Sheepshank is a type of
knot.
Canonical Name: sheepshank.
Variant Name(s): None.
[completed picture]
Category: bend.
Origin: Ancient.
Related knots:
Releasing: Non-jamming. Holds shape under tension but may fall apart if the tension is removed.
Efficiency: 46%.
Caveat: spills[?] if not under tension from both ends.
Uses: The main uses of the knot are (in decreasing order of usefulness):
- secure a load in a way that can be easily undone when no longer needed, but provides a block and tackle mechanism allowing a load to be secured much more tightly than is otherwise possible.
- shorten a rope (though there are better ways to do this)
- bypass a section of frayed rope - useful in poor economies where rope is expensive
Comments:
Structure:
Tying:
The knot is constructed as follows:
- pull a section of rope back and lay it alongside the rope, so that the rope forms a Z approximately 20 cm long.
- flatten the Z so that there are 3 sections of rope lying alongside each other, with two U-bends where the rope reverses direction.
- at each U-bend, grasp the U-bend in one hand, thus holding two of the rope sections. With the other hand form a small loop in the remaining section and draw it over the U-bend so that the loop forms a half hitch and stays there if the free end of the rope is pulled taut.
- repeat at the other U-bend.
The result is a flattened loop which is held at each end by a half hitch. If the sides of the flattened loop are pulled away from each other, the flattened loop ends pull out of the half hitches and the knot falls apart, but if the free ends
are pulled taut then the knot remains secure.
This knot is extremely useful for tying loads down such as on a trailer or truck. The knot has two features which make it invaluable here:
- it provides two loops, one at each end of the knot which can be used to pass a rope through.
- the knot remains secure under tension, the coarser the rope the more secure it is
- the knot falls apart easily when tension is removed.
The last of these attributes is invaluable. Other knots will bind tightly and be almost impossible to undo if the knot has been placed under great tension. This wastes time, rope and tempers when trying to unload when a load has been delivered. The sheepshank by contrast will fall apart immediately.
Typical use in tying down a load on a truck is:
- start with one end of the rope tied in a clove hitch around a rail. If the rope is reasonably coarse and this clove hitch is held under tension then it will remain secure.
- pass the rope over the load, around a rail on the other side of the truck and back over the load to near the original clove hitch
- pull the rope reasonably taut and then form a sheepshank about one metre from a rail on the side of the truck.
- pass the free end of the rope around the rail on the side, then back through the loop on the sheepshank nearest the rail, then back to the rail.
- pull hard on the free end of the rope to tighten it. The structure of the knot provides a leveraging effect like a block and tackle, so that considerable tension can be brought to bear to secure the load.
- when the tension is sufficient to secure the load but not damage it, pass the rope around the rail and tie it in a series of half hitches. If the rope is likely to bind and be difficult to untie then use a loop of the free end, so that each half hitch can be undone by pulling on the free end of the loop.
For securing loads in this way, only 3 types of knot are required: