Ulstein’s X-Bow finds another application in National Geographic Endurance’s viewer-friendly design bound for polar waters
If Lindblad Expedition’s National Geographic Endurance lives up to its billing, Ulstein’s revolutionary X-Bow could become the default design for expedition vessels.
Until now the decade-old, snub-nosed X-Bow has been mainly seen on offshore vessels, but suddenly its bigger potential has become apparent on Lindblad’s latest launch, a 124.4-m long and 21-m wide pocket cruise ship with a complement of 126 passengers.
Over 100 vessels now boast the Ulstein-patented X-Bow, but National Geographic Endurance is only the second cruise ship to use it, the first being SunStone Ship’s Greg Mortimer delivered last year. Although the sea-kindly and rugged virtues of the X-Bow are well documented – Lindblad describes it as providing “the smoothest and most comfortable ride imaginable in all sea behaviour,” it has been cleverly adapted for expeditions into pristine regions as a result of a brains trust between designer, builder and owner.
“[We had] a workshop between owner, class society, yard and designer in the project phase to clarify the [nature of] the intended operations and the areas of those operations so we could clarify any technical or operational risk and find solutions to minimise these risks,” reports Ulstein in a special briefing for Passenger Ship Technology.
The result was a document entitled the Polar Code Assessment Report that among many other things, spelt out the dangers the ship could encounter. The parties were targeting Category A of PC(5), broadly defined as “year-round operation in medium first-year ice which may include old-ice inclusions.”
Ulstein explains that first, the lines of the bow were “adjusted to meet the guidelines of DNV GL’s ice-class notations in order to avoid increased ice loads”. To make the calculations that would make the hull strong enough to withstand the strains and stresses of hitting a berg or some other immovable object, Ulstein ran some heavy numbers under a process known as finite element method, the most widely used discipline for solving problems of engineering and mathematical models involving, for example, structural analysis, heat transfer, fluid flow, mass transport and electro-magnetic potential.
“Much time and resources were spent to meet the polar code requirements,” recalls Ulstein about the pursuit of the rigorous Category A standards. But the effort was clearly worthwhile – National Geographic Endurance is able to operate all year round in polar areas even though that is not Lindblad’s intention. “But by having the PC(5) notation, the vessel is able to enter polar areas earlier and go further than vessels with less extensive ice-strengthening,” adds Ulstein. A vessel for all seasons, in short.
In the polar regions, the vessel must be ready for anything. In extreme circumstances ice could accumulate on the vessel and affect its stability. Vital air inlets could freeze up in sub-zero temperatures that could reduce the intake of air to the main engines. And in the all-important matter of evacuation in the event of an emergency, all life-saving appliances must be operable in conditions of extreme cold and in darkness. After all, emergencies do not occur in ways and at times that best suit the operator.
Some risk-mitigating solutions were already on the table while others were found during the progress of the project. Eventually, the Polar Waters Operational Manual summed it all up and parcelled out the various responsibilities. “Some of the risks were operational and typically issues for the owner and some were technical and typically issues for the yard.”
Poland’s award-winning Crist shipyard, which had already built X-Bowed vessels, was handed the construction contract under Ulstein’s supervision while the latter conducted the finishing works.
The adaptability of the X-Bow is immediately apparent. Its overall shape was redesigned, albeit without sacrificing its sea-going virtues, to facilitate panoramic views. “Cut-outs in the upper part of the bow were introduced to generate viewpoints [and] ‘observation wings’ – in effect, platforms extending beyond the beam of the hull – were introduced to create other viewpoints just aft of the bow,” explains Ulstein.
Clearly visible in the picture, these observation areas are designed, Lindblad says, “to connect guests to their environment and be the ultimate platform for exploration.” Additionally, the X-Bow was chosen because it provides, Lindblad says, “optimal forward and straight down-the-sides viewing [without the need] to lean out over the deck rail.”
On National Geographic Endurance, even the cabins are designed as look-outs, with 75% of them having balconies. All up, passengers will get what they are paying for – a ringside seat to a pristine and largely untouched world. A notation known as Silent(E) reduces noise released into the sea so as not to disturb the wildlife – National Geographic Endurance has eight inaugural Arctic itineraries on its programme.
And exploration being an important part of expedition cruising, Zodiac has devised an innovative loaded system which gets passengers ashore with the minimum of fuss and maximum safety. Lindblad describes it as a “hyper-efficient” system. Zodiac was not able to supply information about how the system worked but it is being adopted by other expedition cruise lines.
Technically, National Geographic Endurance bristles with a full array of technology that has helped give the ship the highest ice-class rating of any purpose-built passenger vessel. National Geographic Endurance will be able to sail deeper into the pack ice by virtue of bigger fuel and water tanks, zero-speed stabilisers and, greatly assisting manoeuvrability, ABB Azipods.
These twin 3.5-MW electric propulsors meet the highest ice-going class requirements. A gearless steerable arrangement, the electric drive is mounted in a submerged pod outside the ship’s hull. A hybrid cooling system, which combines direct cooling via surrounding seawater and an active air-cooling system assures high performance in polar regions.
“Azipod propulsion has the proven ability to cut fuel consumption by up to 15% compared to traditional shaft-line propulsion systems,” ABB marine and ports managing director Juha Koskela explains in a release. [See box]
Two stabilisers from SKF are installed on each side and are used during transit and at zero speed to reduce rolling. Two Brunvol tunnel thrusters, each with a diameter of 2,000 mm and a rating of 1,000 kW, provide back-up during berthing.
General Electric built the engines, each connected to an ABB generator. For redundancy purposes, two engines are installed in each of the two enginerooms – a requirement under IMO’s Safe Return to Port (SRtP) regulations. The engines are environmentally friendly – they do not need scrubbers to meet Tier III emission standards because of GE’s combustion recirculation technology. In fact, the engines comply with the US Tier 4 standards.
Under the skin, Ulstein has deployed a time-saving system of managing cables that PST first highlighted. Called EZ-Path, the innovation was devised by STI Marine. It is a transit system that can accommodate as many cables – and types of cables – as necessary. And National Geographic Endurance has 4,000-6,000 m of them.
ABB will also play a major role in the operation of National Geographic Endurance through its Ability System 800xA, an umbrella service that integrates power, propulsion and vessel management systems into a single platform. Both crew and onshore teams have access to all the information required to operate the vessel in the most efficient way. All systems will be connected 24/7 to ABB’s remote monitoring and support centres. The Swiss group has seven of these land-based centres that deploy remote diagnostics and predictive maintenance services to slash operational expenses.
According to ABB, these stations technically known as Collaborative Operations Centres, can reduce the cost of repairs and maintenance by 50% and onsite attendance by technical personnel by up to 70%.
National Geographic Endurance embodies the latest thinking on SRtP, which has continued to evolve in the last decade. Technically speaking, SRtP requires passenger vessels longer than 120 m to be designed with at least three main vertical zones built into the vessel to improve the odds of survival in the case of a flood or fire. The principle is that passengers and crew can stay safely on board even if the vessel has to limp to port without anybody having to be evacuated.
“The scale of SRtP compliance sets great challenges for ship design,” Deltamarin, a specialist on the regulations explains. “Many systems need to be doubled or their operation in a damaged situation needs to be secured in other ways”.
National Geographic Endurance has become a template for an as-yet unnamed sister ship. Also to be built by Ulstein, the vessel is scheduled for launch in Q3 2021, bringing Lindblad’s polar fleet to four ships.
The allround ability of ABB’s Azipods
ABB’s electric Azipods continue to confirm their virtues in expedition shipping as well as for other passenger vessels. In mid-2019, a study by independent researcher Deltamarin assessed the potential savings of an Azipod-equipped ropax vessel with one running on conventional shaft line propulsion. Astonishingly, the study showed that savings in annual fuel costs per vessel could be as high as US$1.7M. The consequent reduction in CO2 reductions was measured at around 10,000 tonnes a vessel per year.
The research was based on a simulation of seven existing routes powered by twin 10-MW mid-power Azipod units. Citing the research, ABB has launched a new series of mid-power Azipods ranging between 7.5-14.5 MW, plugging a gap between the low and high-power systems already in the market. One of the attractions to the expedition cruising market of electrically driven Azipods is they are quiet and smooth-operating, important qualities in the quiet and often remote regions that are increasingly on the visiting list.
According to ABB president of industrial automation Peter Terwiesch, the new range of mid-power Azipods are suitable for middle-sized cruise ships such as National Geographic Endurance. Highly versatile, this latest model is also in demand from ferries, ropax vessels, larger offshore construction vessels and shuttle tankers. ABB has booked other breakthrough orders in the passenger ship sector for its Azipods, including one for an LNG-powered Viking Line ship due for delivery in late 2020 as well as for a duel-fuel and battery-powered ferry that Wasaline will operate between Sweden and Finland.
According to Wasaline chief executive Peter Stahlberg, there are multiple benefits from Azipod propulsion including “the superior manoeuvrability that allows the ferry to operate a precise schedule [which is] crucial for a busy route.”
On expedition cruise ships, the benefits of Azipod-type propulsion could be even greater. As Lindblad senior vice-president for newbuilds Nikolaos Doulis, says, “ABB Azipod propulsion offers major safety benefits with exceptional fuel consumption, high performance in demanding ice conditions, and remarkably improved onboard comfort.”
National Geographic Endurance has dispensed with stern thrusters because ABB’s Azipods provide all the manoeuvrability required.
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