Will a Short Sheath Give Amsteel Adequate Friction for a Knot?

Maybe, but be careful. Make the sheath as tight as possible to the Amsteel.

In this quick study, I took three sections of 7/64" Amsteel (1650lb avg breaking strength), and put a bury splice on one end for a full strength termination. I took short sections from 5, 6 and 7 mm kernmantle cords, removed the core strands, and slid the sheaths over the Amsteel on the other end. I then knotted a figure 8 in the sheath-covered amsteel of each test section. The 5mm sheath was nylon; the 6 and 7mm sheaths were polyester (supposedly both nylon and polyester have ~ the same coefficient of friction, at least 3x that of UHMWPE). Amsteel is made of Dyneema, a patented form of UHMWPE.

The knot was pulled in opposition to the bury splice, using a crane scale for measurement and a come-along for the force.

In both the 6mm- and 7mm-sheathed samples, the Amsteel simply pulled through the knot at well below breaking strength. For the 5mm sheath, the Amsteel broke in the knot at 1058 lb, ~64% of full strength, and pretty typical for a figure 8 knot.

Below is how the 5mm and 7mm samples looked before the test (at left), and how the 5mm section appeared after.


It was a little tricky to thread the Amsteel through the sheath. I first stiffened the end of the amsteel with glue (Superglue should work), then put a small safety pin in the very end of the Amsteel. Then I milked the safety pin through the sheath.