lifelines
- Thread starter Ken13559
- Start date
There is an artical in Sail magazine re lifelines. I think that it said that suspendings an 11lb. [5kilos] should cause a sag of about 2 inches. Practical sailor also had antical. But it was more on the new Denema lifelines.
The important thrust of the artical is that the uprights holding the lifelines be designed to break or bend at about 1200 lb. Otherwise they will rip a hole in the deck.
The wire lifelines are about 3000 lb. The fabric lifelines are about 8000 lb., so either kind will work. I redid my wire lines in Denema myself. It's a good job to do in the winter. C.S. Johnson now makes the fittings for fabric. However all you really need are a couble end pieces for your old fittings, i used a produce called Splicing Nuts instead of splicing. I have a description on this site a couple of years ago. Look up lifelines.
The rule most commonly referenced, and what the PS article was based upon, is the IASF Off-Shore Special Regulations. This version listed below is for near shore racing, but other rules are located in the same area.
http://www.sailing.org/tools/documents/OSR2014Mo323122013-[16069].pdf
The lifeline rules are in 3.14. The line for boats up to 43ft must be 4mm SS or equivalent will all fittings of comparable strength, and the line must not deflect more than 50mm under a 4 kilo load. They do NOT need to be tight, they are just trying to limit the tendency of some boats to rig really loose lines so that they can hike further. If you over tension the lines you will bend the stanchions. Just get the slack out.
"The important thrust of the artical is that the uprights holding the lifelines be designed to break or bend at about 1200 lb. Otherwise they will rip a hole in the deck." This is misinterpretation. If you consider the tight rope effect, 1200 pounds is a very easy figure to reach with only a light fall (tension is typically 4-8 times greater than the applied force, and wire does not absorb energy). What they should have said was that the pulpit or pushpit will most likely bend at ~ 1200 pounds (naval academy testing) and that the fittings must be design NOT to pull out of the deck.
What I believe they dangerously misinterpreted was this Naval academy testing, where they demonstrated that the pulpit collapsed at 1200 pounds. Not a surprise for any engineer reviewing a typical railing structure. Too spindly and too much leverage. What the report said, however, is that "Lifeline stanchions, like a rudder stock, should ultimately fail in a bending mode. If they are stronger than the deck or the hull that supports them, the resulting damage is a hole in the boat. The art of engineering and boatbuilding is coming up with structures that answer such complex challenges." The best failure mode is for the railings to bend but remain attached to the boat.
http://www.practical-sailor.com/iss...lifeline-test-reveals-weak-spots_10874-1.html
http://www.practical-sailor.com/iss...lifeline-test-reveals-weak-spots_10874-1.html
http://www.sailing.org/tools/documents/OSR2014Mo323122013-[16069].pdf
The lifeline rules are in 3.14. The line for boats up to 43ft must be 4mm SS or equivalent will all fittings of comparable strength, and the line must not deflect more than 50mm under a 4 kilo load. They do NOT need to be tight, they are just trying to limit the tendency of some boats to rig really loose lines so that they can hike further. If you over tension the lines you will bend the stanchions. Just get the slack out.
"The important thrust of the artical is that the uprights holding the lifelines be designed to break or bend at about 1200 lb. Otherwise they will rip a hole in the deck." This is misinterpretation. If you consider the tight rope effect, 1200 pounds is a very easy figure to reach with only a light fall (tension is typically 4-8 times greater than the applied force, and wire does not absorb energy). What they should have said was that the pulpit or pushpit will most likely bend at ~ 1200 pounds (naval academy testing) and that the fittings must be design NOT to pull out of the deck.
What I believe they dangerously misinterpreted was this Naval academy testing, where they demonstrated that the pulpit collapsed at 1200 pounds. Not a surprise for any engineer reviewing a typical railing structure. Too spindly and too much leverage. What the report said, however, is that "Lifeline stanchions, like a rudder stock, should ultimately fail in a bending mode. If they are stronger than the deck or the hull that supports them, the resulting damage is a hole in the boat. The art of engineering and boatbuilding is coming up with structures that answer such complex challenges." The best failure mode is for the railings to bend but remain attached to the boat.
http://www.practical-sailor.com/iss...lifeline-test-reveals-weak-spots_10874-1.html
http://www.practical-sailor.com/iss...lifeline-test-reveals-weak-spots_10874-1.html
