ANY simple enough, stable knot would nip/grip a penetrating line / a returning eye leg very efficiently, if this line enters in it and exits from it in the proper, optimum "Eskimo" like way, and follows an L-shaped path. The only thing we should avoid, is a too convoluted / too complex nub, which will absorb a great portion of the tension that otherwise would had reached the penetrating line more directly, without being dissipated across a larger area of the nub, or being obstructed by loosely tensioned segments.
If we relax the TIB condition ( which led me to the
Pretzel loop ), we do not even need to tie a
double overhand knot -based nipping / gripping nub, as shown in my previous post (1) : the
single overhand knot is enough. If we let the penetrating line enter into / exit from it as shown in the attached pictures, i.e., so that
the overhand knot "works" almost as a Clove hitch ( which, as we know, is a very tight knot when tied around ropes ), we get a quite satisfactory, simple and stable solution (*).
All those nubs need not be clinched hard around themselves before they become loaded ! The only thing we should pay attention to, is to dress them correctly, so they will remain "balanced" when they will be pulled by their three limbs ( and they will nor rotate around themselves, or capsize ). As the nubs becomes more convoluted, they become more stable, but they also consume, within their own segments, a significant portion of the tension that would otherwise reach the penetrating line and increase the friction forces which will immobilize it.
When we find such a tight nipping / gripping nub, the next thing we may think and try is to use it as base for a secure
fixed eyeknot, by adding a collar, a-la-bowline - because it is natural to imagine that an already very tight nub, helped by a collar that reduces the tensile forces which reach the last segment of the Standing Part, would be an ever more secure solution. However, the fixed end-of-line loops, in general, and the bowlines, in particular, do NOT work like this. In the adjustable loops, we need as tight nubs as we can get, even if they may become almost jamming, because we have one, only, line of defence against the slippage of the returning eyeleg, while in the fixed loops, where the penetrating line can follow a much more convoluted path than an L-shaped one, and we can also have collars, it is the other way around ! The nipping structure of the bowline, the knot tied on the Standing Part before the eye, is based on TIB knots, which do not "close" around themselves, and run the danger to become difficult to untie. That is why we should better avoid ANY not-TIB knot on the Standing Part before the eye ( that is, a not-PET solution ), but we also be careful when we use such a knot
even on the Standing Part after the eye - during a heavy loading, even the tension delivered on the nub through the returning eye leg ( which is 50% of the total ), can force the nub to clinch around itself too tightly, and become difficult to untie.
1.
http://igkt.net/sm/index.php?topic=5322.msg35761#msg35761(*) To be precise, the nub of the adjustable loop shown in this post has the geometry of a
Clove X hitch ( X = crossed continuations of the ends into the nub ) - which, topologically, is not equivalent to the unknot any more, as the parent
Clove hitch, but to the
overhand knot. To some knot tyers, it would be easier, perhaps, to start from a
Clove X hitch, and penetrate it by the returning eyeleg, than to start from an
overhand knot.