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Old 12-05-2016, 06:53   #1
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Attaching Dyneema Sheets to Headsail Clew

I have new Dyneema headsail sheets, hurra! They are lovely things of Marlow Racing 78 D2. The racing Dyneema (Iíll never use the cruising crap again) is a totally different deal, with the cover fitting tightly with the core, with an excellent ďhandĒ. My rope pusher in Portsmouth made beautiful soft eyes in the ends of them.

So now I need to figure out how to hook them up. I had originally thought to use Dyneema soft shackles, but Iím slightly nervous about the security of them. I guess I shouldnít be, but I canít help it. Considering the tons of force they will have to carry.

Therefore, I am thinking about using a simple spliced loop of 8mm D12 Dyneema, cow hitched to the clew, and then cow hitched again through the soft eye in the sheet. The splice is roughly as strong as the base material, and the base material is doubled, so this should be mega strong, no? And totally secure? To take it off, I will have to thread the entire sheet back through the loop (since itís cow hitched), but the new sheets are so light and easy and pleasant to handle, that I just canít see this as being a big problem.

Any reason not to do it this way?

Or any better way I haven't thought of yet?
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Old 12-05-2016, 07:06   #2
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Re: Attaching Dyneema Sheets to Headsail Clew

soft shackle really is the way to go. I use this method to splice them:

Better Soft Shackle

I also make a couple wraps of velcro around the middle just in case...but I don't think it's necessary at all. if you use the same diameter dyneema as the core of your sheets the sheets will fail far before the soft shackle.



The shackle is going to be stronger than your loop, and with the forces applied untying the cow hitch is going to be very difficult.
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Old 12-05-2016, 08:57   #3
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Re: Attaching Dyneema Sheets to Headsail Clew

I have used the soft shackle attachment to Samson MLX (dyneema) sheets with eye splices for years. Never a failure.
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Old 12-05-2016, 09:53   #4
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Re: Attaching Dyneema Sheets to Headsail Clew

Dock head,

It may feel weird, but soft shackles are really the way to go. Once in place I have never had one let go from flogging. I actually think they are more secure than typical snap shackles.
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Old 12-05-2016, 10:58   #5
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Re: Attaching Dyneema Sheets to Headsail Clew

Well, that sounds like a consensus.

I guess I'll have to make up some of those.

My sheets are Racing D2 78 with breaking load of 9274kg.

I have a supply of 8mm and 9mm single braid Dyneema, but I guess I'll need something heavier?

Or maybe not? The 9mm D12 has breaking strength of 6940kg, and Evans Starzinger tested soft shackles at 170% of the line strength, so maybe that's plenty?

Load testing
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Old 12-05-2016, 11:31   #6
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Re: Attaching Dyneema Sheets to Headsail Clew

It really only makes sense to use soft shackles, although there are other (more expensive) options. Or ones which utelize some metal in there construction, which, if memory serves, you were trying to avoid.
Here's a small sampling as to other options, & more aren't hard to find. Sailboat Soft Shackles and Loops | APS Any big line stockist will have many, many options available.

BTW, why did you get Dyneema sheets, now? As not long ago, well, to put it politely, you were vehemently in the "anti" camp, on them.
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Old 12-05-2016, 11:33   #7
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Re: Attaching Dyneema Sheets to Headsail Clew

^^

either the 8 or 9 mm is probably 'strong enough' with a straightforward soft shackle but you can do two easy things to make them much stronger.

(1) is to double them thru the eye/clew (eg make the soft shackle longer and wrap them twice around before closing).

(2) use the "stronger" design - which has buried tails and the button knot (rather than the diamond knot and cut tails). This is both stronger (220-250%) and eliminates one common failure mode (tails slipping into diamond knot)


I have a whole bunch of 12mm heat set dyneema single braid left over from a break test I recently did of splices (of throat angle and bend ratios) - I could make some REALLY strong soft shackles with it if anyone wanted them . . . . but I personally would prefer for most applications to use 8mm and either or both of the two tactics above, because the stopper knot gets bulky with bigger diameter line.
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Old 12-05-2016, 11:54   #8
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Re: Attaching Dyneema Sheets to Headsail Clew

I'd go with the 8 or 9 and be more than satisfied
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Old 12-05-2016, 12:09   #9
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Re: Attaching Dyneema Sheets to Headsail Clew

BTW, I would use 150% as the typical strength for the 'better' soft shackle for a casual DIY, and 220% for the 'stronger' design - you can do consistently much better than that with both designs if you make them well . . . . but I have test broken samples from various 'amateurs' and would say the above figures are representative of their results.
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Old 12-05-2016, 13:04   #10
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Re: Attaching Dyneema Sheets to Headsail Clew

A "High Strength" soft shackle utilises a Button stopper instead of a Diamond, allowing the tail to be buried and in doing so it increases the strength of the soft shackle. It also makes the shackle much easier to use single handed not having the tails poking out of the stopper and snagging insertion. I am simply not game cutting them too short on a Diamond stopper.

I found online instructions fot the Button stopper difficult to follow and posted a thread last year with what I think is a clearer explantion:

Instructions for Tying the High Strength Soft Shackle & Button Knot


Quote:
Originally Posted by Seaworthy Lass View Post
Instructions I have found for tying the Button
(some of these appear downright scary, and viewing is not for the faint hearted ):

Evans Starzinger: http://www.bethandevans.com/pdf/button.pdf
Grog Animated knots: Stronger Soft Shackle | How to tie the Stronger Soft Shackle | Splicing Knots
Allen Edwards: How to Tie A Button Knot

One of the above may work for you, but I initially struggled. The Button is a bit complex to weave correctly the first few attempts, but that wasn't actually the hard bit. The main difficulties I had with it were:
1. In the very final step working out exactly where to poke the ends relative to the standing ends
2. Dressing (ie tightening) the knot.

I have found easy ways to overcome these problems so I thought I would photograph the steps with my explanations in case that helps anyone. The tips can be used in conjunction with other instructions such as the ones linked above if you find any of them make more sense to you. Once you know what you are aiming for, I think the Button becomes no harder than the Diamond knot to tie.

There are probably several YouTubes too, but my internet is too poor to access these. If anyone has any recommendations, I will add them here.

Instructions will follow when I set up a tripod and sort out the photography.
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Old 12-05-2016, 13:14   #11
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Re: Attaching Dyneema Sheets to Headsail Clew

By the way, I have come up with a cross between the High Strength and Better soft shackles, incorporating the best features of both.

This is how the new BB soft shackle looks:



Instructions for the BB soft shackle can be found here:
http://www.cruisersforum.com/forums/...le-155714.html

Anyone with testing equipment? I am confident enough of the design that we have been using it to attach snubber to chain.

SWL
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Old 12-05-2016, 13:49   #12
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Re: Attaching Dyneema Sheets to Headsail Clew

One more vote for "the better soft shackle." Personally, I like to oversize them a bit both in length and material size, just so that they are easier to manage with gloves in the winter. While your splicing, make about 6, in different sizes and strengths. You'll find uses for them, I promise. Handy as duct tape.

Zero chance of failure or coming loose. Not a tough application.
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Old 12-05-2016, 14:02   #13
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Re: Attaching Dyneema Sheets to Headsail Clew

Quote:
Originally Posted by thinwater View Post
One more vote for "the better soft shackle." Personally, I like to oversize them a bit both in length and material size, just so that they are easier to manage with gloves in the winter. While your splicing, make about 6, in different sizes and strengths. You'll find uses for them, I promise. Handy as duct tape.

Zero chance of failure or coming loose. Not a tough application.
In my riggers kit I have premise ones out of everything from 1.75mm to 8mm. I never seem to have the size I want however. They just get used up to fast... And my wife likes to give them away as bracelets.
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Old 12-05-2016, 16:07   #14
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Re: Attaching Dyneema Sheets to Headsail Clew

Hijacking Dockhead's thread slightly, will a soft shackle reduce the tendency of the sheets to catch on a baby stay? which is something I am suffering from at the moment. Particularly noticeable when sailing single handed and you don't have a crew to watch or time the head sail cross the boat.

Peter
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Old 12-05-2016, 16:12   #15
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Re: Attaching Dyneema Sheets to Headsail Clew

Quote:
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Hijacking Dockhead's thread slightly, will a soft shackle reduce the tendency of the sheets to catch on a baby stay? which is something I am suffering from at the moment. Particularly noticeable when sailing single handed and you don't have a crew to watch or time the head sail cross the boat.

Peter
Yes, if you have tied two sheets on (as opposed to one line and cow hitch).

Splicing the ends of the sheets and using a soft shackle reduces windage too .

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