Onrust Dock of 5,000 tons
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Onrust Dock of 5,000 tons under construction in Amsterdam on 25 June 1878 | |
| History | |
|---|---|
| Name | Onrust Dock of 5,000 tons |
| Builder | Koninklijke Fabriek |
| Laid down | 14 June 1879[1] |
| Launched | 6 June 1880[1] |
| Commissioned | 1880 |
| Decommissioned | 1924 |
| Stricken | January 1926 |
| Home port | |
| General characteristics (as completed) | |
| Length | 100.00 m (328.1 ft)[2] |
| Beam | 27.00 m (88.6 ft)[2] |
| Draft | 1.516 m (5.0 ft) (empty)[3] |
| Depth of hold |
|
Onrust Dock of 5,000 tons, was a floating dry dock which served in the Dutch East Indies from 1881 till 1924.
In 1876 the Dutch navy became interested in the construction of a new dock for the Dutch East Indies. This would later be called Onrust Dock of 5,000 tons. At the time it was clear that the naval situation in the East Indies was changing. The first of the unprotected Atjeh-class cruisers were under construction, and the small battleship HNLMS Koning der Nederlanden had been launched. At the time of the proposition, the ironclad HNLMS Prins Hendrik der Nederlanden was sailing to the Dutch East Indies. Most of these ships all had about 3,500 tons displacement, while Koning der Nederlanden displaced 5,300 tons. A dry dock that could lift 5,000 tons could lift all these ships, except (perhaps) for the Koning der Nederlanden. When Onrust Dock of 5,000 tons had been assembled in the Dutch East Indies it was said to be meant for the two armored ships.[3]
The order for Onrust Dock of 5,000 tons can also be considered from the context of the Aceh War increasing the demand for dry dock capacity.[4] The new dock would replace the 1843 wooden dry dock that was in use by the East Indies at the time.
Construction and commissioning
Design
In May 1876 a commission to design a new dry dock for the naval base at Onrust Island was appointed to oversee construction. The staff consisted of: Dr. B.J. Tideman (chief engineer of the navy and adviser for shipbuilding in Amsterdam); J. Strootman (chief engineer of Waterstaat in Assen); Jhr. H.O. Wichers (Captain-lieutenant and chief of the equipment department of the navy), and J. de Hoog (engineer for shipbuilding at the Dutch Society of Insurers).[5] Tideman was the designer of Batavia Dock which was still on the slipway at Untung Jawa (Amsterdam Island). Strootman was one of the designers of Onrust Dock of 3,000 tons, which had been assembled in Surabaya and was already in service.
Ordering
In September 1876 450,000 guilders were brought on the colonial budget for 1877. The total cost of the new dry dock was estimated at 969,000 guilders including transport.[6] On 21 November 1876 there was a tender for the dry dock. Of 14 offers, 7 were discarded because they contained conditions. The others were:[7]
| Name | Place | Country | Offer |
|---|---|---|---|
| Koninklijke Fabriek | Amsterdam | Netherlands | 781,000 |
| Kon. Mij. de Schelde | Vlissingen | Netherlands | 788,976 |
| Société J. F. Cail & Cie | Paris | France | 797,000 |
| Meursing & Huijgens | Amsterdam | Netherlands | 834,950 |
| P. Haverkamp | Amsterdam | Netherlands | 859,000 |
| Nederlandse Stoomboot Maatschappij (NSBM) | Rotterdam | Netherlands | 865,000 |
| Christie, Nolet en de Kuijper | Rotterdam | Netherlands | 951,000 |
Construction

Construction was said to have started at the end of 1876. Others say it started on 11 May 1877.[8] When the ministers for the navy and the colonies visited the Koninklijke Fabriek in October 1877, substantial progress had been made.[9] On 25 June 1878 Onrust Dock of 5,000 tons had been put together in Amsterdam.[8] The Koninklijke Fabriek sent a model of the dry dock to the Paris Exposition Universelle (1878).[10]
Assembly in Surabaya
On 16 October 1878 there was a tender for unloading, assembling, riveting and finishing Onrust Dock of 5,000 tons in the Dutch East Indies. The only offer received came from the Koninklijke Fabriek for 660,000 guilders.[11] A similar tender in the Dutch East Indies failed, because no offers came in. The navy then decided to assemble it with its own staff, some brought over from the Netherlands.[12]
The dry dock was transported in 8 shipments.[12] On 10 June 1879 the first parts of the dock arrived in Surabaya.[3] On 9 September 1879 SS Prins Hendrik arrived with parts of the dry dock.,[13][14] she had left Amsterdam on 19 July 1879. On 4 October 1879 the last shipment arrived.[3]
On 14 June 1879 assembly started at Surabaya.[3] On 18 October 1879 a series of photographs were taken.[8] On 16 November 1879 the last plate was attached, and about one-third of the riveting was complete.[3] By March 1880 the job was expected to be finished in 1.5 years.[15] On 6 June 1880 Onrust Dock of 5,000 tons was launched by raising the water level in the dock pit where she was assembled. The dock had been assembled within a year. Therefore, the state shipyard at Surabaya claimed that it could compete with European commercial and state shipyards with respect to both cost and time.[1]
Characteristics

Onrust Dock of 5,000 tons consisted of a big pontoon of 100 m long and 13.50 m wide. In the center the hold was 3.80 m and on the sides only 3.60 m, which increased strength. One longitudinal bulkhead and 14 transverse bulkheads divided her into water tight compartments. The longitudinal bulkhead was just below the blocks on which the keel of any ship using the dock would rest. The sides of the dock were 6.75 m wide at the floor and 2 m wide on the top. On the top the promenades were protected from the sun. They were connected by the 'bridges' that closed off the dock at both sides.[2] In total about 2,760 tons of iron were used to construct the dock.
The dock could submerge till it had 6.30 m of water above the blocks. On the inner side of the dock each side had two heavy beams on a rack. These were used to position a ship exactly above the blocks where the keel should be. The ship would then be supported by two rows of tumble beams.[2] (cf. the model)
The dock had four centrifugal pumps with a total capacity of 3,200 m3 water per hour. The engines were directly connected to the pumps. These had a 330 mm diameter cylinder with a stroke of 300 mm making 180 revolutions per minute. The boilers were of the Cornwallis system with Galloway pipes. The boilers had a 2 m diameter and were 9.50 m long, the steam pressure was 5 atm. In case of defects to a pump, the other pumps could take over its job.[2]


