Thursday, September 19, 2013

Vertical Darwinism: Rappel Knots

"That climb was EPIC! do we get down?"

On larger climbs, rappels can be longer than one rope can span. That means you need a solid way of connecting two ropes for rappelling. Clearly a knowledgeable decision needs to be made with inputs from all climbers in the party. There are many ways to join 2 ropes together for rappel. Most commonly in the climbing world you will encounter one of these three. They differ in complexity, profile, and security.  Here is a brief run down so you can make your voice heard in the discussion.

Figure 8 Bend  "Ol' Trusty"
Complexity: High  
Profile: Large  
Security: High

Pros: Just like the figure eight tie-in knot it is familiar and easy to check. It is a strong knot that has a great safety record if you dress it well and back it up with your standard fisherman knots.
Cons: It's large profile takes more rope to create and also gives it a better chance to hang up on jagged rock features. It takes a bit more time to tie than some others and can be moderately difficult to get undone after the rap.

Double Fisherman's  "It works for"
Complexity: Medium
Profile: Small
Security: Medium

Pros: This is a well recognized way to join two ropes together. It has many applications for cord of all sizes from ropes to bracelets to accessory cord loops.
Cons: This knot has a tendency to fuse tightly and can be very difficult to undo. It's small profile easily slips into cracks and may hang up. There is no official back up for this knot (except another knot).

Flat Overhand a.k.a. the EDK "European Death Knot?  Really?"
Complexity: Low
Profile: Medium (offset)
Security: Medium

Pros: This very simple knot has an offset profile which has a tendency to align the cords and rotate the knot away from the rock and thereby snag less on the way down.
Cons: Testing has found that this knot weakens the rope more than the other two. Also, under high tension, there is a possibility that it may roll repeatedly toward the end of the rope. This may have been the reason for the American nickname of the "European  Death Knot." According to a tension test on 11mm dynamic rope, the knot rolled at 1400, 1940, 1990, and then broke at 2070 lbs of tension.

*Sidenote- The Flat Figure Eight (the 8 version of the EDK) has a high likelihood of rolling over and should NOT be used for rappel!

Whichever you choose there are always two rules you must remember.
1. Leave plenty of tail on both ropes to lessen the chances of slippage and rolling.
2. Always use similar diameter ropes. Thin and a thick cords are not a good match. Keep your cords within a few mm of each other.
*Bonus- While you are at it, throw some stopper knots in at the end of your rope if you are at all concerned about having enough rope to get down.  Just make sure to UNTIE them BEFORE starting your retrieval pull.

Which knot you prefer and which one works the best for your situation is up to you and your climbing party. Each method has its benefits and drawbacks. The important thing is that you understand the risks involved and accept responsibility for your choices. A majority of incidents occur on the descent. How you get down is an important decision that should be agreed upon before you leave the ground. A windy, rainy, shivering summit is no place to engage in a heated debate about safety and comfort level of all involved. This is a discussion to be had with your climbing partners before the climb. May I suggest in the car whilst driving through Nebraska?

For More Climbing Knots:
Animated Knots by Grog

Tension Testing:

Climb Smart MN is a grassroots approach to climbing education based on community and charitable giving. For information on donation based climbing lessons visit ClimbSmartMN and follow us on Facebook. With over ten years of climbing instruction, coaching, and guiding experience,  Chris Hesselbein strives to better the climbing community through personalized technique and safety education.

1 comment:

  1. Here's an added exception to the general rule of using two similar diameter ropes. If your ropes are dissimilar you can tie them together using two independent figure-8s. One figure 8 is tied as a first figure 8 on a bight, and the other as a second figure 8 is a follow-through figure 8 where you run the loop of the second figure 8 through the loop of the first figure 8. For example, I have lead on a single rope (e.g., > 9.8 mm), and to save weight, brought a second half/double rope (e.g., < 8.6 mm) to do a double-rope length rappel (as opposed to using a retrieve-line). This worked great and is solid (although of course the knots give a larger profile, so beware of hang-ups!).