Rope

[pantheraba]

Cool to see quantified how each wrap adds to the friction...thanks.

 

[theTreeSpyder]

Important note, the eye can be fooled.
A single Turn and Half Hitch has only 1 radian Pi power arc of Nip and Brake forces and Round Turn has 3 such power arcs. On the graph above jumping backwards on the exponential growth rate shows single Turn left way behind; not in the running... This carries into all kinds of systems and knots.
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i think a base knot of 1 Turn just hangs on, But Round Turn(RT) different class if performed on the mount (also Crossed Turn base of Clove is Round Turn with more enforced friction) or on the Standing Part is great increase in knot forces.
>>But not RT or Crossed Turn on host mount, followed by RT on Standing Part because the RT (or Crossing RT) on host consumes the 'power' needed to get strength return from RT on Standing.
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The 3+ half circles this way, or upgrading Square Knot to Surgeon's (as linear 3 half circles are close to more perfect knot of long eye splice) i think is an extension of the above 3 half circle arc on bollard theory above; only 3 arcs now alternating/opposing/self balance used to apply to linear pull as some key to knot workings.
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i think these things here are key to all knots and all other rope friction systems as well.

 

[theTreeSpyder]

My 'hook' imagery of proper right angle support of rope pull as ABoK shows as best
>>Then multiple bearings (not solo) of pull for 'lengthwise' pulls as an errant angle of pull.
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Replacing the rope hug effect of sides collapsing in to support (like rigid metal doesn't)with steel no hug
>>more clearly shows the needs of the linear pull load of the system
>>rope hug should be extra pepper, not main dependancy!
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Specifically here of course as anchor for all the brake forces shown above to be applied against
>>but applies to all such geometries of pull, in flexible and rigid devices.
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Pile Hitch is great study of 2 well known base knot forms combined and interwoven where each lowers the loading to the other!

 

[theTreeSpyder]

More hook imagery as decision making field guides:

 

[theTreeSpyder]

Another Best/required reading, free online production is Life-On-a-Line Dr. D.F.Merchant
A very passionate plea for rescue correctness, and the means to do so!
Constantly come back to Pure Inline models of this correctness in all forms here too from educated author.
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Stronger Fig.8 via softer arc thereby closer to straighter line(s) of support:

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AMEN: ABSOLUTELY SAGE ADVICE FOR LINES AND THEIR BUILDS:
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Personally would give Spanish Windlass (tourniquet twister with stick) to tighten brace lines for stakes.
>>But even in these extraneous examples, the Pure Inline mantra fits!
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This and previous book / above Technical Paper BOTH, Very Strongly helped build my views and understandings of working rope.
above Technical Paper: The Mechanics of Friction in Rope Rescue presented to International Technical Rescue Symposium 1999
by Stephen W. Attaway:GA.Tech Masters Structural Engineering + Computational Mechanics (modeling stresses, displacements) Ph.D.
>>mostly for Porty friction model, to then extend to ALL knots,
but then also sift out some yin-yang/reciprocal force of grip on host math in the successive half circles quoted (friction co-efficient removed)
to explain differences shown AND as a separate exploitable/valuable item of it's own inside the secret world and force lines of knots, et all working rope.
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Even the 2nd best selling MILLENNIUMS old text in the world of all time and likewise core of human thought and development stands as: "Euclid's Elements" (of Math, Geometry, Logic etc.) points to sifting to straight line models!
>>#1 strategy of digestion and sorting; and what to chase thru there lists as:

"The technique of abstraction, based on ignoring physical considerations which are seen as merely incidental.
Whether it was a rope, a piece of wood or any other physical object was irrelevant.
It was all about properties of 'straight lines' connecting at angles, nothing more.
These lines are simply mental constructs and the only entity necessary to the solution of the problem.
The process of abstraction is about getting rid of all the nonessential elements and considering only what is fundamental." (LINK)

i find the 'Pure Inline' mantra here too.
Seems like they were talking about us: force, rope, wood, straight lines etc.!
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educatedclimber.com/ashley-book-knots/ (.pdf) remains the best all around reference; now seen online.
But, the books above present more openly the base , 'abstracted' principles for weighing and measuring all rope works for me;
that i always try to more manually sift and 'abstract'; on own from Ashley; to these the fewest to remember as most deep, pivotal points.

 

[theTreeSpyder]

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For screw links i prefer 7 screw threads, more than only 4 etc.
>>Smaller diameter stock than standard carabiner for same strength
Finger tight, might have to wrench loose.
>>sometimes finger tight -1/8 turn so can't jam impact to seat past finger tight(hopefully)for production use
exception would be remote or permanent use:seat strong.
>>can also add Locktite, but has grit and input more torque for same seating.

 

[theTreeSpyder]

Very nice raw redneck power, nice reverse solution
of large log length arc input into much smaller log diameter to concentrate effort input into smallest output movement
>>for greatest power return from 2x crank arm length input position from axle ÷ axle(spooler) diameter
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Usually do this kinda winch, as more vertical, Spanish Windlass perhaps capstan models.
>>Plenty of larger arc input all the way around.
But Horizontal Winch of same design runs larger input arc dead stop into ground
>>but then flip/flop center axle, to reverse input direction AND KEEP OUTPUT DIRECTION as solution!!
Also, power of wraps and turns on the 'drum' to leverage against tightness, prusic safety, real ods-cool seen this shown between saplings w/o side stakes(as option)
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i specifically do not favor knot (~2:30-3:30) he calls Constrictor(??), not to frame (but probably has tow pkg. to bumper anyway but still prefer to frame round screw link forever kept in favorable hole usually for strong rounded face mount) but then to that thin, sharp/squared hole
>>thought he was going for Adjustable Hitch (very favorable) but still prefer pulling on round face, direct to frame (at least to start thinking)
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<iframe width="560" height="315" src="https://www.youtube.com/embed/QFDGGht3CQU" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
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i learned can to can't as what about a working farmer going from when can see, until couldn't.
>>Then sometimes feeding, before/after
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Later personally became this line that defined if could win or not inside, and what thing (to then focus on) made all the difference.
>>Sometimes even handicapping self or overloading past normal to put self in that maze and see what it takes to get out etc.
>>keeping up with biggers was part of it always and all ways; sometimes even then showing them how to move and do better.
With imagery of strength of weaker is a more sensitive device to read and tune by, than one that can just overcome! Bigger tries to bulldawg every wall and win as always has, smaller looks to finesse, align, ballast and slip out after aligning windows as has always done.
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Systems with fewest parts lends best to this of course>>As they even alone can show and highlight fail points already easiest etc.
>>to me, this is one of those of minimal parts, real raw power display, ingenious reverse etc. Illustrating in very few parts, what every similar system needs, and a very smart solution, safetys etc.

 

[lxskllr]

Clever. I think weighting the line would be prudent to help prevent lashback in case of breakage.

 

[theTreeSpyder]

DEFINITELY, could use branch or tarp over each end to confound recoil Thanx!

 

[lxskllr]

Any reason I wouldn't want to use this rope for rigging purposes(prusiks and such)?

Diameter (mm) 9.5
MBS Rating (lb) 5,237
Elong. at 300 lb (%) 1.2

https://sterlingrope.com/store/work/ropes/water-rescue-ropes/ultraline

It's a water rope with a spectra core, and polypro sheath. A little stretchy, but the breaking strength is reasonable. It probably doesn't take heat well, but for rigging, the only heat will be generated by local force. I got it in my bag of rope ends, and would like to use it for something productive.

 

[Jonny]

A prussik which will be used for what?

Isn’t 1.2% not really stretchy at all?

Sounds slippery... thinking poor knot holding. Like you said, falls apart with little heat, in this case probably the core as well as jacket. Polypro doesn’t take abrasion well.

There’s a good reason so many ropes in this industry use polyester, especially in the jacket. Mostly abrasion resistance, ok with some heat, low stretch (which isn’t ALWAYS a good thing in rigging or climbing), holds knots and grips well. Just relatively inexpensive, tough and durable stuff that performs well and begins to give obvious warning signs when it’s reaching retirement time, barring overloading and hard abuse.

I don’t know a lot about spectra except if used in the wrong termination or weighted at an extreme bend radius it is self abrasive ( try searching info about the bridges on the old Weaver Cougar saddles), it’s very strong and often found in cores making it hard to inspect.

I’m not a boat guy... maybe if you know someone that is they might use it?
Might be handy for non critical utility stuff like tie downs... probably handles the same if it gets wet and freezes, if not it’ll probably shed the ice easier than other materials.

I’m sorry but I can’t say I’m 100% positive about all I wrote, it’s all just kinda the impression I’ve gotten over the years. Do correct me if I’m wrong... it could be important.

 

[lxskllr]

A prussik which will be used for what?

Isn’t 1.2% not really stretchy at all?

I was thinking for joining ropes, attaching pulleys for redirects, progress capture...

1.2% isn't a lot, but that's at 300#. I wonder if it keeps going. Is it 3.6% at 900#?

I should just try it out when failure isn't a huge problem. There's a few ways I could see it being an issue, but the best way to find out is to do it, and see what happens.

There isn't enough of this particular cord to be useful for boating I don't think. I got a bunch of 3/8 grabline, and that would be nice for a compact throw rope that could be stowed on your PFD. Maybe I'll get back into whitewater, and I can use it myself, or if I get motivated, I could put something together, and sell it. Probably not though.

 

[Tree09]

Everything you make out of rope is handy, really anything you make out of anything is. I wouldn't recommend using it for rigging tho, after the cougar thing I've been all polyester all the way. At least you know it's not gonna turn to dust by internal friction. Since it's in the core, you can't inspect it at all. Probably why it is advertised as a rescue rope, designed to sit in a locker on a boat until shite hits the fan and you need a strong rope to tow or something. Small diameter so it doesn't take up room and strong. I do believe that kind of rope is common on racing sailboats tho, but they don't care about the lifespan if it works.

 

[Brocky]

Spectra is very similar to dyneema, very slick so knots don’t hold well under heavy loads. It’s not self abrasive, those are aramids, Technora and Kevlar. The polypropylene would grab better than nylon and polyester, it’s not as slick. This two materials combined will float making it a good water rescue rope. It would probably work very well for a hitch cord, as long as you keep in mind the lower melting points.

 

[theTreeSpyder]

Would favor high melting point for friction hitch, as this cord gets as much friction as all of host life line.
Would be typically dividing load on that leg of host life line between both ends of Prusik collectively.
>>See sample load 100# on one end of cord/other end secured as 100# to cord
But pulls from both ends as only 50# tension on cord transferred to lifeline bearing full 100# tension hardness of full not half load.
>>thus visualize 50# on 1 end of cord ballasted by 50# other end of cord.
>>so 50# of force trying to grip tighter 100# leg>>doable by coil mechanic only
>>visualize cord gripping steel pole to hold you type model
Put more on your side by choosing cord that has better means to more dent host life line.
>> more than just coils, look at no response as 100% strong, always look for a second stop mechanic , especially in life support. Let the hardness of cord work for this, even on higher tensioned host line grabbed.
>>leave behind cord gripping 'firmer'(than cord) model, and raise mechanic to cord is as firm or firmer than the higher tensioned line it grabs.
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Choose typically smaller diameter cord than host life line for same force funneled into smaller footprint of higher pressure.
>>prefer stiffer , non elastic cord for less relief of these forces, less hard seating if stretched into coils, and less play/slop in system.
Cord should then feel stiffer, harder than life line side by side, both relaxed.
>>but still flexible enough to seat on host life line.
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Would simply choose cord from lines offered for this, super especially if new.
As generic like from boating catalogue would lean towards sta-set as a basic hard, strong, polyester, double braid. 50-75% of proposed host line diameter.
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Something to be said for getting cords and ropes designed for task. Our Arborist lines are laid and sometimes even coated for our usages that would more quickly shred common lines. This environment has rigors and lessons like few other.

 

[theTreeSpyder]

Cracking the code
>>and so by extension can fill in the blanks:
(otherwise known as mebbe i don't get out enough cuz find this exciting)
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i didn't think 180 degrees would yield this much?!
This is for the load force turns only
NOT the 'drawn together' force of making a Half Hitch under a 180degree turn
>>the drawn forces under centerline of host mount are NOT part of the load arc math shown
the drawn together frictions add to the math, but NOT part of half circle /radian arc counts on chart.
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Just like best nips in the power rope arc of load, NOT the drawn together forces to Half Hitch.
>>Nip forces in single turn reduce from top/opposite load pull to centerline of host mount
>>while conversely Nip forces build greater to centerline from drawn together force of Half Hitch.
The load force want rope to pull away under centerline in single turn, the drawn force fights just enough to bring Half Hitch together to overcome load force wanting to be straight legs, then from the drawn together Half Hitch, frictions increase up to centerline

 

[theTreeSpyder]

Distilled to show this is TOTALLY degrees(really radians) of contact
after setup for exponential growth, of a given friction, on a circular object >>And where those numbers come from!
>>ie same brake friction force from same rope on 4" or 48" matching material
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Thus, larger host drum/pipe/branch/capstan would be for strength and softer arc deformity of rope around arc
>> NOT brake force by size of branch/pipe etc. which is determined by the amount of half turns
extending to inside of knots, friction hitches (knot internals and friction hitch rope on rope grabs) etc.
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This, re-affirms:
Rope only supports on the inline axis, in the tension direction.
Thus, a straight line is the basic rope component, and half circle arc back to same axis is second basic rope component
>>straights only connect points >> the half circle arcs are the base of the knot's/system's magic

 

[lxskllr]

Makes sense. An infinite radius(a flat plane) would have virtually zero braking power.

 

[theTreeSpyder]

Not if no force downward/but across, round is a special gradually changing landscape, with flexible rope device mating around arc(s).
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Cracking the code:
>>should also note, these calcs are not for the bottom half of limb grabbed by Half-Hitch>>this is a drawn together/not load powered frictions
>>the Draw to half Hitch position is ADDED (not exponential) load friction force added to load powered radian force arc chart shows
>> thus lower half of Half Hitch is worst Nip position too; as not part of the load powered radian force arc(s)
In Half-Hitch there is only 180degrees, of chart's exponential frictions TOP half of branch/host mount OPPOSITE load pull side
>>the lower drawn together rope ends to make actual Half-Hitch do NOT count in this math exponentially, just add a bit of frictions after.
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Friction co-efficients for materials are a standard stated chart, of not very many rope on self/wood/metal references
>>i think spreadsheet calculations shown can decode what been seeing, feeling and questioning in many ways
>>and can't find any other chart of such comparisons as even serially in 1 material mating pair, let alone cross comparisons of materials
>>rope condition of worn, glazed, dirty, wet etc. can change critical coefficient some
This, is key to many questions and usages, as arc frictions rule in knotting.

 

[theTreeSpyder]

Benchmark 10x friction leverage of control leg over load leg @ 3arc Round Turn paper shows as nylon rope on aluminum brake as .25 friction co-efficient.
Seeing is believing, pull back the curtain shroud of mysterious patterns for the math to show the connective points lined up to a fabric contiguous flow can better see logic in.
The math reveals the commanding forces as a pattern, as field thumb-rule to paste to a few benchmarks, for better feel of what truly is going on.
So see/reconfirm more concretely and can back it up in standard ropes we use to this formula, RT very good, but not in Dyneema etc. Then how much more friction hemp has, thus why some knots not used anymore, as don't work well in the lower 'frictive'(knudeNoggin) hemp; is jsut not something ya say, heard, seems so, but prove-able to deploy with more confidence etc.
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Once again, the capstan math on support doesn't include drawing ends together as to HH, that is not an load empowered arc,
>>it is a draw together of unmounted area of line, that load force wants straight, but draw overrides enough to bring ends together in HH

 

[theTreeSpyder]

Taking capstan math full circle (so to speak); back to beginning, re-describe knots, even more confidently steering attention to arcs etc.
Knots and rigs made of straight lines and the half arcs.
Look for lines not to be pure straight/need truing to cosine math;
But frictions and grips that give knots controls, are from the half circle arcs of the capstan math.
Defining most of knotting until enter extreme elasticities in for (more)deformations.
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My simplified view of 'paste' and 'pinch' in 1arc single Turn, to understand Clove 'paste' crossing and Cow type 'pinch' in 3arc RT re-arrainged to these forms:
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Adding HH to the mix to be able to release line now and still hold, tracing thru power arc capstan logic of turns on host /mount
>>adding same theory to HH's around standing, finding RT + 2HH as 3arc on support by RT, held by 3arc 2HH's as benchmark model
>>even tho Bitter End doesn't Nip most properly inside the power arc of capstan math, but rather in the weak Nip of draw of ends together against load force's wishes.
>>Anchor Hitch corrects with Bitter End easily placed inside the power arcs to Nip better.
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As side note: Heard IRS agent yesterday describe an audit as an autopsy w/o advantage of dying first!

 

[Marc-Antoine]

Thanks to decode this mechanic Kenny.
It's always nice to connect the "why" and the "how to".

 

[theTreeSpyder]

i think leads to more confident and competent decisions,
but also, to check and tune senses against and to the math.
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My take on similarities of Overhand Bends: Zeppelin/Rosendahl , Riggers and Alpine
>>and why Rigger's more prone to jam than other 2.
How related to basic forms , descriptions of force flows and mechanix i see this is based on

 

[theTreeSpyder]

i think Sailor Hitch is amazing knot with many lessons, tho a much lesser known lacing.
Worst features are don't untie from pull side (like favor after lowering)/ need access to top side for upper hitching and placing pulley etc.
and, loads minimal section of line do to 'top nip'/ opposite side of mount than load pull which is great
>>unless small host mount; like shipping dock hook as small size in ABoK , especially when same hook is diameter or larger than line diameter(@ ordinary line stiffness).
Pile is great for shipping dock hook if line not too big/stiff
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Else, just have to know how to tie, is similar to Pile Hitch; is see both as 'Crossed Backhands' per almost a Clove plus, or maybe almost Cow plus as hybrid of both.
>>Better Nip and less deformation/greater strength retained if load/load hardest from the Cross Hitch leg
So has that strength and Nip, with the easy untie of Cow after HARD loading.
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Add coils to Pile's Cross Turn side and pull lengthwise across tail and can carefully load weight on a receding taper and will lock down!
>>lengthwise being most aberrant angle of pull X aggravating condition of unfavorable taper
Add coils likewise to Sailor Hitch to pull lengthwise away from coils again trapping tail under again, and get Sailor Gripping (or Gripping Sailor) Hitch.
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Whole point of Sailor Hitches to me tho, is to position the crossing flat on top against downward pull.
This is always best Nip position, but needs host mount to have proper contours (that Sailor architecture lends to situation) to hold the highly valued positions
>>so i use Bitter End as handle for this, or slip the Bitter End for 2 side pull handle (or mod if not slipped/will show later)
When hit the top nip correctly, the rest of lacing relaxes considerably as almost un-needed , including side tension on Standing Part IBeam of support to load, thus more rope strength efficiency. So well is the hang from this point, that Ashley notes won't scrub/saw branch to and fro like side nip strategy of Clove. Top nip is that unique.
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[theTreeSpyder]

Capstan equation for brake force has more to do with using as pipe wrench against radial resistance than as windlass were a pipe would be more of just take up reel for linear lift resistance. Same tools against different points of resistance of different types change the machine were force input 'voltage' into same leverage multiplier forcing same lacing onto same host; force just terminates against different load types.
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Dry ashes can help grip also. Pipe etc. can get rope burns from fight to turn if lots of resistance. Sliced inner tube /rubber flexible sheet can give better grip than ashes and some surface protection against marring if issue.