Jack Lines

[tsimoht]

Forgive this stupid question, but I must ask it. When I was last in Seattle, I was speaking to Brion about Jack Line's, and he said something that I did not understand at the time, but I think like some others I was too confused and embarrassed to ask this question then.

Brion said something like that he would never have jack lines lay flat on the deck. Maybe I do not remember this part well, but he also said something about connecting them to the mast. The thing about this that stands out to me is that every time I have seen jack lines on a boat, whether in some fancy advertisement or on an actual-in-the-world-boat, the jack lines are flat on the deck.

Please help me. I am just confused and when in this state I do not like to pretend to know more than I do.

Anyone?

[Robbie.g]

Just guessing, but Brion may have been expressing the fact that jack lines on the deck have two features;
1. even if your tether (connecting you to the jackline) is the shortest it can be and still enable you to move, it is still long enough that you can still be tipped outside the guardrails.
2. The loads on the jackline and the anchors for such are under considerable load if you tip over the side, especially if the line is pre-tensioned.
I'm presupposing that deck jacklines follow the very common, running down the side decks, fastened at or around the forstay tang and at a padeye aft of the turning blocks.

Whilst a jackline that is inboard, (as near to the centerline of the boat),have some more helpful features; because of the layout of may boats means that the jackline can also be quite high for the first part to the mast, you would therefore have a shorter tether. A solution like this means that in the event of a slip, you would be more likely to stay within the confines of the guardrails, and out of the ocean. Further, as the jack line is split in to 2 (along the lines of cockpit-mast and mast - forestay tang) the forces on the anchors would be lower, as each leg is shorter and the jackline will probably not need to be under the same kind of tension as a deck mounted version.

It's all in the 'Bible'.....

Regards

[tsimoht]

Hello Robbie G.

I appreciate you taking the time. You are right; I should have looked in "the bible". You description makes sense.

Greg

[csandys]

Reading in "Rigger's Apprentice" pg 366, Brion says "Seize a big D-ring to a lower shroud, attach the lifeline to a strongpoint aft, lead it through the D-ring, and make if off forward".

I am a little confused. Like the line runs above the lifelines along the edge and not down the center of the boat. It would seem to me to run it down the center of the boat so it would catch you if you before you go over.

Chris

[Brion Toss]

Hi there,
First, we now seize the D-ring to the upper shroud, in most cases. About chest-high. That way you have a high lifeline in the middle of the boat, where you need it most.
Some folks prefer inboard lines, mounted on the cabin top; this allows a shorter tether, making it unlkely that you will end up in the water, but it doesn't provide a fetch-up-against barrier like the outboard ones.
Johnson Marine is promising to produce a sort of mega shroud cleat, with a hole in it suitable for the jackline. This would replace the D-ring, which can be ... tricky to install correctly. How about if everyone here emails them: info@csjohnson.com. TELL them you want them to produce this item, and soon. I have been pestering them about it for years, but I think they need to hear from the sailing community. Say something like, "I understand that you are considering producing a shroud cleat, suitable for chest-high jacklines. Do it soon."
I am sure that if they get enough requests, they'll get into gear. It might also help to hear from potential vendors of the fittings. Please take a moment to harass them today.
Fair leads,
Brion Toss

[tsimoht]

Hello again,

Okay, I am confused still. I am not meaning to be stupid, but I guess I just cannot help it.

In general I know what a jack line is, and what it is for. Sometimes we use the same term for different meanings, so to avoid confusion, may I define some terms the way I am using them, and if I am using them incorrectly, please someone correct me--please!

All of these are in some way to keep the sailor on the boat, but they differ by place and attachment.

Life lines, the lines, usually wire-rope now (sometimes coated) running bow to stern along the boarder of the boat.

Tether, the line or lines, usually webbing now, connecting the sailor to the boat, usually via a jack line.

Jack line, the line, usually webbing now, running, in part or in whole, from bow to stern, just inside the boarder of the boat or near centre line of the boat.

Please forgive my pedantic character, but I am slowing down, because I want to make sure I understand what Brion Toss just wrote, and I have a similar, but somewhat modified version or my original question:

Firstly, I want to know what it means to provide a "fetch-up-against barrier" as Brion used in his last e-mail.

Secondly, I want to know, still, why you would not want your jack lines running "flat".

I believe Robbie g attempted to answer this question by explaining the force on the jack lines, especially on the anchors, would be diminished by getting them off the deck, but maybe I did not understand as well as I hoped. I was thinking something like the same way the force compressing the mast is diminished by inducing and angle in the shrouds and stays. Am I wrong?

What is the advantage of having them run through a d-ring or shroud cleat? It seems if the jack line does this, then it is necessary to disconnect yourself from it for a moment to reconnect yourself to it on the other side of the shroud. Isn't there a disadvantage to this? I would think you would want to remain attached the entire time.

I realise if you have a double tether then you can always be connected, but many people do not have these, so the danger still exists. Not that this really increases the danger any more than being out in the first place.

I realise people have better things to do than to teach me what should be obvious, but if you have a moment, this would be one grateful man.

Thank you

Greg

[csandys]

I'll second that question.

I "think" I understand the idea of having the jackline elevated, so you don't step on it, and it adds another level of "catching you". The part I question is, if the jackline runs along the border above the gunwales, then if you start to go over, your teather would be slack and not catch you.

Now if you are reaching and on the windward side, then the odds of falling leeward and being caught by the teather makes sense.

I noticed the guys on the Volvo Ocean Race have the jacklines running on the deck close to the gunwales.

Are the teathers only supposed to catch you when you do go over?

[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