Revolution in the rigging

The advent of rod rigging and Nitronic 50 some years ago resulted in both weight and windage savings, especially as the hefty terminals could be done away with, explains Jon Morris of Marine Results International. “But it all came at a massive hike in costs,” he says, and although now the greater proportion of boats over 40 foot have it fitted, “The price difference still means that the smaller end isn’t really going to be that interested.”

Tim Watson of Pro-Sail Management explains that with the appearance of PBO (poly-phenylene benzobisoxazole) in the marine world, things changed again. The story is that Future Fibres founder, Tom Hutchinson, was involved with tethers for the wheels on Formula 1 cars, and also being a yachtsman he realised that that this composite fibre would also hold rigs up in boats with a minimum of stretching. “Suddenly all the racing boats started to use PBO,” says Mr Watson.

It wasn’t long before the trickle down effect took hold. With the upping of manufacturing volumes there was a cost reduction and super yachts started to use the material.

Lighter keels
This in turn sparked something of a revolution. “If you can make the mast and rigging lighter, you can make the keel lighter,” says Mr Watson. “And if you can make the keel lighter, you can make it shallower. Mr Morris adds that it’s not just a question of the super yachts getting closer into the shore, “It means that the boats handle quite differently: you have less of a loading moment, and all in all it makes them easier to sail.”

On the other hand, PBO can be successfully retrofitted, and these days with greater ease. Mr Watson says, “In the bad old days, the spreader tips had to be changed, which used to mean cutting off and re-laminating a new tip. However, on a recent project, we used a ‘Replacement Tip Cup’ which took most of the pain out of the change over – it’s nice to know the manufacturers are thinking about things like this.”

However, Mr Morris adds that the big jump in efficiency can cause unexpected difficulties. “If you try retrofitting some of these very efficient systems onto an older boat, the loading suddenly peaks. When the ‘give’ gets taken out of one section, you find other things have to take up a lot more strain. In short, you need to find someone who knows what they are doing.”

Not for everyone
And there are other points to consider. Not all vessels will be suitable for PBO. For example Mr Watson says, “One of our clients has an 80 ft yacht which is privately owned but also has an amount of charter time. We got together and discussed the pros and cons of different types of rigging on the boat at some length but it’s been decided that it would be best to stay with rod.”

It’s partly an issue of maintenance, and PBO needs special handling because while it has the required weight-to-stiffness, it really doesn’t have many other desired characteristics. “It hates water, and it hates light” explains Mr Morris. So, it has to be completely encapsulated. “You only need to crack the covering either through repeated rubbing from a halyard for example, or land on it hard with another piece of gear, and that’s it – you’ll have to replace the whole section.” This in itself is obviously a big deterrent for the usual charter boat market.

Mr Watson adds that while on a race boat the crew will do a rig check before every race, with performance boats having a shore team, cruise boats really need fit-and-forget rigging. “Apart from the annual maintenance, you just want it to do its job,” he says.

Safety margins
Mr Morris agrees and explains there is no real way of calculating the stress on a boat since there are just too many factors to take into account, so all you can look at is how the boat will be used. “The difference in operational duty has to thoroughly covered – your margins of safety have to be that much higher for cruising boats: the faster and racier the boat, the lower these margins get,” he says, “and then you are reliant on re-rigging and thorough checks.”

But the move over to the next-generation carbon is another big step up – especially in price. Although it promises to be more "user friendly" than PBO, the cost will keep it out of the hands of smaller boats for quite some time to come.

With the introduction of carbon a number of alternative construction methods have been introduced. Each one has its relative strengths and weaknesses, says Phil Anniss of Future Fibres. “No single fibre or technology can offer itself at the single best solution now.” He points to competing project needs; weight, windage, usability, durability and price. “The right package could involve PBO, carbon, Dyneema, Kevlar, or a combination of all four.”

Technology development
The Volvo Ocean Race illustrates the development of rigging technology. Ten years ago, composite rigging barely had a presence in the Volvo 60 fleet. Four years later saw the radical new Volvo 70, and the whole fleet started using PBO composite rigging with an associated leap forward in weight savings.

Three years on for the 2008/09 edition, while some were still using PBO lateral stays, others used EC6 from Southern Spars. The performance difference between the two was minimal – and the arguments about which had the edge were debatable.

One of Future Fibres´ latest developments is ThermoSet Carbon (TSC) which relies on epoxy pre-impregnated carbon tow, wound to the required length which is then consolidated and cured into a solid rod. This development process results in even thinner and lighter composite rigging. Although it’s not as big a change as the introduction of PBO, “you’re still looking at approximately 4 to 5% in weight savings and 10% reductions in windage. Not huge gains, but significant enough,” says Mr Anniss.

But whereas Mr Morris says replacement rigging will probably continue to be needed every eight years for quite some time, simply because both the market and the insurance bodies “won’t sign off on it”, Mr Anniss has a different point of view.

He says that the time is coming when sailors just won’t talk about the lifespan of their composite rigging and it will simply becoming a non-issue – although he adds that some competitors have been overstating the claims for carbon “as a way to get into the market.”

Longer lifespan
However, he adds that generally people are still cautious about composites as it is relatively new technology. He points out that as the race teams are supposed to push their boats to the limits, it’s easy to push them too far. He adds: “All composites actually last longer than metal rod in tests. When you put carbon or PBO through an aggressive 100,000 cycle test, you will still come away with a residual safety factor of two – but when you put rod through the same test, it explodes after around 80,000 cycles.”

However, while composite has proved its general fatigue resistance, the terminals at either end of the cable, where fibre meets metal still need special attention.

“Having investigated other options, we kept on coming back to the ‘continuously wound’ method as the best and most reliable way to go.” This process means that the fibre is wound between two end pieces into a simple loop. “No other process shares the load as equally throughout the fibre bundle and you don’t need to have any heavy, structural, metal end fittings to transfer load,” says Mr Anniss. “And because you’ve got good load sharing, you can use fewer fibres to achieve the same performance characteristics.”

The best application of solid carbon is on the side-stays. For long cables, due to their rigid state, Future Fibres ships them before the curing process and then cooks the cables off, on site.

Flexible carbon
While solid carbon rigging works beautifully for static lateral rigging, its application for the harsher environment of fore and aft rigging presents some challenges. To achieve the best in both weight and windage, some race teams have used solid carbon for aft runner cables, but the obvious problem with this is that you need a soft strop for the bottom few metres of the cable where it has to turn around the boom – and it’s a bit of a compromise.

Knowing this, Future Fibres started to look for a more flexible carbon cable and experimented with alternative matrices to give a product with the right combination of strength and flexibility. The result, the FlexC cable, uses a dry carbon fibre which is impregnated with a blended matrix developed by the company’s R&D team. The impregnated fibre tow is wound, consolidated and then covered with a braid layer for chafe protection and the result, says Mr Anniss is a cable that combines the stiffness, strength and excellent fatigue resistance of carbon fibre with the flexibility, impact resistance and general handling benefits of a dry fibre cable.

On the ropes
For the ropes themselves, Dyneema is still the standard for most applications as it has low stretch characteristics with softness and flexibility, and importantly, it doesn’t absorb water. However, if you are doing something like easing off the runner tail or jib sheet on a winch, there’s a good chance that you could heat the rope up enough to melt a pure Dyneema fibre. So, woven polyester or PBO/composite jackets are used to dissipate the heat.

“Of course,” says Mr Morris, “if you are racing a Volvo boat, you might just go for the PBO woven jacket, and simply be prepared to throw it away three legs out of five. It’s lighter, but it fractures easily and sprays you with brown fibres. Not nice, but a minor inconvenience if you are racing.”

Mr Morris has another, very interesting point to make. “While you couldn’t do it with wire, getting back to rope gives you the option of getting rid of a lot of the deck equipment.” He points to the last Volvo race, in which there was a boat that went right back to basics, losing all of its hardware, and relying on rope technology – which meant going back to splices instead of hard metal shackles, block and tackle fittings instead of powered winches.

“While it might sound like a step back into the past, I actually think it’s a lot safer, the hardware can cause a lot of accidents, whether it’s a D-ring on the end of a swinging rope that hits a carbon mast, or a person in the wrong place. And all you need to do, really, is make sure that the lines are running round smoother corners, instead of onto bearings. It takes a lot of the complication – and the weight - out of the deck equipment.” He adds that while there will always be a place for the power technology, “it is nice to have the option”.