Break Test of Modified Trilene "Knot" in Amsteel

Harlan W S, July 19, 2022

Pure Dyneema (UHMWPE) tends to make weak knots. Joel Hartter (MS thesis) found ~1/3 the rated breaking strength for bowline, figure 8, and double fisherman; that test used slow pulls and 9/16" Amsteel. My own tests with 1/8" amsteel showed just 25% for a water "knot." Amsteel is generally spliced, rather than knotted, a practice that limits flexibility of configuration.

This quick test measured the breaking strength of a modified Trilene knot (really a hitch) in 1/8" (2500 lb bs) Amsteel on a carabiner. This setup could be used to put a connection point in the middle of a long Amsteel line. In ~1 second pull, the hitch broke at ~59% of the rated cord strength. A disdvantage of this connection: the Trilene hitch is very hard to untie, once weighted. (With nylon line, the Trilene hitch is up to 100% strength.)

Note that commercial "Dyneema" slings typically contain 35-50% nylon by bulk, and are much easier to knot (nylon has 3x to 4x the coefficient of friction of Dyneema). Furthermore, since the weaker nylon reduces the rated breaking strength of the unknotted sling, the ratio (knotted breaking strength)/(rated breaking strength) is inherently higher.

01
Before
 02
The pull setup. The dynamic
rope acts as a buffer to
keep the force from increasing
too fast. The load cell was
recording at 40 Hz. I let my
Jeep roll downhill till stopped
by the rope, then I hit the gas
and the break was in about
1 second.
03
After: the cord broke
at the hitch
 04
After: one of 12 strands
of the braided cord
was left in the "hitch"