SailNet Community

SailNet Community (http://www.sailnet.com/forums/)
-   General Discussion (sailing related) (http://www.sailnet.com/forums/general-discussion-sailing-related/)
-   -   Jackline system (http://www.sailnet.com/forums/general-discussion-sailing-related/98999-jackline-system.html)

Joel H. 04-29-2013 09:45 PM

Jackline system
 
5 Attachment(s)
After reading everything I could on safety harnesses and Jacklines, (with the conclusion being to stay out of the water and on deck), I came up with a system to allow me to move about my 27' Catalina while assuring that I cannot end up overboard. (It's not easy on a small boat like mine to have a workable system that won't end up being too loose/long to actually keep you on deck).
Anyway, attached are some photos of my system for tensioning a jackline on the centerline of my boat regardless of weather the hatch is open or closed, or any other variable. Also, I can use the same type of device to make my lanyard adjustable to be able to shorten or lengthen it as necessary, while moving about.

The neat little device you see in the pic that makes it all possible is from the mountaineering world and is called a "TIbloc" They work with a carabiner and any reasonable size line to lock the line at any point, (like a Jumar).
I welcome any thoughts or criticisms.
I won't bore everyone by describing every fixture, I'm hoping that the photos will be self explanatory. But if it interests you I will answer any questions.
Joel H.

Faster 04-29-2013 10:04 PM

Re: Jackline system
 
I'd suggest you use webbing rather than line.. it doesn't 'roll' underfoot like rope can.. also if you put a lot of twists in the webbing it's much easier to 'snag' when you want to clip in. (webbing lying flat on deck can be difficult to get a shackle/snaphook underneath it) Stretching the whole package up off the deck a bit helps too.. your setup may work well with that.

Joel H. 04-29-2013 10:24 PM

Re: Jackline system
 
1 Attachment(s)
Oh, yes the pic doesn't show it but the line/adjuster is only at the companionway it is webbing from there foreword. I like your recommendation for twisting the webbing, thanks.
I highly recommend people check out these "Tiblocs" made by Petzl. They are cheap and quick to attach to a line for any reason, as well as ascending the rig. They seem like great emergency gear.
Cheers,
Joel H.

RichH 04-30-2013 11:05 AM

Re: Jackline system
 
The problem with tubular or flat double or triple ply webbing is the undue stretch that occurs under (shock) load when wetted. For 'climbing' this is good as it adds 'shock resistance' during impact (increases the 'time' of the impact); but, on a boat may cause the geometry to cause one to 'rebound' outside the limits of the lifelines.
In mountain rescue we hardly ever use 'webbing' for situations where the 'tether' attachments are at near horizontal and where the impact loads are perpendicular to the restraint line (ie. Tyrolean Traverse, etc.), we use 'rope' for all 'horizontals' (a similar config. to the jacklines set on boats); plus, all such 'traverse' lines are always set up 'slack' and allow a LOT of stretch so that the trigonometry of configuration does not develop infinite force in the traverse lines. If such a line is 'taught' and you push/pull at 90į to the run of the line and the line does not 'stretch', the force can be multiplied many times (can approach infinite force) that of the applied perpendicular force. In trigonometry, such a situation would be equal to "dividing by the trigonometric SINE of the deflection angle" of the line from its attachment point ... Inotherwords, apply force at 90 degrees to a very taught line and the attachment connections of that very tight line can possibly develop forces that approach INFINITY, which can break the rope, pull the connections out, etc.

The good thing with webbing used as jacklines is that the stretch upon impact, etc. allows the attachment angles to increase to comparatively very large angles with a corresponding lessening of the induced tension developed in the 'rope'/webbing. The downside is when webbing becomes wetted and unduly and increasingly stretches and you 'can' have a functional failure .... your body at full impact load can now be beyond the boundary of the deck.

Simple speak Rx: when setting up webbing jacklines on a boat, run them across the cabin top instead of the deck and leave them slightly 'slack', NEVER bar-tight!!!!!! Wet them thoroughly and TEST them with your body weight (impact) to be sure that youre getting large angles of deflection from the axis between the connection (to the boat) points when fully loaded by impact of your body weight perpendicular to the 'run' of the jackline .... but test them and adjust them so that the 'stretch' that occurs, keeps you onboard. When testing, If little 'stretch' occurs in the jackline and the connection 'angles' remain less than ~10į when you (test) impact, you risk pulling the connection points out, due to the possibility of the generation of infinite force along the axis of the webbing. Rope/wire cable doesnt stretch like webbing, so you have to set up with more 'slackness'.
I use a tether with three connections: one to the harness, a connection at the terminal end of the tether (in the cockpit usage), and one close (about midway) to harness for moving along the deck.

;-)

Barquito 04-30-2013 01:20 PM

Re: Jackline system
 
How does is work when the hatch is closed? Would is tend to push the hatch open again? Is is difficult to get through the hatch?

dvuyxx 04-30-2013 01:33 PM

Re: Jackline system
 
Which is preferable? A life vest with the harness built in our a separate harness?

BayWindRider 04-30-2013 02:11 PM

Re: Jackline system
 
I also use a jackline system while onboard my Catalina 27. I crisscross two 30ft sailboat jackline straps (steel hooks on one end) that are attached to the pedestal and the bow cleats. If itís really bad weather I can attach the stern straps to the stern cleats. I use to repel in the Army so I donít trust a PFD with a steel ring as much as a dedicated harness. Heck, I still remember how to tie a swiss seat for repelling, but I wouldnít want to be dangling from it for any period of time. I use the mustang sailing harness and feel itís pretty comfortable under load. I also use the Stearns SoSpenders tether that attaches to the jackline and the mustang seat. This tether has a quick release that you can untether rapidly. The jacklines run along the inside of both deck handrails. I find this system adequate and really love the extra protection while taking down the mainsail in a chop. I do recommend that you test your system out while at the dock. This way you can adjust how far will it stretch under load, how the seat feels under load, and if any parts of it fail.

BayWindRider 04-30-2013 02:15 PM

Re: Jackline system
 
Quote:

Originally Posted by dvuyxx (Post 1023410)
Which is preferable? A life vest with the harness built in our a separate harness?

I would say harness since I wouldn't want a vest to support my body weight. If your hanging from a vest the weight will be at your armpits. The harness would shift the weight to your hips freeing your arms to pull yourself up. Just my .02 cents.

jimgo 04-30-2013 03:46 PM

Re: Jackline system
 
I think the idea wasn't that this was just a life vest, but rather a vest with the harness built in, like these:
Mustang Deluxe Inflatable Life Jacket / PFD with Harness

TakeFive 04-30-2013 04:09 PM

Re: Jackline system
 
OK guys, I have NO experience with clipping in, but I will be singlehanding this weekend so I've been studying up.

There is a real problem on the 27' and smaller boats with getting a tether that's long enough to have room to move around, yet that length allows you to dangle over the side. This is especially a problem on the foredeck where the boat gets narrower.

Some of us who have furlers also have an extra unused halyard from the masthead. What about clipping onto that halyard in addition to a traditional tether when on the foredeck? In the event of a fall, the halyard keeps you from dangling in the water, and the traditional tether keeps you from getting a "wild ride" off the side of the boat if the mast sways in rough water. It seems like the two in combination would be a good combination.

This was suggested to me by a guy on the Catalina 25 forum, who says he read about it in one of the Pardeys' books on cruising. It would seem to me that the halyard would allow you to use a longer tether on the bow.

What do you guys think?


All times are GMT -4. The time now is 12:00 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012