Why Dyneema standing rigging?

We know that our decision making process can seem strange to others. 🙂 For example why would we remove a working diesel engine to go for an electric motor. We imagine there will be many who will also be wondering why on earth we are switching from “normal” stainless steel rigging to Dyneema (just to be clear not all at once though).

Vida has a Ketch rig. So two masts and they are entirely independent of each other (no Triatic stay connecting them). We think we are the only Rival 38 with a ketch rig (one other has been converted from ketch to sloop). It is something we like, not just because ketches look great.

We love the safety features of a ketch, obviously having a spare mast to get you home if one breaks is a big one. Having more but smaller sails makes things lighter to move, hoist, reef, and trim. There are more sail plan options when the wind gets up (or if something breaks). The mizzen can be used to stabilise the boat both when sailing and when at anchor.

Against that there is more stuff (to buy, inspect and maintain), more weight, generally slower performance (particularly upwind where the mizzen doesn’t help much and adds windage).

When it comes to the rigging the costs are clearly higher (not quite double because while there are about twice as many components they are smaller sizes than they would be with a sloop rig).

Current condition

The mizzen mast is a replacement (not sure when or why it was replaced). The main mast is sound although it has had quite a few changes made to it over the years and needs some freshening up. We have removed the mainsail roller furling which had been fitted to the back of the mast and got a new boom with slab reefing.

The rigging is about 8 years old (but some of it is original) and insurance only provides cover for the first 10 years.

So we know we need to be working to refresh the rigging before we end up living aboard and crossing oceans in a few years time.

Staying with Stainless Steel

When it comes to refreshing the rigging the obvious choice would be to get a professional rigger to do the job and stay with stainless steel. We would have to change a lot more of the rigging if we did it ourselves as the stainless steel wires go into swage fittings and that isn’t a DIY option. Alternatively at considerable cost when changing the stays we could switch to Sta-Lok fittings which we could fit ourselves.

As we are refitting with the goal of living aboard and world cruising in a few years we are taking a long term perspective.

As you replace more things to achieve longer term peace of mind and reliability the cost of staying with stainless steel grows. At the moment it is all a bit of a mixed bag of original and replacement parts. We don’t have detailed records of what was changed when. So we have a mixture of stainless steel (main mast) and original bronze (mizzen) turnbuckles. We have a mixture of stainless steel and bronze toggles. Some of the bronze toggles have stainless steel pins and some still bronze. We have all original bronze chainplates which have not been removed and checked (I have written several posts about the issues and our solutions, start here). Some of the connecting plates etc at the mast are starting to rust and there are mixtures of stainlesss steel and aluminium components where there is some galvanic corrosion.

We would be looking at thousands of pounds to completely re-rig in stainless steel and that would probably need to add having custom made stainless steel chainplates that would have a known condition and be long enough for better backing plates.

So Dyneema?

Dyneema has been used for boat rigging (in small numbers) for about 20 years. See this: DYNEEMA RIGGING Q&A PETER GREIG which includes:

Insurance companies are accepting Dyneema rigging. It has been around for 20 years and there is no recorded failure anywhere in the world from professionally done splicing. However stainless steel cases have a huge amount of claims

Dyneema rigging potentially will outlast stainless steel. Only severe chafing from something very sharp could affect it, but the same way it would affect wire anyway. I have recently worked on a boat that I rigged 15 years ago and which has done 6000 miles in that time – there was absolutely no deterioration visible.

Advantages

  • Weight. Much, much lighter than stainless steel. This reduces the loads on the boat and reduces heeling making sailing faster and more comfortable. This has driven the adoption on racing boats.
  • DIY. Dyneema line is easy to work with using very basic tools. So it is perfectly possible for us to do all the work ourselves.
  • There are no special components (especially to connect and tension wires), so a cruising boat can easily carry the spares needed to re-rig the entire boat anywhere in the world. Potentially all you need is line, thimbles and low friction rings. Not only can you carry everything but it is small, light and won’t rust.
  • Stronger. Dyneema rigging has to be sized for stretch which means that when you size for the same amount of stretch you have many times more strength.
  • Inspectable. There are no hidden parts, all the Dyneema can be seen and checked. The two forms of damage (chafe and UV) are very visible long before failure.

Disadvantages

  • The line itself is expensive (100m of 8mm 1×19 Stainless Steel £576 vs 100m of 11mm Dyneema £1,360)
  • Dyneema is stretchy compared to Stainless Steel so you have to fit larger sizes (eg as per above 11mm instead of 8mm).
  • Dyneema is vulnerable to chafing (rubbing) wear. However, problems are very visible and it is possible to protect it with sleeves or seizing.
  • Dyneema is vulnerable to UV degredation. Again this is visible when it happens and most chafe protection will also provide UV protection.

Conclusion

We are switching to Dyneema first for our Mizzen mast and then for the main mast (except the forestay) for the following reasons:

  1. We can do everything to switch to Dyneema rigging ourselves which saves a lot of money.
  2. We can sort our concerns with our chainplates to solve the weakest link in the rigging with something that is stronger, that we can inspect, repair and replace ourselves.
  3. We will save a lot of weight which will improve our sailing performance and comfort.
  4. We can carry everything to be able to re-rig everything, anywhere.
  5. We will not have to rely on others expertise to properly check the condition of the rig.

In return we recognise that we are likely to have a few hassles

  • We might have to hunt more carefully for surveyors and insurers
  • Tuning the rig will be a slower process (we are going to be using lashings to tension the shrouds and they are slow to untie, tension and tie up).
  • More work to get us afloat the first time because we are not “just managing” with the problem chainplate.

Outstanding Issue

We will not be able to replace the forestay with Dyneema as we have a roller furling system. This includes an aluminium extrusion which covers the forestay and rotates to roll up the genoa sail. This would quickly chafe through the Dyneema. We don’t plan to review this until either the genoa sail or the roller furler need replacing.

Plans

Mizzen mast first due to the problem chainplate. Making the smallest changes to the mast that we can, so reusing the existing connections as much as possible.

Sail for at least one season.

If all has gone well then do the same to the Main Mast.

At some point in the future upgrade the mast connections to use Colligo Cheeky Tangs for simplicity, strength and weight saving (but this will cost a couple of thousand pounds). The good news is that this change wouldn’t require any changes to the rest of the rigging (just slip the top thimble out so the eye splice goes over the Cheeky Tang. This will shorten the shroud/stay a little but the lashing will be able to cope with the change.

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