as a lengthwise pull hitch, maybe no need to be very tight.
The truth is the exact opposite ! Of course, if you want to have as few round turns as possible. With maaany round turns, you do not need aaany hitch !
We should only compare apples to apples, i.e., hitches with the same number of wraps. To be able to enhance the ability of a given number of wraps to grip a given pole, the only thing you can do is to have those wraps pre-tightened as much as possible. Knot tyers have not paid much attention to this, because Ashley s chapter on hitches is very poor, indeed - but we should remember that Ashley is dealing with manila ropes and wooden spars, where friction forces are much higher. (1)
sometimes I tried that tackleclamp, got it very tight around a smooth pole, but it just could nt hold lengthwise pull. it slipped along the pole.
So, you should tie it some more times ...
A not-very-tight, loose hitch that slips along a pole LESS than a very tight hitch ( with the same number of wraps, and on the same pole, of course ! ), uses GLUE !
KnotGod does not intervene in the workings of his creation - so I can not see what will make the one to hold and the other to slip... By the same token, the only way to loosen a hitch, and enable it to slip along the pole without removing one or more wraps, is to loosen them. If You do the opposite, It does the opposite, but you should always compare apples to apples, same number of wraps, same pole, same load, same direction of pull, etc. - in short, ceteris paribus.
just common gleipnir's one turn nipping is enough for a hitch.
seems no need to make it double or triple.
If you are speaking about the Double simple-hitch-la-Gleipnir, I have seen that the second turn, that makes the "nipping tube" longer, offers more room to the standing part / tail twist - so those two segments embrace and remain tightly attached to each other, squeezed upon each other by this longer "nipping tube" and by the pressure coming from the surface of the pole. Remember, the simple-hitch-a-la-Gleipnir is superior to a simple Gleipnir hitch only if it is tied around a round object of a relatively small diameter.
1.
http://igkt.net/sm/index.php?topic=4155.msg25243#msg25243