Using a rope to make a tensionless tree anchor
Need to secure the end of a rope around a stout tree? Provided the tree is not oozing with sap, and you have a bit of extra rope, here's a good way to do it.
This is known by some as a “tensionless” anchor, because there is no knot that's under load or tension. I prefer to call it the “tree wrap”, as it's more descriptive. This is one of the strongest anchors you can build, because you’re using the entire strength of your rope, with no loaded knots which weaken it. One main benefit, it's very easy to untie when you're done, even after a huge load.
First off, have a good look at the tree. The American Alpine Institute blog has a good memory jog for this, "Five-and-Alive." The tree should be at least 5 inches in diameter, 5 feet tall, and alive with a good root base. Be wary of trees that could have a shallow root-base, in dirt, sand and/or on top of a rock. Thanks AAI, good advice! (Personally, I’d consider a 5 inch diameter as the absolute minimum, larger is better!)
Starting with one end of the rope, take a few coils in your hand, and pass them around the tree trunk 4-5 times. This may well take more rope than you think, so start with a bit extra. Tie a figure 8 on a bight or overhand in the end of the rope, and clip this bight to the load strand with a carabiner to close the rope system.
If you tie this correctly, the friction alone from the rope on the tree bark will support the load, and the carabiner at the end should never see any force at all.
Rigging this close to the base of the tree reduces leverage and increases strength. This is more important if the tree is at all marginal. (If the tree is unquestionably strong, it doesn't really matter.)
Try four wraps as a minimum to start. Add more if needed.
Try to keep the loops reasonably tidy, but if they get a bit crossed up it's still going to be fine.
This should not damage the tree (especially if it's one part of a multi piece anchor) because the force is spread out over many rope strands, and not gouging into the bark. If you wanted to be extra nice to the tree, feel free to put in a backpack or something similar between your rope and the tree trunk.
If you're doing this on a conifer tree, there's a good chance you're going to get sap onto your rope. YUCK! This is something you want to avoid if at all possible, so try not to use conifer trees.
If you do get tree sap on your rope, hands or anywhere else, you can use mayonnaise, believe it or not, to clean it off quite effectively.
Another good option to secure the end of a rope around the tree is a bowline, either one strand or two.
If you REALLY want to go with elegant minimalism, you can skip the carabiner entirely, and tie a rewoven figure eight around the load strand. That's pretty cool, an anchor you can hang a truck from that doesn’t use a single piece of metal!
