I sailed in some rough water not long ago. The full 3 to 5 knots ebb current was against 25 knots wind. The sea was about 6 to 8 feet high. Wave splashed all over the cockpit. Although I was on tether, I grabed the life line as hard as I could. However, my skipper told me, the life line could snap and throw me into the water. Anybody knows the strength of the 3/16" steel life line or heard of the similar things about life line snaped in storm? Thanks Frank
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Don Evans
Lifeline Wire
The breaking strength of 3X16" is about 4700 lbs. But thats in a perfect world. I have read from others that usually the fittings snap before the wire, as swaging can reduce the strength by 20 to 30%. Also the stanchions can snap and bend before the wire snaps. Lifelines, especially vinyl covered tend to be ignored so there integrity can be lost long before anyone remembers to replace them. I replace mine evertime I replace my standing rigging (about every 10 years). Don
The breaking strength of 3X16" is about 4700 lbs. But thats in a perfect world. I have read from others that usually the fittings snap before the wire, as swaging can reduce the strength by 20 to 30%. Also the stanchions can snap and bend before the wire snaps. Lifelines, especially vinyl covered tend to be ignored so there integrity can be lost long before anyone remembers to replace them. I replace mine evertime I replace my standing rigging (about every 10 years). Don
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Rob
Life line snapped
Frank,,,as far as Im concerned, they are there as a last resort..... We bought our 46' morgan last December....I was going over things in the cabin while our surveyor was reviwing things on deck ..The owner was just telling me that he had 2 new life lines in a box in the forward berth but had not installed them yet.....He had been using an awning attached to the life lines.after awhile it cut through the vinyl coating so he was hesitant of the load capability...........WELL As we were talking away.....our broker yells for help on deck!!! Our surveyor had tested the life line with his full weight and did not expect what happen to happen...........IT SNAPPED....and over he went....water was about 50 degreesand air temp under 30 degrees.......well we had a quick man over board drill........needless to say, I negotiated...ALL new life lines....... I consider them a last resort and check them and their connections often for wear.
Frank,,,as far as Im concerned, they are there as a last resort..... We bought our 46' morgan last December....I was going over things in the cabin while our surveyor was reviwing things on deck ..The owner was just telling me that he had 2 new life lines in a box in the forward berth but had not installed them yet.....He had been using an awning attached to the life lines.after awhile it cut through the vinyl coating so he was hesitant of the load capability...........WELL As we were talking away.....our broker yells for help on deck!!! Our surveyor had tested the life line with his full weight and did not expect what happen to happen...........IT SNAPPED....and over he went....water was about 50 degreesand air temp under 30 degrees.......well we had a quick man over board drill........needless to say, I negotiated...ALL new life lines....... I consider them a last resort and check them and their connections often for wear.
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Jeff G.
Strength of wire can be decieving
Due to the way life lines are rigged and the method you applying weight, your weight is amplified greatly. When ever weight is added to a line under tension and the angle between the weight an the support is greater than 45 degrees, you are amplifying the tension on the wire. As the wire approaches being straight the tension approaches infinity. Not only that, you are not a static weight. When you hit the lifeline, chances are you are moving. When you initially hit the lifeline there is a shock load that doubles the impact force plus the energy of your movement. So a 200lb person could easily impart a force of 1000lbs if tossed against a life line. For static life lines in my industry, a taught steel cable to hook a safety line to has to be 1/2" steel if it a horizontal cable. Of course there is a hefty safety factor built in. Keep your safety lines in good shape. If you can live without the coated cables you will be better off. The vinyl coating locks in moisture and prevents you from seeing any degredation in the cable.
Due to the way life lines are rigged and the method you applying weight, your weight is amplified greatly. When ever weight is added to a line under tension and the angle between the weight an the support is greater than 45 degrees, you are amplifying the tension on the wire. As the wire approaches being straight the tension approaches infinity. Not only that, you are not a static weight. When you hit the lifeline, chances are you are moving. When you initially hit the lifeline there is a shock load that doubles the impact force plus the energy of your movement. So a 200lb person could easily impart a force of 1000lbs if tossed against a life line. For static life lines in my industry, a taught steel cable to hook a safety line to has to be 1/2" steel if it a horizontal cable. Of course there is a hefty safety factor built in. Keep your safety lines in good shape. If you can live without the coated cables you will be better off. The vinyl coating locks in moisture and prevents you from seeing any degredation in the cable.
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Gord May
lifeline Stength...
JEFF G. I had a litlle difficulty understanding your “Strength of Wire..” posting. I know how hard it is to write a clear & concise technical treatise - so I’ve summarized my understanding of Wire Rope Applications, for your comment, critique, or correction: Assuming a 3/16" Diameter Stainless Steel (304) Wire Rope of 7x17 Construction: Breaking Strength (Tensile Strength) = 3,700 Lbs. TS ÷ 5 = WLL Safe Working Load (Working Load Limit) = 740 Lbs. A WLL of 740# ÷ a 200# Man would safely arrest a fall of about 3.7 feet - a fair compromise between the the worst that could happen, and the likeliest short-fall situation. Machine Swagged or Swageless (Norseman, Sta-Lok) Terminals develop the full 100% of rope strength (hand crimped terms develop about 65-70%). Lifelines are horizontally supported through 360 degrees. Recoil force primarily applies to lines with appreciable stretch, such as Nylon, Dacron, Poly’, etc. Wire rope has no appreciable stretch over moderate distances. Hence, the 45 degree loading prohibition does not exactly relate to lifeline applications. The likleiest failure mode might occur through the Stanchion Support System (bent/broken tube, bases or fastenings) - not the wire line. The construction industry typically uses ½" galvanized plow steel 7x19 wire rope, vertically supported at 30 Ft. centers, with a 4700# TS, and permitting or requiring: Permits a 15" Sag over 30' span Permits a vertical fall distance of 5 Ft (strait down) Requires a capacity of twice the anticipated dynamic load. A professional Engineer can design & test (and “Seal”) of “other” specifications. I’m not certain that Construction Static Lines and Boat Lifelines compare well. *OMO* Regards, Gord
JEFF G. I had a litlle difficulty understanding your “Strength of Wire..” posting. I know how hard it is to write a clear & concise technical treatise - so I’ve summarized my understanding of Wire Rope Applications, for your comment, critique, or correction: Assuming a 3/16" Diameter Stainless Steel (304) Wire Rope of 7x17 Construction: Breaking Strength (Tensile Strength) = 3,700 Lbs. TS ÷ 5 = WLL Safe Working Load (Working Load Limit) = 740 Lbs. A WLL of 740# ÷ a 200# Man would safely arrest a fall of about 3.7 feet - a fair compromise between the the worst that could happen, and the likeliest short-fall situation. Machine Swagged or Swageless (Norseman, Sta-Lok) Terminals develop the full 100% of rope strength (hand crimped terms develop about 65-70%). Lifelines are horizontally supported through 360 degrees. Recoil force primarily applies to lines with appreciable stretch, such as Nylon, Dacron, Poly’, etc. Wire rope has no appreciable stretch over moderate distances. Hence, the 45 degree loading prohibition does not exactly relate to lifeline applications. The likleiest failure mode might occur through the Stanchion Support System (bent/broken tube, bases or fastenings) - not the wire line. The construction industry typically uses ½" galvanized plow steel 7x19 wire rope, vertically supported at 30 Ft. centers, with a 4700# TS, and permitting or requiring: Permits a 15" Sag over 30' span Permits a vertical fall distance of 5 Ft (strait down) Requires a capacity of twice the anticipated dynamic load. A professional Engineer can design & test (and “Seal”) of “other” specifications. I’m not certain that Construction Static Lines and Boat Lifelines compare well. *OMO* Regards, Gord
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Paul K
US Sailing/USNA study
USSailing has a link on their website to a study done by the Naval Academy on lifelines pertinent to this discussion.
USSailing has a link on their website to a study done by the Naval Academy on lifelines pertinent to this discussion.
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