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Splicing Tiny Dyneema

AaronD

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Aug 10, 2014
537
Catalina 22 9874 Newberg, OR / Olympia, WA
I've been using single-braid dyneema (Amsteel, Endura 12, etc.) for a variety of applications. It's lightweight, incredibly strong, and easy to splice. In fact, it's so strong that for lightly loaded applications (on my small boat), I thought I'd try something even smaller.

The smallest Amsteel is 7/64" (~2.8 mm). It runs about $.30/foot, and is rated for 1600 lb breaking strength (so ~320 lbs working load at a 5:1 safety factor). Samson also makes a single-braid dyneema product called Lash-It, that's about 1.5mm (rated 500 lbs, or ~100 lb SWL). I picked up a 180 foot spool for $18 on WM's 40%-off-line sale.

I wanted to add a messenger line for my 2:1 spinnaker halyard - a nice application for really thin (and low windage) line. I thought some others might be interested in my experience with this tiny line. (Note: I did this before reading Samson's site that calls Lash-it 'not spliceable'. In my experience, splicing is doable, but not trivial).

First, I found that my standard wire fids won't fit in it. I've always made wire fids from a random spool of wire I had laying around. As it turns out, it measures .035" (I never thought to measure before). That's too big for this line, so I picked up a bit of tiny piano wire on Amazon. I bought .010". It's working, but I'd recommend something in between. Maybe ~.020". If for no other reason than that the .010 is SHARP! I left a little blood on my desk during this project; caveat emptor.

I wasn't sure if I could separate the braid enough to do a Brummel splice, but finish nails of a couple sizes (dulled just a bit on the grinder) worked well (then I can get a normal fid in to widen it a bit). If you have a tiny dull pick, that would work too.

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The strands are pretty close to the limit of my aging eyesight, so I know my tapers aren't great. But for low loads, I think it'll work.

While I was at it, I replaced my fixed topping lift line* (for the same reasons). With a boom that only weighs around 30 lbs, the topping lift load can't be any more than ~15 lbs; well within spec for this line.
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The 'hand' is stiffer than Amsteel - it seems to be braided a little tighter, so it's more prone to hockles (no surprise in a product that's really intended for lashing). I don't think that will be a problem for the topping lift line (which stays fixed in place), but it might be annoying for the messenger line. TBD.

I may replace my flag halyards as well (1/8" solid-braid nylon only lasts a season or so in the UV, even up here in the cloudy PNW; dyneema would probably last me for decades). Same for my backpacking bear hanging lines** (the stretch in my nylon lines is annoying).

In theory, you could make really tiny soft shackles with it (~1k lb breaking strength using Evans Starzinger's design). I haven't tried that yet; I tend to think that 2mm or 2.2mm would be a better minimum there, but I might give it a try sometime.

If you're interested, there are a few other options for tiny dyneema - NER makes a 3/32 Endura 12 (~2.4mm). Apparently it's used for spearfishing tethers, so there's lots on eBay.

* My topping lift is designed as at https://www.catalinadirect.com/inde...opping-lift-kit-std-rig-cp-22-c-25-c-250-.cfm and https://stingysailor.com/2018/07/21/boom-topping-lift-solution-2/, with a mini block at the end of a fixed line from the masthead. With a short control line, a cheek block, and a cleat on the boom. This Lash-It setup replaces the larger fixed line.

** That would be to hang food away from bears, not to hang bears. If you need the latter, I'm afraid you're on your own (and probably at the wrong Internet form - see https://darwinawards.com instead).
 
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Likes: heritage
Oct 1, 2007
1,734
Boston Whaler Super Sport Pt. Judith
Amazing. The caution I would offer is that as the lines get smaller, they become more difficult to grip and painful for a loaded line. Something to think about.
 
Oct 22, 2014
16,100
CAL 35 Cruiser moored EVERETT WA
@AaronD I also have a new founded affection for dyneema/Amsteel line. Not so much with the sizes you are using. I am playing with 3/8ths down to 1/8th. Since finding a YouTube video of Brian Toss tying a Buried Crown knot back in 2015 during a demonstration in Tasmania at the end of the Hobart, I have been tying soft shackles for all sorts of boat uses.

The one I did the other day has a theoretical breaking strength of 10,000 lbs is feather light and cost about $2.50.

I think it is an ideal way of attaching my preventer line for the mainsail while on a downwind sail.
 
Last edited:
Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
How fun. I can’t remember the last time I’ve done an old-school splice. Every line on my boat is either single braid or core dependent line. I still have an array of old circular fids, but now the D-splicers rule. The fids are now simply to create penetrations for Brummell splices.

Every year I buy 100 feet of that stuff and just put in my rigging bag. By the end of the year it’s gone.

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AaronD

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Aug 10, 2014
537
Catalina 22 9874 Newberg, OR / Olympia, WA
Amazing. The caution I would offer is that as the lines get smaller, they become more difficult to grip and painful for a loaded line. Something to think about.
Agreed, and thanks for pointing that out. I only intend to use this tiny stuff for fixed lines (e.g. the fixed portion of my topping lift) or for really light load applications (messenger lines, flag halyards, etc.) where there won't be any significant load to pull.

For some running rigging applications, I've used cover from Sta-Set and replaced the core with Amsteel or Endura 12 of appropriate dimensions (5/32 for 1/4" cover and 1/4" for 3/8" cover seem to work well for me). But that's probably a different topic; I just wanted to offer a bit of experience in case anyone else wanted to work with the really small stuff.