Thimbles needed in Dyneema Lifelines

[ereiss]

I've searched and search but can't find the answer (although I know it must be in here somewhere. Can I splice the ends into the fittings or portions of my pushpit and pulpit without having a thimble in the line?

Love the site, ready to take on this project.

Thanks

[Brion Toss]

Hi,
Thimbles are there to preclude chafe, and especially with HM lines, distribute the load among more yarns. Radius is where it's at. A round brass or stainless sail thimble, like we use, is fine. It also gives a place to lash to, to tighten the lifeline. You can also ring hitch the line onto a bail. Just be sure, in the latter case, that there are no sharp or rough bits. Also be sure that the bail is up to the load, both because you don't want it to carry away, and because if it is strong enough for the load, it has a big enough bearing surface for the line.
Fair leads,
Brion Toss

[seawolf]

Hello,
I just finished a lifeline project with Amsteel line and like the finished product.
I used round brass thimbles on both ends forward and aft to lash to stainless shackles that I had on the aft rail and deck fitting forward.
I found the thimbles on the Duckworks web site.
If I could figure how to send some pictures, I would and it may help.
Bob

[andert]

Gents who've done this...

Do you use any kind of end hardware to form the gate? I see Johnson Marine has some fittings for rope lifelines, and there was another elegant pelican hook out there...what about the end that the pelican hook hooks to? Just a sail thimble, or do you splice on some kind of eye fitting?

Thanks,

Todd Anderson
Earendil
Allied Seawind

[Ted Reshetiloff]

Im in the process of making a set myself right now. I am putting an eye (mobius Brummel) in on end, then cow hitching it to the bail on the pulpit. Im using colligo terminators on the other end with 1/8 dyneema for lashing. Doing the same for the gates accept no colligo terminator just a cowhitched eye and a Johnson Pelican hook.

Im using 1/4" amsteel for the uppers and 3/16 for the lowers. Im also attempting to prestretch the amsteel prior to making the sections by loading up the line and letting it sit for a while then unloading and reloading a few more times. Using the cocpit primaries for this. No thimbles though, hope I'm not branded a heretic.

[andert]

Nobody expects the Spanish Inquisition! Seriously, thanks for your advice. I think I am going to use sailmaker thimbles in stainless steel, with shackles on the pulpit and pushpit ends, so's I can unhook 'em easily, with a pelican hook from Victory Marine for the gate. I thought maybe I'd serve the eyes and on down the splice where the line goes through the stanchions to form the gate...a touch of the traditional, and a little extra chafe resistance?

[rroberts]

I'm using 5/16" T-900 for my lifelines, with a breaking strength of about 7300 lb. and a Factor of Safety of 15, it gives me a Safe Working Load of about 500 lb., so for me (the heaviest person on the boat) that's about 2.2 g's I can be thrown into them at.

Anyway, for thimbles, I used Bainbridge's 5/16" wire rope hearts, they're big but have a large radius, these are then french lashed to the terminals with 1/8" single braid Amsteel. For the cockpit lifelines, I'm splicing directly to the Johnson terminals. As the Working Rope book notes, a tight radius is bad, and as Brion noted in this thread, you can ring hitch on, but the radius on the line in the ring hitch is still as tight, if not tighter, than the splice for the Johnson hardware. To hold a more open radius, once the splice is finished, I'm serving over the radius with Robline Whipping Twine 08. I'm also serving over the lifeline in way of the stanchions to provide some additional chafe protection as well as prevent rust and staining. Done up with whipping twine the same color as the line flecking, it looks pretty sharp.

Ryan

[Mountsbay]

In the context of people being thrown against lifelines I would have thought that the important issues would be to do with the geometry of the system and how much energy the system could absorb by deformation. Very high tensions can be generated by applying a relatively low load in the middle of a taut line if it is very low stretch and its ends are fastened to rigidly fixed points. If there is some slack in the line initially the tension created will be much lower - ie geometry matters. A given weight dropped from a given height might break a low stretch line (eg spectra) but not break a weaker but more elastic line (eg nylon) - ie energy absorption by deformation matters. Obviously the weight of the thrown person also matters as does the speed with which they hit the lines. If somehow the person were thrown up at the lifeline rather than down at it that would matter too. I am not sure what is means to say that someone is thrown into something at 2.2 g's but perhaps that matters as well.

[John D]

If you're going to directly connect your dyneema lifeline to your pulpit, don't ring hitch to the bail. Ring hitch to the nice fat stainless steel tube. Place the hitch inside the bail, so it can't slide up or down the tube. Using the bail as the connection point means bending the dyneema into a much smaller radius turn.

Even when lashing from a thimble in an eye-slice to a pulpit (or pushpit) go around the larger tube and just use the bail to keep the lashings from sliding.