[Update] I have written a lot about Dyneema standing rigging so I now have a guide to it all in: Dyneema / Synthetic Rigging Summary[End Update]
When you look at the strong opinions about the way you end your Dyneema shrouds it makes all the other strongly held opinions seem conflict free 🙂
This is a bit chicken and egg in the sense that decisions about
a) how you will tension your shrouds at the connection to the chainplate and
b) how you can connect shrouds to the mast
will have a definite impact on which options for terminating your shrouds are relevant.
There are very strong opinions expressed with fervour about how strong some of these solution are and how long they might last. Some people will argue that some solutions must not be used to cross oceans yet I think people have crossed oceans with all these solutions.
So what are the options?
- Plain eye splice with optional chafe sleeve. I’ve only seen this suggested at the mast. There the eye splice can be either hooked over a Colligo Cheeky Tang [Tula’s Endless Summer] or a attached to the loop of a stainless steel T fitting with a luggage Tag loop (sometimes called a Cow Hitch) [Free Range Sailing].
- Eye splice onto a Low Friction Ring. Can be tensioned with a lashing or lashed to something else such as a shackle. [Free Range Sailing]
- Eye splice with optional chafe sleeve onto an open stainless steel thimble. Can be used at top of bottom of a shroud, plus for deadeyes [Rigging Doctor, Sailing Zingaro]
- Eye splice with optional chafe sleeve onto closed stainless steel thimble. Can be used at top of bottom of a shroud, plus for deadeyes [Sailing Zingaro, Tula’s Endless Summer]
- Eye splice with optional chafe sleeve onto a Colligo line terminator. Can be used at top of bottom of a shroud, no need for a deadeye [Tula’s Endless Summer]
- Blue Wave stainless steel eye clamped to Dyneema. Can be used at top of bottom of a shroud (with a turnbuckle) [I haven’t seen these in use].
So I’ll consider them all and how they are typically used at the mast or chainplate as appropriate. First a picture of each (I haven’t included every combination of a chafe sleeve or not.
Or duck and run time?
If you can afford it then Colligo Marine have stock items for every type of mast connection (of which, if your mast is suitable I think the Cheeky Tang is brilliant for saving weight and reducing the number of components and connections) and for the chainplate they have solutions for both turnbuckles and lashings (or both). They are really well sorted for ensuring the Dyneema bends very gently and also that loads are very evenly distributed to Clevis pins etc.
But at the same time the Colligo Marine stuff is really expensive. We would be talking about thousands of pounds per mast. So they are far outside our budget.
Some of the solutions concern me. Attaching a Dyneema loop to anything by a Cow Hitch or Luggage Tag does not seem suitable for a critical high load like a shroud. To me the bend radius looks very tight and will surely be a weak point.
Also I’m not keen on the Blue Wave terminals (they have a range of them with different connections). I’m sure they are carefully engineered but for me a key safety feature of Dyneema is being able to visually inspect it.
While I think Low Friction Rings are awesome for lots of applications, I’m not convinced that they are a good fit for this purpose. If you fit a large eye splice to avoid a tight bend then it looks like the low friction ring could fall out. If the ring is held in firmly then either the dyneema has to bend sharply or there is a lot of time consuming labour to apply whippings. Even then if the ring is used for tensioning via multiple strands of lashing line people have reported a tendency for them to bunch together and jam.
I think the open thimbles look a bit problematic. In some of the images they look like they have opened up and an open sharp end is very close to the dyneema. It feels to me as if they are a bit close to a catastrophic failure if something catches on them and bends them open.
With both types of thimble a critical issue is what they are attached to. With their first attempt Sailing Zingaro used wide toggles into the thimble and it created point loadings on the sides as they didn’t sit properly. With a Cleivis pin the diameter of the pin might be so small relative to the thimble that again their is a point loading. This is most likely to be a problem at the mast end when trying to find a way to connect to the existing fittings on the mast (or a deadeye to a metal chainplate). Thimbles are at their best with a lashing either for tensioning or to lash them to something.
Conclusion for Vida
Now that we have decided on our Dyneema chainplate solution (but with a closed stainless steel thimble instead of a low friction ring) the lower end of our shroud is obvious, a matching closed stainless steel thimble. That should make tensioning as simple as possible and it is a pretty cheap solution. As our chainplate solution means we don’t need a deadeye or a toggle we save quite a bit of money and weight.
The top of the shrouds is more tricky. Consider this example of what we have now.
All our shrouds end up at through bolts and there are these riveted plates to stop the bolt holes becoming elongated. All the current shrouds have swaged end fittings that are held by a clevis pin through two plates (or tangs). On the mizzen we have 4 x single connections and 2 x doubles. On the main we have 2 x double and 2 x single (I am ignoring the main mast backstay and forestay at the moment).
One option (the cheapest) would be to get longer clevis pins and prise apart the plates/tangs far enough to fit a closed thimble in (but if we are looking at 11mm Dyneema shrouds on the main mast that is going to be quite a lot of bending of the stainless steel).
Another option would be to fit slightly longer bolts through the mast so that instead of bending the plates/tangs apart we separate them at the bolt with a few washers. We still fit the longer clevis pins.
If we could afford it then Colligo Cheeky Tangs would be great.
We are looking at a fourth option which is to make our own version of a Cheeky Tang. We start with a longer bolt through the mast. On each side of the mast we have a two large penny washers with the largest diameter spacer we can find between them (looks like about 25mm). A dyneema look goes over the spacer and the penny washers stop it falling off. That gives a bend radius of over 2:1. We would join the tops of the penny washers with a small bolt (or maybe a cable tie) to stop the dyneema loop jumping out. The lower side of the outer penny washer would be cut away to provide a smooth route out for the dyneema.
No decision yet until we get the sizing sorted and see how the thimbles fit in the existing tangs.
Big update: see Dyneema Termination and Chainplate update
4 thoughts on “Termination of Dyneema Shrouds. The most contentious issue?”