Great, it’s good to know where you’re at with splicing. Naked eye splices use the cover only between the eyes, making the second brummel easier to do. The core is spliced first like a single braid and the cover added after. For the true naked eye, the eyes are coated with something to make clipping easier. Usually DIYers use electrical tape, but lots of other options, pros use a urethane base coating, but very expensive for the commercial stuff, a light dip in plain urethane would be just as protective. The eyes can also be covered before splicing, using something like paracord cover, as long as the main cover will slide over, like the bottom two in picture below.
3mm would be the size of Amsteel to use, to test to see if the cover will fit over the eye, take a small piece and make an eye with short bury, this will be how large the splice will get. Try to slide the cover on the small spliced piece, going over the eye first, if it goes, then the cover can be added later. If it doesn’t fit then the cover will have to be put on after the first eye is spliced and then bunched up out of the way for the second eye.
I make the cover bunchy, but not too much, on these to make them flexible, the slack can make the middle flexible, and also in the splice area bendable enough to be included in the hitch for shorter legs.
In the picture, the top two eyes are from a commercially made hitch cord, the next is 3/16” Amsteel in 8mm UltraTech cover. The next was an attempt at flexibility in the splice area by using a larger diameter cover at the splice and sewn together. The TRC has the separate covered eye also, but the core is six separate strands in a continuous loop, just shown for the covered eye.
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