Boat show

The Volvo Ocean Race is the premier fully crewed yachting race. Other events follow a round-the-world format, but only this one offers competition for professional teams on-board state-of-the-art composite racing yachts.

As a test it is without parallel; some rival races feature amateur crews and so proceed relatively slowly, others feature fast boats but crews of just one person — which is immensely testing at a human level, but the boat itself will rarely be driven at 100 per cent.

Hence for the designers, engineers and builders the Volvo Ocean Race remains the ultimate test. The product is spared nothing in the drive to win.

The race, which runs every four years, starts from Vigo in Spain on 6 November, and a new class of boat has been specially created by the organiser.

The Volvo Ocean 70 may be only some 10ft longer than its predecessors (the VO60s), but the comparison ends there. In terms of key parameters the new boats carry double the sail area (aka horsepower) and are balanced by highly loaded, hydraulically canted (or movable) keel fins that support a 4.5-tonne bulb at the tip.

At 12.5 tonnes, these bigger and more powerful new boats are around a tonne lighter than their smaller predecessors. Plus, they will be crewed by two fewer people: nine men or 11 women. So for the control systems the pressure is on.

Performance is extraordinary. Records already broken in training include the mark for the greatest distance sailed by a monohull yacht in 24 hours. A new benchmark of 529.5 miles was established by Spanish entry Telefónica MoviStar in the Southern Ocean in May with speeds of over 35 knots.

This event, formerly known as the Whitbread Round The World Race, is one of yachting’s most epic challenges. Over nine months and nine legs, seven teams will do battle for 32,700 miles that will take them from Vigo in northern Spain to Gothenburg in Sweden, via Melbourne, Rio de Janeiro, New York and Portsmouth. Participants spend weeks on end pushing their boats to the limit 24 hours a day. But as well as testing the crews the event also provides a stern challenge for the designers and engineers involved in making the racing yachts a reality. In a situation that has parallels with F1, the teams designing yachts for the Volvo Ocean Race must find innovative ways to extract performance improvements from a heavily prescriptive set of design parameters. The seven teams signed up for the race so far are the two ABN-AMRO boats from Holland, Sweden’s Ericsson Racing Team, Team Pirate from the US, Brasil 1, Australia’s Premier Challenge and Spain’s MoviStar. Though no UK team has yet announced that it will participate, there is still plenty of home-grown interest. From individual crew members to large amounts of design and construction work, UK maritime know-how is a key element of the competition.

As well as making the boats manageable by a small crew, the central challenge for those engineering the VO70 centres on tying together the main structures: hull, rigs and foils. Inany sailboat power derives directly from ‘righting moment’.

The more stable — or stiff — your craft, the more sail area you can load up. The more sail area, the faster you go. Whereas with conventional fixed-keel designs, and subsequent water-ballast configurations, adding stability meant adding mass, moving keel technology enables you to achieve more power with zero weight penalty (aside from the canting mechanism).

The French even have a new word for canting-keel monohulls: the monomaran. But to cant your keel reliably takes deceptively tricky engineering: forcing it over, ensuring it remains secure and avoiding failures of the highly loaded keel fin.

The fundamentals of large canting-keel designs are akin to swinging a truck off the end of a thin, 4m aerodynamic foil.

Imagine throwing the whole structure around unpredictably, generating dramatic accelerations in every axis and ensuring that the product survives nine months ofracing. Nor should you forget the aggressive saltwater environment or the client breathing down your neck, challenging every gram of weight — because 500g off your structure means 500g that can be put on to the keel bulb, where it can start to do some good.

The other key area is the rig, which today consists almost entirely of carbon for the spars and the high-performance fibre PBO for much of the rigging (although the increasingly popular application of carbon and PBO films in sail cloth is denied the Volvo Race fleet for reasons of collective reliability).

Remember that the weight of the rig is trying to undo all the good (in otherwords, the power) from the keel bulb. And in pitching — the enemy of yacht performance in open water —unnecessary weight up the rig is doubly bad news.

As well as having rules governing overall dimensions, the race also features controls on materials and their use.

Volvo’s automotive philosophy of‘performance with safety’ is well known and the company is applying it to the hazardous activity of ocean racing.

Volvo had considerable influence in specifying the allowable materials and construction parameters and, while the boats are indeed light and powerful for their size, to date they are proving to be satisfactorily rugged.

Primary laminates are limited to glass, aramid and carbon fibres of modulus no greater than 240 gigapascals. Cores may be of any closed-cell PVC orSAN foam or non-metallic honeycomb. All epoxy, polyester and vinylester resinsare permitted, though cure temperatures must not exceed 95°C for the hull and125°C for the appendages and spars. In the case of spars only, a higher nominal fibre modulus of 300GPa is allowed.

Titanium, long popular in the race boat industry, is still permitted for fittings, although only if the product is commercially available. This means that elaborate customised titanium fabrications, a speciality of the marine industry, are out.

Minimum panel weights are employed as the principal control on primary structures, ranging from11kg/m2 for the forward lower hull area, exposed to slamming and collision loads, down to 5.7kg/m2 for the deck.

Substantial collision and grounding load cases must be proven prior to certification.

The component area that has proved most vulnerable in recent ocean race history is the movable fin itself, where both system and structural failures have been unpleasantly common. Here Volvo demands substantial redundancy, with dual-hydraulic circuits in the canting mechanism and specified steels and alloys being stipulated for the fin itself.

Though increasingly common elsewhere,  composite fins are still filed under ‘not quite yet’ by the race organisation. As well as the canting keels, the new VO70 carries a small 1,200-litre water ballast tank set well aft in the hull to optimise fore and aft trim.

Driving hard downwind through the Southern Ocean sees everything from spare sails to toothbrushes stacked in the stern; even on a boat of this size a nose dive can prompt a full — and life-threatening— pitchpole where the yacht flips endover end.

In every area of the VO70 there are examples of interesting new technologies. The compulsory media station features full film and sound editing and transmission facilities set within the harshest possible environment, while permanent mini-cameras on deck can be activated by a ‘red button’ sited by the helmsman for those interesting moments.

Aloft, modern rigging technology sees the thinnest, lightest PBO ropes imaginable, where once thick stainless steel cables would have been standard. Rope, of course, is much easier to repair at sea.

Navigation hardware has reached agood stage of ruggedness, with displays and keyboards now remaining waterproof under the harshest conditions.

The ubiquitous Racevision 2tactical computers, developed by Brookes& Gatehouse and Diverse Yacht Systems, centre on a stand-alone portable computer, wirelessly connected to the numerous instrument feeds — and the master screen can be dropped in the water without any obvious effect.

Meanwhile, B&G’s Wave TechnologyProcessor controls all tactical navigation functions with on-board rate gyros constantly updating and refining essential wind and performance information.

Spare a thought for the modern race navigator, constantly juggling polar performance information that is being automatically updated; meteorology data, now fed centrally to the fleet from the race office as grib files (in the last race internet access bills topped £400,000 in the search for better data); personal weather interpretation, and of course the harassed demands of the skipper for improved routeing.

It is no surprise that the best navigators now earn substantial six-figure salaries that frequently match those of the skippers.

Andrew Hurst is a former international yachtsman who is now editor of Seahorse International Sailing.

CANTING KEELS: AN ENGINEER’S VIEW

Canting (or movable) keel systems are now being used extensively in a variety of yacht types. At one extreme the 6.5m Mini Transat designs have keelscanted by rope and tackle, while at the other the140ft Atlantic record holder Mari Cha IV has a10-tonne canting bulb keel that is 6m long and driven by a single 600-tonne ram.

The canting-keel mechanism adds additional performance options at the cost of extra design variables, not only in the attachment and control of the keel but also in additional loads applied to the overall structure. But if you have designed the boat right she will sail faster and more upright, thereby increasing acceleration.

There are a number of ways of arranging the mechanism and hence structure. Smaller boats have used a rope purchase system. For bigger boats with heavier bulbs, hydraulics are the preferred actuator. Redundancy in the system is common but not essential, with most boats having two rams, but duplication is not a guarantee of success.

Generally we favour doing one system properly.

The design also has to take into consideration the possible combinations of heel and cant angle, which will result in a range of different forces on the ram and the structure that attaches the ram to the hull of the boat.

For the forthcoming Volvo Ocean Race the organisers decided to embrace canting keels from the outset.The majority of the VO70’s primary structure has specific requirements such as minimum panel weights, subdivision and so on. This in no way guarantees adequate strength, only that a boat properly designed for the loads need be no heavier than one that is not.

The VO70 rule is very prescriptive about the canting-keel system. For instance, it must have dual systems, each capable of taking full load. Also there are prescribed loads and safety factors. These factors are over double the current industry and American Bureau of Shipping (ABS) standard, although it is not entirely clear why a VO70 might ground harder than any other 70ft canting-keel offshore racer.

One of the design trade-offs here is that while designing a boat for lateral stiffness and stability provides a performance advantage, it does not help much in a grounding situation when the keel ploughs into a rock and is exposed to high fore andaft loads.

Thus the VO70 has very high stipulation for grounding loads which means that additional material must be added to the at-risk areas of theboat’s structure. This additional weight will most likely come out of the bulb, meaning that there is some compromise on performance.

The VO70 regulations fix both displacement and maximum draught, implying that designers will always seek to maximise bulb mass. Anything not prescribed by the rules will be minimised and the saved weight put into the bulb.

The approach for structural engineering is muchthe same as with other existing canting-keel applications, but with a modified philosophy. For example, the structure of an Open 60 designed primarily for the non-stop Vendée Globe Race maybe tougher than an Open 60 engineered for shorter, fully crewed races.

Similarly the Volvo Ocean Race takes place in stages and so allows for maintenance at stopovers, which while influencing design strategy cannot remove the imperative that if your yacht has structural failure you are unlikely to win.

There have been a number of failures of canting keels, perhaps most dramatically on the Maxi yacht Scandia that competed in the 2000 Sydney-Hobartrace. Here the hydraulic rams broke away, the keel fell off and the boat eventually turned upside down.

But although such failures may cause engineers to think again, there should be no knee-jerk reaction. Certainly the industry needs to learn from these problems, hopefully preventing reoccurrence.

It has also been suggested that the boats that recently failed were produced on a tight budget, and it is true that structural engineering is often a relatively small part of the build programme’s budget — typically only one to two per cent of a raceboat’s overall cost.

If nothing else these failures have provided a timely wake-up call ahead of the 2005/6 Volvo Ocean Race, hopefully allowing the engineering lobby a little more ammunition in the battle for extra grams.

Volvo has played a key part in ensuring areasonable balance in the forthcoming race between safety and performance. But as engineers we must remember that safety factors in the rules do not mean that any less effort is required— quite the reverse, in fact.- Rod Fogg.

Rod Fogg, head of engineering at SP Technologies, is a structural consultant who has worked with anumber of the design teams involved in the race.

The 140ft Atlantic record holder Mari Cha IV, top right, has the largest canting-keel installation to date with its huge bulb keel, bottom right, driven by a 6m, 600-tonne ram.