Atjeh-class cruiser

In the 1860s the Netherlands had given priority to building an armored fleet for coastal defense in Europe. Meanwhile, the Dutch East Indies were primarily defended by the steam corvettes called screw steamships first class (Djambi-class corvette, Zilveren Kruis-class corvette). In late 1870 the minister for the navy ordered the first ship meant to replace these,[1] the ironclad Koning der Nederlanden. Somewhat later the government decided to replace part of the screw steamships first class by unprotected cruisers (ongepantserde kruisers), even though these would also be called screw steamships first class. Later, the armored part would be supplemented by the ironclad Prins Hendrik, which would be sent to the Indies in 1876. A third armored ship was planned, but postponed 'in order to first gain more experience in the use of armored ships in the tropics'.[2]

The first requirements called for a ship of no more than 200 men, costing less than 1.5 million guilders. It would be armed with 1 central 23 cm Armstrong RML, 2 18 CM RML (fore and aft) and 4 12 cm breechloaders. The machines could not be compound, and the cruising speed should be 11 knots, with a trial speed of 14 knots. The proposed design was a ship of 72 m long, 11.32 m beam, draft 5.66 m and 2,345 ton displacement.[3]

This ship would have been considerably longer and narrower, and somewhat bigger than the preceding Zilveren Kruis-class corvettes. The result would have been a screw corvette with a sloop-like armament. With considerably higher speed and better armament, it might have stood up to foreign designs. However, while judging this design, it was noted that the steam engines were too vulnerable. Therefore a new requirement was added, demanding that the engines should be below the empty load line, and behind the coal bunkers.[3]

At least two subclasses can be discerned in the Atjeh class. The first three ships had traditional steam engines, later ships had compound engines, which led to a substantial difference in power and range. The second group was also somewhat larger in overall length and draft.[4]

Beam was largest for Johan Willem Friso. She was planned to be different from the second group (De Ruyter, Van Speyk, Doggersbank and Kortenaer), but when the last two were burnt, she had to re-use the engines of Doggersbank (which had not been installed yet), and the stern of Kortenaer. This made her almost equal to De Ruyter and Van Speyk. Nevertheless, her depth of hold was also significantly larger than that of the other two.

The requirement to place the steam engines of the new unprotected cruisers below the load line necessitated the design of a substantially bigger ship. This new design was approved on 18 December 1874. The ships of the class would be 92.00 metres (301 ft 10 in) long overall, and 80.00 metres (262 ft 6 in) (between perpendiculars). The beam would be 12.50 metres (41 ft 0 in), depth of hold 10.00 metres (32 ft 10 in), and maximum draught would be 5.56 metres (18 ft 3 in) fore and 6.10 metres (20 ft 0 in) aft. Displacement would be 3,180 ton.[5]

The ships would be made of iron, covered with wood and zinc.[5] The third ship of the class, Koningin Emma (ex-De Ruyter), would use steel for that part of the hull which was above the load line, and also in some other parts of the hull. This would save weight.[8] As mentioned, under water, the hull was iron covered with teak and then zinc. This gave cathodic protection, making that the zinc corroded instead of the iron, and the zinc caught the stuff that grew on the hull. The Iron and wood were connected by Haij's Marine Composition. On Atjeh this connection was made without closing the seams. On Tromp, these seems were closed, and contact nails were hammered through the wood to make contact with the iron hull, so the galvanic effect was increased.[9] The last ship, Johan Willem Friso, would use copper on the outside, instead of zinc.

The specifications for the steam engines of the class were made by the inspectors of the national steam service, F.H.P. van Alphen and F.W. Hudig. Next the Koninklijke Fabriek van Stoom- en andere Werktuigen and Fijenoord together made a design for the engines.[10]

The ships were equipped with reciprocating engines, which were rated at 2,500 kW (3,300 ihp) and produced a top speed of 14 knots (26 km/h). On her trials, Atjeh made the required speed by steaming 14.5 knots. The engine had 2,750 ihp and a modest coal consumption.[11]

The steam engine for Atjeh was built by the Koninklijke Fabriek van Stoom- en andere Werktuigen. Those for Tromp were built by Fijenoord.[12] The steam engines for Koningin Emma were built by Koninklijke Fabriek.[13] The steam engines of De Rutyer, built by Fijenoord,[14] would be of the compound type, according to 'Sell's' system. This enabled the use of the machine as a regular steam engine, with lower pressure. This was useful if the boilers were weak, or in case the ship was fighting batteries.[15]

The first three ships had a machine to lift the propeller. With some provisions this enabled the crew to clean the propeller without visiting a shipyard.[16]

In 1878 Atjeh made a trial cruise in the North Sea. With a wind of 5-6 beaufort, she made 8.5 knots under sail. This was deemed very good for a steamer with auxiliary sailing capacity.[17]

When Atjeh was laid down, she was reported to get an armament of one central 23 cm RML, 4 15 cm Krupp breechloaders (2 fore and two aft), and some 12 cm breechloaders in the sides.[18] Obviously, the two 18 cm RML's of the first design had been replaced, but the 23 cm RML was still part of the plan at that time.

When she was launched, the armament of Atjeh had been determined at 6 17 cm Krupp breechloaders. These were all placed on the gun deck. One near the bow, one near the stern, and four more to the center of the ship. Large gun ports in bow and stern would enable these guns to fire along the line of the keel.[19] The broadside would be 4 17 cm guns. One hoped to still add four more 12 cm breechloaders, and after launch this indeed proved to be possible.[20]

Therefore, the first ships were finished with six 170 mm (6.7 in) guns and four single 120 mm (4.7 in) guns. The fourth ship, De Ruyter, was planned to have 8 12 cm breechloaders from the start.[21]