Quote:
Originally Posted by Bob Pingel
Yes, comprehensive testing like this would be great.
There was some testing (around knot strength actually) in SAIL last month.
Checkout the Layline site, they have done some elasticity testing on their "punisher".
Bob
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Thanks for the heads-ups, Bob & Deralte (that one re bear nibbles will be a hit with the
rockclimbing set!
). But, Bob, I've now checked the on-line Sail TOC's for Jan'07,
Dec & Nov 2006, and don't see a hint of any ropes or knots testing: can you please
provide a link to that? (maybe a copy ... ?)
And, yes, the Layline stretches are good to see--and have several levels of tension.
(They had at one time a video of a rope breaking--oddly over an extended few seconds.)
Quote:
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I found it interesting that they developed their own baseline breaking strengths -- these were far higher than the published tensiles. I believe most published tensiles are fairly conservative. I also under understand that many tensiles are determined from a spliced sample -- so by definition a proper splice is 100% efficient.
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One should expect that the baseline is tested, not quoted, and be disappointed when it's not.
There was a test of gel-spun HMPE fishlines a few months ago, and the differences
between rated & actual strengths in the lines was HUGE--to 270%*!!! And then there
will be knot testers who presume to determine efficiencies w/o determining the material
strength? --and then such determinations get compared w/each other, and ... .
[*
Sport Fishing mag., Aug.2006, pp. 62-68]
I have found it intriguing how, in a table of strengths per size of various ropes, one
might be significantly higher in some sizes, then slowly or even suddenly lose that
lead and even trail, then come back again; and how the proportion of strength per
material might be inconsistent.
The Cordage Institute made some noise about their insisting on spliced strength vs.
ISO (?) or some international standard that uses other methods. But splicing takes
skill, which varies; and, of course, one would like to know of the splice's efficiency.
(Notably pathetic, e.g., was
Practical Sailor's testing in which their eye splices pulled
out well under the load ultimately borne by bowlines!!)
As for other characteristics, yes, isn't is amazing at some of the assertions: UV has
NO effect on HMPE; or is it that HMPE is only "good" but not "excellent" in UV resistance;
or "excellent" up until about 3 years when more Samthane (?) coating is needed?!
--ditto on the abrasion resistance, with various anecdotes of toughness and resistance
to cutting, yet often polyester is rated higher!?
(As for PBO, the anecdotes I've heard aren't about rapid deterioration in months, but
nearly HOURS! --and yet that material has appeared (at a price!) as part of a sheath
for frictional heat resistance!?)
.:. Ya gotta wonder!