Danish feeders for hub-and-spoke world of mega ships and mega ports

Danish feeders for hub-and-spoke world of mega ships and mega ports NEW purpose-built feeders are being designed to suit the hub-and-spoke world created by the advent of mega ships and mega ports. A leading exponent of new designs is the Danish naval architect company Knud E Hansen, which has fashioned three types in the 2,000-TEU range.  The first was conceived to specialise in calling at small, narrow, up-river ports, such as the Chao Phraya that flows through Bangkok into the Gulf of Thailand. Navigating such waters requires a vessel to have a shallow draught - no more than 8.2 metres in the case of Bangkok, reports London's Port Technology International.  "The dual arrangement makes up for the relative small diameter of the propellers," said the company's chief architect Jesper Kanstrup.  "The total propeller disk area of the two propellers corresponds to the area of a single propeller with a diameter of approximately 7.4 metres and further, the counter-rotating propeller will recover some of the swirl energy produced by the main propeller, which increases the overall efficiency," he said. A second design includes a vessel which does not require such a shallow draught and which will have a 3,800 TEU capacity. With draught not being a primary consideration, this design sees the feeder vessel fitted out with a larger diameter, slower-turning propeller. Unlike most feeders, the deckhouse of this vessel is positioned slightly forward amidships to maximise the number of container slots on deck considering the UN International Maritime Organisation's line of vision from the bridge requirements. The added number of slots can be utilised in real-life loading conditions because the vessel is wider and has a higher stability than most feeder vessels of this size.  "This prepares the vessel for LNG and dual-fuel propulsion - attributes that are becoming increasingly sought after," said Mr Kanstrup. "Here, we have a square block below the deckhouse, in which we can either have HFO tanks or LNG tanks."What's more, the vessel can be built with HFO tanks and easily retrofitted for LNG the day the infrastructure for LNG is sufficiently developed if a dual-fuel engine is installed in the first place, he said. The third arrangement sees the application of a hull shape suited for carriage of both partial and full container loads. The problem arises due to the differing ways in which a vessel behaves based upon its load. A large container vessel, when carrying few containers, offers shallow draught, but has so much stability that accelerations are too high, causing problems for the lashing gear and the crew. Said Mr Kanstrup: "In this situation, you don't want anything more than sufficient stability and so a narrow hull is preferable. "The problem being that, when you come to carrying a full load you require a wider water line for additional stability. "So the ideal hull would have inclined hull sides with narrow water lines at shallow draught and wider water lines at deeper draughts, which, however, is not the most practical design considering the vertical quays in ports." The solution, as the company sees it, is instead of a conventional hull, one takes a hull with inclined sides, but mirrors the triangular sections in each side to create a trimaran or a "stabilised mono-hull" with a narrow main hull with vertical sides and outrigger hulls with a triangular cross section, but vertical sides towards the quay. "We were looking for something that answers the slow steaming problem. With the advent of slow steaming, for certain goods, air freight has become a more popular choice as the cargo arrives faster.