I Googled BAMA Freiburg and following a trail Finden, Akten, Digitalisiert Bestande, Militar I came to Section RM 134, Schwere und Mittlere Kampfschiffe der Reichmarine und Kriegsmarine. The last ship given is Tirpitz and for this I opened file 134/186 Kriegserfahrungen mit der Schlachtschiffen Bismarck und Tirpitz (Ausarbeitung des Oberbaurats Werner Krux). This is in German but not Gothic script and there are around 66 pages. This report was written after the war from memory but is believed to be broadly accurate. There are two sections and an Appendix. The first section deals with the experience of damage to Tirpitz and how the repairs were made, and the second section gives recommendations for new construction. The Appendix has tables and graphs of speed and cruising range of Bismarck and Tirpitz. Krux though that although battleships were now vulnerable to the heaviest bombs that they were still powerful ships and that countries would continue to need them as long as other countries had them. Looking back he noted that the advantage of attack over defence and vice versa had changed several times in the past and might do so again.
The damage to the machinery of Tirpitz caused by the X craft fell mainly into three categories: fractures in machine housings, squashed foundations and damage to rotors and bearings. All housings were of cast steel. Cracks 35 cm long occurred in flanges 45 mm thick. These were welded. The cast iron used in the machinery housings of Sperrbrecher (blockade breakers) could not be welded and needed to be replaced. The crumpled machinery mountings were straightened [probably deformations pulled out]. Rotors were repaired by carefully heating one side. Welding had improved since the ship had been built and it proved possible to weld damage to the splinter bulkhead and to the bottom of the torpedo bulkhead that had originally been rivetted. On the other hand, damaged to the torpedo bulkhead close to and above the armor deck was repaired in the original rivetted scheme. Dents in armor decks and the torpedo bulkhead caused by bomb impacts were not welded and just left as heating would have led to embrittlement. These depressions in armor decks were filled in to level them out.
Bismarck and Tirpitz were well balanced between their offensive capabilities and resistance to damage. In general, emphasis on one characteristic of a warship leads to lower capabilities in other characteristics and perhaps a weakening of the ship as a whole. However, Bismarck and Tirpitz did have weaknesses in individual aspects of their construction and equipment.
The ship building steel St 52 used in the hull construction of Tirpitz and Bismarck was stronger than the older St 42 and allowed considerable saving of weight in the hull which could be used for other purposes. St 52 showed a different pattern of damage to St 42. Basically a shell than went through an St 42 panel left a hole with the edges turned in. One that went through an St 52 plate left a hole from which cracks radiated in all directions, which meant the need to replace a larger area of material. St 52 was strong but rather brittle. Krux thought that the advantage it brought in weight savings had been dearly bought. Krux also criticised the fact that the hull bottom plates in Bismarck and Tirpitz were between two and six millimetres thinner than those in Scharnhorst. On the other hands, the hull sides in all these ships were 16 mm thick.
Future construction should feature sprung machinery mountings to increase resistance to shock. The mountings for the steam pipes and electric cables should also be sprung. Bismarck and Tirpitz had sprung mountings for the superheated steam pipes and these proved unproblematic in service. However, the mountings for the saturated steam were not sprung and broke after shocks. Cables, where they went through bulkheads, were watertight when a ship was new but inevitably became unwatertight as time passed. However, putty was suitable for sealing purposes and putty should be available throughout a ship. A new type of cable passage was in use in the later part of the war. This was promising but there was too little experience with it by the end of the war to know if it was entirely successful. Cables should not be attached to the insides of torpedo bulkheads as had been previous German practice.
The command transmission system of new ships should be improved to make commands from the captain immediately available to those they concerned. In Bismarck and Tirpitz commands were relaid through section heads, such as the gunnery officer or first engineer. Krux says that there would likely be breakdowns in the command transmission system in battle. However, he did surmise that the BuM (command and announcement system) in Bismarck did function to the end from the fact that the order to open the sea valves throughout the ship was apparently implemented.
A useful characteristic in a warship boiler, especially in battle, is the ability to keep the boiler fired up if there is a temporary cessation of the feedwater supply. But the Wagner Deshimag boilers used in these ships did not allow this because they had a narrow range of acceptable water level in the boiler. The Benson type boilers used in some German ships were satisfactory in this respect. Krux said that a part of the Wagner Deshimag boiler was too small [the steam drum at the top I think it was]. Again an advantage in space or weight had been expensively bought. The layout of equipment in each boiler room should be the same to ease crew familiarity. The electric generator plants should all be diesel powered in new ships as diesels were independent of the boilers. In Tirpitz and Bismarck there were many transformers. This was made necessary as different items of equipment operated at different voltages. This also meant that there were various power circuits in the ship, an arrangement that added to complication, weight and the potential for breakdowns. In fact, in 1944 welding equipment was operated using the searchlight power circuits; Tirpitz has separate circuits for searchlights and welding equipment. There should be a considerable reduction in voltages used and circuits in new ships. The electric switch rooms should be larger in new ships. In Tirpitz, switches were so close together that there was a danger of short circuits if a board was deformed even to a small extent. It was also dangerous to change fuzes. The switch boards should also be further from the floor. In Tirpitz even a small amount of floodwater in a room could give rise to problems. Equipment on the Zwischendeck was haphazardly laid out because the arrangement had not been decided on early in the design process. New construction should avoid the problem. In general, equipment should be easier to use and personnel should be better trained. Designers should have secondments on ships so that they had practical experience of how things worked.
The conventional bomb that penetrated both armor decks in August 1944 showed that the 80 mm area of armor deck was too thin. Deck thicknesses had been determined on the basis of artilleristic considerations. But bombs endangered the whole deck so the deck should be one thickness. What the material was to be used was an open question. Strength and ballistic tests showed that the upper limit in thickness for Wh was 115 mm [Krux's memory was slightly out on the thickness of the sloped section of the lower armor deck]. Wh plates of greater thickness than 115 mm showed too great a spread in their resistive values. If the other military characteristics remained the same then a heavier armor deck, together with the need to increase beam to maintain the same level of stability, would result in a larger ship than Tirpitz.
There was also a need for some relocation in the crew living quarters. In Bismarck and Tirpitz typically one type of specialist crew lived in one area of the ship. But this meant they could be wiped out in a surprise attack. It was desirable to disperse specialist crew living quarters to several areas in the ship. It was also desirable to house crew close to their action stations to reduce to time needed to put the ship at full readiness for battle.
Added later: The appendix gives range at various speeds for operation of Bismarck and Tirpitz with one (center), two (wing) and three shafts. Ranges were about 12500 nm at 12 knots with one shaft, 10500 nm at 15 knots with two shafts, and 9200 nm at 16 knots with all three shafts. All figures were for oil fuel with a heat content of 8800 kcal/L [a relatively low figure].
Neil Robertson
The damage to the machinery of Tirpitz caused by the X craft fell mainly into three categories: fractures in machine housings, squashed foundations and damage to rotors and bearings. All housings were of cast steel. Cracks 35 cm long occurred in flanges 45 mm thick. These were welded. The cast iron used in the machinery housings of Sperrbrecher (blockade breakers) could not be welded and needed to be replaced. The crumpled machinery mountings were straightened [probably deformations pulled out]. Rotors were repaired by carefully heating one side. Welding had improved since the ship had been built and it proved possible to weld damage to the splinter bulkhead and to the bottom of the torpedo bulkhead that had originally been rivetted. On the other hand, damaged to the torpedo bulkhead close to and above the armor deck was repaired in the original rivetted scheme. Dents in armor decks and the torpedo bulkhead caused by bomb impacts were not welded and just left as heating would have led to embrittlement. These depressions in armor decks were filled in to level them out.
Bismarck and Tirpitz were well balanced between their offensive capabilities and resistance to damage. In general, emphasis on one characteristic of a warship leads to lower capabilities in other characteristics and perhaps a weakening of the ship as a whole. However, Bismarck and Tirpitz did have weaknesses in individual aspects of their construction and equipment.
The ship building steel St 52 used in the hull construction of Tirpitz and Bismarck was stronger than the older St 42 and allowed considerable saving of weight in the hull which could be used for other purposes. St 52 showed a different pattern of damage to St 42. Basically a shell than went through an St 42 panel left a hole with the edges turned in. One that went through an St 52 plate left a hole from which cracks radiated in all directions, which meant the need to replace a larger area of material. St 52 was strong but rather brittle. Krux thought that the advantage it brought in weight savings had been dearly bought. Krux also criticised the fact that the hull bottom plates in Bismarck and Tirpitz were between two and six millimetres thinner than those in Scharnhorst. On the other hands, the hull sides in all these ships were 16 mm thick.
Future construction should feature sprung machinery mountings to increase resistance to shock. The mountings for the steam pipes and electric cables should also be sprung. Bismarck and Tirpitz had sprung mountings for the superheated steam pipes and these proved unproblematic in service. However, the mountings for the saturated steam were not sprung and broke after shocks. Cables, where they went through bulkheads, were watertight when a ship was new but inevitably became unwatertight as time passed. However, putty was suitable for sealing purposes and putty should be available throughout a ship. A new type of cable passage was in use in the later part of the war. This was promising but there was too little experience with it by the end of the war to know if it was entirely successful. Cables should not be attached to the insides of torpedo bulkheads as had been previous German practice.
The command transmission system of new ships should be improved to make commands from the captain immediately available to those they concerned. In Bismarck and Tirpitz commands were relaid through section heads, such as the gunnery officer or first engineer. Krux says that there would likely be breakdowns in the command transmission system in battle. However, he did surmise that the BuM (command and announcement system) in Bismarck did function to the end from the fact that the order to open the sea valves throughout the ship was apparently implemented.
A useful characteristic in a warship boiler, especially in battle, is the ability to keep the boiler fired up if there is a temporary cessation of the feedwater supply. But the Wagner Deshimag boilers used in these ships did not allow this because they had a narrow range of acceptable water level in the boiler. The Benson type boilers used in some German ships were satisfactory in this respect. Krux said that a part of the Wagner Deshimag boiler was too small [the steam drum at the top I think it was]. Again an advantage in space or weight had been expensively bought. The layout of equipment in each boiler room should be the same to ease crew familiarity. The electric generator plants should all be diesel powered in new ships as diesels were independent of the boilers. In Tirpitz and Bismarck there were many transformers. This was made necessary as different items of equipment operated at different voltages. This also meant that there were various power circuits in the ship, an arrangement that added to complication, weight and the potential for breakdowns. In fact, in 1944 welding equipment was operated using the searchlight power circuits; Tirpitz has separate circuits for searchlights and welding equipment. There should be a considerable reduction in voltages used and circuits in new ships. The electric switch rooms should be larger in new ships. In Tirpitz, switches were so close together that there was a danger of short circuits if a board was deformed even to a small extent. It was also dangerous to change fuzes. The switch boards should also be further from the floor. In Tirpitz even a small amount of floodwater in a room could give rise to problems. Equipment on the Zwischendeck was haphazardly laid out because the arrangement had not been decided on early in the design process. New construction should avoid the problem. In general, equipment should be easier to use and personnel should be better trained. Designers should have secondments on ships so that they had practical experience of how things worked.
The conventional bomb that penetrated both armor decks in August 1944 showed that the 80 mm area of armor deck was too thin. Deck thicknesses had been determined on the basis of artilleristic considerations. But bombs endangered the whole deck so the deck should be one thickness. What the material was to be used was an open question. Strength and ballistic tests showed that the upper limit in thickness for Wh was 115 mm [Krux's memory was slightly out on the thickness of the sloped section of the lower armor deck]. Wh plates of greater thickness than 115 mm showed too great a spread in their resistive values. If the other military characteristics remained the same then a heavier armor deck, together with the need to increase beam to maintain the same level of stability, would result in a larger ship than Tirpitz.
There was also a need for some relocation in the crew living quarters. In Bismarck and Tirpitz typically one type of specialist crew lived in one area of the ship. But this meant they could be wiped out in a surprise attack. It was desirable to disperse specialist crew living quarters to several areas in the ship. It was also desirable to house crew close to their action stations to reduce to time needed to put the ship at full readiness for battle.
Added later: The appendix gives range at various speeds for operation of Bismarck and Tirpitz with one (center), two (wing) and three shafts. Ranges were about 12500 nm at 12 knots with one shaft, 10500 nm at 15 knots with two shafts, and 9200 nm at 16 knots with all three shafts. All figures were for oil fuel with a heat content of 8800 kcal/L [a relatively low figure].
Neil Robertson
statistics: Posted by neilrobertson1 — 2:36 PM - 1 day ago — Replies 0 — Views 184