Th e Final Design

mm.151 Th e fi nal result of this was that the reinforcement of the hull structure resulted in the return to the original 280 mm belt armor.152

Th e torpedo protection system of the 20,000 ton battleships diff ered from the system used on the Radetzky class but it was not much more effi cient. On the battleships of the Radetzky class the 54 mm thick inner side of the double hull was the torpedo bulkhead and the depth of the system was 1.5-2 meters. On the dreadnoughts there was a Koff erdamm, a vault space between the inner side of the double hull and the 50 mm thick torpedo bulkhead and the depth of the system was 2.4-2.8 meters. Between the torpedo bulkhead and the 15 cm and 7 cm magazines bulkheads there was another Koff erdamm of 0.9-1.2 m closed in by a light 9 mm bulkhead. Th e specifi cation of 9 June and especially the attached sketch drawing described a diff erent system arrangement: there was a vault space between the inner hull and a light bulkhead and there was another space for reserve coal between the light bulkhead and the torpedo bulkhead. Th is system was at least 1-1.2 meters deeper than that of Popper. Looking at the plans of the Tegetthoff class, it is obvious that there was the possibility to form a deeper protective system by changing the torpedo bulkhead and the light bulkhead of the magazines without any further serious modifi cations. Th is system would have been 3.6-3.8 meters deep at the boiler and machinery rooms and 4-4.5 meters deep at the 30.5 cm magazines. It is still a secret why the Navy accepted Popper’s arrangement while many of their offi cers and naval architects were fully aware of the fl aws of his system.

On 11 November 1909, Montecuccoli informed Tirpitz in a letter that the Austro-Hungarian Navy was to build 20,000 ton battleships with four triple turrets. In his letter of 26 November Tirpitz expressed his well-wishes to Montecuccoli for “choosing such an original type of battleship”.153 Later Tirpitz became the most vehement critic of the Austro-Hungarian dreadnoughts.

Th e Final Design

Th e displacement of the Tegetthoff class was 5,500 tons or 38 percent greater than the displacement of the Radetzky class, which was the greatest leap in the history of the Austro-Hungarian Navy. Th e greatest part of the increase was the result of the increases to the armament and the armor protection, whereas the speed of the two classes was nearly identical. Th e weight of the vertical armor was 1,300 tons or 35 percent greater, the thickness of the belt armor was increased by 22 percent (from 230 to 280 mm) while the thickness of the casemate armor was increased by 50 percent (from 120 to 180 mm). Th e weight of the main battery including gun turrets rose from 1,833 tons to 2,798 tons (53 percent). Even the price of the new battleships was much greater: 60.6 million Kronen per unit against the 39.3 million Kronen per unit price of the Radetzky class.

Th e main battery of the Tegetthoff class consisted of the same 30.5 cm/45 Škoda guns which were used on the Radetzky class, but twelve of them were mounted on the new battleships instead of four. At the time of the design process (1908-1909), the Navy was content with the 30.5 cm caliber and considered it suffi cient even with the shorter, 45 caliber length version of this gun after reviewing the problems that Škoda had had with the development of the 50 caliber length version. Th e 30.5 cm guns of the Tegetthoff class slightly diff ered from the earlier guns: these guns were designated as K10 and their chambers were 5 cm longer so that they could handle a heavier propellant charge in a longer case. Th e ammunition hoists of the triple turrets were also larger so that they could handle the longer 5 crh projectiles. Th ese more streamlined projectiles gave the gun somewhat greater range. Th e Škoda manufactured fi fty-two K10 guns in total, four of them being spares.

Th e twelve 30.5 guns were mounted on four triple turrets, two turrets were in the bow and two turrets were in the stern all on the centerline and the two inner turrets were in superimposed position. Th is turret arrangement gave the ships a heavy six guns end on fi re capability and a twelve gun broadside fi re capacity. Th e triple turrets were much heavier than originally designed, they weighed 682-692 tons (superimposed turrets were heavier) without the armored cupolas of the turret rangefi nders instead of the 623 tons weight guaranteed by the Škoda. Th e turrets were all electric operated (train, elevation and ammunition hoists). Th e four turrets were fed by four 300 KW turbine-driven dynamos. Breeches, loading cars and chain rammers were hand operated. From

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1913/1914, every turret was fi tted with a coupling device that allowed the guns to elevate together. When the three guns of a turret were coupled together their maximum elevation was reduced and range was thus limited to 18,500 m.154 Each turret was fi tted with a 9-foot Barr & Stroud rangefi nder in an armored cupola on the turret roof.

Th e secondary battery consisted of twelve 15 cm/50 guns in casemates on the Batteriedeck. Th ere were two small armored fi re control towers for the 15 cm batteries on both sides of the ship on the Oberdeck (upper deck). Th e light anti-torpedo boat battery consisted of eighteen 7 cm/50 guns on the Ober deck. During the war three or four 7 cm/50 AA guns were mounted on the roofs of the superimposed turrets. Th e ships were fi tted with four submerged 53.3 cm torpedo tubes, one in the bow, one in the stern and two on the broadsides.

Th e weight of the vertical armor was 5,000 tons. Th e main belt was 280 mm thick tapered to 180 mm under the waterline. Forward and aft of the barbettes of the fi rst and the fourth 30.5 cm turrets the belt reduced in thickness to 150 mm. Th e upper belt and the casemate armor was 180 mm thick. Th e sloped parts of the armored deck were 48 mm thick while the midship part was 36 mm thick. Because the casemate armor ended at the superimposed turrets, the Batteriedeck was reinforced over the magazines of turrets No I, No III and No IV. Th e lack of the side armor (over the upper belt) was compensated by the thickening of the Batteriedeck from 15 to 30 mm in these areas. Th e Batteriedeck was one level above the armored deck (Mitteldeck). In these areas the vertical armor protection was 30+36 mm while over the magazines of the turret No II it was only 15+36 mm, but here the vertical armor reached the Oberdeck which was 30 mm thick

28 Th e torpedo protection system of the Tegetthoff class designed by Popper. Th e maximum depth of the system is 2.6 m. Th e circle indicates the thin (18 mm) outer edge of the sloped part of the armored deck over the 15 cm casemates. Th e barbettes of the 30.5 cm turrets were 280 mm thick above the Batteriedeck. Th e lowest part of the barbettes, which were directly above the armored deck, was 80 mm thick. Th e face and the sides of the turrets were 280 mm and the sloped parts 200-130 mm thick, while turret roofs were 60 mm thick. Th e conning tower had 280 mm thick sides and a 60 mm thick roof. Th e aft conning tower had 150 mm sides and 40 mm roof. As it was mentioned earlier, the torpedo protection system of the Tegetthoff class diff ered from

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the system of the Radetzky class but was not much more eff ective. Th e 50 mm thick torpedo bulkhead ran from the fi rst to the fourth gun turret and the distance between it and the side shell plating was 2.4-2.8 m, which was far from adequate. Th e torpedo protection systems of the Tegetthoff and the Radetzky classes had another serious and common fault. On both classes the last 1-1.2 m wide section of the sloped part of the armored deck (18+30 mm) where it was attached to the side shell plating was only 18 mm thick. As the Austro-Hungarian underwater explosion test of June 1914 demonstrated, a single 18 mm deck could not withstand the explosion of a 45 cm torpedo warhead of 110 kg. A Hungarian diving expedition which explored the wreck of the Szent István in 2008 reported that there was a wide gap between the side shell plating and the above mentioned part of the armored deck above the hole made by the torpedo.155 Th is fault exposed a serious danger that following an underwater explosion not only the compartments under the armored deck would be fl ooded but also the compartments above it could be fl ooded.

Even the Navy was fully aware of the weak construction of the watertight bulkheads of the Austro-Hungarian battleships. Th is was less problematic on the battleships built earlier because their bulkheads had smaller surfaces. Th anks to the weak bulkheads, on these ships it had to store great quantity of timber to support the bulkheads in case of emergency. Th e bulkheads were further weakened with watertight doors cut in them even on the Tegetthoff class which was against the advice of Tirpitz. Th e construction of the bulkheads of the different units of the Tegetthoff-class was not identical. Th e vertical stiff eners (L profi les) of the bulkheads on the Viribus Unitis and Tegetthoff were spaced by 610 mm while on the Prinz Eugen they were spaced by 570 mm. On the latter ship two additional horizontal stiff eners reinforced the watertight bulkheads. At a later date two horizontal stiff eners were riveted to the bulkheads of the fi rst two Trieste-built dreadnoughts.156 In 1914 the Navy made so-called caisson tests with similarly constructed ½ scale bulkheads. Th e test results were not very promising for the Tegetthoffs: converting the data to 1/1 scale bulkheads the engineers of the MTK came to the conclusion that the pressure of a 5-6 m high water column could cause a 30 cubic meters per hour leakage trough the bulkhead.157

Th e shape of the hull and the silhouette of the ship were similar to that of the Radetzkys. Both battleship classes were fl ushdeckers and they had two funnels and two pole masts. Th e Tegetthoff s were extremely beamy ships among the battleships of that time; their length/beam ratio was 5.43 (152.3×28 m). Th anks to the relatively short hull, the lack of the raised forecastle deck and the heavy and voluminous armament, the crew compartments were extremely overcrowded. Th e superimposed triple turrets rendered the ships top heavy and unstable. Th e ships were also bow heavy thanks to their heavy and anachronistic ram. Due to the low freeboard and the shape of the bow they were wet ships. At a speed of 16-17 knots even on calm sea the foredeck was constantly wet. Th anks to all of the structural weight savings, the structure of the hull was weak. During dockings the heavy weight of the triple turrets caused distortions in the structure of the double bottom, especially under the aft turrets.

Th e ships of the Tegetthoff class were the fi rst Austro-Hungarian battleships built with steam turbines. Th e fi rst turbine-powered ship of the Austro-Hungarian Navy was the 3,500 ton scout cruiser Admiral Spaun. Th e weight of the machinery complex of a Tegetthoff class battleship was approximately 1,500 tons (Szent István 1,640 tons). Th e machinery was consisted of two sets of direct drive Parsons-turbines (Szent István AEG-Curtiss) without cruising turbines and twelve coal fi ring Yarrow (Szent István Babcock-Wilcox) watertube boilers with oil spraying. Th e boilers of the Szent István were fi tted also with superheaters. On the three Trieste built ships each stage (HP, LP) of the turbine sets drove its own three bladed manganese bronze screw of 2,700 mm diameter, so these ships had four screws. On the Danubius built ship the two stages were coupled in line together as on the German dreadnoughts so each turbine set drove one three bladed manganese bronze screw of 4,000 mm diameter. Th e design power output of the machinery was 25,000 SHP and the design speed of the ships was 20 knots. Th e twelve boilers were arranged in two boiler rooms, six boilers in two rows in each. Each boiler room had its own funnel. Th e ships could carry 1871 tons of coal and 162 tons of fuel oil which enabled a maximum range of 5000 nautical miles at a cruising speed of 10 knots. Th e Szent István could carry 267 tons of fuel oil.

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