PS Advisor: 11/01/02
In your September issue, Nick Nicholson discusses the merits of bare wire lifelines and makes some very good points. He also speaks of tensioning with Spectra instead of turnbuckles, which I like. What are your thoughts on using Spectra in place of wire for the lifeline itself? It would be relatively easy to splice eyes on the ends then lash it to the correct tension.
Nick tensions the ends of Calypso's lifelines with Yale Cordage's Pulse, a small-diameter braid with a Spectra core and Dacron cover. He said the Pulse, with enough loops to equal the strength of the wire lifeline, lasts a long time. Pulse comes only in five sizes, from 1/16" to 3/16". (It's $18.50 for a 50' spool of 1/8".)
Let's understand the word Spectra. It's a trade name for a gel extrusion fiber owned by Honeywell, which bought Spectra from the original developer, Allied Signal. Spectra is a very fancy, fine filament fiber that other companies use to make line (and other things).
There are other such fibers with somewhat different specific gravities, breaking strengths, modulus, elongation, and abrasion resistance. Some of them are Vectran, Kevlar, Twaron, Technora, Dyneema, and Zylon. Vectran is owned by Celanese, Kevlar by DuPont, Technora by a Japanese company called Teijin Ltd., Dyneema by a Dutch firm, etc. These continuous fibers often are called HMWPE (high molecular weight polyethylene) or UHMWPE (ultra high molecular weight polyethylene). All are used to make rope and other materials, including bullet-proof vests. Rope makers all have different names, usually trademarked, for line made using these fibers, some of which are coming up here.
(Calling a piece of line "Spectra" is, of course, no more incorrect than calling a piece of cloth "Rayon" or "Cotton." It's the filament or thread that gives the cloth or line its name.)
Considering Mr. Wehr's question, our initial thought was that it would be more expensive to use a Spectra-cored rope for lifelines. Wrong.
Let's ignore the hardware for port and starboard gates. (It would be the same for either wire or rope.) And let's use, as a base, 3/16" vinyl-covered 7x7 wire with a breaking strength of 3,700 lbs. The wire for a 40' boat might cost about $125, but the fasteners—four turnbuckles and four toggle jaws, all machine-swaged—would jump the cost to about $270. Eight machine swages (you wouldn't hand- swage lifelines, would you?) on that size wire would cost about $50, for a total of $320.
If you used rope, you'd need—to get the same strength—something like Yale's 3/16" Aracom T (Technora core, Dacron cover, 4,800-lb. breaking strength) or New England Ropes' 6mm T-900 (Technora-Spectra core, Dacron cover, with a breaking strength of 4,400 lbs.). A hundred feet of Aracom T would cost you about $90. The same amount of T-900 would set you back about $135. So, with the cost of the wire not much different than the line, what you'd save would be the cost of the fittings for the wire. If you did your own splicing and lashing, the rope lifelines would cost less than half as much as wire.
We forwarded Larry Wehr's letter to Nick with the conjecture that, aside from cost (about which we were wrong), Spectra might be less desirable from the point of view of UV damage and abrasion where it passed through the stanchions. Nick chimed in with: "I think the issues with Spectra lifelines would be UV degradation and abrasion, as well as stretch. Wire is probably still best. The short Spectra terminations on the ends cost very little, and can be replaced easily."
Still, we went afield with the letter, talking first to Jay Repass, president of New England Ropes in Fall River, Massachusetts.
"I see no reason whatsoever that line cannot be used for lifelines,” he said. “In fact, the United States Navy is using Kevlar and Spectra-cored line for exactly that purpose. The Navy especially likes its non-conductivity.
"UV degradation is not a problem, as long as the line has a Dacron cover. Halyards are exposed and they last for a long time. Abrasion? Maybe a bit more than with wire. But I doubt that it would be appreciable."
A spokesman for Yale Cordage said we could quote Dick Hildebrand, Yale's vice president of sales, as saying that Aracom T would be fine, too.
At The American Group (the uber-name for Samson), David Krupka, the customer rep for recreational marine products, said to use the company's Amsteel Blue (recently renamed from Spectron 12 Plus). It's made to replace wire. Amsteel Blue, a 12-strand single braid made of Dyneema, has a urethane UV coating.
While it's certainly in the ropemakers' interest to have us all switch to rope lifelines, we think the case for reduced weight, reduced cost, elimination of corrosion, and increased "comfort" is strong. A bonus: You could have colored lifelines... maybe one red and one green? Too busy?