Understanding the Double Figure 8 Knot
Also known by its memorable nickname, the 'bunny ears' knot, the double figure 8 is a stable and reliable knot that forms two non-collapsing loops. Its robust structure is derived from the standard figure 8 knot, but with a crucial modification that creates two parallel, fixed loops. This design is what makes it so valuable in situations where the integrity of an anchor system cannot be compromised. The strength and stability of the double figure 8 are central to its application in critical safety scenarios.
Core Applications of the Double Figure 8 Knot
While the double figure 8 has a few variations, its primary use across different fields is consistent: creating a secure, equalized anchor point.
Climbing and Mountaineering
For climbers, the double figure 8 is a foundational knot used for setting up safe anchors. Its main uses include:
- Equalizing loads: It is used to connect to two separate anchor points, ensuring that the force is distributed evenly between them. This prevents a single anchor from taking the full load, which is critical if one of the anchor points is weaker or less reliable than the other.
- Attaching to a harness: Climbers can tie into their harness using the rethreaded version of the knot, providing a secure, dual-loop attachment.
- Mid-line attachment: It can be used to create a strong loop in the middle of a rope, which is useful for creating a masterpoint for a top-rope anchor or other rigging.
Rescue Operations
In search and rescue, the double figure 8 knot's strength and reliability are paramount. It is used to create stable attachment points for securing people or equipment, especially in precarious or high-stress environments. Its predictable nature and ease of inspection are vital for ensuring the safety of those involved.
Rigging and Utility Work
From industrial rope access to general utility work, the double figure 8 is employed to distribute tension and create secure attachment points. This can include anything from hoisting systems to securing heavy objects, where a failure could have serious consequences.
How to Tie the Double Figure 8 Knot
There are a couple of common methods for tying this knot, but they all result in the same secure structure.
Tying the Knot on a Bight
- Form a long bight: Create a long bight of rope, which is a loop where the rope is folded back on itself.
- Tie a figure eight: Using the doubled rope (the bight), tie a standard figure eight knot, but leave the loop at the top of the knot relatively loose.
- Feed the bight through: Take the bite of the doubled rope and feed it back up and through the small loop at the top of the figure eight.
- Dress and tighten: Pull on the two loops to adjust their size and then pull the standing lines to tighten and 'dress' the knot neatly, ensuring all strands are parallel and tidy.
The Rethreaded Method
- Tie a single figure eight: Tie a standard figure eight knot near the end of the rope.
- Wrap around an object: Pass the working end of the rope around the object you are anchoring to (e.g., a tree or bolt).
- Retrace the figure eight: Follow the path of the original figure eight knot in reverse, rethreading the working end through the knot. This is similar to how a figure 8 follow-through is tied, but with the doubled rope.
- Tidy up and seat: Neatly dress the rethreaded knot and pull it tight to seat it correctly.
Comparison: Double Figure 8 vs. Other Knots
| Feature | Double Figure 8 (Bunny Ears) | Double Alpine Butterfly Loop | Bowline on a Bight |
|---|---|---|---|
| Primary Use | Equalizing loads between two anchors | Creating a mid-line loop; not ideal for equalizing | Creates a secure, non-slip loop; loops can collapse unevenly |
| Loop Stability | Highly stable and non-collapsing under tension. | Loops can collapse under uneven tension. | Less stable under uneven tension. |
| Ease of Untying | Moderately easy to untie, even after a heavy load. | Easy to untie, even after a heavy load. | Can be more difficult to untie after heavy loading. |
| Mid-line Use | Can be tied mid-line, but requires more practice. | Excellent for mid-line use, simple to tie. | Not typically tied mid-line. |
Safety and Inspection
Proper dressing and tightening are crucial for the double figure 8. A correctly tied knot will have all its strands neatly parallel, and the two loops should be of equal size to distribute the load effectively. Always inspect the knot before relying on it, and ensure there is a sufficient tail (several inches) beyond the knot to prevent it from slipping. This is a safety-critical knot, and competence in tying and inspecting it is essential for anyone in climbing or rescue professions. For further information on knots and safety, refer to authoritative sources like the Animated Knots by Grog.
Conclusion
In summary, the double figure 8 knot is a highly valuable tool for anyone in climbing, rescue, or rigging who needs a secure, stable, and load-equalizing anchor system. Its ability to create two fixed, non-collapsing loops provides a significant safety advantage over other double-loop knots. By understanding its specific applications and tying it correctly, professionals and enthusiasts alike can ensure a higher degree of safety and reliability in their work.
