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Old 18-04-2011, 03:31   #16
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Re: Knot Question - Spectra Life Lines

However you decide to attach the spectra, I think you will need to test it as you are trying something relativity new.

I like the idea of several (say 4 or 5) turns around the stanchion and then tied off. I would trial the "knot" and then take the line off to your biggest winch (via a fairlead if necessary) and load up the line and "knot" until something gives - lets hope it isn't the stanchion (but I am sure you would stop before that happens).

Perhaps try it on the 6 mm line first.

Another thought is to tension it up very very tight with the winch and then whack it with something big and heavy to simulate a shock load.

At least you then know what the weakest link is!
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Old 18-04-2011, 04:45   #17
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Re: Knot Question - Spectra Life Lines

Quote:
Originally Posted by estarzinger View Post
Interesting idea. I can easily cover the lines for the shrinking but I am not sure how well that will protect them from the heat. Spectra melts at 150c and shrink wrap shrinks at 100c. Thoughts?



Yes, I decided I did not want to do that - might create a stress riser and weaken the tubes. I may just spray on a little contact cement - can't hurt.



Useful perspective. Quite different than the typical marine rigger thought that one should avoid knots in high modulus line at all cost. Not sure why the difference. The difference in perspective - thoughts?

I actually use the fisherman to make small spectra loops on the boat, when they are too small to make the bury. I have never had one break but don't use them in highly loaded applications. But the fisherman can jam under load and be hard to untie (in my experience), so I don't think its the knot.



Don't think that helps, as the splice will not pull thru the stanchion holes, which is the objective.



Yes, exactly. I have a decent radius . . . 32mm tubes and 8mm (top) and 6mm (bottom) lines so I have 4x for the top line, which is just about right. So, my 'only' concern was whether the 'knot' creates a stress riser where it joins the loaded part of the line.

Yes, the knot will jam if under high load, but why should that happen? Lifelines should go many seasons without a load high enough to cause jamming. Perhaps wrapping the line around the tube a few times would reduce that tendancy. My concern is that with Amsteel a knot that is both jam-proof and slip-proof may be hoping too much. I just don't know.

Climbers tend to use knots for 2 reasons: a splice on the end of a rope would make it impossible to pull the roe through gear or to pull it up a crack-ridden cliff without jamming; rigging often has to be modified in the mountains and splice are rather permanent.

However, where permanent conections are acceptable, sewing or splicing are prefered because they are more compact than suitable knots, not so much because they are more secure. In my mind, splicing is important where the ultimate strength of the line will be tested--standing rigging--but not so much were failures are by chafe. Climbing ropes don't fail at knots or at random, they fail where the rope runs over a sharp edge.
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Old 18-04-2011, 21:30   #18
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Re: Knot Question - Spectra Life Lines

Evan
This is what i have contemplated for my lifelines, although I wanted them to be removable just to remove them in the off season.

I planned on a clove hitch around the tubing (within the bounds of the attachment bracket so it would stay in place), and then continue around the tube and finished off with 2 or 3 or 4 half hitches, and then seized. This is how I've secured my amsteel jacklines, but there around 1 1/2 inch tubing. If you tension from the other end, you will soon find if you need additional wraps.

Let us know what you do and how it works out.
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Old 19-04-2011, 03:22   #19
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Re: Knot Question - Spectra Life Lines

Someone suggested that this thread had become over engineered. I think so ! If I was doing this - it would be the splice and hard eye in one end, and a round turn or 2 to get the required tension, with a couple of half hitches. Knot going anywhere, as we say !
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