i think the 4 basic differances Nylon vs. Polyester, each point to Polyester in this usage:
1>as Nick says Polyester has better UV resistance.
2>Also ; As nylon slurps up 1/2 it's weight in water ratings drop.
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3>And Polyester better abrasion resistance >> of particular concern in this usage of constant high frictions on 1 area
4>Polyester less dynamic stretch >> of particular concern in this usage;
>>cord too short to give dynamics to system anyway, would get that from host line or anchor etc.
>>but can be harder to work hitch loose to move if stretched closed around host
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Would favor a range of 50-75% host diameter for cord.
>>larger than 75% host diam. doesn't grab rite, less can seize too easily to make less workable fer us.
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Single leg of host support delivering to 2 legs of cord support about 1/2 host diameter
>> is fair rough math for even weakness of chain.
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These are tight bights by cord around host; the stiffer the cord the less 'strength' as turns tight bight and compressed fibers in cord on tight turn wouldn't carry load/so cord weaker, the way i see it. Stiffer cord, more resistance to tight bight, the more compressed fibers, when only tensioned fibers can be used.
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Spliced perm.eyes rule, Double Noose i favor for temp.eye; favour crossing outer Turn of Dbl.Noose over inner to solidify and make more stable.similar reasons for same in Dbl.Fisherman's: Dbl. is stronger, favour crossing Working End over 1st Turn of Round Turn for Dbl.Fisherman's
i favour eye to eye builds rather than sling shown (personal preference, sling still 2 legs of support)
>>seize down Bitt.end w/tape for extra security
Round Turn of Dbl.Noose gives back some 'strength';
>> that is lost from the bend of the 1st Turn bending Standing Part, deforming form 'pure inline'
>>as the 2nd Turn(RT) then hugs the deformity and 'manages' it better, giving it less 'impact of change'(?)
i visualize difference between TV power cord bend going into system
>> or upgraded to grommet, managing/softening/allowing less impact of change from bend of cord into system
(but then i also visualize rope carrying tension as a kin to water pressure in a hose or electrical 'pressure' in a wire..)
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Animals can chew ropes left overnite etc.
Polyester/Nylon pretty chemical stable, but notably feline uric acid very bad!
>>Constantly treat Life equipment as dear friend that saves life; almost Holy
>> every day, in every way, so permeates very Naturally thru everything you do..
Put lifeline in with throwline, pull throwline back into place with lifeline at nite, leave that in over nite.
>> when ready put lifeline back into place with throwline already there.
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i think we'd favour facing krab gate away from hard surface