Small draught, large payload

A dredger recently delivered to the Belgian DEME group has some surprising features.

The 13,7003 capacity trailing suction hopper dredger, Lange Wapper, which was delivered to its owner, the Belgian DEME group, in May this year, represents a significant step forward in dredger design. The installation of sophisticated shipboard control and automation technology and high performance dredging systems, coupled with the shallowness of its draught in relation to its capacity, should allow the operator, DEME subsidiary Dredging International, to achieve important gains in terms of operational efficiency and flexibility.

Constructed at IHC`s De Merwede yard in Holland, at a cost of around BFr2.4 billion ($60.4 billion), the 20,000 dwt Lange Wapper is 129.8m long, with a beam of 26.8m.

The beam is over 3m wider than normal for a vessel of this type and capacity. However this specification, made as part of the overall design strategy for minimising the draught, has not had the negative impact on travel speed that might have been expected. The top speeds of 15.1 knots loaded and 16 knots empty which have been achieved have surprised even the designers.

Achieving a high degree of operational flexibility was the prime aim of DEME`s newbuilding team, which worked closely with naval architects at De Merwede from the outset. Lange Wapper is suitable for deployment on a wide range of different dredging tasks in various types of location, at sea or on rivers. Also, while it is expected to operate primarily in the European market, it is fully capable of handling typical dredging contracts elsewhere in the world, including Africa and South America, for example.

The main key to the newbuilding`s inherent flexibility is the fact that while it has a draughtft of 8m, allowing the vessel to operate in shallow waters near to coasts, it nonetheless has a payload capacity of 15,000t at this draught, making it economically viable for large scale contracts. The maximum payload of Lange Wapper is 20,500t at a draught of 9.82m.

According to Marc Stordiau, DEME chief executive, “Lange Wapper fits into a new niche. To get this type of capacity, and economy of scale, you would expect a draft of at least 11m. So a ship of this size would not normally be expected to be seen in shallow waters. But this vessel will, and it will surprise many people.”