This weekend, I took my family out for a day at the National Dredging Museum. A great place to experience the history, the physics, the industry and the interesting stories from the people who made the Netherlands the great dredging nation of today. As museums go, they also have a lot of models of old, new and important dredging equipment. One particular model had my interest: the tin bucket ladder dredge ‘Karimata’ form the mining company Biliton.
This particular model used to be part of the collection of the Delft University of Technology. It was standing in the hall between the dredging laboratory, where we received our lectures from professor ‘de Koning’ and the coffee room where we drank hot chocolate in the coffee break. Passing this exhibit, sometimes he would pause and tell an interesting story, or explain how nice the specific kinematics of a bucket ladder dredge is able to cut cohesive clay, or remind us of the difficulty of keeping the ladder correctly oriented in the bank. During a rationalisation of the available floor area and the ‘required educational space’, the model moved to museum.1
The ‘Karimata’ was designed as a floating mining factory. The front side of the dredge was the normal bucket ladder dredge to remove the tin containing sediment or overburden from the mining pit. Usually the dredge started at the shoreline, creating its own pool. Overburden and tailings were discharged behind the dredge through those long chutes at the back. Valuable ore was separated in the refinery at the second half of the pontoon. Cyclones and jigs densified the ore2 and removed the tailings. Eventually, the ore could be loaded on barges alongside the dredge.
Before the ‘Karimata’ was transported to the customer, the dredge had to be commissioned and tested. Normally, such an operation is usually done in a well-defined environment like the ‘Haringvliet’ or ‘Hollands Diep’. This time, however, a more challenging job was proposed. In 1799, the ‘HMS Lutine’ was sailing north of Terschelling. The ship was used for an enormous gold transport in bullion and coins. Unfortunately, the severe storm sank the vessel and only one crew member survived. The gold treasure was still there. Over time, several attempts were made to recover the gold. In 1938, most of it was still not recovered3. The ‘Karimata’ was set on a mission to recover the rest. Eventually, the commissioning was successful4, but only one bar of gold was found and the endeavour was called off. ‘Karimata’ was sent to her customer and used until her end5 in 1953.
And the remaining treasure of ‘HMS Lutine’? Well I think, the villains in the adventure comic of ‘Captain Rob and the Seven Star Stones’ seized it and none is left.
These bucket ladder dredges were successfully used to mine and process tin. Even in the seventies(?) several of these vessels were ordered by a Malaysian company. During a visit in 1995, they were still operating there in a tin mining pit. For the commissioning of those dredges, a consultant was hired to perform some specific measurements on the vessel. As a token of gratitude, he received a big poster of the dredge. After cleaning out his office at his retirement, I received this poster and it has decorated my office ever since.
References
- Deed of donation, National Dredging Museum
- The problem of jigging tin ore, Ports and Dredging nr.47
- HMS Lutine
- Strain Measurements on Gold-Seeking Tin Dredge Established Basis for Scientific Solution of Dredging Problems, Ports and Dredging nr.10
- E.B. 22 Karimata, DredgePoint
