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I'm sure this has been discussed before, but i can't find it. Does the cow hitch have a stronger braking strength then the timber hitch?
I know the CH is a very secure hitch....if your anker point would to twist around it does'nt come lose very easily compeared to the TH.
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Were this a rockclimbing forum, one might find "braking" meaningful, as a belay
mechanism's aspect; the Crossing Knot / Demi-Capstan / Munter Hitch is used.
As for "breaking", in both cases (Timber/Cow), the SPart passes through a bight,
where greatest pressure is exerted. That 2nd dia of the Cow perhaps help round
out the bight, depending on what additional structure is added to the Cow,
and maybe this reduces the cutting pressure on the SPart. But note that it's,
as TreeSpyder argues, the bend of the SPart that's important, as well as what
pressures come to bear upon it.
To this point, I'd like to see the Timber H. version (Ashley's #1669) where the end
makes a round turn before it gets dogged under itself. This round turn should
spread the pressure on the SPart, and also--Prusik-like--provide some grip of
the SPart enabling the structure to be brought up snug to the object; AND it
would reduce the pull on the end working to UNdog it (recalling LuvNik's account
of dropping a load on a Timber H. that promptly spilled and really dropped the
load, fortunately to the owner's pleasure at such a dramatic landing (while LuvNik
needed a change of undies

).
Frankly, I find it amazing that Ashley shows NO securing of the end of the Cow H.,
although he does for the Clove, as the Cow will slip out quite quickly, unless
tied in pretty frictive rope (and around a non-slick object) or a
ring vs.
spar
or
pile--the latter being of most concern to arborist use (i.e., relatively
large-dia object). Or if the hitch is tied in webbing, with the orientation such that
the end is aligned (beneath or atop) the SPart.
It's also a hoot to think someone might think the Cow a modern invention--a knot
so simple!
The "Cow & Better Half" shown here:
www.treebuzz.com/forum/images/upload/9073-cow%20hitch2.JPG
can be made more secure by having the finish "Half" hitch encompass the Cow's
collar bight (so, bitter end backwards the crossings would be: over-over, under
(itself--red under red--), & then UNDER the Cow bight to come around the block's
line. And no more tying, or at least NOT the dogging of the end that's shown above.
Untying this version best begins with prying off (away & down from pile/tree) the
upper Cow collar leg, and then things should loosen up pretty easily.
Along these lines, let me here (you see it first?!

) introduce what I'll call the
"Collared Clove" hitch. Easiest way to reach the knot (though NOT how to tie it)
might be to work from this image:
gpvec.unl.edu/files/ Knots/CloveHitchQrelease.JPG
With this slipped Clove, give the slip-tuck (bight) a half twist such that the left leg
is brought over the other, positioning the end thus between the wraps of the
Clove; now just reeve the SPart up through this slip-tuck eye, and snug up the bight.
As with the Better Half, the end here gets pretty well nipped by other parts, when
loaded.
*knudeNoggin*