I was first introduced the whoopie sling by a construction rigger nearly 20 years ago. We were using a crane to install irregularly shaped catwalk and railing sections in a refinery. They were all unbalanced, but had to be lifted dead level. This meant using three slings and adjusting the lengths of two of them differently for each lift. I’d done this before using either chain hoists or lashings, and both methods are slow and cumbersome. The riggers pulled a pile of odd looking Dyneema slings out of the job box and started rigging up the sections, one after another. Within a few hours, dozens of catwalk sections and supports had been lifted and bolted securely into place.
A few years later I was having some trees taken out of my backyard and the same odd looking slings came out of the truck, this time securing ropes to tree trunks. A few questions later, I learned they were invented by a clever arborist sometime in the 1990s, when Amsteel was becoming popular. Google “whoopee sling” and you’ll find hundreds of posts about using them to rig hammocks.
The standard form of a whoopee sling is a length of hollow braid rope with one fixed eye and one adjustable eye. The adjustable eye is created by making a bury splice with a long exposed tail and no lock. The length of the eye is adjusted by sliding the tail in and out of the rope as needed, then yanking it tight at the correct length. The same Chinese finger trap principle that makes a standard eye splice secure—with the braided outside line contracting around the buried tail— makes the adjustable eye secure.
Because the end of the tail emerges through the side of the rope, rather than being smoothly tapered inside, the strands of the line must bend more sharply, making the adjustable loop about 15- to 20-percent weaker than a spliced eye.
In the right application, the advantages are numerous. It’s strong and simple. There is no painful or damaging hardware to sit on, step on, or lean against. There are also drawbacks. It is impossible to release under significant tension, but this can also be an advantage in some applications—lifelines come to mind. It weakens the line, but this is overcome by going up a size. You can adjust the length, but you can only get it hand-tight. Animated knots video illustrates the process well: www.animatedknots.com/whoopie-sling-knot
Technical Editor Drew Frye is the author of Rigging Modern Anchors from Seaworthy Books. He blogs at www.blogspot/sail-delmarva.com.