LESSONS LEARNED WHILE CRUISING Jamie & Behan Gifford


UHMWPE: Hit Me With High Performance Ultra High Molecular Weight Polyethylene


Rope is a four letter word. Splice


has six letters, but brings out four letter words when attempted. On board cruising boats, good old salt soaked, sun-bleached polyester or nylon lines get the job done and, as the saying goes, if it ain’t broke, don’t splice it. But among all of the flashy electronics and go-fast sailing gear, high-tech UHMWPE fiber rope is a versatile solution provider onboard. And it’s easy to splice! Never heard of UHMWPE before?


It stands for ultra high molecular weight polyethylene. Common uses include flexible cutting boards, plastic grocery bags, and fiber for super strong “spectra” rope. Spectra®


(12 strand) weighs 1.7 lbs/100’ and breaks around 8,500 lbs. All this technical mumbo-jumbo is fine but rope with Dyneema® Spectra®


is too expensive for the budget or


than a comparable all polyester double braid rope. In a 100’ halyard, that is a lot more cost. Compared with a low stretch wire-to-rope halyards (which are generally no longer recommended), the cost gap is smaller. Dyneema®


/Spectra® rope is a true


bargain as an alternative to metal wire or shackles. A cost comparison shows ¼” stainless steel wire is roughly 30% more expensive than ¼” single braid Dyneema®


costs for


SK75 (Endura-12 by


New England Ropes or Amsteel Blue by Samson Ropes). The rope value proposition gets better still when you add swage or Nicopress®


, along with


Dyneema®, are in fact brand names of UHMWPE fiber made by Honeywell and DSM respectively. Both companies offer multiple grades of the fiber of increasing strengths. Spectra® Dyneema®


1000 and


in performance rope. Dyneema®


SK75 are the most common and Spectra®


are so


lightweight that they float. They also have good UV resistance and don’t suffer flex or cycle fatigue, compromises found with other high-tech rope fibers: Vectran®


, Kevlar® , Technora® ,


PBO, etc. The strength-to- weight ratio is superior, but the stretch characteristics offer a paradox. They have effectively no elastic stretch, but do exhibit a kind of permanent stretch called creep. Under load the fibers will elongate, albeit a very small amount and very slowly. A basic comparison of


¼” (6mm) diameter materials shows Dyneema®


/ Spectra®


Single braid Polyester rope (12 strand) weighs 2 lbs/100’ and breaks around 2,500 lbs. Stainless steel (316) 1x19 wire weighs 13.5 lbs/100’ and breaks around 7,300 lbs. Single braid Dyneema® 48° NORTH, MARCH 2011 PAGE 30


SK75


minded sailor, right? Yes… and no. A double braid rope with Dyneema® Spectra®


/ core and polyester cover is about 2½ to 3 times more expensive


Niall (age 11) splicing loop from Amsteel (Dyneema®


SK75).


the wire ends versus splicing. Not all applications are suited to rope over metal. In appropriate applications benefits include: •Easy to inspect for problems; stainless steel is not, and can fail with no warning signs.


•Does not corrode or leave stains; stainless steel does. •Easy on soft materials; stainless steel shackles chew up aluminum toe rails, wire pennants chafe lines/sails. •Soft on skin; broken stainless steel wire strands are called “meat-hooks” for a bloody good reason. •Easy to splice yourself (really!); swaging or Nicopress®


ends often require


professional services. On Totem, we use


Amsteel Blue and Endura-12 in a couple of applications. Both brands are single braid, meaning there is no protective cover, so they are a poor choice in high-abrasion applications such as modern cleats (like a rope clutch or cam-cleat). Outhaul: Instead of wire, we use Amsteel / Endura-12


to connect outhaul car (or clew) to the outhaul purchase system. Wire around the sheave is prone to work hardening, causing broken strands (meat-hooks).


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