For a New Year puzzle, how would members of our community redesign Bismarck if placed in the KM's ship designing office over 1935-6? The ship must carry its 8 38 cm guns in their 4 turrets and follow most of the demands of the KM staff. It will probably have to use the same boilers and turbines. The standard displacement should not exceed the historical approximately 43,000 tons and the dimensions should be no greater with the draft no deeper to allow use of the Kiel Canal.
My own suggestions are that weight could be saved by using a dual purpose secondary armament and omitting a heavily armoured conning tower (basically imitating the design of KGV which of course wasn't available to be copied). If no suitable German DP gun could be found, it might have been possible to buy the design of the Italian 135 mm http://www.navweaps.com/Weapons/WNIT_53-45_m1938.php and redesign the loading mechanism to achieve 12 rpm up to 70 degrees. I am guessing that the total saving may be about 2,000 tons.
The extra space made available on going from 28 guns and 14 turrets to 16 guns in 8 turrets should allow us to mount many more LAA guns. Ideally, we would buy Bofors 40 mm but if that was ruled out, quick development of the M42 37 mm http://www.navweaps.com/Weapons/WNGER_37mm-69_mk42.php should be possible. In either case, it should be possible to mount at least 80 guns.
We can also use the weight saving to add armour. For example, Bismarck's belt had a lower tapering section reducing from 320 mm to 170 mm. If we stretch that tapered plate by 1 metre, it costs for a 170 metre length 170 x 2 x 0.25 x 8 or 680 tons (assuming a specific gravity of 8 and an average thickness of 250 mm). Logically we should also add something similar at the ends which might cost just over another 100 tons.
Another worry might be the facets at the top front of the main battery turrets. If we just calculate cosines, these seem fairly strong. However, there is the phenomenon of "overmatch" where resistance falls off for calibres of twice the armour thickness. As twice 180mm is only just larger than 14", it does seem necessary to use about 10 tons per turret to go to 220 mm thickness.
Another potential problem which I can surprisingly identify occurs in the design of Bismarck's rudders (shown in the photograph at http://www.kbismarck.com/propulsioni.html). The ideal distance between twin rudders might be suggested by images such as http://www.trbimg.com/img-5459649e/turb ... k-20141104. Unfortunately, redesigning the stern to space the rudders at least 10 meters apart will require that water can flow easily to the central propeller. Thus a wider stern will need full scale tank tests. Wide separation the rudders will also imply extra armour around the rudder motor rooms.
The greater beam at the rudders can be compensated by a transom stern because, of course, the KM's staff must have studied HMS Adventure https://naval-encyclopedia.com/ww2/uk/hms-adventure.php and, whilst laughing at the problems of laying mines from such a design, will have taken note of the reduction of wave resistance. It would be nice to imagine that their attachée in Japan had learnt about the potential of bulbous bows to achieve the same. An attractive feature of replacing the graceful shape obvious designed for high speed with a shorter, higher block coefficient shape trying to trick the waves would be that the British, using only dimensions and assuming a British hull form, would calculate a lower standard displacement.
If we want to reassure the British further, we could replace the 320 mm belt with a 300 mm belt and strengthen the scarp to compensate as in H-39 (weight might restrict us to a 140 mm scarp). Then we could encourage a British agent to measure some of the plates before they are installed and ideally see them being fitted. If Bismarck had been shorter than Richelieu and only carried the same belt as Hood, the declared displacement would have been much more convincing.
Finally, if I were a member of Bismarck's crew, I would be worried by the engine rooms for the outer shafts. If one of those were flooded, the consequences would be severe. Might it be possible to make a less symmetric design with them offset and placed one in front of the other? Perhaps we could move Port Boiler Room 1 (second image of http://www.kbismarck.com/propulsioni.html) back and place Starboard Turbine Room to its starboard. Then Starboard Boiler Room 1 remains in position with Port Turbine Room directly to its port side. The row of three boiler rooms 2 remain in position but, alas, we now have only 5 boiler rooms in place. Could we split the remaining two boilers and fit them where Starboard Electrical Plant No. 3 and Port Electrical Plant No. 4 are placed? If there remains space, a generator could perhaps fit into the same room using steam directly from the boiler, which would give that room independent power for fans etc.. We can then fit the electrical plants into the comparatively narrow but long spaces between the turbine rooms and the torpedo bulkhead. One problem is that a shaft will probably go under or through another turbine room. However, that was not a problem with the Midway Class carriers.
Redesigning Bismarck
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hans zurbriggen
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Re: Redesigning Bismarck
Hello Mr. Mostlyharmless,
while I see your points (however all your proposed changes have pros and cons), IMHO main flaw in (Scharnhorst's and) Bismarck's design was KM poor decision to give up Diesel propulsion for large vessels in 1933, coming back to steam and turbines. Researches at MAN were not funded anymore until 1938 (too late): this 5 years gap was an irreparable mistake.
Diesel engines would have given enormous range (even if doing so Bismarck might have been 1 knot slower), much more important than top speed for KM.
DP secondary armament would have been of course very good improvement, if a good automatic gun/mount could have been ready early in war by 1940/1941 (http://www.navweaps.com/Weapons/WNGER_5-45_skc41.php), but I would have retained 6-7 twin turrets per side (24-28 guns in total) to ensure a surface and antiaircraft superior volume of fire (as foreseen by a US Navy post-war report). Weights should not have changed from 6 x 15 cm and 8 x 10,5 cm.
hans
while I see your points (however all your proposed changes have pros and cons), IMHO main flaw in (Scharnhorst's and) Bismarck's design was KM poor decision to give up Diesel propulsion for large vessels in 1933, coming back to steam and turbines. Researches at MAN were not funded anymore until 1938 (too late): this 5 years gap was an irreparable mistake.
Diesel engines would have given enormous range (even if doing so Bismarck might have been 1 knot slower), much more important than top speed for KM.
DP secondary armament would have been of course very good improvement, if a good automatic gun/mount could have been ready early in war by 1940/1941 (http://www.navweaps.com/Weapons/WNGER_5-45_skc41.php), but I would have retained 6-7 twin turrets per side (24-28 guns in total) to ensure a surface and antiaircraft superior volume of fire (as foreseen by a US Navy post-war report). Weights should not have changed from 6 x 15 cm and 8 x 10,5 cm.
hans
Re: Redesigning Bismarck
Hello!
I think that the machinery space would allow a power-plant of 16 MAN M12Z 42/58 diesel engines driving four propellers. These are the same engines as on the Deutschland class, but with 12 cylinders instead of 9 (9480 hp per engine, they were planned for the historical Panzerschiff D in his diesel version, so they should be available). The total would be 144 000 hp after gearing losses instead of the historical 150000. Also, using four smaller propellers instead of three larger ones leads to a loss in efficiency. I would guess top speed would fall by a knot to 29 kt. The diesel power-plant would probably be some 2000 tons heavier. This would have to be compensated by a reduction in fuel from 8294 to 6294 t. However, with this amount of fuel, total range should be 12500 - 13000 NM at 19 kt vs 8525 for the original. The four propeller design should allow steering by different revolutions, as well as a stronger stern. AFAIK, the Deutschland class was capable of running one of its two propellers backwards, and thus was quite maneuverable. I would guess that a four propeller diesel Bismarck would also be more maneuverable. I know that the original could also move propellers backwards, but I think this used the reverse turbines which were much less powerful (I may be wrong here, some clarification from more knowledgeable people would be great).
I would also opt for dual-purpose secondary armament, but go down in caliber instead of up.
The Germans had a 105/65 AA gun firing fixed ammunition. It was bored out to become 127/45 gun firing separate ammunition. These were the standard guns used on German destroyers. The 105/65 twin mount was stabilized in three axles, quite complicated, with low training and elevation speeds and suffered from electrical faults. I would replace both guns with a 120/50 gun firing fixed ammunition. Basically, a bored out 105/65 with the barrel shortened from 6840 to 6000 mm. The barrel would end up slightly longer than the 127/45's 5800 mm. Gun weight should be about 3600 kg - the same as the 127/45. I would use a simpler, and hopefully more reliable dual axle stabilization mount. I would provide it with powerful enough motors to get a training rate of 25 degrees per second (up from 8-10 degrees). Elevation rate should be increased from 10-12 degrees per second to about 15. The mount should have powered ramming and hoists to ensure a high firing rate at all elevations. I would expect a twin mount to weigh the same as the 105/65's mount (27 tons). The gun should fire fixed ammunition with a total round weight of about 34 kg, and shell weight of about 20 kg (similar to the Japanese 120 mm fixed round. The gun can also be viewed as a development of the Japanese 120/45 AA gun). Rate of fire should be in the range of 15-18 rpm, similar to the 105 mm gun. As a result, you (hopefully) get an effective dual purpose gun and mount. The maximum range is now increased to 19500 m at 45 degrees compared to 17400 m for the 127/45 (with maximum elevation of 30 degrees), and the 17700 m for the 105/65 (at 45 degrees). Range is, however, inferior to the Bismarck's 150/55's 23000 m. Secondary battery would consist of 24 120/50 in 12 mounts (instead of 12 x 150, and 16 x 105 mm guns in a total of 14 mounts. The removed 2 mounts should allow space for additional four twin 37 mm AA gun mounts). This would also save about 550 t of topside weight, which can be used for other things.
The other change in armament would be to replace the 37/83 AA gun with army 3.7 cm Flak 36/37. The naval gun was semi-automatic and had a very low rate of fire of about 30 rounds per minute. The army's has a cyclic rate of fire of about 180, and a practical of about 120. This gun would have been a much better option, and was historically available in 1937. With 24 of these guns, the 37 mm Flak battery would be 6 times more powerful than the historical.
A more exotic, and far-fetched option would be to change the aircraft composition. At that point, Germany had Fieseler Fi-167 multi-role carrier aircraft. It was a STOL aircraft with performance similar to the Fi 156. The Fi 156 had a stall speed of 50 kmh (31 mph, 27 kts). This means that with the ship moving at a moderate to high speed against the wind, the Fi 167 would practically be landing vertically. Therefore, it should be possible to land on a small runway at the stern, with turret D turned to the side. The runway may have to protrude a bit to the rear and the sides, but this shouldn't be too much of an issue. Turbulence created by the superstructure would be a problem, but if the Fi 167 was as good as the Fi 156, the aircraft should be fully controllable at 55 km h, so this may not be too much of an issue (I may be wrong here. I know that Admiral Carls proposed the usage of Fi 156 on ships, and that such experiments were carried out, but I don't know the results. I would be grateful if someone can provide some info).
Float-planes can only be used if sea is calm, which is more of an exception rather than a rule in the North Sea, and the North Atlantic. STOL aircraft would be much more useful. The catapult would have to be moved to the stern as well, and the hangar would have to be right in front of turret C (aircraft with folded wings should be able to roll to the back moving by the side, a bit of protruding runway may be needed to facilitate this).
The Fi 167 could also provide a limited CAP. Armament could be increased by 2x20 mm MG/FF cannons with 60 rounds mounted in the top wing. With some aerodynamic clean up (retractable landing gear in a way similar to the Soviet Il-2, retractable rear landing gear, a fully enclosed cockpit, removed support spars at the tail, removed hard-points, etc) top speed could probably improve by at least 10% (from 325 km h to 360 km h, or 202 mph to 225 mph). The goal is to have an aircraft capable of outrunning and outmaneuvering all enemy float-planes. Since a German warship would be surrounded by enemies, the ability to chase away, or shoot down enemy reconnaissance aircraft may be quite important. The British Supermarine Walrus (217 km h/ 135 mph), the French Loire 130 (220 km h/137 mph), the US Vought OS2U Kingfisher (285 km h/171 mph), the US PBY Catalina (315 km h / 196 mph), the British Short Sunderland (340 km h / 210 mph), and the Swordfish (230 km h, 143 mph) would all be in danger. If we can provide Prinz Eugen with at least two Fi 167 (these are bigger than the Ar 196), Bismark and Prinz Eugen could muster between them 6 aircraft for air defense, a nice improvement.
I think that the machinery space would allow a power-plant of 16 MAN M12Z 42/58 diesel engines driving four propellers. These are the same engines as on the Deutschland class, but with 12 cylinders instead of 9 (9480 hp per engine, they were planned for the historical Panzerschiff D in his diesel version, so they should be available). The total would be 144 000 hp after gearing losses instead of the historical 150000. Also, using four smaller propellers instead of three larger ones leads to a loss in efficiency. I would guess top speed would fall by a knot to 29 kt. The diesel power-plant would probably be some 2000 tons heavier. This would have to be compensated by a reduction in fuel from 8294 to 6294 t. However, with this amount of fuel, total range should be 12500 - 13000 NM at 19 kt vs 8525 for the original. The four propeller design should allow steering by different revolutions, as well as a stronger stern. AFAIK, the Deutschland class was capable of running one of its two propellers backwards, and thus was quite maneuverable. I would guess that a four propeller diesel Bismarck would also be more maneuverable. I know that the original could also move propellers backwards, but I think this used the reverse turbines which were much less powerful (I may be wrong here, some clarification from more knowledgeable people would be great).
I would also opt for dual-purpose secondary armament, but go down in caliber instead of up.
The Germans had a 105/65 AA gun firing fixed ammunition. It was bored out to become 127/45 gun firing separate ammunition. These were the standard guns used on German destroyers. The 105/65 twin mount was stabilized in three axles, quite complicated, with low training and elevation speeds and suffered from electrical faults. I would replace both guns with a 120/50 gun firing fixed ammunition. Basically, a bored out 105/65 with the barrel shortened from 6840 to 6000 mm. The barrel would end up slightly longer than the 127/45's 5800 mm. Gun weight should be about 3600 kg - the same as the 127/45. I would use a simpler, and hopefully more reliable dual axle stabilization mount. I would provide it with powerful enough motors to get a training rate of 25 degrees per second (up from 8-10 degrees). Elevation rate should be increased from 10-12 degrees per second to about 15. The mount should have powered ramming and hoists to ensure a high firing rate at all elevations. I would expect a twin mount to weigh the same as the 105/65's mount (27 tons). The gun should fire fixed ammunition with a total round weight of about 34 kg, and shell weight of about 20 kg (similar to the Japanese 120 mm fixed round. The gun can also be viewed as a development of the Japanese 120/45 AA gun). Rate of fire should be in the range of 15-18 rpm, similar to the 105 mm gun. As a result, you (hopefully) get an effective dual purpose gun and mount. The maximum range is now increased to 19500 m at 45 degrees compared to 17400 m for the 127/45 (with maximum elevation of 30 degrees), and the 17700 m for the 105/65 (at 45 degrees). Range is, however, inferior to the Bismarck's 150/55's 23000 m. Secondary battery would consist of 24 120/50 in 12 mounts (instead of 12 x 150, and 16 x 105 mm guns in a total of 14 mounts. The removed 2 mounts should allow space for additional four twin 37 mm AA gun mounts). This would also save about 550 t of topside weight, which can be used for other things.
The other change in armament would be to replace the 37/83 AA gun with army 3.7 cm Flak 36/37. The naval gun was semi-automatic and had a very low rate of fire of about 30 rounds per minute. The army's has a cyclic rate of fire of about 180, and a practical of about 120. This gun would have been a much better option, and was historically available in 1937. With 24 of these guns, the 37 mm Flak battery would be 6 times more powerful than the historical.
A more exotic, and far-fetched option would be to change the aircraft composition. At that point, Germany had Fieseler Fi-167 multi-role carrier aircraft. It was a STOL aircraft with performance similar to the Fi 156. The Fi 156 had a stall speed of 50 kmh (31 mph, 27 kts). This means that with the ship moving at a moderate to high speed against the wind, the Fi 167 would practically be landing vertically. Therefore, it should be possible to land on a small runway at the stern, with turret D turned to the side. The runway may have to protrude a bit to the rear and the sides, but this shouldn't be too much of an issue. Turbulence created by the superstructure would be a problem, but if the Fi 167 was as good as the Fi 156, the aircraft should be fully controllable at 55 km h, so this may not be too much of an issue (I may be wrong here. I know that Admiral Carls proposed the usage of Fi 156 on ships, and that such experiments were carried out, but I don't know the results. I would be grateful if someone can provide some info).
Float-planes can only be used if sea is calm, which is more of an exception rather than a rule in the North Sea, and the North Atlantic. STOL aircraft would be much more useful. The catapult would have to be moved to the stern as well, and the hangar would have to be right in front of turret C (aircraft with folded wings should be able to roll to the back moving by the side, a bit of protruding runway may be needed to facilitate this).
The Fi 167 could also provide a limited CAP. Armament could be increased by 2x20 mm MG/FF cannons with 60 rounds mounted in the top wing. With some aerodynamic clean up (retractable landing gear in a way similar to the Soviet Il-2, retractable rear landing gear, a fully enclosed cockpit, removed support spars at the tail, removed hard-points, etc) top speed could probably improve by at least 10% (from 325 km h to 360 km h, or 202 mph to 225 mph). The goal is to have an aircraft capable of outrunning and outmaneuvering all enemy float-planes. Since a German warship would be surrounded by enemies, the ability to chase away, or shoot down enemy reconnaissance aircraft may be quite important. The British Supermarine Walrus (217 km h/ 135 mph), the French Loire 130 (220 km h/137 mph), the US Vought OS2U Kingfisher (285 km h/171 mph), the US PBY Catalina (315 km h / 196 mph), the British Short Sunderland (340 km h / 210 mph), and the Swordfish (230 km h, 143 mph) would all be in danger. If we can provide Prinz Eugen with at least two Fi 167 (these are bigger than the Ar 196), Bismark and Prinz Eugen could muster between them 6 aircraft for air defense, a nice improvement.
Last edited by StanS on Mon Jan 01, 2024 11:37 am, edited 1 time in total.
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Thorsten Wahl
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Re: Redesigning Bismarck
Dual purpose 12,8 cm triaxially stabilised fully enclosed turret (Rheinmetall) Autoloader
two guns 12,8 cm SK C/40 IV=900 m/s
-10-+85 degrees
weight 88 t therof 38 t armour
automatised ammunition feed
loading cycle 4-4,5 sec
same was available in 10,5 cm
two guns
IV 900 m/s
weight 43,1t therof armour 12,5 t
loading cycle 3-3,5 sec
to kill a aicraft both shells should be equally effective in number of shells fired for a downed aircraft.
as the 10, 5cm shell weights only about half of the 12,8 cm shell a ship may carry double the number of 12,8 cm shells at the same ammunition weight
and ROF was 20-30% higher
If intended role is more anti aircraft id prefer the 10,5 cm
But it would have to be weighed up
against ships(DD size) the usefulness of 10,5 cm projectiles is very limited not to say questionable
US 5" shells proved succesful against japanes destroyers and cruisers.
i would go with the final decision for a uniform 12,8 cm seconday battery
- Screenshot 2024-01-02 072847.png (253.32 KiB) Viewed 57546 times
two guns 12,8 cm SK C/40 IV=900 m/s
-10-+85 degrees
weight 88 t therof 38 t armour
automatised ammunition feed
loading cycle 4-4,5 sec
same was available in 10,5 cm
two guns
IV 900 m/s
weight 43,1t therof armour 12,5 t
loading cycle 3-3,5 sec
to kill a aicraft both shells should be equally effective in number of shells fired for a downed aircraft.
as the 10, 5cm shell weights only about half of the 12,8 cm shell a ship may carry double the number of 12,8 cm shells at the same ammunition weight
and ROF was 20-30% higher
If intended role is more anti aircraft id prefer the 10,5 cm
But it would have to be weighed up
against ships(DD size) the usefulness of 10,5 cm projectiles is very limited not to say questionable
US 5" shells proved succesful against japanes destroyers and cruisers.
i would go with the final decision for a uniform 12,8 cm seconday battery
Last edited by Thorsten Wahl on Tue Jan 02, 2024 2:04 pm, edited 2 times in total.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
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Thorsten Wahl
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Re: Redesigning Bismarck
3,7 cm Flak
the navy already had introduced the 3,7 cm SK C/36 basically the same technical data(IV/ROF...) as the later 3,7 cm M43 but this gun was somwhat expensive.
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loading cycle of the 3,7 cm SKC/30 was somewhat above 1 sec
so max ROF was according KM manuals 55 RPM
sustained ROF 30 RPM
manual ammunition feed accross the deck proved problematic.
the navy already had introduced the 3,7 cm SK C/36 basically the same technical data(IV/ROF...) as the later 3,7 cm M43 but this gun was somwhat expensive.
-----------------------------------------------------------------------------------
loading cycle of the 3,7 cm SKC/30 was somewhat above 1 sec
so max ROF was according KM manuals 55 RPM
sustained ROF 30 RPM
manual ammunition feed accross the deck proved problematic.
Last edited by Thorsten Wahl on Tue Jan 02, 2024 2:03 pm, edited 1 time in total.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
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Thorsten Wahl
- Senior Member
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- Joined: Mon Apr 27, 2009 4:17 pm
Re: Redesigning Bismarck
Regarding propulsion
my personal choice would be twelve "V-Motors" 15.000 WPS each(180.000 WPS total) and four screws.
the motors require about the same area but significanty less heigt compared to Bismarcks machinery spaces. But size of Bismarcks machinery probably came from a "overbording???" redundancy approach.
Two main rudders directly in the propeller flow to improve steerability at low speeds. Rudder blades with somewhat increased area maybe 30m².
(tactical diameter original Bismarck was already about 650 - 700 m at hard rudder.
Despite loss in propulsion efficiency (about 6 percent) compared to an 3 screw design. Total machinery weight about 4000 t.(compared to Bismarcks 2800 t dry weight)
Iowas machinery weighed about 4400 t for 212000 HPs(without overload).
Fuel consumption about 220 g/WPS and hour at maximum load. Compared to about 300 g/WPS and hour for turbines and significant decrease in relative consumption(per WPS and hour) at partial load compared to turbines.
Even stronger structures may fail when exposed to underkeel explosions. And Bismarcks stern survived the torpedodetonation and some battle damage from heavy shells. How much weight do you want to invest? is it worth the additional weight?
if a transom stern was built in, this area would be completly non existent
my personal choice would be twelve "V-Motors" 15.000 WPS each(180.000 WPS total) and four screws.
the motors require about the same area but significanty less heigt compared to Bismarcks machinery spaces. But size of Bismarcks machinery probably came from a "overbording???" redundancy approach.
Two main rudders directly in the propeller flow to improve steerability at low speeds. Rudder blades with somewhat increased area maybe 30m².
(tactical diameter original Bismarck was already about 650 - 700 m at hard rudder.
Despite loss in propulsion efficiency (about 6 percent) compared to an 3 screw design. Total machinery weight about 4000 t.(compared to Bismarcks 2800 t dry weight)
Iowas machinery weighed about 4400 t for 212000 HPs(without overload).
Fuel consumption about 220 g/WPS and hour at maximum load. Compared to about 300 g/WPS and hour for turbines and significant decrease in relative consumption(per WPS and hour) at partial load compared to turbines.
the same is true for a 3 propeller design.The four propeller design should allow steering by different revolutions,...
the stern area of Bismarck was about 10 m long. contribution to ships displacement about 100 t. "whopping" 2 (in words "two") promille from 50000 t displacement...as well as a stronger stern.
Even stronger structures may fail when exposed to underkeel explosions. And Bismarcks stern survived the torpedodetonation and some battle damage from heavy shells. How much weight do you want to invest? is it worth the additional weight?
if a transom stern was built in, this area would be completly non existent
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
Re: Redesigning Bismarck
Hello.
Here are some points from "Battleship Bismarck A Design and Operational History" by William H. Garzke, Robert O. Dulin, Amd William Jurens (More details are in the book).
- Bismarck's propellers were of convergent design and provided only a weak turning moment. Maintaining course without the rudder was impossible.
- The central propeller lead to a longer stern overhang. This lead to structural weaknesses and problems with the armor protection around the steering gear rooms. It also made the stern more vulnerable to explosion damage (torpedoes) due to a "whipping phenomenon" (This is what I meant when I mentioned a stronger stern).
- Having a four propeller design would have increased maneuverability by one third.
I like your dual-purpose mount proposal, I'll update my earlier post.
Cheers,
Stan
the same is true for a 3 propeller design.
I'm not a naval engineer, so I can't really say how efficient a three propeller design can be made regarding steering by different revolutions.the stern area of Bismarck was about 10 m long. contribution to ships displacement about 100 t. "whopping" 2 (in words "two") promille from 50000 t displacement
Even stronger structures may fail when exposed to underkeel explosions. And Bismarcks stern survived the torpedo detonation and some battle damage from heavy shells. How much weight do you want to invest? is it worth the additional weight?
Here are some points from "Battleship Bismarck A Design and Operational History" by William H. Garzke, Robert O. Dulin, Amd William Jurens (More details are in the book).
- Bismarck's propellers were of convergent design and provided only a weak turning moment. Maintaining course without the rudder was impossible.
- The central propeller lead to a longer stern overhang. This lead to structural weaknesses and problems with the armor protection around the steering gear rooms. It also made the stern more vulnerable to explosion damage (torpedoes) due to a "whipping phenomenon" (This is what I meant when I mentioned a stronger stern).
- Having a four propeller design would have increased maneuverability by one third.
I like your dual-purpose mount proposal, I'll update my earlier post.
Cheers,
Stan
Last edited by StanS on Wed Jan 03, 2024 8:49 pm, edited 2 times in total.
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Thorsten Wahl
- Senior Member
- Posts: 922
- Joined: Mon Apr 27, 2009 4:17 pm
Re: Redesigning Bismarck
How great is the ruddereffect from screws for a 4 screw ship. Do you have samples? At least one...would be welcome.- Bismarck's propellers were of convergent design and provided only a weak turning moment. .
This appears wrong, Bismarck was able to maintain a north westerly general (zig zag) course despite heavy seastate, wind up to hurricane strenght and considerable ruddereffect from the damaged rudders.Maintaining course without the rudder was impossible
You may have a look at Bismarcks track during the final battle.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
Re: Redesigning Bismarck
Hi Thorsten,
Some might say "if only there had been a powerful South-South Easterly gale instead, she could have made an average course which would have got her firstly into Luftwaffe protection and eventually friendly landfall..........but there wasn't.
All the best to all for the New Year
wadinga
I think it was not despite but indeed because of the weather on her bow balancing the turning effect of the jammed rudder(s) than she was able to maintain any kind of vaguely stable course. If there had been no wind and surging waves she would inevitably have circled helplessly round and round in circles.This appears wrong, Bismarck was able to maintain a north westerly general (zig zag) course despite heavy seastate, wind up to hurricane strenght and considerable ruddereffect from the damaged rudders.
Some might say "if only there had been a powerful South-South Easterly gale instead, she could have made an average course which would have got her firstly into Luftwaffe protection and eventually friendly landfall..........but there wasn't.
All the best to all for the New Year
wadinga
"There seems to be something wrong with our bloody ships today!"
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Bill Jurens
- Moderator
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- Location: USA
Re: Redesigning Bismarck
Regarding steering issues, two main principles apply:
a) In general it's impossible, or nearly so, to 'steer' with propellers only as to do so would require constant 'riding' of the propeller speeds etc. in order to adjust to slight variations in wind and wave. In the same way that one typically has to manually and frequently adjust the rudder angle of a regular ship in order to keep her on course -- now done mostly automatically -- one would have to constantly 'tweak' the propeller revolutions in order to keep anything like a constant course. Not easy to do.
b) One must remember that in order to make large or rapid course changes with propellers only, one would have to often back at least one of the propellers, or at least slow it considerably. Backing or slowing increases drag considerably, and slows the ship quite a bit. A ship going full-astern on one side and full-ahead on the other would be using full power, but -- in practical terms -- going almost nowhere.
Ships sometimes maneuver in close quarters at very low speeds by 'twisting ship', which usually entails backing one set of screws and going ahead on the other set, but again, this usually involves maneuvers where fore and aft movement is relatively small.
Steering using propellers without rudders? Possible in unusual circumstances, but practically useless. Which is why ships have rudders in the first place. If they weren't really needed, they would -- like sails -- have been discarded centuries ago.
Bill Jurens
a) In general it's impossible, or nearly so, to 'steer' with propellers only as to do so would require constant 'riding' of the propeller speeds etc. in order to adjust to slight variations in wind and wave. In the same way that one typically has to manually and frequently adjust the rudder angle of a regular ship in order to keep her on course -- now done mostly automatically -- one would have to constantly 'tweak' the propeller revolutions in order to keep anything like a constant course. Not easy to do.
b) One must remember that in order to make large or rapid course changes with propellers only, one would have to often back at least one of the propellers, or at least slow it considerably. Backing or slowing increases drag considerably, and slows the ship quite a bit. A ship going full-astern on one side and full-ahead on the other would be using full power, but -- in practical terms -- going almost nowhere.
Ships sometimes maneuver in close quarters at very low speeds by 'twisting ship', which usually entails backing one set of screws and going ahead on the other set, but again, this usually involves maneuvers where fore and aft movement is relatively small.
Steering using propellers without rudders? Possible in unusual circumstances, but practically useless. Which is why ships have rudders in the first place. If they weren't really needed, they would -- like sails -- have been discarded centuries ago.
Bill Jurens
Re: Redesigning Bismarck
Keeping in mind what Bill Jurens said, I guess I have to ditch the idea of steering with propellers, no matter the rudder effects.Thorsten Wahl wrote: ↑Thu Jan 04, 2024 12:54 pm How great is the rudder effect from screws for a 4 screw ship. Do you have samples? At least one...would be welcome.
Tho only option left is to improve the rudder system. I like the Littorio's three rudder design. Littorio had one main (38 square meters) and two auxiliary (16 square meters each) rudders. The auxiliary rudders were placed some 25 meters in front of the main rudder. All rudders had separate motors, and this allowed various combinations, like:
- auxiliary rudders at 0° angle and use of only the main rudder;
- all three rudders used together at the same settings;
- use of the main rudder and only one of the auxiliary rudders;
- use of the auxiliary udders only.
(Source: "The Littorio Class Italy’s Last and Largest Battleships 1937–1948" by Erminio Bagnasco and Augusto de Toro)
On March 28, 1941. Vittorio Veneto was torpedoed by a British aircraft. The torpedo jammed her port auxiliary rudder. She still retained the ability to maneuver as her starboard auxiliary rudder and main rudder were still operable. This allowed her to escape a pursuing battleship group and return to port.
Last edited by StanS on Fri Jan 05, 2024 10:29 am, edited 1 time in total.
Re: Redesigning Bismarck
We have the example of USS Intrepid (Essex class carrier) being able to steer with her props after a jammed rudder via a torpedo hit:Bill Jurens wrote: ↑Fri Jan 05, 2024 4:40 am Regarding steering issues, two main principles apply:
a) In general it's impossible, or nearly so, to 'steer' with propellers only as to do so would require constant 'riding' of the propeller speeds etc. in order to adjust to slight variations in wind and wave. In the same way that one typically has to manually and frequently adjust the rudder angle of a regular ship in order to keep her on course -- now done mostly automatically -- one would have to constantly 'tweak' the propeller revolutions in order to keep anything like a constant course. Not easy to do.
b) One must remember that in order to make large or rapid course changes with propellers only, one would have to often back at least one of the propellers, or at least slow it considerably. Backing or slowing increases drag considerably, and slows the ship quite a bit. A ship going full-astern on one side and full-ahead on the other would be using full power, but -- in practical terms -- going almost nowhere.
Ships sometimes maneuver in close quarters at very low speeds by 'twisting ship', which usually entails backing one set of screws and going ahead on the other set, but again, this usually involves maneuvers where fore and aft movement is relatively small.
Steering using propellers without rudders? Possible in unusual circumstances, but practically useless. Which is why ships have rudders in the first place. If they weren't really needed, they would -- like sails -- have been discarded centuries ago.
Bill Jurens
http://www.researcheratlarge.com/Ships/ ... ering.html
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Bill Jurens
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Re: Redesigning Bismarck
Dunmunro wrote:
"We have the example of USS Intrepid (Essex class carrier) being able to steer with her props after a jammed rudder via a torpedo hit..."
Yes. I'm aware of cases like this, which is why I qualified my statements, e.g. "'...In general, it's impossible, or nearly so...", and somewhat later:
"... Steering using propellers without rudders?" Possible in unusual circumstances..."
Bismarck, far from local repair facilities, alone, in poor weather, likely low on fuel, and in what might be best described as an "extremely hostile environment" would have been unable to undertake most or all of the jury-rigged solutions that Intrepid employed.
Bill Jurens
"We have the example of USS Intrepid (Essex class carrier) being able to steer with her props after a jammed rudder via a torpedo hit..."
Yes. I'm aware of cases like this, which is why I qualified my statements, e.g. "'...In general, it's impossible, or nearly so...", and somewhat later:
"... Steering using propellers without rudders?" Possible in unusual circumstances..."
Bismarck, far from local repair facilities, alone, in poor weather, likely low on fuel, and in what might be best described as an "extremely hostile environment" would have been unable to undertake most or all of the jury-rigged solutions that Intrepid employed.
Bill Jurens
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Thorsten Wahl
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Re: Redesigning Bismarck
Intrepid damage report:dunmunro wrote: ↑Sat Jan 06, 2024 7:20 pm We have the example of USS Intrepid (Essex class carrier) being able to steer with her props after a jammed rudder via a torpedo hit:
http://www.researcheratlarge.com/Ships/ ... ering.html
"The net result of this damage insofar as ship control was concerned was to create the permanent effect of approximately 6½° left rudder. The INTREPID had the advantage of having made the standardization trials for the CV-9 class. One of the tests conducted was to lock an outboard shaft on one side, go ahead full power on the two shafts on the other side and determine the rudder angle necessary to maintain a steady course. This rudder angle during the trial proved to be approximately 6½°."
In case Bismarck the steering effect was in the order of possibly 15 degrees (but only one rudder - rudderindicator). Despite being accompanied by several own ships with no interference by enemy, much better weather and wavemotion and tempoary repairs and optimising sail area Intrepid lost several times its steeerability.
one can expect the main rudder overcoming the effect of an auxiliary rudder.allowed various combinations, like:
- auxiliary rudders at 0° angle and use of only the main rudder;
- all three rudders used together at the same settings;
- use of the main rudder and only one of the auxiliary rudders;
- use of the auxiliary udders only.
(Source: "The Littorio Class Italy’s Last and Largest Battleships 1937–1948" by Erminio Bagnasco and Augusto de Toro)
...The torpedo jammed her port auxiliary rudder.
But how much ruddereffect from a damaged main rudder the auxiliary rudders were able to overcome?
Whats the turning radius of Littoro class with one auxilliary rudder at maximum and the other two rudders in neutral position.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
Re: Redesigning Bismarck
"After having analyzed and for various reasons excluded other options (for example, two side-by-side stern rudders) the choice fell upon a centreline stern rudder and two smaller independent lateral rudders positioned abaft the two outboard propellers, a full 25 meters from the main rudder. This was intended to avoid the possibility that both the main rudder and the auxiliary rudders could be damaged by the same underwater blast; in addition, the arrangement of the two auxiliary rudders in the ‘wake cones’ of the outboard propellers increased their effectiveness so that, if necessary, they could counteract the action of the main rudder in the event that it jammed at a considerable angle." (The Littorio Class by Erminio Bagnasco)Thorsten Wahl wrote: ↑Sun Jan 07, 2024 6:39 pm one can expect the main rudder overcoming the effect of an auxiliary rudder.
But how much rudder effect from a damaged main rudder the auxiliary rudders were able to overcome?
Whats the turning radius of Littoro class with one auxilliary rudder at maximum and the other two rudders in neutral position.
The book mentions that "diameter of the turning circle" with the main rudder at 40 degrees was 836 m at 20 kt, and 895 m at 29.5. I couldn't find information about turning radius with only one auxiliary rudder.