Using composite materials in rigging

While composite rigging is rapidly establishing itself as the norm in the grand prix race world, in superyachts it is still a fledgling business. However, in recent years, a number of superyachts have refitted from Nitronic rod rigging to enjoy the benefits of lighter composite alternatives, while composite is rapidly becoming the norm for new-build superyachts. A bewildering array of options is beginning to appear on the market, each claiming to be superior in one respect or another.

Designers and manufacturers have drawn a great deal of confidence from seeing boats travel successfully around the world in challenging events such as the Volvo Ocean Race and the Vendée Globe, with competitors using modern composite fibres such as Kevlar, Dyneema, PBO, and more recently carbon fibre, in rigging and sailcloth. In 2010’s America’s Cup, Alinghi’s catamaran and the winning trimaran of BMW Oracle Racing used both carbon and PBO rigging in their ground-breaking quest for maximum strength and minimum weight.

As the racing world continues to provide the test bed for new rigging options, so the superyacht world is becoming increasingly comfortable with following in its wake. Phil Anniss of Future Fibres says that new projects, such as the Dykstra 60m Hetairos and the 66m Dubois design currently in build, would not be possible without the use of composite rigging.

‘The size of rigs being built on boats today are so big, you probably wouldn’t be able to use rod rigging because the weight would be prohibitive,’ Anniss explains. ‘Composite rigging is approximately 30 per cent of the weight of Nitronic rod rigging, which means you can make savings throughout the boat, for example, reducing the weight of the bulb in the keel.’

Navtec supplies a wide range of rigging choices to nearly all sectors of the market. For example, the company has supplied the rigging to the French giant trimaran, Banque Populaire 5, which recently set a new transatlantic record. Robbie Sargent, superyacht rigging product manager of Lewmar Navtec, is beginning to see strong uptake of composite rigging in the superyacht markets.

‘Some superyachts would still be using rod rigging, but the majority of newer ones are now beginning to use composite,’ he says. ‘However, for more cost-conscious projects that are still seeking the weight-saving benefits of composite, Kevlar is an attractive option.’

Navtec has just supplied a set of Kevlar rigging for a large multihull, Hemisphere, at Port Pendennis in Cornwall. Although the Kevlar is thicker than the rod rigging it is replacing, generating more windage, Sargent points out that any additional drag is more than compensated by the significant weight saving.

However, to be able to match rod rigging for windage and reduce the weight even further, PBO and carbon fibre are the premium options. After initial scepticism, PBO has gained acceptance as a lightweight and reliable alternative to Nitronic rod over the past 13 years. And just as PBO has earned its reputation for robustness and reliability after millions of hard miles in the racing world, carbon is beginning to follow the same path.

One of the drivers accelerating carbon’s introduction into the rigging market is the decision of two of the high-tech mast manufacturers, Southern Spars and Hall Spars, to start producing their own carbon rigging products. Where a few years ago they were fitting third-party rigging to their bare tubes, now they are increasingly keen to sell customers a total package: mast and rigging together.

For some customers the package is an attractive one, although Sargent points out that when a mast builder is promoting his own rigging it doesn’t mean it’s the most appropriate for the job. He advises customers to ask some hard questions and do their own research before choosing which type of composite rigging.

‘Each type of product has its advantages and disadvantages,’ says Sargent. ‘What’s happened is some of the mast builders have gone into manufacturing one style of rigging, and so they’re promoting their style.’

Navtec, it should be said, is now developing its own carbon product, while Future Fibres has recently gained Germanischer Lloyd approval for its first carbon product, so it will be interesting to see what further developments come out of this rapidly changing part of the market.

Carbon rigging specialist Carbo-Link is not a familiar name to the wider sailing world, although the Swiss company has been producing custom carbon fittings and rigging for Alinghi over the past two cycles of the America’s Cup. Now it is looking to bring its high-end expertise to a broader market.

One of the attractions of carbon fibre is its resistance to fatigue, as Andy Winistoerfer, director of Carbo-Link, explains. ‘It requires a bit of a change in the way of thinking, because carbon has inherently completely different properties which would allow rigging to have a lifespan comparable to a mast tube, and not really need to be replaced as often as is probably the current standard,’ he says.

Although the carbon rigging manufacturers make strong claims for the longevity of carbon in their marketing literature, they acknowledge the limiting factor is not so much the rod itself, but the terminations – how the rod is terminated at the mast and the deck. A lot of development is going into this area, with manufacturers using a variety of different termination technology. Reducing the size and weight of these terminations is one of the key battlegrounds in the racing market, where professional teams will go to great lengths and expense in the quest for reducing weight and windage by a few percentage points, or even a fraction of 1 per cent.

In the superyacht world, where people are still waking up to the huge weight saving to be made over rod rigging, such differences are likely to matter less. Rather, reliability and durability are likely to be the more significant factors in determining which type of composite material to use.

In its early days, critics of PBO pointed out its fragility if the raw material is exposed to UV or saltwater. However, those doubts have subsequently proven largely unfounded, with braided coverings providing ample protection from UV exposure and moisture, and resulting in millions of miles of trouble-free sailing.

Carbon fibre has yet to establish the same track record outside of the grand prix race world, although the majority of the fleet in the last Volvo Ocean Race used Southern Spars’ EC6 product for their lateral rigging, and it proved very reliable.

EC6 is made up of a cluster of rods encased in a braided coating to protect against chafe and impact. Some of the newer products on the market such as Future Fibres TSC, Carbo-Link and Hall Spars’ SCR rigging are constructed from solid carbon. Indeed, SCR stands for solid carbon rigging. The potential advantage of a solid carbon rod is less windage due to the absence of the braided covering and because there are none of the tiny gaps that exist between each of the thin rods that make up a clustered product.

However, the potential downsides are carbon’s resistance to impact and its limited coilability. While carbon fibre has great tensile strength it is also a potentially brittle substance. Sargent believes this is a worry that most superyacht owners won’t want to deal with.

‘You want to be able to go a long distance for many years without worrying about it, and not having to worry about what damage might be done by a boom clattering against it,’ he says.

Hall Spars’ president, Eric Hall, admits he was very worried about how his SCR product would survive the impact tests during the Germanischer Lloyd approval process.

‘I thought we were going to get stopped cold in the impact tests,’ he says. ‘For the GL test they have a swinging one metre arm with big weights on the end, and you watch that thing swing down and you think it’s going to slice through the cable like a knife through butter. But, boing, and it bounces off! So I think it’s probably stronger than you worry about.’

Murray Jones, the four-times America’s Cup winner, is now working in partnership with Winistoerfer at Carbo-Link. He echoes Hall’s concerns that it’s the slacker rigging that’s most at threat from damage.

‘It’s when it’s loose that it’s a little vulnerable and you just have to be aware of those limitations. For instance, we’ve been using solid carbon on the Version 5 Cup boats for the last few years,’ says Jones. ‘We had them on the runners, the forestay and our jumper stays and the solution we came up with for the runners was we just had a soft strap right at the bottom so that even if the runner went under the boom, it was the soft strap that bore against the boom.’

However, Anniss argues that the better way to address the issue of carbon’s impact resistance on longer stays is to build some flexibility into the product, something that he says Future Fibres is currently working on.

‘We’re doing something completely unique,’ claims Anniss. ‘It is a wound carbon, consolidated with braided covers and moulded ends, but it’s flexible. We’re in the middle of a test programme at the moment and will be launching the product formally later this year.’

Ease of coiling is important for logistical reasons, and one of the benefits of composite rigging compared with rod has been the ability to take replacement rigging on a plane to any remote destination in the world and take the rigging to the boat. With rod, you need to take the boat to the yard, and when you’re cruising the South Pacific, for example, the nearest yard could be thousands of miles away.

Winistoerfer’s solution is to bring the coiled carbon rod to the boat and complete the final phase of production on site: ‘Basically you bring an uncured carbon composite to wherever the mast is, and then you cure it on site with electricity,’ he says.

For a Volvo Ocean Race team this is probably an acceptable solution, but for the superyacht world, quality assurance issues will need to be addressed.

One of the benefits of solid carbon rigging is the ability to produce a cable to a more aerodynamic profile. For Alinghi’s catamaran, Carbo-Link created elliptical rigging to help reduce windage.

With Alinghi 5 travelling at up to four times true windspeed, the apparent wind angles were very low. However, for slower boats he acknowledges the potential windage reduction is not so clear. Winistoerfer believes that provided you can keep your apparent wind angle to below 15 degrees, then there are windage benefits. ‘But if your misalignment angles become too big, you are creating more drag compared to a round section,’ he says.

Eric Hall, on the other hand, is much more bullish about the windage benefits of profiled rigging for monohulls, and argues that his new SCR aerofoil rigging creates a lift component as well as a drag component.

The big question to consider before buying any rigging product is the primary function of the boat. Phil Anniss says, ‘We believe it is about selecting the right type of composite cable for the right application. The various rigging elements on a yacht experience wildly different loadings and there is no single fibre out there that can provide the perfect solution for all situations. Yes, we’re excited about the possibilities of our new carbon product, but equally there is a lot further to go with all the composite materials: PBO, carbon, Dyneema and Kevlar.

‘For example, PBO is still the lightest fibre for a given modulus and we have just developed our new Enduro product, which is more flexible than our current PBO cables and testing suggests it will last almost twice as long,’ he says.

However, Anniss points out that Enduro will be tested extensively in the racing scene before they start promoting to the superyacht world. ‘We want this to be “Volvo qualified” before we start piling it out to the wider market. The racing world has been, and continues to be, a great place to trial new developments in real-world situations. By the time the product goes on to a superyacht it will have been through more than a million miles of testing.’