[MHml] Synthetic Rigging

[Bill Gibbs]

Actually rope manufacturers do talk about creep.  And claim big improvements since 1988.  

http://www.thecortlandcompanies.com/psrope/SpectraandPlasmaRopesrev2.pdf

Describes a 3/8" spectra line loaded to 22% of published min breaking strength which showed no creep for the first 10 days of
loading, that's 240 hours.  They continued the test for 3 years and creep did continue.  They also provide graphs of fiber tests
showing the differences in modern spectra types and at different loading percentages.  Keeping sustained loading to 10% dramatically
reduces creep, like 1/5 as much as at 20% loading.

Does spectra creep?  Yes.  "Inches" in "minutes"?  Doesn't seem like it.  Seems like it should be a small percentage of elastic
stretch for the time periods that most of us sail.

Disclaimer - I don't currently have spectra halyards on commonly used sails.  Main halyard is galvanized wire w/ a mast head lock.
#1 jib & screacher is Samson Validator SKB, Dyneema/Vectran blend, same as Lightning single braid.  

Bill
Afterburner


 Bill Gibbs wrote:
>  > On the other hand, what's the big deal with creep?  As the wind
> strength increases, I have to adjust halyard tension anyway.  How do
>> I tell whether this is from elastic stretch in the sail and halyard, or 
>> from creep?  Why should I care?
> ------------------------------------
snip

Spectra has no place as a halyard.  (My opinion)  I mistakenly used a 
Dyneema halyard (similar to Spectra, but slightly less creep) and it drove 
me nuts.  I'd tension the halyard and in 10 minutes my beautiful Calvert 
Main's luff would look like the gathering on a curtain. 

Snip

CS 

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