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Old 02-10-2008, 00:17   #16
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Colours do/can make a longevity difference. If it's an impregnated yarn black is the best for UV. If it's a dyed yarn there is not much in it. Impregnated yarns are better than dyed in many ways.

Red is not good, it's the 1st colour to disappear come evening or underwater. Red is also the less colour stable and more likely to 'run' and turn everything by it pink.

I use Dyneema (Amsteel is a brand name and made of dyneema) but when racing I have to use webbing due to old school rules. I use a 5mm (3/16") dyneema SK75 (which Amsteel is one of) and it's way stronger and slipperier than webbing.

The webbing I have to use while racing must be rated at 2500kg or more, that's 5500lb in that funny old imperial thing.

Things to remember about webbing -
Knots reduce the strength, it's better (stronger) to sew loops in the end. Make the overlap silly large and go silly with stitching. generally the stitching will break down a lot faster then the webbing so a good indicator of when to replace. Not just the stitching, the whole jackline/s.

Nick the edge of a webbing and work on a minimum of 20% strength lose so replace ASAP.

Use polyester rather than nylon. Better over time.

When not in use take them off and store in a shaded spot. They will last piles longer.

If using caribinas and so on make sure they are real good ones, many out there now are crap when talking loads.
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Old 02-10-2008, 09:21   #17
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I haven't found the pigment issue an issue at all. I only deploy the jacklines when I am concerned about deteriorating conditions. They stow in the cockpit locker, alongside the tether lines we hook onto the inflateable PFDs with harnesses. Set-up, using carribiener clips to pad eyes in the cabinside, takes under a minute, keeps the decks clear the rest of the time, and is simply part of the drill. We also rig them prior to nightfall if we are underway, as part of our normal preparations, but there is no fear of UV then. And since they are such a unique color, it's difficult to confuse them with other lines which might get underfoot when things get chaotic.
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Old 02-10-2008, 15:03   #18
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I use old stainless wire rigging (without fishhooks). I run it as close to midships as possible and I don't run it where it can be easily stepped on and I trust it a lot more than webbing.
Don't get webbing that will stretch when it gets wet. Had that experience on my last off shore sail.
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Old 02-10-2008, 16:06   #19
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Well, John. Our "old rigging" would be rod... I think we'll go with the black 1" webbing. We have harnesses/tethers with good carabiners on them - but would like to make a couple of double tethers. Any sources for GOOD carabiners?
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Old 02-10-2008, 18:09   #20
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Why the need? Amsteel is so far over the top of requirements why bother.
I don't know that Amsteel is neccessary but one thing to take into consideration is what will happen to the jacklines when/if you fall against them. If there is too much stretch, as you would find in a climbing rope, The combination of tether and stretch from the jackline may allow you to go overboard. While any jackline is better tha none less stretch is better than more stretch and I agree that Amsteel is over thetop.
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Old 03-10-2008, 00:21   #21
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Quote:
Originally Posted by GMac View Post
....Knots reduce the strength, it's better (stronger) to sew loops in the end. Make the overlap silly large and go silly with stitching. generally the stitching will break down a lot faster then the webbing.......
Just to add to this good advice, something I have discovered (while researching the construction details of a para-anchor) is that the stitching of webbing should be:
  • Longitudinal along the webbing, not transverse (very important).
  • The length of the stitched area should be a minmum of 1.5 times the width of the webbing, perferrally 2 times for smaller sizes of webbing (ie less than 2 inch).
  • 6 rows of stitching usually suffice (2 parallel to the long edge and 4 as a long zig zag).
  • #8 Nylon thread is a good starting point (at least for nylon webbing); I am guessing polyester thread is better for polyester webbing.
This info was provided to me by a structual engineer who carried out a lot destructive testing on the stitching of cargo nets and seat belts but at the end of the day, it's only internet advice
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Old 03-10-2008, 00:33   #22
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That's all correct Wotname. I was going to mention that but thought I would be getting a bit detailed.

And don't get the stitching over the edge of the webbing. Easier to destroy and then the rest goes a lot faster.

Polyester thread, the only way to go.

My overlap or stitched area on my 25mm webbing is about 150mm. More the merrier is my theory, especially on jacklines.
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Old 03-10-2008, 04:41   #23
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GM, well I am well known for being pedantic .

At the risk of thread drift (pun intended), according to my colleagues advice, it is really only the first few and last few stitches in any longitudinal row that carries the load. His graph's of the individual stitch's loads show something like 80% of the load is carried by the end stitches (both ends) of each row; the stitches in the middle carry hardly any load until the end stitches fail.

The length of the stitched row is important because as the end stitches fail, the load is picked up by the next stitches in the line and so on.
Usual proviso applies - IMHO etc.
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Old 03-10-2008, 05:35   #24
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... We have harnesses/tethers with good carabiners on them - but would like to make a couple of double tethers. Any sources for GOOD carabiners?
REI sells quality climbing gear.
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Old 03-10-2008, 06:01   #25
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REI sells quality climbing gear.
For marine use, I prefer Stainless Steel or Titanium hardware to the Aluminum products that climbers & cavers seem to favour.

Suncor hardware:

Suncor Stainless Titanium
and:
Suncor Stainless Hooks & Clips
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Old 03-10-2008, 07:18   #26
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It is about the same price, wears very well, and is easy to splice. I was thinking 1/4 jackline, and 1/8 lashings.

Oh, and it floats.

Chris

Quote:
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Why the need? Amsteel is so far over the top of requirements why bother.
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Old 03-10-2008, 08:15   #27
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REI sells quality climbing gear.
REI carries very good climbing gear, in addition to novelty climbing gear.

No matter where you're buying from, make sure that you look at what forces your carabiner are rated to: measured in kN (kilonewtons).
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Old 03-10-2008, 09:38   #28
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Jack lines

This subject was really hashed out on the www.sailfar.net (look up 'sail bits' page 2)site by a couple of guys such as:
"If the initial deformation of the jack line results in a 20 degree angle and the load is 500# (you plus drag of you in the water) the tension in the line is

tension = 500# / sin (20 deg) = 1432#

That's just the static case. If you add dynamics (you hurtling across the deck before you take up on the tether) and if you have a jack line that doesn't stretch much, and you cinch it up real tight, the numbers get real big real fast.

Ignore drag, assume 3G deceleration when you hit the tether, and assume stretch and tightness limit the angle to 12 deg (seems a decent number <grin>) and you get

tension = 3 * 250 / sin (12 deg) = 4300#

If you use Excel, remember that it does trig functions in radians and you will have to convert."

There is a lot more to it but math makes me dizzy.

Fair wins,

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Old 03-10-2008, 13:35   #29
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GM, well I am well known for being pedantic .
Me too at times.

I just work on the theory more is better than less and besides at 3am in 50kts mine just 'look' bloody strong, a feel good thing
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Old 03-10-2008, 14:25   #30
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Tubular nylon webbing is much stronger than flat poly webbing but for either one, dye is an issue.
"Dye embrittlement" is the term that fabric makers use to describe the way that modern chemical dyes actually degrade the plastic and make it brittle, especially in sunlight (rich in UV). The worse dyes are the red family, followed by yellows. The ones that do the least damage and provide the strongest fibers are dark blue and black. Your best bet would be to check with whoever makes the webbing and ask them if they have specific information, or if you can get it from their supplier.

When I last asked a clothmaker about this it was in reference to spinnaker colors, and he suggested white or blue as the most durable. White has no extra UV protection--but no dye embrittlement problems. Black just never came up, you don't get many calls for black spinnakers.[g]


Nautical-
"I've seen some rigged where the the tether is too long to " That's 70's equipment you're talking about. For the past decade or longer, SOP has been to use a double tether, with one long side and one short side (i.e. two feet and six feet) with the harness attached in the center. This allows you to chose the correct length, and also to STAY clipped on while passing obstructions like the mast.
In theory you always clip on in a manner that will prevent you from going into the water. In practice, you keep a razor sharp knife where either hand can access it--one handed and blind--in case the worst happens. (And that's not falling overboard, that's having the boat turn turtle and trap you beneath it, enfouled in lines or sails.)

John-
The reasons for not using spare wire line are twofold: First, it you are fouled somehow, you can't cut free of it. Second, it is round, and it can and will roll out from underfoot on the deck--throwing someone down. it is durable, and better than nothing, but those are the reasons it is officially unacceptable to groups like the ORC.
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