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Old 19-07-2016, 20:43   #76
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Re: Synthetic Rigging

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Testing has shown that dyneema (as opposed to a HSR variety) looses no strength at 1:1 d/D. So long as the lower pin is at least the size of the lashing line it will carry the full strength. Also keep in mind that the lashings are generally considered replacement items. As they wear or uv degrade they shouldbe replaced, or just replaced every year for safety.

On the cat I use lashings, which work out to be about 10 times stronger than the shroud before any strength loss. On the bigger tri we use turnbuckles because I wanted more repeatability.
I think that testing showed a 50% drop, that was compensated for by the two legs of an eye splice to make it full strength. If thats the case this doesn't apply directly to a lashing, and twice the number of turns would be needed to compensate. However since smaller line is used for lashings, often about 6 or 7mm the bend radius ratio should be much better than 1:1 in most cases. So the reduction in strength for a lashing will be much less in most cases.
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Old 19-07-2016, 21:18   #77
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Re: Synthetic Rigging

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SnowP, I did a google search for "UV resistant tape" and got lots of hits for tapes that make that claim, however I could not find 'service life' data on any of them. I wonder which tape material would be the most UV resistant?

Steve
I dont know, but your average cheap electrical tape copes reasonably well for a year or two (or even much more) before it gets brittle. For me I would just use cheap tape and replace it, or tape over it when it starts to look nasty.

If you tape from the bottom up and overlap it it is pretty watertight. I'd use white to keep the heat down, heat being the enemy of dyneema due to it causing much more creep.

Serving is good, but it adds bulk and weight, both something I am keen to avoid.

For the lower sections which suffer chafe from sheets I'd use plastic pipe covered in white tape.

Serving the whole lot is a fair bit of work and uses a ton of line. But it sure would look good and protect it well. It is quite prone to chafing through and then unraveling, but a good coating of paint would help prevent it unraveling too quickly. It can be repaired but it is moderatly tricky to seamlessly join the old serving into the new repair, especially on small synthetic rope. We used to black it down with a stockholm tar, roofing tar, black paint, and dryer mix. A few times it didn't dry well and then rubbed off on the sails pretty badly.
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Old 19-07-2016, 22:00   #78
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Re: Synthetic Rigging

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Originally Posted by Snowpetrel View Post
I think that testing showed a 50% drop, that was compensated for by the two legs of an eye splice to make it full strength. If thats the case this doesn't apply directly to a lashing, and twice the number of turns would be needed to compensate. However since smaller line is used for lashings, often about 6 or 7mm the bend radius ratio should be much better than 1:1 in most cases. So the reduction in strength for a lashing will be much less in most cases.
I went back and looked and you are absolutely correct. A 1:1 is 50% strength reduction, 4:1 is a 25% reduction. At around 8:1 you get close to full strength.
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Old 19-07-2016, 22:08   #79
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Re: Synthetic Rigging

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I went back and looked and you are absolutely correct. A 1:1 is 50% strength reduction, 4:1 is a 25% reduction. At around 8:1 you get close to full strength.
Interesting, I havent actually seen the table, do you have a link? One thing that interests me is if creep actually can help in this case. Ie over time the higher stressed outer fibres will relax and pass some of the load onto the inner fibres, reducing the strength loss?

On deadeyes and lanyards I have often thought about adding a small turnbuckle to the one of the ends of the lanyard to enable final tensioning and easy minor adjustment. Also since it would only take 1/6 of the load it could be a small cheap type.
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Old 19-07-2016, 22:13   #80
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Re: Synthetic Rigging

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On deadeyes and lanyards I have often thought about adding a small turnbuckle to the one of the ends of the lanyard to enable final tensioning and easy minor adjustment. Also since it would only take 1/6 of the load it could be a small cheap type.
That's an interesting idea, Ben. Do you think that (with the rig loaded up) pulling on the end of the lanyard will overcome the friction in the deadeye and tighten the thing up?

If it worked, that would sure ease the fine tuning of the rig.

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Old 19-07-2016, 23:04   #81
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Re: Synthetic Rigging

Yeah it should do. As always you will get a slight variation on each part due to friction. But it can be worked out with a few devious means, like a tap with a mallet or by over tightning then slacking back. Plus a good hard sail should balance the parts of the lanyard nicely if they aren't already. But its all just theory and ideas at the moment..

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Old 19-07-2016, 23:18   #82
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Re: Synthetic Rigging

Back when I worked as a rigger on the Barque "James Craig" we used a special lever tool to equilise the parts of the deadeye, plus copius quantities of tallow.

I cant remember the details but I think it squeezed the lanyard pairs together then released them milking some slack out each time. Worked pretty well to get them bar tight when combined with a tackle on a tackle.

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Old 20-07-2016, 02:55   #83
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Re: Synthetic Rigging

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Originally Posted by Jim Cate View Post
That's an interesting idea, Ben. Do you think that (with the rig loaded up) pulling on the end of the lanyard will overcome the friction in the deadeye and tighten the thing up?

If it worked, that would sure ease the fine tuning of the rig.

Jim
The problem is that you need to multiply the length of the adjustment by the number of lashing legs - so you end up with a very long turnbuckle to get even an inch of adjustment.
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Old 20-07-2016, 03:08   #84
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Re: Synthetic Rigging

Very true Stu, but you could take most of the slack out of the other end of the lanyard before you start tensioning the turnbuckle. Still it might take a couple of bites at the turnbuckle to fully tension a big rig. Prehaps using this with say a 4:1 lanyard might work better?
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Old 20-07-2016, 06:50   #85
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Re: Synthetic Rigging

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I was wondering if normal white insulation tape would increase the lifespan by cutting UV and chafe. No good for a high wear area, but possibly ok for a normal shroud and easy to replace and touch up. It would take a lot of rolls to do a whole shroud but its quick enough. We sometimes cheated on square riggers and used it instead of parcelling with linseed oil soaked canvas before serving.

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We use black electrical heat-shrink tape as chafe protection on our dyneema mainsheet pendants. Probably not practical for use on an entire shroud, though. Plus, you have to be carefull with the heat so as not to damage the dyneema.

We also use dyneema deadeyes on our cap shrouds. Just replaced them after 5 years in the tropics and they still looked great. All the same, we made sunbrella covers for the new ones which should make them essentially immortal.
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Old 20-07-2016, 09:34   #86
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Re: Synthetic Rigging

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Originally Posted by Stumble View Post
Testing has shown that dyneema (as opposed to a HSR variety) looses no strength at 1:1 d/D. So long as the lower pin is at least the size of the lashing line it will carry the full strength. Also keep in mind that the lashings are generally considered replacement items. As they wear or uv degrade they shouldbe replaced, or just replaced every year for safety.

On the cat I use lashings, which work out to be about 10 times stronger than the shroud before any strength loss. On the bigger tri we use turnbuckles because I wanted more repeatability.
The manufacturer's recommendations are never 1:1 bending ratio though. What testing lab published tests on this and are standing behind those tests? If you're someone with a fully insured rig, only the manufacturer's recommendations are going to be helpful if your rig comes down while you do something other than recommended practice....

Example is Sampson's Amsteel Blue which recommends as large a bending radius as possible but 3:1 minimum http://www.samsonrope.com/Documents/...Manual_WEB.pdf
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