Tail Splice

Load Lab
Test Results - Tail Splice (7x19 GAC to Amsteel Fiber Rope)

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Created by Delbert L. Hall, Ph.D.
ETCP Certified Rigger - Theatre and ETCP Recognized Trainer

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Disclaimer: This site contains the currents results of ongoing research and is not a finished presentation of findings. The information on this site may be the results of a small sample of tests and are NOT conclusive evidence of anything – they are just my results. Take them for what they are. Any conclusions drawn from these results are yours and not are necessarily mine. Go the Load Lab Home to read the complete disclaimer.

In January 2009, I was asked by Chuck Stoltz of the Sandhill Soaring Club to test a couple of tail splices involving wire rope (7 x 19 GAC) spliced to a fiber rope (Amsteel Blue – a 12 strand single braided rope). Chuck’s application was as a tow line for launching sailplanes. See http://sandhillsoaring.org/Glider/glider1.htm to watch a video of a winch launch of a glider. This just seemed far too interesting to turndown.

Chuck sent me two samples to test; each used a different method for making the splice. The first sample/method involved weaving the wires of the GAC and the strands form the rope together. Chuck’s method for this splice was based to two resources: tail splicing instructions from Liros (http://www.deckhardware.com.au/tech_sheets/Rope%20To%20Wire%20Splice.pdf) and instructions in Brion Toss’s book The Complete Rigger’s Apprentice. It should be noted that both of these sets of instructions discuss splicing the GAC to double-braided rope and Chuck was using a single braided rope which has no core, so some minor modification of these instructions was required. Here is a photo of the completed splice to help you better understand what is trying to be accomplished.

The second splice was much simpler and involves running the GAC down the center of the rope and then using a swaging sleeve (or several sleeves) to terminate the tail to the GAC. Below is a photo of this type of splice.

My immediate reaction upon seeing the splice with three sleeves was that this was a waist of sleeves, but let’s test it and also variations with one sleeve and with another with no sleeves (more on this later).

In Brion Toss’s book he says “For any Tail Splice, make the rope within 1/8 inch of being twice the diameter of the wire (rope); a larger difference results in distortion and a weaker splice.” I think Brion may have meant “smaller” difference because I found that the tail splices that I made where the wire rope and the fiber rope were the same diameter, the fiber rope broke at the splice at a tensile load that was less that the min. rated BS of the either the wire rope or the fiber rope (about 25% less). In my samples where the fiber rope was slightly larger than the wire rope, the GAC failed first.

All of the samples used in this test were made using 5/32” GAC (with a min. rated BS of 2800#) and 3/16” Amsteel (with a min. rated BS of 5400#). For each variation of splice I tested only one sample. Every sample in the test failed at the swaged eye termination on the GAC at a tensile force that was greater than the min. rated BS of the GAC. Here are the specific results:

Description of Splice	Breaking Strength
Tail splice with GAC buried in Amsteel and with the wire and fibers woven together	3009#
Tail splice with GAC buried in Amsteel and with three swaging sleeves	3051#
Tail splice with GAC buried in Amsteel and with one swaging sleeve	2923#
Tail splice with GAC buried in Amsteel and with no swaging sleeves	2841#

Since the BS exceeded the min. BS of the GAC, I do not consider the difference in the actual BSs listed above as significant. What these test show is that all of these tail splices will hold 100% of the min. rated breaking strength of the wire rope used.

The tail splice that used no sleeves relied entirely of the contraction of the rope around the GAC (like a Chinese finger cuff) for its holding power. In my sample I buried the GAC approximately 30 inches into the AmSteel. This was approximately 150 times the diameter of the GAC. How did I decide on this number? Honestly, it was the distance that Chuck had buried the GAC into the Amsteel on both the samples that he sent me, so I decided to try it that length by itself. And it worked.