What are whoopie slings?
"It sounds like it would involve a willing partner and a safe word" as one Backpacking Light contributor put it. Admittedly, the phrase "whoopie sling" sounds intriguing.
Simply put, a whoopie sling is a rope designed with an adjustable loop. They were originally designed by arborist's (tree pruning) as a way to securely hang from a tree and adjust the tension of a harness easily. More recently, the backpacking community has adopted them as a unique method for hanging hammocks. See guide to backpacking hammocks.
Why are they so useful?
There are a variety of methods to hang a hammock. However, daisy chain straps and whoopie slings are the two most common.
Whoopie slings are generally much lighter than daisy chains and have, therefore, become the preferred choice for lightweight backpacking. In addition to weight, they are extremely compact and, when folded, can pack down to the size of a toothbrush. They are also extremely easy to use. Having the ability to infinitely adjust your hammock to the exact length desired is a huge advantage.
How do whoopie slings work?
With all of the in's... and out's... and knots of the actual rope, it may seem complicated how they actually work.
There are only three steps needed to setup a whoopie sling and suspend your hammock. First, attach the small fixed eye to your hammock (via a knot, carabiner, etc). Second, attach the larger adjustable loop to your tree straps. Third, adjust to the optimal length and desired tension of your hammock. To adjust the size of the adjustable loop, pull down on the tail end and let the rope feed through the bury section.
The bury section works like a Chinese finger trap - push the ends together to loosen and pull the ends away to tighten. Once you are resting inside your hammock, your body weight will naturally do the pulling to tighten that bury and keep you safely suspended.
Things to Consider...
Materials: Go for minimal elasticity. Whoopie slings are generally made with Amsteel cord. It's a 12-strand single braid that has a great strength-to-weight ratio. AKA - you can sleep easy knowing that you won't fall. Dynaglide is another popular option. It's the lightest and smallest splicable line for whoopie slings available today. Typically not as strong as Amsteel though.
Strength: These lines can be pretty darn thin. You want them to be as thin and light as possible without sacrificing strength. 7/64" Amsteel is commonly used for whoopie slings and has a 1500 lb average breaking strength. I would not get anything with less than a 500 lb weight limit, especially if you have a two person hammock.
Length: Ropes can range anywhere from 2 to 10 feet. A longer rope will provide more flexibility in camp site selection - ie finding the right distance to setup between two trees. Generally, 4 to 8 feet per rope is a comfortable range.
Whoopie-hook: A whoopie hook can be a nice addition to the fixed eye. This helps easily hook in and out of the hammock attachment without any knots.
Dutch Biner: Consider using a dutch biner to attach the whoopie slings's adjustable loop to the hammock's tree straps. This can be used as a water breakage point to prevent rain from running down the into your hammock.
DIY: Feeling creative and want to make your own whoopie sling? It can be a fun day project and only costs a few bucks. See how to do it here.