Joining anchor rodes

[eldergeat]

A while ago there was mention on this forum of an MIT study which gave support to a method of joining two lengths of rope together in a way that retains strength, minimizes chafe and does not rely on shackles and thimbles. Each line must terminate in an eye splice. You pass the opposite end of one line through the eye of the other and vice-versa. You then snug them up. The point of connection resembles a square knot. I have also seen this mentioned a other boating sites, often in the context of hurricane anchoring. Does anyone have a link to this study?

To use the method, you must have access to both ends of both lines. There is a related method that just relies on both ends of a single line. As before, both lines must terminate in eye splices, but now you pass the eye of the first line through the eye of the second, then pass the end of the first line through its own eye. The connection ressembles a cow hitch rather than a square knot. Here is a link to a site dedicated to the Jordan Series Drogue, with an image showing two bridle lines connected to the forward eye of the drogue, using this method:

http://jordanseriesdrogue.com/D_6.htm

Does anyone know whether this method of connection has also been tested? Was it mentioned in the MIT study? Does anyone have experience with this?

[Ian McColgin]

Bad plan. The big thing that causes knoted lines to fail is turning radius and the two eyes made like a squre knot manage that. In addition, it's hugely more trouble to make up than a nice Carrick Bend with siezed ends and that bend has been well tested as weakening the line by but 15 % to 20%.

If you go through all the work of a couple of eye splices, why not make a nice short or long splice with will not weaken the lines for the same work?

[billknny]

I'm not somebody who is often going to argue with Ian, he knows a lot more than I... but in this case before I agreed with him I would want to know if he has data supporting his skepticism about this kind of connection or is just going by his gut.

Cowhitching two spliced loops certainly seems to me to be a valid way of attaching two lines of different diameters, or for semi-permenant connections where a splice is impractical.

This kind of connection would seem to have certain advantages over most knots, in that the load is well distributed over all parts of the connection, with no single point carrying more than 1/2 the total load. Knots have a single lead back to the load, so there must be a higher concentration of forces at at least some of the knots turns. The carrick bend with siezed ends might just be the exception....

Of course, my comments are based on MY gut, so they are worth no more than you paid for them.

Obviously all his comments about this being potentially awkward stand.

Bill

[Dan Lehman]

Originally Posted by Ian McColgin

Bad plan. The big thing that causes knoted lines to fail is turning radius and the two eyes made like a squre knot manage that.

It's not so simple as that--turning radius around metal, e.g., turns out to usually NOT
be the point of failure, I think. In some testing of a Strangle Noose (Strangle/Dbl.Overhand
tied around standing part of noose hitch), the break came at the point of the sharp,
1-dia. turn, but in the mainline around which this turn was made! Ditto for Buntline h.?!

In addition, it's hugely more trouble to make up than a nice Carrick Bend with siezed ends and that bend has been well tested as weakening the line by but 15 % to 20%.

Except for the pulling through of the entire length of ONE of the eye-spliced lines,
which might be seen as simple and not so much trouble, the seizing of the lattice form
of the Carrick bend seems more trouble. And, as the OP asks, where is ANY testing
information about this structure? --it's been referred to (the structure, i.e.) in many books,
but I've NEVER seen any hint of actual test data for it (and that for the capsized form
is well below 80% of tensile, though that might be pretty laid-rope-particular data).
And, to my mind, a LOT of the integrity of such a structure depends upon the seizing
--which must serve to effectively make an eye in the lines, splitting the force to the
end part; and if one seizing fails, the structure will spill.

If you go through all the work of a couple of eye splices, why not make a nice short or long splice with will not weaken the lines for the same work?

For having size-adjustble rode, er, modules--vs one hugely long line (less easily
turned end-for-end to distribute wear, e.g.).

I don't understand the OP's intended distinction between some TWO methods:
these are really the same thing, though the Larkshead form I think is inferior.
In any case, the assertion of needing access to BOTH ENDS in nonsense: one need
only one end: place associated eye around the end-INaccessible eye, then reeve
accessed ONE end through said other eye and haul away--QED.
One could try to improve breaking strength by repeating this algorithm such that instead
of a SquaREef-knot-like structure one had the additional wraps of a Surgeon's knot.
But it seems that of concern then is the amount of slip-tightening and related frictional heat!?
--YMMV.

Another method of joining eyes is to employ a short THIRD bit of cordage, with which
one binds the eyes together in any of several geometries. E.g., bring one eye down
through 2nd eye; pull 1st eye through a little ways, sufficient to ... ; bring the sides
of 1st eye out around and over 2nd eye's; then bind these 1st-eye sides with a cord,
making several wraps, and tucking or tying cord ends (little tension will be on ends).
This describes a sort of extended Reef-like structure, which should be quite strong,
easily implemented, and easily untied.

--dl*
====

[Brion Toss]

Hi all,
First, you might want to see my related post on the Ring Hitch for HM lines, as it is about a similar structure. Next, one of these days we'll do some tests on the seized Carrick Bend, but for the moment I love it as an easily disassembled structure, particularly for very large lines. A few hundred years of field testing has shown that it can work just fine, given good seizings.
That leaves the question of hitching two eyes together. Because the load is balanced going into the know -- unlike, say, the Square Knot that the structure resembles -- there must be, as pointed out above, less tension load or shear on any one part. No doubt there is some weakening involved, but again field testing seems to show that it isn't critical. I'll see if I can come up with some data on this (it's around here somewhere).
Fair leads,
Brion Toss

[Ian McColgin]

Brion's information will surely help. I was thinking of simply the turn, rather as a bowline so weakens a line compared with a splice or even, if applicable, two turns and a taughtline hitch. The fact that such conjoined splices put equal stress on each leg of each splice might, more importantly than sharing the pull strain, share and spread the fiber stresses that travel from the bends in a way less damaging than the way other knots, again the bowline, put all that stress right back up the solo standing part.