Jack Lines

[tsimoht]

Hello again,

After having thought about it some more and after reading csandy's response, I understand now what Brion meant by "but it doesn't provide a fetch-up-against barrier like the outboard ones". Thank you Chris.

I can also see why it is an advantage to have them higher and not flat on the deck for this fetching purpose.

I do not see how these are any more 'out of the way' and not going to be something onto which you can snag yourself than the ones on the deck. You only snag yourself in a different part of the body: the neck instead of the ankle.

So I still do not see the advantage.

Please understand I have read and worked installing things on boats, and know that any decision of placing anything on a boat is a compromise. I am not trying to be difficult. I just know that there are people who know more than I. I am trying to understand. I am trying to learn.

Thank you,

Greg

[Brion Toss]

Hi again,
No offense taken; sometimes I take too much for granted. So let's back up a bit.
The reason we have any sort of jackline or tether or lifeline is that, at some point, sailboats were losing too many crewmembers. Even on big ships, in storm conditions, some form of lifeline would be rigged, if the captain had any sense. The best lifelines would be at least chest-high, because it is difficult to fall past these. But it's not practical to make stanchions this long on small craft, so what we get are those knee-high things. Better than nothing, and they've stopped many a sailor from washing overboard, but obviously we can do better.
That's where on-deck jacklines come in. The early ones were of wire or rope, but it was found that these rolled underfoot, which is why they are now usually webbing. But in order to attach yourself to these you need a tether that reaches comfortably from your harness to the deck. And this tether is then long enough to allow you to fall completely over the lifelines and into the sea, where you might find it difficult -- or impossible -- to get back aboard before you drown. Again, these jacklines are better than nothing, but I believe we can do better still.
Hence the chest-high alternative. The height of the middle portion, where one is most vulnerable, is much better at keeping you inboard. The shortness of the tether means that even if you managed to get past the jackline you couldn't fall far. And the shortness also means that if you are thrown across the deck you can't build up as much speed, making for a dramatically decreased shock load when you fetch up.
To make this work best you need a double tether. I don't see this as a deal breaker, considering the advantages.
Of course, there is a lot to be said for at least pretending that there are no lifelines or jacklines aboard, so you don't get careless.
I hope this make the system clearer.
Fair leads,
Brion Toss

[tsimoht]

Hello again,

I appreciate your patience with me, and I appreciate your answer. It does make sense. I can see the advantage of the shorter tether (so the ol' 9.8m/s squared does not get a good chance of taking hold) and the higher jack line (so they can be fetching (I love this part)). Thank you very much for the well thought out answer and the time.

I truly like this site. I learn great deal from you all. I am glad you are here.

Greg

[Auspicious]

Originally Posted by Brion Toss

Of course, there is a lot to be said for at least pretending that there are no lifelines or jacklines aboard, so you don't get careless.

Indeed. Thus my practice of going forward on the windward side whenever possible. I'm also not shy about crawling when conditions are poor.