Ropes, like people, suffer from fatigue. Unlike people, a good night’s sleep does not reinvigorate them

What is fatigue? Fatigue is any mechanism that reduces the performance of a rope over time in service. This can be abrasion, UV damage, creep, bending fatigue or one of many lesser causes. This article will focus particularly on bending fatigue of high-performance Dyneema cored ropes.

Main picture: the high performance rope shown here is clearly well past its sell-by date and yet the damage is internal, brought about by fibre fatigue as opposed to external abrasion damage (and overheating) – that was once the main driver for a rope replacement

Below: taking account of a logarithmic scale on the x-axis, it is evident that a rope’s fatigue life changes dramatically with even a small change in the life factor; a combination of the critical D:d ratio and load – as is explained in detail in this article.

As modern rope covers are getting more durable, including the increased availability of high-performance blends, they are lasting longer. Also more applications are appearing on boats that place ropes under higher loads and perhaps over smaller sheaves. All this results in fatigue becoming more relevant to sailors, riggers and boat designers than ever before.

A rope is made up of twisted yarns and each yarn contains hundreds of filaments. Every time a rope is flexed the fibres slide across one another, causing the filaments to abrade and eventually to break, thus reducing the strength of the rope. This is a cumulative process and if unchecked the rope will eventually have a strength less than the working load, resulting in an in-service failure.

The rope pictured above shows typical fatigue damage – but note that the broken filaments are inside the braid rather than at the crowns of the plaits, as would be expected if the cause was external abrasion.

There are many factors that influence rope fatigue, the major ones being:
Material: Most modern high performance ropes have a Dyneema core; this material has good fatigue resistance. All the following information is based on testing of Dyneema 12-strand ropes.
D:d ratio: The ratio of the diameter of the sheave that the rope is being bent around to the diameter of the rope. The larger this ratio the better the fatigue life; a small increase in D:d can significantly improve rope life. As a ‘rule of thumb’ doubling of the D:d ratio will approximately triple the fatigue life.
Load: Like D:d the load that the rope is under can significantly alter fatigue life. In testing a 35% increase in load was shown to halve the fatigue life.
Coatings: Most HMPE ropes have a coating or impregnation of some sort, normally there to improve handling, splicing and abrasion resistance and to impart a colour to the rope. These coatings can also alter the fatigue life, with some standard PU coatings actually reducing fatigue life. Special lubricating coatings can extend the rope’s life very significantly.
Rope design: Factors such as twist level, braiding pitch etc can all have an effect on a rope’s fatigue life.

How can rope designers and users make sense of all these parameters? One method is to combine the Load and D:d into a single ‘life factor’ by multiplying the coefficient of utilisation (safety factor) and the D:d ratio, ie a rope with 1,000kg MBL working at 200kg on an 8:1 sheave will have a life factor of (1000/200) x 8 = 40.

Combining these parameters allows us to quickly compare the major factors for each rope design and so start to make judgements as to how a system’s design will affect the life of the rope and how long it can remain in service.

Other factors to account for:
Pre-stretching This does not significantly alter the fatigue properties but it does reduce the diameter for a given strength, which alters the D:d (for the same-sized sheave) and therefore the life factor. What this means is that, compared to a non pre-stretched rope swapping to a stronger heatset rope at the same diameter will give a small improvement in the fatigue life, while swapping to a smaller rope with the same strength will give a small reduction.
Heat As the rope is cycled heat is generated in the braid and the faster the cycling the more heat builds up. At small diameters this isn’t a problem and cycle speed doesn’t affect the life. At larger diameters, though, the heat generated at higher cycle speeds can affect the fibres, reducing the fatigue life. In extreme cases it is possible to melt a rope’s core through the heat generated.
Rope fatigue A huge subject and this article only scratches the surface. However, Marlow’s extensive and ongoing test programmes not only mean that our ropes are designed to optimise performance, but that we are able to offer clear technical advice based on empirical evidence and with race-proven results.
Paul Dyer, technical manager, Marlow Ropes

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Umberto Felci’s new Grand Soleil 58 design does a nice job delivering performance plus contemporary styling typical of a much larger yacht

The collaboration between Felci Yacht Design and Cantiere del Pardo has a long history. It is now 15 years since Umberto Felci designed the GS70, the Italian yard’s custom flagship produced for a German customer. In 2002, in collaboration with Rolf Vrolijk, we also designed both the GS45 Cruiser and the successful GS44 Performance Cruiser, which kickstarted a string of similar designs that for many years dominated IMS racing, winning several European titles. After the GS45, in 2003 we designed the GS50, working with French designer Patrick Roseò.

So after so many years we were pleased to return to work with Cantiere del Pardo, this time with another great studio, Nauta Design. Our task involved the naval architecture of the new Grand Soleil 58 Performance, a fast-cruiser designed and built to the highest production standards.

We tried to create an efficient hull that was able to accomplish the difficult task of sailing fast but that was also easy, safe, comfortable to handle and, last but not least, with generous internal volume.

When we approach a project for a so-called fast-cruiser yacht we have to first look at the compromises that will always be necessary in a multi-purpose boat of this type. This is a matter of sensitivity, balance and a good feel for the client’s objectives more than just a matter of numbers and science.

In the intervening years since we last worked with this yard we have designed several yachts of a similar concept from 45 to 80ft. I think we have sharpened our abilities in this sector but you must still remain flexible as each client has his own priorities. I like to imagine that the ‘race’ or ‘speed’ factors sit on one side of the equation and ‘cruising’ or ‘comfort’ factors on the other. In fact, the understanding of what a client really wants is sometimes the hardest part of the process.

If the race capabilities are central to a project, then more effort will be put into hull and appendage refinement. If an elegant, comfortable cruiser is the goal then other factors take on at least equal importance. But you also know that most customers want the same dream in every area; we are often asked to deliver maximum speed together with maximum comfort! And this was rather the case with the GS58... our brief was for the fastest and most stylish and most comfortable yacht of its type…

To define the hull shape we began with a study of our CFD database looking at the potential differences in performances between chined and rounded hulls, analysed by equalising the main hull parameters including volume, LCB position and especially equalising the righting moment at 20°.

Due to the small performance differences between the candidates analysed, the yard’s decision was to stay with a conventional round-bilge hull in the classic Grand Soleil style. That said, we had to accommodate a wide range of boat and keel weights due to the options that would be on offer. To allow this flexibility without hurting performance a traditional hull was made a bit narrower at the waterline and deeper in profile. The final hull has generous volumes providing plenty of space inside.

The balance between the width of the canoe body and its depth is fundamental to a project like this one. We needed the saloon floor to be high for good visibility and light and of generous area. But we also needed to control beam waterline in order not to overly increase resistance. I consider this ratio the real key factor with this kind of hull, so we undertook a specific analysis to identify the correlation between hull resistance and internal volume.

Three keel configurations are available: a shallow draft keel (2.45m), a deep draft keel (2.90m) and a ‘race keel’ with a draft of 3.15m, manufactured in highmodulus stainless steel with a CNC-machined bulb.
Umberto Felci, Garda

Above: bend your knees a little and it’s easy to convince yourself that you are at the helm of the latest dual purpose Mini Maxi… Go down below and the illusion might continue. The GS58 is a very long way from a typical production yacht of this size with the emphasis very much on creating a mid-sized ‘big boat’ rather than a smaller design that has been over-fertilised in order to cram in as many beds as possible. Most certainly ‘a looker…’

Sleek by nature
With the new Grand Soleil 58 Performance Cantiere del Pardo is trying to increase its grip on a sector of the market in which the Italian brand has been strong for decades: racing in style.

The first public display of the boat was a true grandezza, centrestage at the 2016 Cannes Yachting Festival on Quai Saint-Pierre, where, painted in the deepest, hottest and most lustrous black imaginable, she drew an impressive crowd.

Just a year ago the yard had broadened its range with the 46 LC (‘Long Cruise’), aimed at the comfy end of the mid-sized luxury market. She won European Yacht of the Year, boosting sales as well as confidence at Cantiere del Pardo – which had changed ownership and management a couple of times since 2010 but now seems to be back in calmer waters.

The Grand Soleil 58 Performance is intended to sharpen the brand’s profile in its core market of fast cruiser-racers. Before the first boat was completed four owners had paid their deposit; a further seven boats have been sold since with plenty more serious enquiries. As a result the yard is now restructuring its build process just to keep up with demand. ‘We were pretty stunned by the initial popularity of such a big boat,’ acknowledged general manager Fabio Planamente.

Cantiere del Pardo left nothing to chance. They put together a strong all-Italian team of designers. Along with Umbert Felci and Nauta Design they brought back Marco Lostuzzi, who had previously helped create the popular GS46 LC.

‘We have produced more than 200 boats of around 50ft in the past 20 years,’ says Planamente. ‘We have a big database and so we talked to many of our customers about their expectations of a modern performance cruiser.’

Not surprisingly, the feedback highlighted a somewhat contradictory wish for beauty, power and sailing performance… as well as generous cruising amenities. ‘Owners have grown older,’ says Planamente. ‘They still want to sail fast but they are no longer willing to give up their comforts… In fact, they want more of them.’

So when you step onboard the new GS58 you will certainly not feel as if you are on a raceboat. But don’t be mistaken – more than 80 per cent of the modern interior is veneered foam sandwich, the main bulkheads are composite and the structural hull grid is also predominantly carbon.

Deck layout is split into two parts. There is a guest section aft of the companionway, behind which is the control centre of the boat with winches plus a piano of stoppers. Aft again are two pedestals. The set-up keeps the companionway clear of all ropes and hardware, also maximising the clean visuals of this new yacht.

Grand Soleil offers the GS58 in a variety of flavours. The base boat is an all-rounder. But with a generous options list you can customise it to taste – from ORC or IRC-optimised racer with tall carbon rig and deeper keel to a full-on luxury toy with airconditioning, generator, dishwasher and multiple fridges…

We sailed a model a notch or two up from the standard boat in terms of power, but not with the maximum performance possible. It came with carbon rig and membrane sails, with a big Code 0. Sailing any luxury 58-footer at 8.5kt in 8-10kt of wind at 90° TWA is still something of a novelty to this sailor. With 11-12kt TWS you are quickly up to 9.5kt. If you are looking for a boat perfectly suited for Mediterranean conditions this may be it.

With the 58 Performance you do not just get Grand Soleil’s latest racer-cruiser, you also get a ticket to a GS58 circuit to be launched in 2017, hooking the class into five of the most iconic Mediterranean regattas including the Rolex Middle Sea Race.

My friends at Seahorse tell me that Cantiere del Pardo is already working on a scaled-down and souped-up 48ft version of the 58, due to launch in 2018. Who called the performance cruiser market down and out?

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Zhik R&D manager Tom Hussey says there’s no tougher a sport for testing the waterproofness and durability of modern technical clothing than offshore racing

In the past decade Zhik has listened carefully to the wants and needs of the world’s best smallboat sailors, with Zhik the gear of choice for many of the sailors at Rio 2016 including all the team members of three of the most successful nations: Great Britain, New Zealand and Australia. The gold and silver medallists in the dynamic 49er class – Pete Burling and Blair Tuke (NZL) and Nathan Outteridge and Iain Jensen (AUS) respectively – are among the better-known names who have been wearing Zhik for many years now.

Flexible but dry, Isotak 2 (main picture) and the Zhik accelerated wear machine (above). Test fabrics are made into pockets that contain a control ‘test ball’. These fabric pockets are then placed in a rotating drum that simulates impacts against hard edges and also flat surfaces covered with non-slip grip. Test balls are shaped to simulate the parts of the body and other hard objects that impact a boat through the fabric

R&D manager Tom Hussey says, ‘When we started making neoprene garments back in the early days of the company, it was amazing what sailors were prepared to put up with. Or rather, they didn’t have much choice because most of the wetsuits available had been developed for surfers or athletes from other sports. For sailing they were pretty clunky, heavy and inflexible. Since then we’ve listened carefully to the world’s best and most demanding sailors to give them what they need, to create garments that are warmer, drier, lighter and more durable than what had previously been available.’

Recently Hussey and the team at Zhik have started to ask the same searching questions about offshore gear. ‘The goal was to produce the toughest, most durable kit that we could; it needed to outperform existing kit from rival brands.

‘We’d picked up on comments off the round-the-world boats that some of the supposedly best gear wasn’t making it through an entire long leg without degradation in key features; when we tested used clothing “from elsewhere”, we quickly identified areas for improvement – in materials in particular. So material became our immediate priority.

‘It’s surprising that there hasn’t been a suitable standard to test for waterproof durability. What’s common in the industry is a hydro - static test, where you put a whole lot of water pressure on one side of the fabric and see if it leaks through.’

While this method provides a good indication of the initial waterproofness of a fabric, Hussey says it doesn’t give you any idea of how the textile will maintain its waterproofness through the active life of the product. ‘There is currently no industry standard method that simulates the high levels of wear in the kind of wet, extreme conditions that are experienced by foul weather gear in the most serious offshore events.’

So Zhik approached the Royal Melbourne Institute of Technology (RMIT) to develop a waterproof durability testing method specifically to simulate accelerated wear and tear in wet conditions (when the waterproof membrane is most vulnerable). The method involves placing waterproof textiles in an accelerated wear device that simulates impact and abrasion always in wet conditions. Each textile is pressure-tested to determine waterproofness after defined intervals of accelerated wear (see table).

This has provided Hussey and the R&D team with a much more meaningful way of experimenting with different combinations of materials and bonding techniques. The result is their most recent version of Isotak, a new multilayer membrane. ‘It’s the membrane we use throughout our Ocean range,’ says Hussey. ‘It is in our Isotak Ocean range and new Isotak 2 range, the only difference being that the Ocean has a much thicker, heavier and tougher outer shell fabric. Ocean is our most extreme, most durable product, while Isotak 2 has extremely high levels of waterproof durability, although it’s much, much lighter, less bulky and more flexible.’

Without being prepared to reveal the full magic recipe – the closely guarded combination of materials and methods that have gone into Isotak – Hussey says the secret lies in how you combine various component materials. ‘It’s the knowledge and experience we have gained from exhaustive testing that we believe gives us a competitive advantage; it’s a matter of how we combine all the waterproof layers to make something very, very tough, while also maintaining the same high breathability. The membrane layers that go into Isotak combine to work really well to provide a longlasting waterproof durability.’

Above: not an easy thing to model. Wear calculations are based on an estimated number of impacts encountered in one hour’s sailing, multiplied by the typical hours of activity in one day. That impact total is then applied using Zhik’s accelerated wear machine. For example, 14 days of extreme offshore sailing works out to just over 1,800 impacts, which is equivalent to 30 minutes in the machine

According to independent tests run by RMIT, Zhik’s Isotak outperforms the acknowledged industry leader in offshore garments by a factor of at least 4:1. ‘RMIT’s independent testing has shown that Isotak reaches the same or lower level of degradation after 120 minutes of accelerated wear testing, compared with just 30 minutes for the industry standard.’

Hussey is excited by the results and can’t wait to have some offshore professionals wearing the Zhik garments in next year’s big round-the-world race. ‘But obviously we don’t just stop where we are today. We are always looking to the next thing, and the next. There are lots of different membranes, lamination methods, composites that you can produce; there are a lot of different things coming out all the time. So we’re always keeping an eye on what’s going to work best for extreme sailing that some of our bestknown customers take part in.

‘One of the major problems we come across is a lot of products, particularly with waterproof textiles, are targeted at the outdoor industry and so are frequently geared more towards breathability than outright waterproof durability. So it’s really, really good for climbing a mountain, or cross-country skiing, but not the best product for sailing.

‘You’ve got extremely different environments and requirements in the products. A very small leak in a sailing garment is a fail, whereas when you are skiing down a hill in light, dry snow it isn’t going to worry you so much. Having the absolute highest breathability possible is a much more important factor for some of these other sports.

‘Of course breathability is very important for sailing as well, and Isotak delivers at least the same level as any other offshore clothing product. But compared to land-oriented products we are laser-focused on the fact that you have to ensure that your garments do not leak while you’re mid-ocean.

‘So a lot of what we do is looking beyond the outdoor industry standard and aiming for something that’s best for our intended use. And that’s really where this testing method originates. Because the amount of wear and tear sailors put on their garment is significantly more than in any other outdoor sport – certainly any outdoor sport we’ve been made aware of!’

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No need to be self-obsessed when cold and damp on the rail… become an active member of your boat’s data acquisition and management group

Load sensors and data gathering have been a familiar part of the sport going back to the late era of IOR – in particular the final generation of IOR supermaxis like Bill Koch’s data-muncher Matador³. Today the technology is prevalent from the America’s Cup to big offshore trimarans to VO65s and including most of the modern superyacht fleet. The demand for data from raceboats is continually increasing – but it’s a form of technology that to date has been relatively inaccessible to the mainstream sailor, not to mention many designers and builders.

However, for some time Spinlock has been working on developing load-sensing technology that is accessible to the wider world of sailing, as the company’s marketing manager James Hall explains: ‘Spinlock has been measuring load on ropes and rigging for 20 years, but recently more and more people in the sport have acquired an appetite for data and the performance benefits data can bring to a team if used correctly.’

The benefits are many and varied, including:

• validating design loads, static and dynamic
• validating line choices
• validating winch and block sizes
• adding in or taking out purchase
• as an accurate and repeatable trimming aid

‘We’re finding it’s not just sailors who are interested in the data,’ says Hall, ‘it’s also boatbuilders and designers looking to validate actual loads against design predictions. The same is true for sparmakers while sail designers want to understand more about the loadings on their sails and modify their designs accordingly.’

A feature of Sense load cells is Bluetooth connectivity, allowing data capture to phones and tablets via the Spinlock app. According to Rán project manager Jan Klingmüller, this opened up their data to the whole sailing team. ‘With your iPhone in your pocket it’s picking up data all the time, giving you backstay tension and mainsheet loads etc.’ Klingmüller admits he finds it all a bit addictive. ‘The more you use it the more ways you find of using it. We now use it to weigh our motorbikes…’

Spinlock offers two ranges of Sense products – Digital and Wireless – with several models working through the tonnage spectrum: 5, 10, 20, 30 and 50T. The units are simple to attach into a system using soft loops, so can be moved around the boat and installed or removed in seconds.

‘America’s Cup world has always been good at data capture,’ says Hall, ‘but less so the Mini Maxi fleet or the TP52s. But we’re seeing that changing quickly now, as teams realise this kind of data capture offers the incremental gains that can make a massive difference in a tightly contested fleet.’

The Sense tools have also proved important to the rapid development of the M32 catamaran on the World Match Racing Tour. ‘The builders of the M32 used Sense load cells to validate loads during development and then better tailor their deck equipment to the live loads encountered.’

If there’s one part of the sailing world that needs no persuading of the importance of measuring and limiting load, it’s the superyacht race circuit. With owners commissioning yachts for cruising but then catching the racing bug, it’s easy for design loads to be exceeded. This makes it vital to know how highly you can load up sheets and running backstays, for example, before fittings start to rip out of the deck with potentially catastrophic consequences.

‘With larger yachts and superyachts in particular,’ says Hall, ‘insurance liability is becoming ever more onerous. If a rigger has made a soft loop for attaching a block, they need to prove it is properly tested and that the recognised certificate has been issued. More and more we are seeing riggers turn to load sensors to validate their work.’

According to Andrew Martin, product development manager at Oyster Yachts, Spinlock’s Sense products have become integral to the testing process at Oyster. ‘We use Spinlock products for weighing spars, for running winch load tests and for halyard and sheet load tests to build up empirical data.’

Alex Thomson’s Hugo Boss team have been using Spinlock equipment for load testing their Imoca 60 leading up to the Vendée Globe. ‘In a development class like the Imoca 60, everything needs to be as light as possible while being strong enough to do the job all the way around the world – so using the Sense load cells has been a vital part of the testing process for Hugo Boss,’ says Hall.

Comanche is another state-ofthe- art campaign that tests the edges. Every element of this super powerful 100-footer has been designed around achieving the perfect compromise between weight and strength. Project manager Tim Hackett says: ‘We used a 5T Spinlock load cell for Puma in the Volvo, which we used for checking sheet loading, load testing at the dock and so forth. On Comanche our maximum sheet load is around 9 tons – we’ve used the Spinlock gear for testing winch pods, leads to the primary winch pods and setting up configurations.

‘It’s an easy tool to set up, so sometimes we’ll have the load pins in the winches and runners during a big manoeuvre, using it as a check-in to make sure the boat’s permanent gauges are giving us the correct information…’

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