[MHml] Synthetic Rigging

[Creighton Smith]

 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?
> ------------------------------------
> Back in 1988 I had a 2:1 spectra halyard and needed to adjust the
> halyard as the combination of stretch and creep (presumably) used up all
> the luff downhaul travel. Doesn't matter whether it is called stretch or
> creep, needs to be reduced. I changed to a vectran 1:1 halyard and the
> mainsail head came less distance down the mast under load (less stretch?
> less creep? who cares?) so I no longer ran out of luff downhaul travel -
> problem solved.

It's actually easy to differentiate stretch from creep.  Stretch is a 
one-time phenomenon.  Load it up and it stretches WHILE THE LOAD IS 
INCREASING, then it stops stretching.  Creep keeps happening as long as a 
load is on the line.  Tensioning the line helps only for a short time until, 
as a result of the tension on the line, it creeps more and your luff tension 
goes away.  Again.  And again.  Ad infinitum.  Rope manufacturers don't talk 
much about creep-it's their dirty little secret.
Stretch is elastic, it returns (snaps back) to it's original length.  Creep 
is forever, your line is now, and stays, longer.  Creep keeps happening and 
in extreme cases can result over time in the line perceptibly reducing in 
diameter as it increases in length.
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. I bit the bullet and 
bought Vectran (which doesn't creep).  Problem solved.  This is a 570sq ft 
main with a single part halyard.  49ft luff.
If a 2-part halyard is used a cheaper solution is Sta-Set X, which is a 
strand-oriented dacron made by New England Ropes.  It has about the same 
ultimate strength as double braid with much less stretch and costs the same. 
(Dacron doesn't creep) It's a bear to splice. With the 2-part halyard, the 
load is halved for the same luff tension. (less stretch)
I don't think Afterburner is a stasetX candidate, the loads are probably too 
high, but for the rest of us, for whom line size and weight aloft are not 
such considerations it might be worth consideration.
But please, Paul, don't use Spectra, even at 2:1 it will creep.  And drive 
you round the bend.
When my now 5 year-old Vectran halyard requires replacement I may very well 
go 2:1 with sta-set X.
Creighton
P.S.  Don't splice halyards.  The splice tail, which is usually a foot or 
more long does not take kindly to going through the sheave.  Periodically 
cut the knot out and retie a meter or so down line, or swap ends.  Going 
through that sheave really beats the line up
P.P.S.  The more stretch the halyard, the more it goes back and forth 
through the sheave, which causes wear and is why halyards nearly always 
break at the   masthead.  Yes, I know, knots in high tech line reduce the 
strength shockingly, but you're not going to load it more than 25%max, 
anyway.
CS