I'm reviewing some manufactured anchor bridles, with a focus on catamarans, but certainly they are applicable to all boats and towing. Specifically, I'm intested in araingments that terminate in a hook or shackle at the apex, not a rolling hitch or something similar, chain plates (like hooks but with 2 eyes), since they use 2 separate legs and do not require and eye splice, and likewise not the possiblity of using 2 legs joined with a shackle. All of these are legitamate alternatives, but not what I'm curious about.
Typically an eye with thimble is used, with a y-splice attaching the 2nd leg, all covered with serving or webbing chafe gear. While I sure this is near line strength when the angle between the legs is shallow, what happens as the angle grows? At anchor the angle would certainly be less than 60 degrees; however, when tying to a mooring the angle could be as much as 120 degrees, to prevent the ball from striking the hulls.
The same sequence of splices is possible. I have seen them seized, either with heavy tread/cord or metal ferrels. Same question; what happens to strength at 60 degrees and 120 degrees?
Knots are also possible. A figure-8 is about 80% straight pull and about 65% 180 degree pull. Though a thimble is not practical, other chafe gear is.
2 legs joined with a shackle is very prone to failure as the angle becomes too wide' I'm sure many of us have destroyed a shackle when it shifted such that the load cam on cross-wise and the threads stripped. 2 legs to a plate is tough on the plate but can be designed for, like this one:
So, what is the best y-splice option?
I've looked for test data on-line and not found this specific item; a Y-splice or seizing tested to destruction at angle. I suspect the failure point at smaller angles will be near the eye and not in the legs, but as the angle grows that cannot remain true.
While I'm sure the vast majority fail due to chafe and all of this is academic, I need to be diligent in my investigation.