Quote:
Originally Posted by Brion Toss
Hi again,
I so admire your work. It seems like now would be the time to put your configurations to some formal testing; might I see if I can arrange some? The idea is that we can get some accurate numbers, but also that we can address some other variables.
For instance, the short bury is for two legs, evenly loaded. But people learned the hard way (i.e. injuries and fatalities) to bury the core in double-braid splices, because the load sometimes comes on one leg, in the real world. Also, shock loads and cyclic loads might make a big difference. The one thing we don't want is to trumpet some Fabulous New Idea, only to have it fall apart when it matters.
Fair leads,
Brion Toss
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I can certainly make some up and send them to you. However, what I have is Amsteel. Perhaps Samson would be interested.
From an engineering standpoint, it would be great to know the strength of the individual parts of the shackle. If the same size line is used, then the diamond stopper loop is the weak point. That can be made stronger by just going to the next size up for the stopper loop. Knowing the strength of a normal soft shackle would give me that as it has the same failure mechanism but I have seen online numbers between 120% of line strength (too low -- I don't believe it) to 180%, closer to what I believe. Next would be the strength of the eye itself. That should be something over line strength but we could probably just call it line strength. Finally, the strength vs. bury length for the main loop. Of course, if it is used as I am assuming and is constricting the yacht braid eye splices, it is going to be stronger.
I am wondering if you already have some of these numbers, the normal soft shackle, the strength vs bury length. I know you did some work in coming up with your 72 diameter number but am not sure if you did anything down to the 21 diameters I am using. Obviously these need to be stitched or they will just slip at low forces.
If these numbers do not exist, then best guess would be to use 3/16 for the shackle and 1/4 for the stopper knot and do some testing. As I said, I am happy to make up some samples.
One final point. I have two designs. One with the eye buried and one with the eye just passed through. I like the one with the eye just passed through as it is shorter and easier to use but I am less confident of the construction. But that is another variable. I also did the design with the diamond knot in the center between two shackle eyes. I don't like that because it is weaker and solves a problem I am unsure even exists.
I hope I am not making this too complicated.
Allen