very hard to predict. The whole thing had to be re-spliced twice and re-tuned several times – but after two or three test sails in increasing wind speeds, the whole thing finally seemed to be perfectly tuned and the shrouds sat tight as a drum.
Sailing! The joy of looking at the new rig powered up and sailing the boat in its new manifes- tation is hard to describe in words. But I’m happy as a child on Christmas Day every time we go out. The next adventure will be learning how
to sail this beast properly, and further opti- mise the rig. The project has made it clear to me how enormously complex the con- struction of a rig like this really is. I thought I knew a lot before – I even published a book on sail and rig tuning. But I learned enough during these two years to write another one, this time on carbon/Dyneema- based rigging only. Do you want to do this yourself? As you
can see, it’s do-able. But it’s a huge project. Also, it’s not cheap at all and very time consuming. So I feel like putting out a dis- claimer right here: don’t try this at home. Or, on the other hand, go ahead. Just be aware of the full extent of the project.
Dyneema is here to stay Dyneema standing rigging in itself, though, is really not that complicated… if you use the right resources and are willing to pay for the initial transition. In the long run it will be cheaper than the alternatives. With more knowledge, experience and
more production gear on the market, boat manufacturers will probably soon start to put this to you as an option. I promise to report further on longterm usage, but feel convinced that Dyneema rigging is here to stay and will be seen on more and more boats in the future.
What you need to know By replacing steel wire with Dyneema you can expect an approximate weight reduc- tion of 80 per cent, while to achieve similar stretch properties a bigger-diameter line is obviously selected. This means breaking strength ends up two to five times higher than steel wire. Looming failure is easier to detect, renewing lines can be done rela- tively cheaply and easily. But it has to be done correctly. Here are the most impor- tant issues to keep an eye on… In some rigs the weight reduction from
using Dyneema over steel wire or rod can be equal to changing the mast tube from aluminium to carbon. In general, weight saving is the most common reason for choosing Dyneema for standing rigging. A lighter rig has very noticeable effects on the whole sailing experience: higher stability and ability to carry more sail area (or less need for reefing), more speed, less pitching. All these are benefits for cruising yachts.
A heavy motor sailor with a short mast will probably not notice much effect. But any reasonably good sailing boat,
52 SEAHORSE
A Class40 tube forms an excellent starting point for a project like this. The demands of coming out of a competitive ocean racing class mean that build quality is generally to a high standard and there are plentiful parts available. And the history is easily checked…
especially on the light side, will benefit to some degree. On Chi, which is an extremely lightweight, high-performance cruiser, the effect is rather dramatic.
Easy to inspect Another advantage is that upcoming issues are easily detected before something serious happens. Breakages in steel will typically come suddenly and unexpectedly, most often due to corrosion or micro- cracks that can be hard to see before a failure. Dyneema standing rigging consists of lines spliced around large-diameter ter- minals that are easily inspected. The lines are also dimensioned so they can lose half of their strength and still be as strong as the steel rigging they replace.
Easy to renew Dyneema can basically fail in two ways: UV degradation and chafe. Both will lead to a fuzzy surface that is easily spotted. Life expectancy for lines is eight to 10 years, maybe a bit shorter in the Tropics, probably quite a lot more in northern waters. Fittings can be reused, splicing in new lines is easy and not very expensive. You can do it yourself without special tools or machines anywhere in the world. Just bring a coil of rope on the boat.
Use the right fittings To maintain theoretical working loads the lines must not be bent excessively. You need a nice, big radius. Colligo Marine recommend a radius of five times the line diameter. For example: a 10mm line should be spliced around a 50mm termi- nal. This way you will not risk breaking fibres in the bend.
There are three types of stretch Dyneema stretches in three different ways. Splices will obviously stretch under load, until finally settled. The same goes for line construction largely because the line is braided. Diagonal fibres will straighten under load until they can’t go any further. This too will set permanently after being loaded heavily enough. Unfortunately, the third stretch is permanent. Creep is a mate- rial property that varies a lot across differ- ent Dyneema types and how they are pre- treated with heat and/or pre-stretched. But it’s there. This type of elongation happens primarily close to break strength, which is why lines are dimensioned to work at about 10 per cent of break strength – where creep becomes a minimal issue.
Two to five times stronger When dimensioning steel rigging you will typically look at righting moment and other factors affecting the rig. You add a safety factor and end up with a reasonably dimensioned wire or rod. Dimensioning Dyneema you will look for a number that keeps creep to an acceptable level… All Dyneema will stretch more than
steel when comparing equal dimensions; but by dimensioning for creep you end up with a line with a breaking strength two to five times higher than the steel wire you would otherwise have used. The higher safety margin becomes an added bonus. On Chi standing rigging is in Dynice
Dux, a heat-treated, pre-stretched SK75 Dyneema line produced in Iceland by Hampidjan. Breaking strength is around 16 tons. Colligo has rigged around 800 boats with this type of line, claiming no known failures to date.
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