Using a rope shackle for the jib

Moderator: GreenLake

Using a rope shackle for the jib

Postby GreenLake » Tue Oct 05, 2010 11:30 pm

The clew of the jib is often tied into a knot at the middle of the jib sheet. Simple and effective, but you need to completely remove the jib sheet when you want to remove the sail.

You could tie a loop in the middle of the jib sheet, and use a shackle to connect to the clew. Works, but now you have a piece of metal flying about when the sail flogs.

Alternative is a rope shackle. There are different designs. I made mine from a short length of Amsteel which is very light, even at a bit larger diameter, and easy to splice and knot. I put an eye splice at one end, and a manrope knot at the other end. That sounds more complicated than it is - if you want to fill a rainy evening with it, better make some for your friends as well.

When I push the knot through the splice, I have a loop, and any amount of tension will lock it (I made my eye splice tight enough that it takes some force to push the knot through, but that might not be necessary).

Anyway, that forms a loop. To tie the loop to the jib sheet, I use a Prusik knot, which is not one of the standard sailing knots, yet really easy to tie. A Prusik knot is a sliding knot, remotely related to the rolling hitch, but symmetric.

Now all I need to do to attach my jib is to push the eye splice through the clew cringle, and lock it with the toggle. I can leave the jib sheet rigged - which not only saves time, but allows the crew to remain on the deck for the entire operation - no more crawling all over the boat to find the ends of the jib sheets and undo the figure eight knots :)

Because the Prusik knot could slide when not loaded, I marked the center point of the jib with tape, but it's stayed put so far.
~ green ~ lake ~ ~
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Re: Using a rope shackle for the jib

Postby Tipster1 » Sun Sep 22, 2013 8:11 am

Would you mind posting a photo? Thanks?
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Re: Using a rope shackle for the jib

Postby GreenLake » Sun Sep 22, 2013 4:20 pm

That was an early effort, so I'm not keen on memorializing it in any way :D .

Also, I have since found an excellent site: l-36.com where you can find quite detailed instructions on making a better rope shackle. Instead of a manrope knot, they use a diamond knot (they are a bit related, but the diamond knot is the better choice) and their "eye", while not more difficult to make, can be opened when slack and slides shut under tension. This one is worth adding to your "kit".

When you close a rope shackle, you have a loop. With that loop you tie a Prusik knot around the middle of your (single piece) jib sheet. If you look this link, that should give you an idea - it's a dead simple knot. If that link doesn't do it for you, look for the use of Prusik knots/loops in climbing on google.

All you do after tying, is to position the part of your shackle that can open so that is in the middle of the loop that's formed after you tied the Prusik knot (where the big bulky knot is in the animated Prusik knot). To rig your jib, you open the shackle, feed one end through the clew on the jib, and close it. Voila.
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Re: Using a rope shackle for the jib

Postby kokko » Mon Sep 23, 2013 8:27 am

The rope shackle would be easier with 3-strand
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Re: Using a rope shackle for the jib

Postby Tipster1 » Mon Sep 23, 2013 12:18 pm

Thank you both. The L-36 site should keep me occupied for quite a while!
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Re: Using a rope shackle for the jib

Postby GreenLake » Mon Sep 23, 2013 10:12 pm

kokko wrote:The rope shackle would be easier with 3-strand


Actually, I would respectfully disagree here.

Three strand is fun to splice, but hollow braid is "way more funner."

The painful ropes are double-braid and the like, which double your work because you need to account for mantle and core, but hollow braid is child's play - no tucking under and over, just Brummel splices and buried tails.
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Re: Using a rope shackle for the jib

Postby jdoorly » Mon Sep 23, 2013 11:09 pm

+1 to GL, however it is hard to find consistant direction on bury length. For 1/8" dyneema I have seen 3", 6", and 9" aka "70 diameters". Therefore all my standing rigging splices are 'footlongs' with stitching and whipping! And I sure would like to hear more on the subject of eye (thimble) diameters...
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Re: Using a rope shackle for the jib

Postby GreenLake » Tue Sep 24, 2013 11:57 am

The bury length depends a bit. Much dyneema is oversized for the job, and in that case going to the lower limit for bury length would seem fine, esp. also if you lock the splice by using a Brummel or some other means. For rope shackles the bury can easily be the entire length of the shackle and still not hit the longer bury lengths you note; however, for example if you use it with a Prusik knot like I was describing, you would get additional pressure/friction from the knot, so I wouldn't worry about your shackles coming undone.

For standing rigging, being very conservative sounds like a good idea.

(Disclaimer: I don't have actual measurements/failure experience to back me up, other than that my splices have all held so far. The guy who writes L-36.com does post some strength tests, I believe, but I don't remember for what rope or type of splice.).
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