Chuck,
There are two things unknown to me that make me hesitate
when considering UHMWPE for standing rigging:
1. How long can we expect it to last on an "ordinary" sailboat in
"ordinary" use if appropriately sized and properly installed?
2. Is there any way to inspect the lines for deterioration or loss of
strength?
And finally,
Would you recommend it for replacing the rod rigging that most of us are
still sailing around with on our C&Cs?
Would such a conversion be likely to wind up more or less expensive for
parts than conventional wire rigging?
The new fibres and ropes are not so new anymore and I am guessing that
there is enough field experience now that these are not unreasonable
questions.
Thanks for your helpful contributions to the list knowledge base.
Steve Thomas
C&C36 MKI 1980
C&C27 MKIII 1978
------ Original Message ------
From: cnc-list@cnc-list.com
To: cnc-list@cnc-list.com
Cc: csgilchr...@comcast.net
Sent: Saturday, July 24, 2021 9:21 AM
Subject: Stus-List Re: Wire vs. Dyneema check stays
Full disclosure, I work for a rope company. But a few things so
say regards to Dyneema. First of all Dyneema is a brand name that comes
in a wide range of “models”. The actual material is UHMWPE or Ultra
High Molecular Weight Polyethylene. A Dutch company DSM makes the yarns
with subtle differences in order to achieve different characteristics
such as strength and elongation and something called “creep”. The
grades of Dyneema are categorized by an SK number with the higher
numbers yielding higher performance, generally speaking. However DSM is
not the only company that makes UHMWPE yarns. Honeywell makes an
equivalent yarn called Spectra which also comes in different grades.
Finally there are generic offerings, typically Asian made that are often
much cheaper than Spectra or Dyneema but quality tends to vary.
A rope maker can choose which yarns to use in a particular rope, using
the fibers to make either a 12 strand hollow braid or to use the high
modulus fibers as the core in a low stretch double braid with an outer
cover braid of a high wear or YV stable material like polyester. Doing
the latter adds weight, but dramatically increases longevity. Even if
UHMWPE is used just for the core, most companies will still coat the
yarns in a urethane bath to provide additional protection from chafe and
to provide color coding.
Finally, some rope makers will use a process called heat setting the
Dyneema rope by pre-stretching and aligning the fibers and then exposing
the rope to a heat process that removes most of the creep (non
recoverable elongation on a molecular level). There’s usually a slight
reduction in overall strength with heat set ropes, but far less stretch.
It is these heat set ropes that I would recommend for any standing
rigging application. UHMWPE is quite slippery and achieving proper
tension and maintaining it under load can be challenging without the
proper terminations and fittings.
Several companies like Colligio and Blue Wave offer specific hardware to
create standing rigging solutions that provide adjustments and
tensioning solutions.
Hope this helps..
Chuck Gilchrest
S/V Half Magic
LF 35
Thanks to all of the subscribers that contributed to the list to help with the
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