[MHml] Synthetic Rigging

[Ross Hobson]

from my knowledge of working with a rope manufactur and discussion with a number of others on this subject:
 
halyard increase in length is invariably strech -
 you load and unload and the the weave relaxes and tensions = strech 
- even prestrech has this phenomenon, it is due to the non parallel fibre arrangment of the rope construction.
if you have paralell fibre constrction ropes (they do exist) you cannot splice them. so you have to tie a knot
 
knots (at best) weaken any line by a minium of 60% and often much more - so surprise surprise it is where the line fails. a good splice can achieve excess of 80% of line strength. I have seen my own splices tested on a load cell to demonstate this, and not all splices are equal...
 
creep occurs after prolonged (days rather than hours) continuous load at a high level of the %max /working load of the line/fibre, unlikley in the loads we see in yachts (unless you are offshore for weeks never adjusting a halyard or you have them in a bobstay or simmilar)
persoanlly i have upped the diamater of the line so the load is less than 50% of break in this situation and not had any problems - creep comes down to working close to the line load limits
 
old spectra and newer ones are not the same material (eg spectra 75, spectra 2000 etc) - so comparing 1990's with present day is not like with like.
 
many manufacturers build the rope with inner sleeve (to grip the slippey spectra core to the cover) and then non spectra covers - so a 10mm dia 'spectra' rope may only have a 6mm spectra core.........
other manufactueres have developed ways around having any inner sleeve so you get more core for your diameter (and you pay for it) eg 8mm or more core in a 10mm dia line
 
Then some manufactureres also add non spectra fibre to the core to keep costs down - you pay for what you get!
 
Ross