cannot bend it too tight. Hampidjan recommends 5 to 1 as a minimum static ratios, and 10 to 1 for dynamic loads like blocks and halyards. This means the radius you bend this rope around a fitting cannot be less than 5 times the lines diameter.
    With the new Colligo fittings available, and the rope, I went to work. The rope is a hollow 12 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. Very important not to tie this stuff like regular ropes. Brion has a story of a rigger who tied this stuff up for going aloft. Tragically the knot slipped and he fell to his death. It looks like rope, feels like rope, but is not rope. Not like we are used to thinking of rope anyhow. 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, 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 SS wire is many. With the Terminators and distributors there are no more worries about stress cracking and corrosion, 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 Bearing 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, not this small of a 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, 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, exotic boats that have this kind of advancement. Here you have super light weight, much stronger, something a guy can do his self, and it cost no more than SS wire” (maybe even less)

    Some of the concerns I have heard as people have looked at the rig are. UV? How does UV effect it with? Dynex Dux is rated “best” amongst the synthetic ropes. (certified by Lloyds, the insurance company’s like that) 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. Year number two is coming up for the next test. A study conducted on Dux at the University of Auckland on UV say there is not as big of a change after the first year. There is a degradation of the outer coat, and the inside of the rope is not as effected. Time will tell. I have running backstay’s that are 3 years old and I do not see any visible change in the rope. Same color and slick properties. I have had rope two years old that I have re-spliced and could see no difference. So far the word is “at least 5 years” but we need to have it out there for that long to find out.
    And now there is covered Dux available. It is a factory weave applied very tight over the Dynex Dux. It will increase the diameter only slightly. The 7mm Dynex Dux will be 8.6mm. 8.6mm is close to ¼”wire in size, but is over twice as strong. This option should remove any doubt about UV or chaff concerns.
    The strengths and properties that Hampidjan have posted are certified by Lloyd’s and are the only ropes to have this stamp of approval.
    I originally went with 7mm rope for all my stays, and went with 9mm for the head stay and stay sail stay. By going up a small increment I gained a huge jump in strength .7mm Dux is 15,000 lbs. Strength and 9mm Dynex Dux has a breaking strength 27,500 lbs! One reason for going up one size, I was concerned about chaff, as I have bronze hanks. I thought I would gain a lot if there was chaff problems there. 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. No more fumbling with a SS shackle to secure a halyard to the sail. No more getting whacked in the head by that heavy, hard thing!
    I have replaced all my SS shackles under my blocks. Heck they are slick enough I am even using them in place of blocks on my bows for the anchor bridal! I anchored for 3 months with no visible wear on the “softies”. I am really trying to abuse the stuff, to see just how much wear and tear they can take. So far so good. The material will flatten under a load, but you can “massage” it back to life with little effort. No more paint being rubbed off by steel shackles, I like that.
    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 need.
    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 fwd. drive. We built to 8 kts. of boat speed with a drifter and mainsail up. 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. You can remove a bunch of weight with just this one change. It is fun to weigh the difference. The rope is 1/9 th the weight of similar sized wire, and almost twice the strength!
    Running back stays would be another good place to start with Synthetic Ropes.
    Some important points. 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. It comes from the commercial fishing industry. It is not yet well known in the Yacht world. It is heated and stretched. It is much different, but it looks the same! And much the same way you can harden and strengthen steel, they have done the same with this base material SK-75.
    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.
    Let’s use my Searunner and the 7mm Dynex Dux for an example. The breaking strength is of 7mm Dynex Dux 15,500 lbs. The 15% mark is 2,325lbs. As long as the constant load or pretension is under 2.325 lbs. my shrouds will never creep. In fact tests have shown that it will creep less than SS wire! It is the incredible strength that gives you such a huge margin of safety. Twice the breaking strength at 1/9 the weight!
    So that is it. That’s my story, from the Bearing Sea, to the Sea of Cortez. What I have learned from this very enjoyable project.
    You can do it your self, 1/3 the price of PBO and other exotics, more durable, lighter by a huge margin over wire, and available to the little guy. I have shed serious weight from up high where it really counts. The boats motion and handling have improved dramatically. What’s not to like?
    I had a well know multihull designer recently tell me it will not be too long before he stops designing boats with wire!

    Some questions

    How tough is it, will it chaff?
    Dynex Dux is tough. It certainly is not steel but it is the toughest synthetic
    line available. The hardest part about splicing this line is cutting it. Many sailors
    are using Dynex Dux for forestays with Bronze Hanks.
    The lashing tensioning system really does not look safe or easy to use to me. Can I
    use turnbuckles for tensioning?

    Yes, you can use conventional turnbuckles for tensioning. We can now splice and
    pre-stretch any length to within 5/16 of an inch. If a more precise method of
    tensioning is needed, than turnbuckles are the way to go. In addition, we have
    designed the line terminators to fit certain production turnbuckles.
    Lashings do have their place though. Literally, all of the sailors that have
    purchased from us that were skeptical about using lashings have become
    comfortable with them after using them. The weight advantages over turnbuckles,
    along with the cost of replacing turnbuckles, make lashings more attractive.
    I have heard that Dynex Dux will deteriorate in the sun very quickly due to UV
    degradation. How often will I have to change my standing rigging due to UV

    The base fiber for Dynex Dux is Dyneema SK-75. It is widely known as the best
    synthetic fiber for UV resistance. Having said that, we like to work with real
    numbers, so we are doing an ongoing UV study on our boat in Western Mexico
    (where it rains about 3 days a year).
    In addition, a study was completed by the University of Aukland several years ago
    that showed some initial UV damage occurrs externally, causing the outer layers to
    become relatively opaque to UV, and then the rate of damage decreased.
    With the data we have today, we can easily predict a life of 5 years or more for UV
    exposure. This compares to an 8 year recommended replacement interval for steel.
    We also believe, as new data comes in, that the life expectancy will go up.

    This from the manufacters
    DSM Dyneema is the inventor and manufacturer of Dyneema®, the world’s strongest fiber™. Dyneema® is a superstrong polyethylene fiber that offers maximum strength combined with minimum weight. It is up to 15 times stronger than quality steel and up to 40% stronger than aramid fibers, both on weight for weight basis. Dyneema® floats on water and is extremely durable and resistant to moisture, UV light and chemicals. The applications are therefore more or less unlimited.

    Dyneema® is an important component in ropes, cables and nets in the fishing, shipping and offshore industries. Dyneema® is also used in safety gloves for the metalworking industry and in fine yarns for applications in sporting goods and the medical sector. In addition, Dyneema® is also used in bullet resistant armor and clothing for police and military personnel

    Spectra® fiber is one of the world's strongest and lightest fibers. A bright white polyethylene, it is, pound-for-pound, fifteen times stronger than steel, more durable than polyester and has a specific strength that is 40 percent greater than aramid fiber.

    Spectra® fiber a polyethylene fiber that is produced using a patented gel-spinning process. Polyethylene is a remarkably durable plastic, and scientists at Honeywell have captured the tremendous natural strength in the molecular backbone of this everyday plastic to create one of the world's strongest and lightest fibers. The gel-spinning process and subsequent drawing steps allow Spectra® fiber to have a much higher melting temperature (150°C or 300°F) than standard polyethylene.

    With outstanding toughness and extraordinary visco-elastic properties, Spectra® fiber can withstand high-load strain-rate velocities. Light enough to float, it also exhibits high resistance to chemicals, water, and ultraviolet light. It has excellent vibration damping, flex fatigue and internal fiber-friction characteristics, and Spectra® fiber's low dielectric constant makes it virtually transparent to radar.

    Spectra® fiber is used in numerous high-performance applications, including police and military ballistic-resistant vests, helmets and armored vehicles, as well as sailcloth, fishing lines, marine cordage, lifting slings, and cut-resistant gloves and apparel. Honeywell also converts Spectra® fiber into the Spectra Shield® family of specialty composites for armor and other applications.

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