Marine Engineering by The Chelsea Magazine Company

MARINE ENGINEERING Produced by Racecar Engineering and Yachts & Yachting

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How Formula 1 influences boat design DREAM TEAM

An all-British entry for AC35?

CHELSEA ARINE M MAGAZINES

SAILROCKET Designing the fastest boat in the world AC DESIGN New rules for America’s Cup 35? CHELSEA ARINE M MAGAZINES

AMERICA’S CUP 35 – BRITISH TALENT FEATURE – TITLE

Dream team

he next few weeks will be critical for Ben Ainslie if he is to mount a viable campaign for the next America’s Cup. But there’s a formidable amount of British talent in every discipline he might need to form a ‘dream team’ for AC35.

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While Britain may not have had an entry in the 34th America’s Cup, there was no shortage of British expertise among the four teams in San Francisco last summer. With each team in this cycle including more than 100 people, this clearly goes far beyond the 11-man sailing

squad, and includes boat builders, designers, shore crew and financial backers. Here following is a selection of some of the top British talent that could form the backbone of a truly patriotic challenge that would have every chance of success…

ACEA/GILLES MARTIN-RAGET

Ever since Ben Ainslie helped guide Oracle Team USA to victory, the sailing world has been buzzing with speculation regarding a potential British Challenger for the ‘Auld Mug’ and who might be onboard. Here we throw some names into the ring…

Oracle Team USA during the last match of the 34th America’s Cup in September 2013

“While Britain may not have had an entry in the 34th America’s Cup, there was no shortage of British expertise on show” Technical and management Craig Mitchell

Mitchell is director of the Alpari World Match Racing Tour, and was right in the thick of the action as on-the-water umpire for the 34th Cup in San Francisco, giving him arguably more

experience of running match racing than almost anyone else on the planet.

Adam May

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An aeronautical engineer by training, May has always had a long interest in wings on boats, most Marine Engineering u Digital Supplement

ACEA/BALAZS GARDI

ACEA/GILLES MARTIN-RAGET

AMERICA’S CUP 35 – BRITISH TALENT

Ben Ainslie potentially has a vibrant hotbed of British talent to call upon for AC35

Adam May has America’s Cup experience and famously put a wing sail on a foiling Moth

Essential manpower needed for an America’s Cup campaign extends far beyond the 11-man sailing team, through to boat builders, designers, shore crew and financial backers

recently achieving fame by putting a wing sail on a foiling Moth. He has solid match racing experience, having won both world youth, and national match racing titles. He worked for Victory Challenge during the 2007 America’s Cup and was a technical coach for Team Origin’s TP52 programme in 2010. In the most recent Cup he worked with Luna Rossa, responsible for performance and analysis.

Green Marine Britain is home to one of the world’s most successful builders of hi-tech raceboats, Green Marine. The lead partner in the building of the Volvo 65 fleet for the next Volvo Ocean Race, Green Marine has also built AC boats for Luna Rossa and Mascalzone in the past. Marine Engineering u Digital Supplement

Malcolm Barnsley An unsung hero of Paul Larsen’s successful SailRocket campaign, Barnsley is a naval architect who can boast nearly 30 years of breaking down established boundaries in sailboat design. He was responsible for the revolutionary foils of SailRocket 2 that enabled the boat to smash through the 50 knot barrier that had prevented previous record holders from bettering their own records.

Caterham Group The Formula 1 world – in which Britain is a leading player – has increasingly strong links with sailing. When he started to assemble Team Origin in 2010, with a plan of competing in the 34th Cup, Sir Keith

Mills held talks with 30 F1 engineers. Since then, Caterham, among others, has entered the sailing world in a big way. While very British in its branding, the Caterham Group is actually Malaysian-owned, A Caterham boat in the America’s Cup would certainly be a great advert for the company, but it would almost certainly carry Air Asia branding (part of the wider group that owns Caterham).

Mike Gascoyne The chief technical officer of Caterham, Gascoyne has been involved with the design and development of a large number of Formula 1 cars, and has sailing experience having built a Class 40 that raced in last year’s Transat Jacques Vabre. He

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AMERICA’S CUP 35 – BRITISH TALENT

started his career studying for a PhD in fluid dynamics at Cambridge University, and has worked almost exclusively in Formula 1 since 1989. However, he has long had a keen interest in sailing, and built the Caterham Challenge using the Akilara RC3 as a basis. The America’s Cup would be a logical next step for Gascoyne.

Keith Sexton

Ian Pattison

Matthew Tasker

A former manager of North’s UK sail loft, Pattison was the supervisor responsible for production of the company’s 3DL sails in Minden, Nevada. In 2001 he joined the Alinghi team as sail loft manager, remaining with them for three ACs, before joining Luna Rossa for the 34th AC.

Another former North sailmaker who subsequently joined the Alinghi campaigns, before moving to Luna Rossa for the last Cup.

yachts, Brooks has been involved with three America’s Cup campaigns, including one with Alinghi.

A boat builder who started his career building raceboats at Green Marine, Sexton has participated in every Luna Rossa America’s Cup campaign since 1997. In 2010, he was part of the Alinghi team working on the construction of the Alinghi 5 catamaran.

Wolfson Unit

Will Brooks An accomplished structural engineer specialising in composites for top-level racing

This offshoot of Southampton University has been working for America’s Cup teams for more than 30 years, providing tank testing and wind tunnel modelling, as well as computational fluid dynamics calculations using the university’s supercomputers. In 2011 the Unit was awarded the Queen’s Anniversary Prize in recognition of its track record in performance sports engineering, combining expertise in yacht racing, Formula 1 and the most recent British Olympic team. ME

GETTY

ADRIAN NEWEY

One name that is almost certainly at the top of Ben Ainslie’s list is Adrian Newey. The 55-yearold is widely seen as the best engineer in Formula 1. After graduating from the University of Southampton with a degree in aeronautics and astronautics, Newey has spent his entire career working in motor racing. His designs have won 10 F1 World Championships and seven Indianapolis 500s. ‘Adrian is a big sailing fan, there’s the potential for him perhaps to get involved, cast his eye over our design team and what we’re looking at doing,’ Ainslie admits. ‘To have the advice of Adrian or many of the very smart people involved with Formula 1 industry in the UK would be a great boost for us as a team. Newey is clearly a genius in anything to do with competitive design, and he’s got a great profile, but I would hate for anyone to think we were trying to prise him away from Red Bull Racing.’

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Newey himself claims to be happy in his current role at Red Bull, and his boss Christian Horner seems confident that he will remain. ‘Firstly, Adrian has always expressed an interest in the America’s Cup since the McLaren days,’ says Horner. ‘At some distant point in the future it is feasibly something he may get involved with, but he thoroughly enjoys what he is doing at the moment. He is in the halcyon period of his personal career and he enjoys the environment he is working in. ‘It’s not just about Adrian, it’s about the team of engineers that work with him and support him, without which none of it would be possible. Adrian is always the first to recognise that as well. He’s far from retirement age and I think he would find it hard to find any challenge that would stimulate him in the way that Formula 1 does. He’s an enormous part of the

team, and the technical team, in many ways, has been built around him to embrace the way that he works and how he operates.’ Newey’s engineering approach is rather anachronistic in so much as he draws all of his designs by hand while almost every other designer in Formula 1 uses a 3D CAD system. It is unlikely that Newey would design the AC35 challenger himself, as he has never designed a boat of any description. However, it does seem likely that when the AC35 technical regulations are released he will be giving them a thorough read, and will work closely with whoever is leading the actual design process. If Newey does get involved it will likely be as a design consultant, and with the AC35 not taking place until 2017 it will not place great demands on his time.

THE F1 CONNECTION

F1 thinking takes to the water

Technology from top-level motorsport is finding a place in sailing, with electronic, aerodynamic and simulator technology crossing over more frequently and effectively Marine Engineering u Digital Supplement

otor racing is boring. That seems to be the point of view of a growing number of key technical figures within the motorsport industry, who for many years have had their technical freedom continuously reduced to the point where most people struggle to tell two cars apart. ‘If the regulations continue to become ever more restrictive, we’ll eventually get the point where the car’s more or less designed by the rulebook,’ says Adrian Newey, the man who penned the designs of the last four Formula 1 World Championship-winning cars. ‘You’ll then have, effectively, GP1 cars where the differentiators are the engine and the driver. For me, it’s not Formula 1. One of the big things that differentiates F1 from almost all other sports, with perhaps the exception of the America’s Cup, is that combination of man and machine. You can have a great car with an average driver and you won’t win, a great driver with an average car you won’t win. It’s about both.’ Speculation mounted when Newey mentioned the America’s Cup, as it was not the first time he had raised it. Would this be the link between world-beating British technology and sailing talent that could power a Union Jack to a future America’s Cup victory? Meetings between Ben Ainslie and Newey at the Abu Dhabi Grand Prix did little to slow the rumour mill, and Ainslie himself was openly keen on having the cutting-edge technological know-how from Formula 1 deeply embedded in his planned America’s Cup challenger. The British fervour, however, is slightly tempered by the fact that both Ainslie and Newey have very Austrian Red Bull backing! The parallels between high performance sailing and motorsport have existed for many years. It is not just in the multi-million dollar race machines, huge financial commitments and high-intensity race series of the 34th America’s Cup either. In fact one of the reasons that you will find a cluster of motor racing car constructors in the East of England is that many of them wanted to tap into the fibreglass and composite expertise of the Norfolk boat builders almost three quarters of a century ago.

Air and sea

From a developmental perspective, the two sports are already closely aligned; composite materials such as carbon fibre, Zylon and Kevlar have revolutionised the creative scope available to both marine and automotive designers. Computer modelling has long augmented expensive and time-consuming tank and wind tunnel testing. The 3D virtual design methods used to model, test and optimise components offer designers and engineers the capacity to redevelop parts. For example, Newey’s Red Bull’s RB9 was made up of over 6500 parts, and at times underwent some 1000 design iterations in the space of a week and up to 30,000 changes in a season. In sailing there are few classes that could accommodate that level of adaptation, but the final matches of the America’s Cup saw both boats undergo numerous alterations: Oracle Team USA reportedly filed for a new certificate (the equivalent of a homologation document) every race for the first 15 races. With millimetres making all the difference, reducing weight and drag is a common denominator across both sports. IN ASSOCIATION WITH

THE F1 CONNECTION

The technical know-how that brought about Sebastian Vettel’s F1 championship-winning Red Bull (above) could carry over into sailing, with Adrian Newey referring to sailing as a ‘parallel universe’ to motor racing’

‘It is a parallel universe in many ways,’ says Newey. ‘The base technology is the same, aerodynamics and hydrodynamics are almost the same thing apart from the air/ water interface being a different thing. There are lightweight structures, control systems, simulation software and its all about man and machine.’ Technologically, the sports are also steering ever-closer courses. One of the standout similarities is in the use of foils to manipulate fluids. In motor racing, wing angle adjustments are a key part of a car’s setup and are constantly changed. On-board the AC72s, the ability to alter foil angle is not only fundamental to adjusting the angle of the sail to the wind, but essential to making the boat ‘fly’ on its hydrofoils. Understanding the airflows around the foils in this transient state is almost identical to modelling a drag reduction system (DRS) wing in F1. In the marine world, this innovation is the culmination of design developments that range from the canting keels of the Volvo 70s and Open 60s to radical multi-hull hydrofoilers such as L’hydroptere. In motor racing the technology largely comes from aviation. But DRS itself replaced a fluidic switching device known as the f-duct, and this understanding of fluidic switches is something the sailing world has yet to exploit. However, it is only a matter of time. Methods of energy reclamation and storage also feature as major innovations for both sports. Although

not new, the technology that stores or reclaims energy otherwise wasted through heat and other sources is now being re-used in order to add speed. For F1, the hybrid system stores energy – otherwise lost through heat generated by the brakes and exhaust – as electrical energy which is then returned to the driveshaft via electric motors at the press of a button. On-board the AC72s, stored energy also played a big part – although it wasn’t so easy to come by! Of the 11 sailors on board, 10 could be grinding, and of those 10, four were doing so in order to pressurise a number of hydraulic cylinders that lifted the hydrofoils in and out of the water. The concept is alien to most sailors, as grinding traditionally translates to winching. However, in the AC72 these four grinders constantly work to keep the cylinders pressurised. The hydrofoils enter and exit the water at high speeds due to the sudden release of the energy stored as pressure by the grinders, giving the helm three seconds in which to set the foil using a button on the wheel. Those wheel-mounted buttons and the electronic controls of the hydraulics are straight out of Formula 1 transmission technology. Chris Draper, helm of Luna Rossa Challenge, explains that the control systems for all the hydraulic functions have taken technology directly from Formula 1, although there were a number of rule restrictions which limited their use. But even at this level, he says: ‘F1 are light years ahead.’

Pushing the limits

That gap between F1 and sailing, even at AC level, should come as no real surprise. In Formula 1 there are 19 or 20 races per season with 11 teams working flat out to develop their cars. The America’s Cup, however, only happens about once every four years, has only a handful of competitors and has a somewhat convoluted format compared to a racing season. ‘The fact is that because it is competition you get the results of the work from time to time,’ adds Newey. ‘You could argue that this is the big difference between AC and F1, because the main event is only once every four years or so. You have a much longer period to wait before you know where you are’. Formula 1 has undisputedly had another advantage, that of significant corporate backing over several decades, particularly since the early-1990s when most

“F1’s philosophy of questioning everything can be taken on in sailing – a team doing this will make huge leaps forward” Marine Engineering u Digital Supplement

Real-time analysis, common in motorsport, is finding its way into sailing, aiding engineers, and adding to the potential within the sport for spectators and broadcasters alike

races were first broadcast live. With the increased television coverage, multinational money poured into the sport, development has spiralled and the cars have become some the most advanced competition machines on Earth. But corporate backing is now very evident in the sailing world too. Budgets are increasing, and with budget increases come advances in technology. ‘If you take motorsport as a global umbrella of competitive man and machine as a sport, where else is there where you have significant budget for the engineering side?’ asks Newey. ‘The answer really is only in the America’s Cup.’

Where next?

A key question is: what might filter down to the rest of the sailing world? In engineering terms, the most valuable asset offered by F1 engineering is a huge increase in the reliability of component manufacture and testing. Ever greater precision – thanks to triple or quadruple testing to the point of actual breakage – or by using ultrasound and x-ray technology to

assess potentially devastating fractures at a microsopic level, is standard practice in Formula 1. Laser-guided measurements are also a common tool, which means that build quality can be assessed without the need for human touch, with measurements taken in microns. The arrival of the Resource Restriction Agreement (RRA) in Formula 1 also sees many suppliers and engineers with rather more free time than they would want, so they are actively looking for new challenges, with many now looking to sailing. In a partnership between SAP Extreme Sailing Team and McLaren, the sailors were given the opportunity to see how F1 technology is employed. Extreme 40 and America’s Cup sailor Pete Cumming believes that it’s not only the tools and expertise that might directly cross over. ‘The F1 philosophy of questioning everything can be taken forward into sailing. The designers bring fresh thinking and approaches combined with increased precision, especially in one-design racing. A team with this benefit will make huge leaps forward.’

Fresh thinking is central to another new partnership, this time hoping to use F1 knowledge to make an impact on the offshore scene. Caterham Composites had previously worked in partnership with Alex Thomson Racing, transferring their experience and technology on to a Vendée Globe campaign, and their ultimate goal is to work with an America’s Cup team.

Electric avenue

Motor racing has been reliant on electronic data acquisition systems for many years, with engineers able to analyse every aspect of a car’s performance in real-time. The techniques behind this are already finding their way into sailing, and the Swiss Alinghi boats featured some electronic systems which came directly out of the Formula 1 supply chain. So the use of these motorsport electronic in sailing is not completely new – another IN ASSOCIATION WITH

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THE F1 CONNECTION

company at the forefront of motorsport – Cosworth – worked with the British Olympic sailing team in the run-up to the 2008 Games. The focus of this was the Pi Garda data logger system, which records data from sensors ranging from GPS and windspeed to strain gauges. This can then be used for performance comparison against theoretical targets, analysis of tacks against wind shifts and many other features. Since the 2008 Games, Cosworth has worked with a wider range of teams, including boats such as IMOCA 60s, using both the original Pi Garda equipment and a more sophisticated product developed from F1. Similarly, back in the 2010 America’s Cup BMW Oracle Racing had some 250 sensors across their then-revolutionary wing sail, giving out 90 million bits of data per hour of sailing. Competitors in the last Volvo Ocean Race and Barcelona World Race have used similar sensor systems. One problem is that on a sailing yacht it is very easy to capture too much data to analyse effectively. An F1 car completes an entire lap in approximately 90 seconds. Compare this to what a yacht does in 90 seconds, and it’s clear that a different strategy for capturing data is required. Yet a high

sampling rate is still required, so that the peak loads that occur when the boat falls off a wave, for instance, are still recorded. Increasingly accurate data also needs to be presented differently, and here again sailing may learn from Formula 1, instead of multi-function displays that both driver and sailor can easily become too preoccupied to scrutinise in any real detail – the so-called analysis paralysis syndrome. Similar technology was put to good use in AC34. Team Oracle USA wore displays mounted on their wrists. Via wi-fi, these displays offered tacticians real-time customised information in a graphic format, such as rope load balance and wing sail performance. Some 300 sensors on the USA boat also measured everything from strain on the mast to angle sensors on the wing sail, with up to a gigabyte of data being processed per day from the boat. Not quite at the level of a 2014 F1 car, but catching up. This visualisation technology developed by Stan Honey, director of technology for AC34, came not from Formula 1 but from NASCAR’s racecar tracking system, using telemetry sensors on board the AC72s together with GPS modules which tracked each boat to an accuracy of better than 2cm.

GPS trackers have of course been carried for many years in many major yacht races, even mass-participation events. But the ability to combine accurate positions with real-time data has made tracking – for media, spectators, sponsors and coaches – more exciting than ever before. Software firm SAP, the official technical partner of the Extreme Sailing Series, has been working hard on changing how the sport of sailing is presented. Stefan Lacher, head of technology at SAP, explains: ‘The core of the sailing data we are currently able to analyse is from GPS trackers on the boats, that transmit location every two seconds. In addition we collect wind and sometimes current data to get a good understanding of the environment. Even with a rather small number of sensors, quite a large amount of data actually arises – such as speed, average speed, distance travelled, ETA and so on. ‘We are now experimenting with several additional sensors – such as heel angle, sail shape, even the heartbeats of the sailors – and developing the accuracy of the data available from wind and current sensors on the course.’ The Extreme Sailing Series ‘stadium racing’ format already has live online leaderboards and 3D visualisations of race progress for

“The ability to combine accurate positions with real-time data has made tracking more exciting than ever before” Marine Engineering u Digital Supplement

THE F1 CONNECTION

Sir Keith Mills hopes to follow F1’s commercial lead to significantly increase the profile of the Vendée Globe and Barcelona World Race

spectators, making this data available for post-race analysis by teams and coaches. The technology also holds an appeal for amateur sailors – SAP has worked with the 505 world championship. GPS tracking was integrated with wind measurements and current analysis, plus other factors, to give sailors a detailed overview of their progress and show areas where they could improve.

The human element

With developments made possible by technology from materials reliability to media presentation, the gap between F1 and sailing looks set to narrow further. One man hoping to help make this happen is Sir Keith Mills. Having bought the IMOCA global commercialisation rights earlier this year, he plans to follow in Bernie Ecclestone’s footsteps and use the F1 model to increase the profile of the Vendée Globe and Barcelona World Race. He hopes to bring the races to a larger audience, and in doing so attract more teams and further investment. Central to this will be using broadcast technology to capture and distribute footage as it happens. As Sir Keith has identified that sharing the sailors’ experiences with viewers is key to making sailing appealing as a spectator sport. The ‘superhuman’ effort is a factor F1

audiences are familiar with – the average F1 race requires physical exertion on a par with running a marathon. The AC34 brought it home to sailing fans, with live on-board sound capturing the exhaustion of the grinders, while teams also dealt with high g-forces sailing at high speed. AC34 also saw techniques developed from F1 implemented in training to bolster athletes’ fitness and decision-making ability during the race. Responsiveness and alertness exercises were used in both F1 and AC34 to optimise competitors’ mental ability while at the very extremes of physical exertion. In the absence of existing equipment available to strengthen and condition F1 drivers to withstand the strains of racing, specially designed rigs have to be built. In a similar way, AC34 sailors recreated the trampolines of their AC72s for their own training. The next step may lie in the use of simulators, which have been used for many years to test and analyse F1 engineering. Most recently, ‘driver-in-the-loop’ simulators have enabled drivers to take the place of a mathematical programme within the simulator, enabling improvements to be made in areas where computers would have naturally over-compensated. Mike Gascoyne, an F1 designer who has turned his attention

to sailing, initially with the Caterham Challenge project explains: ‘This is now normal practice in Formula 1, and we see ‘sailor-in-the-loop’ simulators and using vehicle modelling in areas such as autopilot development as being very interesting.’ The one thing all this physical and mental training shows is that despite all the technology, the human element is still key. The consensus among sailors and drivers is that there’s little risk of the skill factor being taken away. If anything, having more technology increases the demands on the athlete. ‘Just as in F1 there is no technology that can tell a driver how late he can brake into a corner, or how much speed he can carry through a corner, there will never be any technology to replace the skipper’s feel of the boat, sail choice or how to combat the physical demands of offshore sailing,’ says Gascoyne. ‘You can just give them tools to make better decisions or more reliable equipment. In F1 the best drivers stand out and end up in the best cars, I’m sure this will also always be true in sailing.’ One thing is certain, the more motor racing technology that arrives in the marine world, the more optimised the designs will be and that process is likely to start with the next America’s Cup. ME

“There will never be technology to replace the skipper’s feel of the boat, sail choice or how to combat sailing’s physical demands” Marine Engineering u Digital Supplement

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TEXTREME FABRICS

Light

& strong In a bid to reduce weight without compromising performance, Oracle Team USA turned to TeXtreme carbon reinforcements

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TeXtreme Spread Tow carbon reinforcements reduce weight, increase performance, and give better surface smoothness in advanced composites

he America’s Cup has always been a quest for lightweight solutions producing better and lighter structures – and the 34th running of the competition was no exception. One significant difference from previous campaigns, however, was the financial climate, which dictated that some more cost-effective solutions had to play a larger role. In order to meet these demands, Oracle Team USA turned to TeXtreme Spread Tow carbon reinforcements, with which substantial weight savings were achieved.

TeXtreme Spread Tow carbon reinforcements are a novel type of composite reinforcements typically used to reduce weight, increase performance and give better surface smoothness in advanced composites. The basic principle behind the TeXtreme Technology is to weave a fabric using thin Spread Tow unidirectional tapes instead of weaving with yarns as in conventional fabrics. TeXtreme Spread Tow reinforcements are already used in Formula 1, high-end sporting goods such as bicycles, golf shafts, ice hockey sticks and advanced aerospace

applications, and have now taken the step into the AC72s and America’s Cup. Chasing lightweight, cost-effective solutions was a major theme of last year’s campaign for the Oracle Team USA. Development from the start was focused on qualifying new materials in order to save weight and achieve the structural performance required for the new highIN ASSOCIATION WITH

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TEXTREME FABRICS

performance catamaran class. With time pressures, and a requirement for the highest possible performance that are significant to remaining competitive in the America’s Cup, Core Builders Composites evaluated TeXtreme for both practical manufacturing considerations and for mechanical strength and stiffness requirements. After seeing positive results from their initial evaluations, both Core Builders Composites and Oracle Team USA discussed and identified the benefits that TeXtreme could offer to this challenging build. Dirk Kramers, head of structures of Oracle Team USA, says: ‘With the huge time pressure our design department and builders are under during a competition like this, there is only so much time to evaluate new materials. That is why we were so pleased with TeXtreme, as it turned out to offer both the weight savings and performance we were looking for at the same time as

proving process-efficient. The flexibility in the material range also helped us to find the optimal reinforcement for each application and its specific needs.’ One of the paradoxes with carbon fibre reinforcements and prepreg is that the less something weighs, the more expensive it becomes. This is especially true for traditional woven cloths and unidirectional prepregs with fibre areal weights lower than 200gsm – once below 100gsm, the price per kilo of fibre is substantially increased. TeXtreme is less expensive than traditional 1k carbon woven reinforcements and brings unique benefits of performance increase in terms of weight savings and surface finish, which is critical to untreated and unpainted surfaces that a weight-driven programme demands. Carbon unidirectionals can go even lower in areal weight – commonly available down to 50gsm and in some cases even lower. However, all of the laminates used in the

“The range helped us to find the optimal reinforcement for each application” Marine Engineering u Digital Supplement

Oracle Team USA AC72 have reinforcements in at least two directions. Consequently an 80gsm TeXtreme cloth would have a 20 per cent reduced weight compared to two layers of 50gsm unidirectional tapes. There were other advantages of using TeXtreme cloth over two layers of unidirectional tapes. First there were reduced labour costs. It was possible to put down half the number of plies as opposed to the two layers of unidirectional tape. Depending on the application, TeXtreme was used both at +45/-45 and 0/90. Normally, when placing unidirectional fibres on the bias, this is very tedious as the unidirectionals need to be cut and placed manually at the exact degree desired. The Spread Tow tapes in the TeXtreme fabrics are always perfectly aligned, so putting down +45/-45 became very efficient. Another time-saving aspect is the handling properties of TeXtreme, especially for the dry cloth. Conventional dry materials have nothing but a selvedge to hold them together which means that as soon as you start cutting them, they need to be handled in a gentle way to stop them falling apart. With the TeXtreme cloths this is not a problem,

Core Builders Composites purchased several TeXtreme variants which have been used in a host of different applications. The engineers were impressed with the surface finish and laminate quality of the parts they’ve made using the materials

thanks to the binder that keeps the fabric together. An additional advantage is the increased toughness, due to the interleaved Spread Tows of unidirectional fibres. Core Builders Composites purchased several TeXtreme variants that have been used on different applications and for different purposes. The materials were purchased as both dry fabric and prepreg. TeXtreme 160gsm cloth used on exposed surfaces where the increased skin thickness/ toughness offset the weight penalty. The TeXtreme 100gsm cloth was used widely on the construction of the wing elements and

fairings. The TeXtreme 80gsm cloth was used in the lightest weight fairings, typically on a foam sandwich rather than honeycomb. Tim Smyth, general manager of Core Builders Composites, says: ‘TeXtreme products have provided us with a wide range of aerial weights and fibre styles to choose from – all at very competitive prices compared to other options. We have been very content with the surface finish and laminate quality of the parts we have made using TeXtreme. It has given us options in processing laminates in a way which reduces lay-up time at the same

time as improving quality. In addition, using this material has also brought us weight savings that would have been impossible to get from any other composite reinforcement, considering the performance requirements we have.’ The most visible usage of TeXtreme on the AC72 is the flap noses and aft portions of the main element hard shell. The flap noses are primarily in torsion and are stiffness and strength critical. The angle of the flap laminate is optimised to provide the correct torsional stiffness profile along the length of the aerodynamic foil. Because the flaps are quite exposed, durability of the honeycomb structure also had to be considered over reduced weight at all cost. In contrast, the aft portion of the main element hard shell was designed to be as light as possible. Here the thin sandwich laminate of TeXtreme and lightweight foam core form the extended hard shell of the IN ASSOCIATION WITH

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TEXTREME FABRICS

Oracle Team USA putting its crew through their paces in February 2013, in preparation for the 34th running of the America’s Cup

wing main element and deliver increased aerodynamic performance. The only structural requirement was to be sufficiently rigid to maintain the aero shape. For the construction of the flap noses, either dry fabrics or prepreg could be used, but in order to meet the tight schedule, the prepreg laminate was preferred for the large flap noses. Of the chosen TeXtreme variants, the 80gsm dry cloth was the lightest solution. For some applications, Core Builders Composites combined dry cloths with prepreg glue film or resin film as there was a significant cost premium for the prepreg option. So the prepreg was reserved for the larger panels where the labour savings offset the additional cost. In order to manufacture the flaps as light as possible, normal prepreg sandwich construction methods were critically assessed to determine whether weight or cost could be saved. Typical prepreg sandwich panel construction could be either multiple cure (one for outside skin, core bond and then inside skin) or single co-cure of the skins and core adhesive. A single co-cure of the skins and core adhesive is more efficient, but using such light areal weights invariably leads to dimpling of the skin into the core – and given the aerodynamic requirements

of the part this solution was unacceptable. Therefore the decision was made to go with the multiple cures, constructing the skins separately and then bonding them to the core without full vacuum to prevent dimpling. Another benefit with this approach was that it allowed for the inside of the skin to be sealed against moisture ingress. Again, to reduce weight different methods of bonding the Nomex honeycomb core were assessed, and it was determined that if the adhesive was placed only on the core face as opposed to all over the surface of the skin, this would give a lighter solution than normal prepreg construction. The key to achieving a lighter ambient solution is that the adhesive was only where it was required – the surface of the honeycomb cells. Weight savings from using TeXtreme would be in the order of 100gsm – which over approximately 50m2 of flap nose area equals 5kg – representing a significant weight saving. The tooling for the flap noses would typically be done as a female mould. The difficulty is in achieving a good quality skincore bond without the risk of bridging the core in the apex. On a male tool, this could be avoided by being able to pull the core down on to the shape. The difficulty with male tools is that the level of finish and tolerance

might not be as good. A unique compromise was found that was achievable with the toughness and flexibility of the TeXtreme fabrics. Specifically, the skins were pre-cured and then draped on to a male former. The skins would have the finish of the flat table and using an over-expanded honeycomb, it was possible to pre-bond the core to the outside skin and drape the half sandwich over the inside skin that was already draped on the former. This construction method allowed the former to be manufactured for ambient and vacuum, rather than for elevated prepreg cure – a huge savings for the team made possible by TeXtreme. ‘To summarise, TeXtreme made it possible for us to achieve great weight savings in the wing flap application alone to a total of 5kg, and the total weight for the whole AC72 ended up on a substantial number,’ says Smyth. ‘This came without comprising on performance and safety in the design of the composite parts. That in combination with the possibility of improving the performance and surface finish of the laminates, together with the reduced time spent on labour made it a very attractive solution to us – and we will definitely keep it in mind for upcoming projects.’ ME

“TeXtreme made it possible for us to achieve great weight savings without compromising on performance or safety” Marine Engineering u Digital Supplement

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Established 30 Years 1983 - 2013

SAILROCKET 2

Built for

speed Overcoming the stability problems of its predecessor, Paul Larsenâ&#x20AC;&#x2122;s recordbreaking craft combines nautical and aeronautical concepts to smash through the 50 knot barrier By TOBY HEPPELL

Marine Engineering u Digital Supplement

Paul Larsen’s recordbreaking journey began with a design proposed in The 40-knot Sailboat, a 1963 book by US rocket engineer Bernard Smith

t was many years ago I first met Paul Larsen, currently the fastest sailing human on Earth. Back then he had just launched the first iteration of the speed machine that would take him into the record books. And I must say, at the time I was highly sceptical this would be the case. Even with the scepticism I remember being impressed by the conviction held by the Aussie as he explained the concept behind Sailrocket in a pub in Southampton, UK with a glass of rum and Coke in hand. In the latter part of 2012, over a decade after the launch of that first boat, Larsen and his team finally hauled themselves into the record books, smashing the outright World Speed Sailing Record by almost 10 knots – the biggest single leap in the record’s history – taking it to 65.46 knots (75mph). As should be clear by the time that passed between this first launch, and the second boat breaking the record, the team’s eventual goal did not come easily and it is a story of two parts – one of perseverance and technological innovation. Though Vestas Sailrocket 2 is a boat packed full of development, the basic concept behind the design itself is not, in fact, a new one. The design on which Larsen based the first and second iterations of his boat was thought up by American rocket engineer, Bernard Smith and outlined in his book The 40-knot Sailboat, published in 1963. ‘When I first read the book, I thought about it and started to wonder how no one had ever done it before. I then started to look again at all the other boats around and started very quickly thinking “my God – they are all flawed!”’ Larsen explains. ‘From that point on, it was a 10-year journey to finally break the record.’

Winning formula

Any sailboat relies on two basic components to produce forward motion, that of the sail to produce thrust and some form of underwater foil to turn that thrust into directional stability. The proposal set out in The 40-knot Sailboat is to develop a vessel that more equally balances the forces of the sail and keel. Larsen quickly realised that employing a vertically stacked sail/keel arrangement – whereby weight is added to the keel to counter the forces generated by the vertical sail – was unsatisfactory. Additionally, although multihulls go some way to improving the efficiency equation, they do not provide much of a balancing of force vectors, simply going about the countering of righting moments in a different way. Both of these concepts can be viewed as something of a brute force cure to the problem, and certainly not a particularly elegant one, adding either weight or width to counter heeling force. On Sailrocket, in order to provide balance, the wing is placed on a leeward float and canted to windward at an angle of roughly 30 degrees. This float is then connected to the main body or fuselage by a 30ft long beam, shaped to provide aerodynamic lift at speed. At the aft end on the main body of the boat lies the foil, the outer part of which is angled to generate downforce. This is balanced by an upward lift on the inner part of the foil, which pierces the surface. The upward force increases strongly with submergence, while the downward force is nearly constant. As such the foil holds a stable depth while providing a nearly constant force component along the foil/sail axis. With the first iteration of the boat, when the foil did not work properly, it ‘let go’ of the water, allowing the nose to rise, which in turn generated more lift on the crossbeam and the entire boat took off – a video of the boat performing a backflip can be found on http:// www.youtube.com/watch?v=8Ow8QbXhZJU. Moving the cockpit of the boat forward in Sailrocket 2 was an attempt to counteract IN ASSOCIATION WITH

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SAILROCKET 2

The 50-knot barrier in speed sailing exists due to the effect of cavitation, which increases drag on the boat, impeding its progress through the water

this, so that if the foil lets go, the bow tips slightly forward, creating negative lift in the crossbeam which prevents the a flip. The separation between the wing and foil provides a significant amount of the righting moment. As the aero and hydrodynamic forces are in a constant state of self-levelling as the boat accelerates. It should also be noted that the entire boat is designed to work with the assumed apparent wind generated while at 50 knots – the boat was sailing with a 72 knot apparent wind during their record run. To this end, looking at the boat from the top down the entire body is out of alignment with the main floats by some 20 degrees (the floats pointing in the intended direction of travel). This is purely so that at speed the fuselage is directly aligned with the direction of the apparent wind the team would be experiencing.

ROCKET STAGES 1 From a standing start, Sailrocket is incredibly difficult to get under way. At this stage the forces on the wing are actually pushing the leeward float down into the water 2 At 25 knots boat speed, the wing pulls the rear pod free of the water, shedding a third of drag 3 At 45 knots the leeward pod, lifts free and takes to the air thanks to lift generated by the winglet, wing and crossbeam 4 At roughly 50 knots, the anti-cavitation foil effect kicks in, allowing the boat to continue to accelerate beyond previous known limits

Marine Engineering u Digital Supplement

The whole aim with the project was to create a machine upon which the various forces exhibited were all in perfect balance with one another. To this end, when the boat was properly setup, Larsen says his job as pilot or skipper is much easier than some might expect. ‘I have often said that Sailrocket at top speed doesn’t need that much skill to control,’ he explains. ‘Once it is there, I can cleat the wingsail, let go of the steering and it will do 500m at 65 knots and that is because of all the work that has come in the build up to the run.’ Obviously, the skill in getting a boat designed to work in a balanced and efficient way at 65 knots underway and through the low-speed range is significant!

Wing setup

It has been well understood for a long time that a solid wing sail is a much more efficient beast than a soft sail, particularly when at speed and sailing on high apparent wind angles (effectively a very tight reach). Other than the canted angle supplying lift, the wing on Sailrocket is a relatively straightforward one. It is made from a series of carbon fibre ribs skinned over with a lightweight membrane, with a rear single rear flap to determine shape and mainsheet to sheet on or off. As with the rest of the boat, the setup is entirely uni-directional, so the wing is a slightly asymmetric section with a significant aim being to reduce any negative lift effects associated with letting the wing out at speed.

What is particularly unique about the setup, however, is the wing extension that runs through a 60-degree bend at the end of the wing. The job of this wing extension is varied, but can be broken down into two main features. In terms of airflow on the wing itself, the winglet does a similar job to one on an aeroplane wing. That is to say, it makes the wing more efficient by blocking the flow of high-pressure air to the low pressure side of the wing at its tip, and so reduces vortices generated there – effectively tricking the wing into appearing longer than it is. The second use for the wing extension only comes into play when the boat is up to about 40-45 knots. At this speed, the lift generated by the winglet and the crossbeam are significant and will lift the leeward float completely clear of the water. The only parts of the boat in the water at this speed are the forward float – a very flat skipping surface with a small steering foil penetrating the surface – and the aft foil which is pulling down hard and holding the boat in the water. This final point has led to some debate about how to classify Sailrocket. The argument goes that, at this stage the ‘boat’ is more aeroplane, held on the water, than boat travelling over it. To a degree the question is moot. The WSSRC considers the craft acceptable as a speed sailing craft, which is all that is required. Larsen does not seem particularly bothered if the boat is seen as half plane/half boat, and indeed the

Moving the cockpit of the original Sailrocket forward helped to avoid problems like this dramatic backflip

Paul Larsen says that Sailrocket 2 doesn’t need much skill to control when it’s at full speed – the hard work is setting it up to be able to get that fast

Illustration of force alignment on the design – the upward force increases strongly with submergence, while the downward force is nearly constant

comparison is evident in the name Sailrocket. He has stated on more than a few occasions that were the boat dropped from a height it would glide back to the ground to a degree.

Foil design

As the team got faster and faster, so they started coming up against an age-old problem in the world of speed sailing, the 50-knot barrier – often referred to as sailing’s speed of sound, for good reason as we shall see. This speed barrier exists thanks to the poorly understood effect of cavitation. Many of those who took physics at school might have done a popular experiment that goes a long way to explaining the phenomenon. A glass full of water is put inside a jar and the pressure sucked out to create a vacuum. At a certain point the water starts to boil which is broadly speaking what occurs when a foil starts to cavitate. At around 50 knots (though it should be noted that the actual

speed at which this phenomenon occurs can vary based on a number of factors, including water temperature and salinity among others) this is exactly what happens to a foil – the pressure drops at the trailing edge, and the water around it boils. The drag then created by these bubbles causes the boat to slow down dramatically. As Larsen explains: ‘Imagine going fast in your car, and suddenly you open the doors and pop the bonnet! You hit a wall and need huge amounts of power to overcome it. This can also lead to a loss of control.’ Traditionally, all water-based foils are a similar shape - a relatively fat rounded leading edge, tapering down to a very thin trailing edge, providing a teardrop crosssection. In order to overcome the problems associated with cavitation, Larsen and his team developed a new foil design, which went against the common wisdom of many hydrodynamicists. The foil is a wedge shape whereby the trailing edge is

totally flat. At low speed this is a disastrously draggy shape and works poorly, creating a draggy mess of bubbles in the void left behind. But use enough brute force to drag that slow foil section up to world recordbreaking speeds, and suddenly something really quite exciting happens. As the foil starts to plow a trench in the water, a hole is created at the trailing edge for a fraction of a second. The faster the foil moves through the water, the deeper this hole becomes. At speed the water starts to flow around this hole or trench in the water and forms into the classic teardrop shape of a normal foil section. However, this is a normal foil shape with a difference. Because the trailing edge shape is made of nothing but air, cavitation is unable to take effect on the shape allowing the foil to continue faster and faster. Again this is an idea that is not new per se. This wedge shape has been used for many years on high-speed motorboat propellers, but had never successfully been transferred into a foil on a sailing boat, though not from a lack of trying. To a degree this is the success to the success of the Sailrocket team, and their persistence. They spent 10 years building on their knowledge base and designing foil after foil. They took a design with potential, developed it, incorporated that which they learned from a first iteration into a second and continued to persevere, safe in the knowledge that eventually the time would pay off and eventually they would make the leap to sailing speeds never before considered possible. ME

IN ASSOCIATION WITH

Marine Engineering u Digital Supplement

AMERICAâ&#x20AC;&#x2122;S CUP 35

Future

designs Following an incredible conclusion to AC 34, attention has now turned to the shape of the next event

Marine Engineering u Digital Supplement

The America’s Cup has long been the high point of technical innovation in sailing. Indeed, many see the event as more design competition than sporting endeavour. The modern era of the cup has retained this design contest feel, even if it was not always hugely obvious. However, 2013 saw a new class of boat introduced, which usually sees design moving rapidly forward as teams get used to the new rules and find the ideal corner of the design envelope. This will be the case once again for the next America’s Cup, as yet another new class is likely to be introduced, though all the signs currently point to a slightly smaller, refined version of the AC72, used in 2013. We have yet to get much of an idea about what the next America’s Cup class will look like as we await the final rules to be decided by the Defender, Oracle Team USA and the Challenger of Record, Hamilton Island Sailing Club – these are expected in spring 2014. Although we do not currently know the rules the new boat will have to fit, there are a few areas that Oracle have been quite vocal about in their future plans, and a few areas that the Challenger of Record have mentioned that at least give us an idea of what the boats might be like. Key factors being discussed are: development of hydrofoiling, cost reduction (including team limits, one design elements and boat size) and nationality rules.

Oracle Team USA skippered by James Spithill, alongside Emirates Team New Zealand skippered by Dean Barker, during race day five of last year’s America’s Cup

PAUL TODD/OUTSIDEIMAGES.COM

The foiling question

Interestingly, one of the major areas of development in the most recent America’s Cup was never intended to feature on the designs. The rules set out for the 34th AC went to a number of lengths to prevent foiling developing in the class. Perhaps the two most significant were those controlling the banning of pitch controls for rudders and the banning of any articulated flap of any sort on the main foils. These rules initially led most observers assuming we would see the C shaped foils that have become popular in offshore catamarans, which provide elements of lift without supporting the entire weight of the boat. Indeed, this is the setup that the Challenger of Record, Artemis, came up with on their first boat. This sort of foil was also used by both the Challenger, Oracle and Defender, Alinghi in 2010 with their trimaran and catamaran respectively. Here the commonly-held view is that the more load these foils take, the faster the boat goes, up to a point. Typically anything over 50 per cent lift – ie 50 per cent of the hull weight supported by the foil alone – is workable. However, once over that 50 per cent boundary, the longitudinal stability of the hulls disappears to such a degree that the boat becomes uncontrollable and will be slower round a course. Additionally, the pressure on the leeward portion of a curved foil at this point makes the foil unstable. As one designer put it, you would get a squirt of water from the underside of the foil and the boat would begin to porpoise, popping up on the foil and dropping off again. Previous foiling classes have relied on two features to overcome these problems. The International Moth is the prime example of what could be called a classic foiler. IN ASSOCIATION WITH

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AMERICA’S CUP 35

Challenger of Record, Artemis Racing, testing an AC72 in San Francisco south bay in April 2013

The boat has a T-shaped main foil with an articulating flap along the aft edge of the horizontal part of the T. A sensor wand on the bow automatically adjusts this flap. In this way, if the boat is losing height, the wand is pushed further back, which changes the angle of the main foil flap, which in turn changes the height out of the water. With the rules preventing this system, teams were faced with the issue of how to control the ride height of the boat in a different way. The solution was to come up with a foil with a horizontal section that was turned up at the tip. This controlled ride height in two ways. Firstly, as the boat rose out of the water, the tip would break the surface and so lift would be reduced. This lift reduction also occurred thanks to the boat’s leeway. As the load was transferred from a long hull to a small foil, so it would slip sideways (leeway) and so the curved up portion of the foil would have a reduced lifting effect in the water. In this way, the foils would control the height of the boat in an automatic way without a flap and wand system. However, height is just one component – the other is longitudinal stability. Again, looking at the Moth, this is delivered by another articulating flap on the rudder T foil, which can be manually adjusted

while the boat is under way, but this, too, was banned on the AC72. With the AC72 banned from adjusting rudder cant angle while racing, they had to set this at the start of the day, based on the conditions likely to be encountered, and rely on other means to control stability. This was achieved by teams manually adjusting the angle of the whole daggerboard, using a button system on the helmsman’s steering wheel – though it was severely limited by the amount of power the grinders were able to pump into the hydraulic system. It seems that, no matter who you speak to – designers, hardcore fans, or relative newcomers – foiling as a part of this America’s Cup was a hugely positive thing. Certainly it seemed to draw a lot of interest from those outside the world of sailing and offered the sort of technical innovations we have grown accustomed to in America’s Cup racing. As Iain Percy, Artemis Racing’s skipper/leader, said in a recent Yachts & Yachting interview: ‘When the replica schooner America goes past, Oracle’s Version V boat goes past, and then one of these monsters foils past you at 40 knots, it’s just bloody hard to say that the world would not think we were crazy to go backwards. I think we have to embrace what we have here.

Manually adjustable rudder flaps that can be operated while moving would make a foiling setup a lot safer, faster, and more controllable Marine Engineering u Digital Supplement

The concern was that it would not be tactical racing. There has been more tactical racing than almost any Cup we have seen.’ However, it is also more or less a universal acknowledgment that incorporating manually adjustable rudder flaps that can be operated while moving would make the foiling setup a lot safer, more controllable and faster. So we can expect to see a rule that opens up this area, and these will likely be a big design focus next cycle. It will certainly be very interesting to see what combination of flaps, foil articulation and shape might be employed to achieve the most effective foiling solution. Already this technology is filtering into other classes, with the C-Class Catamaran World Championship featuring a number of foiling boats and a new foiling production catamaran now on the market. It would seem foiling is increasingly the future direction that the sport is taking. Interestingly for something that has always been so integral to the speed of a boat, the design of the hulls is one of the areas being most mooted as one-design for the next AC. ‘These boats are spending more and more time out of the water,’ comments 1983 Cup winner, John Bertrand. ‘There is a lot to be said for introducing a one design hull and allowing freedom of development in the foils and wings.’ This is a position that has been echoed in a number of areas by a number of industry folk, including the designer of the rules for the 34th AC and later designer for Emirates Team New Zealand, Peter Melvin, who has stated that you can spend a lot of money on hull design for it to make very little difference on a foiling boat.

ACEA/BALAZS GARDI TH.MARTINEZ/SEA&CO

There is also a consideration that making hulls and beams one-design could ensure that they are significantly over-engineered, hopefully increasing the safety of all boats and avoiding a repeat of the tragedy that befell the Artemis Team and the tragic loss of Andrew Simpson, when their boat broke up in a capsize. Despite the cost of development and the struggles with the San Francisco breeze, solid wingsails are likely to make a return for the 35th AC. This is despite a number of factors working against them. Percy again: ‘The boat itself is not the biggest cost. It would obviously bring down the cost a little if you were five foot shorter, but it is custom design and engineering that requires a load of skilled people, which – if limited – could bring down the cost. One would like to see all these people that are here [in San Francisco] able to spread among more teams, because there did not need to be quite so much engineering in custom builds, and the wings took a lot of man hours to build. If there is a way we could simplify that rule, it would help.’

Costs are not just in the R&D work involved in the wing, as Bertrand explains: ‘One of the biggest issues with the wing is that to start with it was taking 30 people ashore to step the wing at the start of each day – although they managed to reduce the number needed by the end of the Cup.’ To a degree, this staff increase is offset by the reduction in the sailing team needed on the boat. In simple terms, a wingsail carries significantly lower sheet loads than an equivalently-sized soft sail. This means an AC72 with soft sails would need significantly more crew onboard in order to trim the sail. Additionally, this reduction in load means the wing/mainsail trimmer is controlling the sail on a single line led to a winch, not a line with lots of purchase. This makes the power generated by the wing more controllable, more quickly than a soft sail. Another bonus with the wingsail is that, although it would not be significantly quicker in a total straight line than a soft sail, it is much faster through manoeuvres. When

the rule for the 34th AC was first announced, many were concerned that a matchrace taking place in catamarans would not be a tactical affair. In fact, we saw some of the greatest tactical battles in recent AC history, and this is in large part due to how manoeuvrable the boats were. In 2010, the giant catamarans competing were allowed to use stored power to trim sails, something that was banned for 2013. Essentially on the AC72s, everything has to be manually driven, so to get enough oil flowing through the boat they used rotary pumps, which are linked to the pedestal grinders. The grinders are essentially pushing oil throughout the system for the entire race. There is no stored energy in an accumulator tank or anything – it is just manpower pushing oil through pumps. It has been pointed out by a number of sources that were stored power allowed on an AC72 it could be sailed by four people instead of the crew of 11 required without it. Broadly speaking, this is seen as a positive and certainly footage of the grinders manning the pumps and the audio of them all struggling showed the level of athleticism required to sail professionally in the modern era. There are a couple of hesitations, however. In race eight of the America’s Cup this summer, we nearly saw a disaster from Team New Zealand as a last minute tack saw them almost capsize. During the live coverage, Dean Barker could clearly be heard shouting ‘hydro’ and it was clear the boat had tacked, but the wing had not. This is almost certainly due to a lack of power in the hydro systems. It was only thanks to the quick thinking of Barker, throwing the boat into another tack that prevented a full capsize. Certainly a powered hydro system would not have seen this happening. Whatever rules we see introduced, perhaps the thing we can be most sure of is that we will see a wide array of ideas and technical innovation. As we stated earlier, whenever a new class is developed for the AC we usually see wide performance differences, especially early on. This year was no different – we were just extremely lucky that the two teams in the final managed to both utilise one another’s ideas to move their boats from dramatically different corners of the design envelope and provide one of the most exciting finals in AC history. Even if the AC72 rule remained, it would be a big ask to top that performance. We just hope that the new rule will provide some close racing and a host of extra challengers. ME IN ASSOCIATION WITH

Marine Engineering u Digital Supplement

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