Aha!
Hi again,
Partly you are victim of the World's Least Logical Measurement System, aka the Metric System, partly it appears that New England's instructions are in error, and partly, you are making stuff up on your own. Splice bury length should be determined by how much friction you need to generate to assure absolute security; bury less than that and you risk having the splice slip, and bury more than that and you weaken the rope and make the splicing process needlessly difficult. On halyards, you can also limit hoist height by having the splice reach the sheave sooner.
I use 48 diameters of the rope for covered HM fibers, and this corresponds roughly with the fid-length method, but is much easier, I believe, to calculate. And the formula actually works fine with the Metric system (10mm x 48 = 480mm = about 1ft 7"; 3/8" x 48 = 1ft 6"). Even if you had been splicing 7/16" rope the tail you are using seems way long, and that is because the New England on-line instructions specify "3 full fid lengths". Samson's chart corresponds to my 48 diameters. I need to see what New England has to say. Meanwhile, going to a larger fid size for a "safety factor" is to assume that a generous safety factor doesn't already exist; why would you do that? This is like making your standing rigging one size bigger before going offshore -- it sounds prudent, but has no logical basis, and can actually make things less safe.
In this case you started with someone else's mistake, and then amplified it completely off the chart, and wound up with your 8" shrinkage. I doubt that the splices you made are actually dangerous, but in the interests of an optimal splice, please use the proportions that thousands of splices have been shown to work. By learning to splice, you are joining a great and enduring community of artisans. Work with us.
Fair leads,
Brion Toss
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