Author Topic: Constrictor and Strangle biding in surgical ligature knots  (Read 1346 times)

mcjtom

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Constrictor and Strangle biding in surgical ligature knots
« on: June 21, 2022, 06:18:58 PM »
A nice paper on a set of tests on the holding ability of a bunch of binding knots on surgical sutures.  The interesting part to me is the comparison of the Constrictor [#1249] with the Strangle [#1239].  The Constrictor wins (it basically holds better), which is common lore, but I haven't seen any testing done on it - on the suture, or on other cords. 

It seems to make sense to me considering that the riding turn in the Constrictor presses down on two strands on top of each other (higher friction between two ropes than a rope on the object, plus more transverse elasticity/rebound to keep the construct tight) whereas in the Strangle the riding turn presses two strands flat against the object, more or less.
« Last Edit: June 21, 2022, 06:22:58 PM by mcjtom »

Sweeney

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Re: Constrictor and Strangle biding in surgical ligature knots
« Reply #1 on: June 22, 2022, 12:11:15 PM »
It seems to make sense to me considering that the riding turn in the Constrictor presses down on two strands on top of each other (higher friction between two ropes than a rope on the object, plus more transverse elasticity/rebound to keep the construct tight) whereas in the Strangle the riding turn presses two strands flat against the object, more or less.

I agree - I do use a strangle knot occasionally but only because it has a slightly neater finish and holding ability is not paramount.

Sweeney

Dan_Lehman

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Re: Constrictor and Strangle biding in surgical ligature knots
« Reply #2 on: June 26, 2022, 07:46:26 PM »
And then there come the **multiples** of these two
binders, where I think one will find the constrictor
to be of diminishing appeal :: going "multiple" means
that the width/length --span along bound axis-- will
increase, and increasingly the C.'s had-been-perpendicular
(to axis) ends will be separated; whereas the S.'s will
remain parallel.

With the strangle, one can use several wraps for making
a whipping, and put in an extra crossing of the buried
ends :: I find that in mason line 4-5 wraps work well with
the extra crossing; with 30#? nylon monofilament fish line,
7-8 (and I usually will finish the knot with a bight from the
whipped-rope's end (i.e., bight'd whipping tail points INwards
along line) and put in a few wraps of sailmaker's whipping (is it?)
in that, then cutting both of the whipping tails short at the
end of the rope).

The strangle also can work nicely with a Gleipnir'd sort of turn
in the middle (i.e., one of its "multiple" wraps will wrap ONLY
the two ends of the knot, not the bound object) ; this serves
well when binding something that isn't nicely round/convex,
so the nipping of pure cord-on-cord is needed.

--dl*
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mcjtom

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Re: Constrictor and Strangle biding in surgical ligature knots
« Reply #3 on: June 26, 2022, 08:02:19 PM »
The strangle also can work nicely with a Gleipnir'd sort of turn
in the middle (i.e., one of its "multiple" wraps will wrap ONLY
the two ends of the knot, not the bound object) ; this serves
well when binding something that isn't nicely round/convex,
so the nipping of pure cord-on-cord is needed.
Any chance for a sketch or a picture?

Dan_Lehman

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Re: Constrictor and Strangle biding in surgical ligature knots
« Reply #4 on: June 27, 2022, 06:09:56 PM »
Dang, I'm pretty sure that I posted a photo of the binders
in pink mason line on 'T'-cross-section'd laundry soap cup
holders --my tying them to part of the washer needing a
secure attachment to the cup : noose-hitch around cup
and then at-cup & at-end strangles to secure line running
out the T-shaped handle.

Tie a dbl.strangle (at least double) around something;
then gently pull out the "something"/object so to be
able to collapse the center wrap to be no longer around
this object but just the 2 strangle ends,
carefully reinserting your something (in small cord,
a pointed pencil comes to mind).

It's not an easy knot to tie,
as you have this present then disappearing object
to surround, or to wrap it but then wrap only the
cord ends --one of which isn't there yet, as you're
still wrapping/tying the knot!

The point/need to the above was to get good nipping
(cord around cord, not around the smooth FLAT plastic
cup handle) and also the secure gripping on the handle.
Absent this "around cord only" wrap,
the strangle would be trying to find pressure against
its ends to hold tight --the flat smooth plastic not at
all helping.

--dl*
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