Knot for joining rappel ropes
Various knots are currently used for joining two rappel ropes. There are many discussions on this topic and some people find it difficult to make a choice. To help with this, we present here the advantages and limitations of the three main knots used (flat overhand bend, figure-eight and flat overhand bend with stopper knot).
Warnings
- Carefully read the Instructions for Use used in this technical advice before consulting the advice itself. You must have already read and understood the information in the Instructions for Use to be able to understand this supplementary information.
- Mastering these techniques requires specific training. Work with a professional to confirm your ability to perform these techniques safely and independently before attempting them unsupervised.
- We provide examples of techniques related to your activity. There may be others that we do not describe here.
We provide the results of a series of tests done on each knot.
The tests were done using two new pieces of PASO GUIDE 7.7 mm rope.
A slow pull of 150 mm/min is done on the joining knot. 5 tests were done for each configuration. 30 cm of tail is left on each knot.
Flat overhand bend correctly tied but poorly tightened:
First capsize between 2.5 and 4 kN.
13 capsizes on average.
Tail remaining at end of test: 0 cm.
Release at around 10 kN.
Flat overhand bend correctly tied and tightened:
First capsize between 4 and 7 kN.
14 capsizes on average.
Tail remaining at end of test: 0 cm.
Release at around 11 kN.
Advantages:
- Easy to tie
- Fairly easy to untie
- Reduced risk of jamming during rope retrieval
Limitations:
- Does not work with ropes of different diameters. For ropes of different diameters (PUR LINE and VOLTA GUIDE), capsizing starts at around 3 kN with a well-tightened knot.
Figure-eight knot correctly tied but poorly tightened:
First capsize between 0.6 and 1.2 kN.
4 capsizes on average.
Tail remaining at end of test: between 5 and 10 cm.
Breakage at around 17 kN.
Figure-eight knot correctly tied and tightened:
First capsize between 3 and 5 kN.
3 capsizes on average.
Tail remaining at end of test: between 15 and 20 cm.
Breakage at around 17 kN.
Advantage:
- Fairly easy to tie
Limitations:
- Risk of capsizing at very low loads when not correctly tightened. Capsizing "consumes" the tails and the knot can come untied
- Does not work for ropes of different diameters. Begins to capsize at around 1.5 kN (PUR LINE and VOLTA GUIDE)
Flat overhand bend with stopper knot correctly tied but poorly tightened:
The stopper knot does not capsize
Tail remaining at end of test: 30 cm.
Breakage at around 15 kN.
Flat overhand bend with stopper knot correctly tied and tightened:
The stopper knot does not capsize
Tail remaining at end of test: 30 cm.
Breakage at around 15 kN.
Advantages:
- Works with ropes of different diameters
- The knot does not capsize
Limitations:
- Somewhat greater risk of jamming during rope retrieval
Finally, it is essential to remember that whichever knot is chosen, it must be correctly tightened while leaving at least 30 cm of tail. Simply pulling on the two strands together on each side of the knot is insufficient. The 4 strands must be individually tightened.
