Moderator: Tim White
Scott McCrea wrote: You can do a tensionless hitch on a bight in the middle of a rope.
Phil Winkler wrote:two half hitches.
GroundquestMSA wrote:What knot would you use if you wanted to tie the midpoint of your rope into an anchor but for some reason couldn't use a tensionless hitch. Say you are tying into a rail or angle iron with small diameter. Also assume that you haven't any other material with which to build an anchor. Would a bowline work ok with such a doubled rope? I don't know what this would be called. Besides a bowline. A carabiner could be added to the tail (which would be in the form of a bight) and clipped to the loop in place of a backup knot? OR Would you just tie a fig.8 bight and clip it to he main with a carabiner?
Scott McCrea wrote:Tensionless hitch on a bight: two wraps and biner back into the main. Just like on a tree. Diameter of the anchor (angle iron) doesn't really matter. I would pad the angle iron though.
Stridergdm wrote: the number of wraps is independent of the diameter of the post (basically the smaller the port, the tighter the "angle" formed by the rope so more force is imparted over the smaller surface area).
GroundquestMSA wrote:After playing with the tensionless hitch on a bight on 2" square ladder rung (closest I had to the little angle iron I may have to rig from), I guess that it would hold, but it wouldn't be "tensionless". Remove the biner and the wraps slip off immediately, no matter how many there are. Of course, with the carabiner in place, it worked fine, it's just not the tensionless hitch I'm used to; the one that works almost entirely by friction between the anchor and rope.
GroundquestMSA wrote:Stridergdm wrote: the number of wraps is independent of the diameter of the post (basically the smaller the port, the tighter the "angle" formed by the rope so more force is imparted over the smaller surface area).
The good old capstan equation right?
I should correct something I said earlier.GroundquestMSA wrote:After playing with the tensionless hitch on a bight on 2" square ladder rung (closest I had to the little angle iron I may have to rig from), I guess that it would hold, but it wouldn't be "tensionless". Remove the biner and the wraps slip off immediately, no matter how many there are. Of course, with the carabiner in place, it worked fine, it's just not the tensionless hitch I'm used to; the one that works almost entirely by friction between the anchor and rope.
Even in this setting the biner is not under tension unless the rope is loaded/unloaded repeatedly. However, the carabiner does keep the hitch from failing. I remember Eliah Kagan arguing that the tie-off in a TH was vitally important and kept the hitch from collapsing and failing. While many of us have demonstrated that this is not the case in some settings, such as when wrapping a big rough tree, it is true when wrapping a small diameter, low friction anchor.
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