Rick,
I think you made a typo, decimal in the wrong place, at least
according to their formula. Should be 3.4% (3.42144) for 1/8 inch 7 X 19 type
302/304, according to my calculation using their formula for estimation.
I checked because I found it difficult to imagine any wire surviving a 34%
elongation, and the point is moot anyway since the breaking strength that size
and type wire rope is 1760 pounds. Even my little C&C27 uses, and is specified
for, 5/32 wire in the halyards. I don't know how to calculate halyard loads,
but I would be surprised to learn that the actual loads ever get anywhere near
to the breaking strength of a halyard in good condition, that is also the
nominal size that the boat's designers called for. An unintended jibe maybe?
Seems to me it would have to be some sort of extreme shock load.
Steve Thomas
C&C27 MKIII
----- Original Message -----
From: Rick Brass via CnC-List
To: David Knecht ; cnc-list@cnc-list.com
Sent: Monday, September 29, 2014 9:42 AM
Subject: Re: Stus-List Wire-rope halyard
You really need to do all the math, not just look at the elongation spec.
9mm Crystalyne (3/8 diameter is about the smallest practical for a winch or
your hand) has an average break strength of 11500 pounds. So you need 3300
pounds of tension to get 7" of stretch.
The average man can generate 50 pounds force on a winch handle, so you need a
size 65 winch. And I'd bet that 3300 pounds exceeds the strength of the luff
rope and fabric used to make your sail anyway.
And, btw, according to the calculator on the Loos website, the stretch of
1/8" annealed stainless 302/304/316 wire rip is 34% when subjected to a 3300
pound load. So you need to do all the math when evaluation wire to rope
halyards as well.
Rick brass
Sent from my iPad
On Sep 28, 2014, at 17:18, David Knecht via CnC-List <cnc-list@cnc-list.com>
wrote:
Crystalyne has a 1% elongation at 30% of breaking strength. With 60’ of
line, that is 7 inches (not that we are normally anywhere near breaking
strength). Seems like a lot to me. The higher tech lines are around 0.5-0.6%.
Wire is presumable around 0. Dave
On Sep 27, 2014, at 8:05 AM, Josh Muckley via CnC-List
<cnc-list@cnc-list.com> wrote:
I replaced all mine with Yale Crystaline. Love the stuff. When rope
wears it frays. I can live with that. When wire wears it makes fish hooks.
Ouch! Wire also chews up the shives. I can also end for end rope or simply
freshen up the ends if needed.
Josh Muckley
S/V Sea Hawk
1989 C&C 37+
Solomons, MD
On Sep 27, 2014 7:52 AM, "Joel Aronson via CnC-List"
<cnc-list@cnc-list.com> wrote:
David
I'd consider Dyneema 75 with chafe covers at both ends. Very low
stretch and weight. Cheaper than. warp speed ( no offense Edd).
On Saturday, September 27, 2014, David Knecht via CnC-List
<cnc-list@cnc-list.com> wrote:
I need to replace the genoa halyard on my boat and am wondering about
the disadvantage of wire-rope over high tech line. The original spec line is
wire-rope. From what I have priced, wire-rope from APS is cheaper than a
dyneema type very low stretch line (Warp Speed/Endura) and about the same as
somewhat low stretch line (VPC). I see the advantages of wire-rope as price
and essentially no stretch. The only disadvantage I see is a bit more weight
aloft, but as a percentage of the total weight aloft it seems insignificant.
Am I missing something? Dave
Aries
1990 C&C 34+
New London, CT
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Aries
1990 C&C 34+
New London, CT
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