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And now for the new Fair Leads. It's a guest column, courtesy of Mr. Pete Scala, one of Ropemaking's Esteemed Elders. This piece was originally written as a letter to "Sail" and "Practical Sailor" magazines, to follow up on recent testing of knots in high modulus ropes. Settle yourselves in for a little science, a little history, and a lot of ropemaking savvy.

The first High Modulus Polymer Fiber 'rope' was sold over 30 years ago, for the Cornell Univ.antenna guy on the Radio Telescope at Aerocibo in Puerto Rico, using the still-experimental DuPont organic fiber they called PRD49. This was the non-conductor they needed, with a high elastic modulus, almost matching steel. Years later it was successfully marketed as Kevlar 49Æ for aircraft composites, canoes, kayaks, etc. This first early application as a rope or cable, was published in the IEEE journal because it replaced a non-conducting glass rope as an antenna guy and was an option to wire rope for tall radio towers and masts.

The high elastic modulus fiber or HMF (21 million psi) was much lighter and cheaper to install on towers, but most Radio Stations chose the lower-cost steel, as did commercial yacht dealers. We could match stainless steel in cost, such as for a 3/8"d 20,000lb BS rope, but steel wire rope was, and still is, the riggers' choice. Instead of stainless steel for standing yacht rigging, the HMF cables can be a lower weight corrosion-proof option.

The terminations for the original Kevlar guys were standard wire rope socket fittings, using a commercial epoxy potting compound, as is used today. The sockets are reliable, and commonly used to calibrate the HMF rope break strengths, though achieving only 80% to 90% of the rope strength determined with eye splices. . The 1970 rope design was a simple parallel fiber with an extruded urethane jacket, comparable to the many miles of parallel polyester balloon tethers produced by our colleagues at Columbian Rope.

While parallel polyester fiber can withstand the internal buckling, High Modulus Fibers, (HMF) , however, are severely degraded by cyclic bending. Parallel yarn construction is therefore not recommended, and certainly not for any running rigging, but for linear tensile applications, parallel or a minimal twist of the yarn is passable. For the skeptic, this design using Kevlar 29Æ has for over ten years been the standard for the Life Lines on the US Navy and Coast Guard ships, replacing Steel. For terminations, the Navy had selected special Electroline tapered split sockets because of the ease and reliability of the assembly on board.

The break strength of a rope or cable is rated by the manufacturers' method of testing, and if you use their socket, splice, spit, rate of loading, etc., then your application will be properly fitted.. What the customer actually does with the rope, is however, quite incredible. Our old friend Frank Haas after 40 years as Chief Engineer at Columbian Rope, spent another 20 years as a consultant and court expert on liability cases . A summary of his law suite cases would be invaluable as illustrations and cautions, matching the maritime law history of what some can do with a ship, much less a lowly 'rope'.

As for Knots - many fishermen tell you their brand of knot is l01% efficient. After over 30 years with the Cortland Line Co., it is proven that with the best of techniques, practices, and TLC, knots will put compressive stress on the fiber line or monofilament, and decrease the operating strength, whether a small leader line or a massive tug rope. Nylon's success is due to its tolerance of surface defects, abrasion and compression. The higher the fiber modulus,the greater the degradation, where fibers rub, run, or cross over.

When the British ICI introduced HMF ropes, they devised their own sockets, and listed their Break Strengths accordingly, using a tapered plug that could be hammered in to compress the fiber ends. . That would sell bigger expensiveropes - but the assemblies were reliable and easy to use at sea.

If you put a knot in the HMF line, however, then it was much like the accepted behavior of a hockle in a steel cable - the big bang and point of failure, whether Kevlar, Vectran, Spectra, Technora, or Zylon (PBO), etc, as well as the hemps or nylon, etc. For any rope, the best termination is a splice, or the swagging for steel wire rope. But when you are in rough waters, in trouble, you use your best sailors with their best knots, and touch your St. Christopher medal as you go below. If you are rigged with the right Safety Factors, and your lines are clear, spliced and well served, you will make port.

The High Modulus Synthetic Fiber Ropes have to be treated much as high strength aircraft parts built with high strength alloys and Safety Factors of 1.1, which means lots of testing after careful design. There are, however, some very large sizes and successes, such as the Vectran bacstay of 150,000 lb. BS for a new giant Trimaran, and conventional half million pound Spectra tugboat ropes. But the customers are pros with deep pockets, careful design, and long experience, plus well-tested prototypes and proof-tested shipments of the ropes, with their terminations.

You do justice in quoting Brion Toss, whose expertise includes splicing steel rigging,the finest combination of low cost and high strength. I first met Brion some 20 yrs ago, splicing steel rope at his bench in an old Odd Fellows Building, in Brooklyn, Maine -- this was way down on Eggemogin Reach, with his faithful great black Newfie at his feet.

Brion has been rightly cautious of the modern materials, much as many trust only wood. HMF ropes have to be treated as expensive Space Age materials, and not like the inexpensive Low Modulus (and very reliable) synthetic fiber ropes:the Nylons and Polyesters (As an aside, the Polyethylene is the lowest cost,and floats, but it both stretches and creeps, and UV destroys it rapidly, yet it is great for lobster traps).

As your article emphasizes, knots detract from the strength of all ropes. While the modern HMF's are ten times the cost, and de rigeur for the top line racing yachts, they require both special fittings and proof-testing. The one application, long past due, is to replace the stainless life lines on the family yacht with its HMF counterpart, which is not a dramatic feature, until your heavy lightning storm. Otherwise , stay with what your sailor knows how to rig, and is most forgiving.The HMF materials have to be treated and tested as if they were exotic alloys of Titanium or Beryllium. Note that most fittings have NOT been designed or tested for the HMF applications. If you splurge on a Vectran Halyard to reduce the stretch or creep, then beef up the shackle and clew, because the tensile load can get much higher, and possibly beyond the winch or mast design.

HMF standing rigging is in vogue, but as a reminder, it is the hull at the mast step that takes the loads. Recall the scene in the last America's Cup that saw the Graphite hull buckle , and the boat sink. Steel rod or HMF stays do not stretch much, while the graphite masts are great in compression, which calls for precise design, testing, and measuring. The ambitious upgrading may have fatal results, and always at the worst times, in storms and races when the stresses are greater than normal. HMF rigging can be very successful and at the cutting edge, but careful safety factors have to be built in,and never with knots.

For the splicing and testing of High Modulus Fiber ropes and cables, such as Kevlar, Vectran and Spectra check out the Web Page: www.cortlandcable.com.

   Fair leads,

      Brion Toss