If you are working with low friction rings, sooner or later you’re going to work with Amsteel and other high molecular polyethylene (HMPE) ropes, and that means learning to splice-in rings.
Sure, you can use ball bearing blocks with Amsteel, but often you won’t want to; blocks that match the working load of Dyneema are expensive and large, and the lines inherent slipperiness makes the rings relatively efficient. However, the extreme slipperiness and low stretch also makes knots inefficient.
Knots in HMPE rope seem secure at low load, but when the pressure is on, they slip, generally at 20- to 35-percent of the ropes breaking strength. Dyneema knots can reduce a ropes strength by as much as half, much more than other materials. Stitched splices are an option in HMPE, but these are difficult to make strong enough.
Fortunately, 12-strand, hollow-braid ropes, like Amsteel, are very easy to splice. Even Dyneema lines with a polyester cover, such as New England Ropes Endurabraid, are relatively simple to splice; typically 12-strand core is spliced, and the cover is just buried. There are only three basic splices, and they are all related.
Photos by Drew Frye
Don’t learn to splice with old rope. It is stiff and makes learning difficult. Use contrasting colors when practical; this makes differentiating between core and cover easier. Work slowly to start; snagging a strand inside a rope can ruin a splice.
Bunching up the cover makes extracting the core, inserting a fid, moving the fid, and sliding the cover easier. You can lock-stitch with heavy polyester whipping twine, but you can also pull out a single strand of the rope you are splicing. This makes for a nice match.
Leave your tails longer than they need to be to start; you can always trim them. Every time you bury one line inside another, the rope is shortened an inch or two; allow for it. Splicing always introduces a little construction slack in the line, so the line will stretch back to the desired length over time or after hard loading settles it.
Commercial fids make the job easier, but in our demonstrations we are using a cut-off hollow aluminum knitting needle (the angle of the cut is important, and polish it smooth). In the field we’ve used a ballpoint pen, a cooking skewer, and a bit of wire, but that is no way to learn. Buy the fids. You will need a sharp knife and scissors to work with HMPE and they will dull quickly.
The most common splice, as well as the easiest to learn, the eye splice forms a foundation for all of the other splices. Key features, such as opening the braid to insert the fid, the long bury, and tapering the end are constants through all 12-strand HMPE splices. Eye splices are particularly useful for terminating lines and mounting low friction rings.
Long Bury Splice
Like all double braid splices, the strength in the long bury splice is like that in a woven paper finger trap. The harder the inside line is pulled, the more tightly the outside braid contracts. The taper at the tail avoids an abrupt direction change at the most highly stressed part of the splice and adds about 20 percent to the strength of the splice.
The Animated knots demonstration (www.animatedknots.com/longbury/index.php) does not show the lock-stitching step-about 4 inches of low-tension big stitches with heavy whipping twine-which is vital to the stability of the knot when not under tension. (Remember how you escape from the Chinese finger trap by releasing tension and sliding it gently off your fingers?) Samson shows the full procedure: (www.samsonrope.com/Documents/Splice%20Instructions/12Strand_C1_Eye_Splice_WEB.pdf)
A variation on the long bury splice, the Brummel provides an alternative to lock stitching. Though it looks strong, remember that it is no stronger than the long bury splice, and it does not reduce the need for the long bury.
The popular notion is that the Brummel splice is more resistant to chafe, but that is false, as witnessed by the fact that commercial splicing of Dyneema lifting cables use a long bury splice with stitching.
In a long bury splice, the stitching is buried deep in the splice. It doesn’t carry any load, it only serves to prevent the tail from slipping out under zero load. As soon as there are a few ounces of pressure, the outer sleeve of the splice clamps down on the buried section, locking it in place.
In a Brummel splice the line is woven through the weave of the Dyneema rather that passed up the center of the core. Two passes create a lock. But this lock will not be enough without being followed by a long bury.
It can be difficult to position the Brummel lock accurately. Position is important when both ends of a line are loaded.
Despite its drawbacks, a Brummel splice looks neat and we often use this method. Note that the tail bury must still be 50-70 diameters long and that it must be tapered the same as the long bury splice (www.animatedknots.com/brummeldemo/index.php).
The most common application of this splice is not to make a line longer, but rather to make a loop. Because an eye splice requires a minimum 50:1 bury length (70:1 is better), the minimum practical length of a strop is about 110 rope diameters, or about 20 inches for 3/16-inch line.
However, by using a thimble or low-friction ring to create a turning radius that is three times the diameter of the rope, a 1/8-inch line can be used to create a loop of the of the same strength that will only be 10 inches long.
This is one of the more popular ways of mounting low friction rings. Lash the ring into bight formed where the two ropes meet and the rope is doubled. A string of half hitches will take care of the job.
The procedure is basically that of making side-by-side buried eye splices. Lock stitching is used. See website (www.samsonrope.com/Documents/Splice%20Instructions/12Strand_C1_End_for_End_WEB.pdf).
The Grog Sling is simply a variation of the end-to-end splice using a Brummel Lock. See website (www.animatedknots.com/grogsling/index.php).
A combination of a Long Bury Splice, a modified Brummel, and a knot, soft shackles are a handy tool on any boat. We always hang a variety of lengths and diameters from the handles of our boat tool bag. They can quickly solve a lot of rigging problems. We discussed these at length in Going Soft on Shackles, April 2015.
Loggers and construction workers use these to make adjustable length rigging and lifting slings. We’ve used them in many test rigs related to anchoring and pull-testing. On boats, Colligo Marine recommends then for adjusting the tension of synthetic lifelines. We’ve used them to secure deck cargo.
Basically, the whoopee sling is a length of hollow braid with an eye on one end and an adjustable eye on the other, made by simply leaving a long length of tail hanging out and putting a stopper on the end of the tail so it can’t pull through. It’s about 30 percent weaker than an eye splice, but that’s still pretty strong when spliced in HMPE.
The eye can slip when not loaded, but the stopper knot of back splice will prevent it from pulling through. See website (www.samsonrope.com/Documents/Splice%20Instructions/12Strand_C2_Whoopie_Sling_AmSteel_AmSteel-Blue_WEB.pdf).
Splicing instructions always seem to contain a lot of cryptic steps, but if you break it down, they are all easy. There are only a few principle techniques to master, and learning happens quickly. If you really want to dive into the topic of splicing Brian Tosss The Complete Riggers Apprentice covers the topic in much more detail.