The Blackwall hitch is a GREAT knot. ( It occupies one of the 12 places in my personal Pantheon of "old" knots, and I believe it will stay there, for ever). It may be considered as the pinnacle of what people call, without giving much thought on this, "half hitches" - a class of knots which includes quite different structures ( many of which are nothing but disguised nipping loops/turns ).
Of course, in this great era of great knot parroting ( and not-great knot parroting - the only thing that is always great is the parroting itself
), where most "knot users" WATCH pictures of knots, but they do not actually tie and try them, and they do not even imagine they could tie them differently, or modify them, this knot is almost unknown. The internet popular super-markets, which advertise / promote / sell knots, present it as a hitch tied on a hook, so most people, who have never used or even got close to a big hook ( like those used in construction work, for example ), believe that this is not a knot they will ever "use". I had not seen any of those knot-sellers to mention that the part of the hook utilized by the hitch is no different from the part of a same-size ring, so the Blackwall hitch can be tied on/within a ring as well. And, of course, nobody mentions that it can also be tied within the tip of a tensioned bight - perhaps they believe that this could frighten the naive customers !
However, the Blackwall hitch within-a-bight, as I use to call it, is nothing but the incarnation of the "original" Blackwall hitch tied within the rope of the bight is less slippery than the "corresponding" hook or a ring, it may work even better.
Therefore, it is no surprize that the very first knot that crossed my mind when I was trying to figure out how to attach the Tail End of the Yoke hitch to the bight of its "second" wrap, was the Blackwall hitch within-a-bight. Less convoluted, less prone to jamming, consuming less material, requiring less tucks than the overhand knot-based solutions ( ABoK#1821), in short, a clever minimal knot, which should always be the first thing we try when we have to attach an end to the tip of a tensioned bight.
One can understand my surprize when, after the first, after the second, after the 12th try, the Blackwall hitch within-a-bight itself remained firmly attached where I had placed it - but the Yoke hitch as a whole, based on it, failed to work, even once ! By pulling the Standing End against the pole, all that one does is to force the transport of its entry point from the "rear" to the "front" side of the pole, without tensioning the wraps themselves at all. The two wraps and the pole rotate relatively to each other, but the tension one would had wished to be generated by this motion remains notoriously absent : the wraps do not start to shrink when they should had to, so they do not stop sliding on the surface of the pole, so they do not stop rotating, so their crossing points ( the two parts of the tackle ) do not stop approaching each other, until they finally close the gap, "kiss" each other, and the whole "tensioning" phase terminates - without any tension. This is exactly what one would had anticipated a "Tackled hitch" should behave, if he had only "watched" Tackled hitches, and had not actually tied properly and tried carefully a sufficient number of them, a sufficient number of times. In the attached picture, one can see the initial stage of the Yoke hitch with a Blackwall hitch within-a-bight finish : Not very different from the much less clever solution of the slipped overhand knot or the ABoK#1821 shown in previous posts - yet it seems that the less clever solutions work, and this more clever solution does not !
Why is this so ? Why this clever solution does not contribute ( someway, I do not know how ) in the early shrinking and the subsequent tightening of the wraps of the hitch during its transformation imposed by the pull of its Tail End against the pole, while the dumb solution based on the overhand knot does ( also somehow, I also do not know how ) ? ? ? I simply do not know...
