My yacht club recently conducted Lifesling training based on the syllabus of The Sailing Foundation in Seattle. We chose to test our hoisting tackle at the dock but with a live, wet sailor. Even after two hours of classroom training, nobody got it exactly right the first time!
To review, the rig consists of 150' of 3/8" polypropylene braided line, one end tied to the boat and the other formed into a loop passing through the D-rings on the arms of the U-shaped buoy. The loop is supposed to be large enough so that after pulling the MOB up to the boat as high as possible and cleating the line off, a hoisting tackle can be shackled into the loop at the rail. Thus during hoisting, the standing part is unloaded and the loop acts like a sling; as the strain is taken, the ends of the buoy come together, holding the MOB even if unconscious.
My question relates to the knot used to tie the loop. To follow this you will need to see the picture:
The upper line is the standing part going to the boat; the two lower sections are the loop. The right-hand part ot the loop passes through the knot and is seized (stitched, in this case) to the left hand part of the loop. When the hoisting strain is on the loop, the knot can upset, putting 1/2 the load on the seizing. FWIW, during our practice the 5 Lifeslings were all rigged this way but the seizing were all different and two came mostly undone during the hoist.
Two questions:1. Does anyone know what kind of a knot this is?
2. What is the best way to rig this gear.
Inasmuch as I think this an inappropriate way to make the loop, I am looking at making a continuous loop with an end-for end splice, and tying the standing part to the loop with a double sheet bend (with the bitter end securely seized to the standing part. Since the lines all showed abrasion just from one hoist, I plan to use a more robust line for the loop like 12-strand Spectra or perhaps NER Flightline.
All comments appreciated.