Tests on Cow's Tails used in caving and canyoning

Read the full article here (original French article can be found on the website of EFS).

Series of tests on Cow's Tails used for progression on  semi-static rope: Conclusion

Cow's Tails currently on the market that are entirely manufactured, whether they be single or double, symmetrical or non-symmetrical, are not appropriate for either caving or work on ropes. In particular, Cow's Tails made from sewn tapes, in widespread use by cavers and rope workers, can pose a real risk. The tests have, in effect, shown that a Fall Factor 1 shock load could exceed 15 kN (test 6) when the recognised maximum for work equipment according to the European Standards is set at 6 kN.

However, it is possible to use manufactured goods by linking them to the harness with a knot to specifically perform a shock absorbing role and thereby serving to keep the shock load for a Fall Factor 1 fall within acceptable bounds. Different manufacturers offer lengths of dynamic rope with pre sewn ends. With a 150cm Cow’s Tail, it is therefore quite easy to make a pair of nonsymmetrical Cow's Tail, which is ideal for both caving and rope work. It can be joined directly to the harness tie-in point with a Figure of Eight Knot, an Overhand Knot or a Clove Hitch.

From the point of view of shock absorption, Cow's Tails made from dynamic rope and knots at both ends achieve the best results. The effect of the diameter and of the weave of the rope on this shock load is not significant. Furthermore, the results are similar for knots that are well tied and knots that are badly tied, that is when the ropes cross over each other, and also whether they have been pretightened or not. This method also allows the lengths of the Cow's Tails to be adapted to the size of the user. 

Figures of Eight Knots, Overhand Knots or Clove Hitches can be used at the harness end. 

At the other end, a Figure of Eight Knot or an Overhand Knot and also a Barrel Knot can be connected to the karabiner. The Barrel Knot is being increasingly used by cavers and has the advantage of holding the karabiner in place. It is, in effect, completely secure and furthermore is the knot that provides the best results in both the static and dynamic tests.

Source: http://british-caving.org.uk/rope/lanyard_tests_v6.pdf

Instruction video on how to construct these cow's tails: