Today I have a couple pics of some anchors I made at home. I was able to procure some 6″x6″x0.25″ plates of 6061-T651 aluminum. I cut these down into 2″ strips, laid out some hole patterns, and drilled/milled the stuff until I was left with two pieces for each anchor.
A trip to the hardware store, and I put these together using shoulder bolts, spacers, and nuts. I still need to add some sort of strap to them for connection to the tree, my plan is to sew some dog-bone style straps to one end of the anchor.
Each anchor replaces a rap ring and a carabiner, and the eventual goal is to use this type of anchor on a longer line (> 100′).
So far, I’ve made three of these, and they work great for the 50′ lines I usually set up. I don’t have a method for testing their break-strength, but calculations show they are fairly heavy duty. Here are a couple photos:
Expanding on my thoughts about the “double-bight” line locker, I have modified the method I use to attach the fixed-end of my Slackline to a tree. Thinking about how this works, I was able to eliminate the water knot and replace it with a double-bight line locker
This method has one advantage, and one disadvantage as compared to using a traditional water-knotted anchor.
Advantage: there is no knot in the line. In general, knots tend to weaken the anchor. I am not sure how much, and I know the weakness is reduced if you use a third strand of webbing to beef up the knot. (See here)
Disadvantage: There is only one level of webbing going around the tree. With a traditional water-knotted anchor, the anchor is doubled around the tree. This puts less stress on the anchor itself. However, for shorter lines (< 100 ft), I am not sure how much of an issue this is. Here is a photo of a fixed anchor some guys made (red line) to secure a 70′ Slackline. It uses only one wrap around the tree (similar to my method) but uses a knot (which my method eliminates).
Below is a photo and link to a short video (1 min) describing what I’ve done.