Redesigning Bismarck

[dunmunro]

Basically, you can have a dual rudder/larger rudder with better maneuverability with an increase in drag, but then a jammed rudder is harder to overcome using the props.

[Steve Crandell]

IIRC when the IJN tested Yamato's aux rudder they couldn't turn the ship at all with the main rudder centered. It was essentially useless.

[wadinga]

Hi All,

It often forgotten that ships operate at the boundary layer of two fluids, one vastly less dense than the other. However air can move at far higher velocities and thus exert considerable effect on the course of a ship through wind resistance (windage). The larger the hull and superstructure, particularly in the case of aircraft carriers, the more important windage is. Video evidence of the chaos modern, monstrous, "barn-door" cruise liners can get into when manoeuvring in harbour in a strong breeze, despite modern innovations like powerful bow and stern thrusters, is readily available on the Web.

It was found by going ahead standard on one side and back two-thirds to full on the other, that the yaw could be reduced and a reasonably accurate course could be steered at a speed of advance of four to five knots. Due to a strong Kona wind blowing.........

This case of USS Intrepid shows how wind on one bow could be balanced by unequal thrust from the props (equivalent to having a jammed rudder). In her case the desired course back to Pearl was achievable, whereas Bismarck could only go in the opposite direction to that towards safety.

The Kriegsmarine had their own ideas for redesigned Bismarcks in the H-39 through H-44 designs, sketches of which are included in Siegfried Breyer's works. These "pipedream" designs still have the separate surface and AA secondary armaments of the Bismarcks but incorporate improbable and perhaps impractical hull fins extending outboard aft to protect props and rudders. There seems to have been little consideration that such additional "deadwood" would have rendered the rudders relatively ineffectual.

Speaking of ineffectual, the auxiliary rudders of the Littorios must have had quite disturbed waterflow due to being close to the hull side. The ideal place for a rudder is right aft where the waterflow from port and starboard sides comes back together and from where it can exert steering effort through a very long "lever" against the tendency of the hull to go straight ahead. I expect this is why Torsten would like to know whether two tiddlers could have overcome any problems with the main rudder.

All the best

wadinga

[Mostlyharmless]

Having started this, I felt that I shouldn't hide away even if I don't know anything about designing ships. The most significant question seems to be whether to stay with the steam turbine propulsion or to go to Diesel and the related issue is whether to keep three shafts or go to four.

The four shaft choice obviously allows one to use two rudders as shown in the image of USS Abraham Lincoln that I linked to above. The only Post WW2 three shaft design that may be relevant was that of the British CVA-01 https://web.archive.org/web/20121107082 ... /cva01.htm which has a similar beam and draft to Bismarck but is longer and has a greater displacement. This was planned to make 30 knots with only 135,000 shp but perhaps propellers had improved. CVA-01 was designed to have 3 rudders but not in the Littorio arrangement as shown in the drawing from D K Brown and George Moore. I suspect that the CVA-01 design is the best 3 shaft design. The snag that didn't worry the CVA-01 designers is needing to carry armour for three rudder motor rooms.

[paul.mercer]

Hi All,

It often forgotten that ships operate at the boundary layer of two fluids, one vastly less dense than the other. However air can move at far higher velocities and thus exert considerable effect on the course of a ship through wind resistance (windage). The larger the hull and superstructure, particularly in the case of aircraft carriers, the more important windage is. Video evidence of the chaos modern, monstrous, "barn-door" cruise liners can get into when manoeuvring in harbour in a strong breeze, despite modern innovations like powerful bow and stern thrusters, is readily available on the Web.

It was found by going ahead standard on one side and back two-thirds to full on the other, that the yaw could be reduced and a reasonably accurate course could be steered at a speed of advance of four to five knots. Due to a strong Kona wind blowing.........

This case of USS Intrepid shows how wind on one bow could be balanced by unequal thrust from the props (equivalent to having a jammed rudder). In her case the desired course back to Pearl was achievable, whereas Bismarck could only go in the opposite direction to that towards safety.

The Kriegsmarine had their own ideas for redesigned Bismarcks in the H-39 through H-44 designs, sketches of which are included in Siegfried Breyer's works. These "pipedream" designs still have the separate surface and AA secondary armaments of the Bismarcks but incorporate improbable and perhaps impractical hull fins extending outboard aft to protect props and rudders. There seems to have been little consideration that such additional "deadwood" would have rendered the rudders relatively ineffectual.

Speaking of ineffectual, the auxiliary rudders of the Littorios must have had quite disturbed waterflow due to being close to the hull side. The ideal place for a rudder is right aft where the waterflow from port and starboard sides comes back together and from where it can exert steering effort through a very long "lever" against the tendency of the hull to go straight ahead. I expect this is why Torsten would like to know whether two tiddlers could have overcome any problems with the main rudder.

All the best

wadinga

Hi Wadinga
Out of interest, didn't the two 'Nelsons' have the same problem manoeuvring in a strong wind?

[chuckfan3@gmail.com]

Hi All,

It often forgotten that ships operate at the boundary layer of two fluids, one vastly less dense than the other. However air can move at far higher velocities and thus exert considerable effect on the course of a ship through wind resistance (windage). The larger the hull and superstructure, particularly in the case of aircraft carriers, the more important windage is. Video evidence of the chaos modern, monstrous, "barn-door" cruise liners can get into when manoeuvring in harbour in a strong breeze, despite modern innovations like powerful bow and stern thrusters, is readily available on the Web.

It was found by going ahead standard on one side and back two-thirds to full on the other, that the yaw could be reduced and a reasonably accurate course could be steered at a speed of advance of four to five knots. Due to a strong Kona wind blowing.........

This case of USS Intrepid shows how wind on one bow could be balanced by unequal thrust from the props (equivalent to having a jammed rudder). In her case the desired course back to Pearl was achievable, whereas Bismarck could only go in the opposite direction to that towards safety.

The Kriegsmarine had their own ideas for redesigned Bismarcks in the H-39 through H-44 designs, sketches of which are included in Siegfried Breyer's works. These "pipedream" designs still have the separate surface and AA secondary armaments of the Bismarcks but incorporate improbable and perhaps impractical hull fins extending outboard aft to protect props and rudders. There seems to have been little consideration that such additional "deadwood" would have rendered the rudders relatively ineffectual.

Speaking of ineffectual, the auxiliary rudders of the Littorios must have had quite disturbed waterflow due to being close to the hull side. The ideal place for a rudder is right aft where the waterflow from port and starboard sides comes back together and from where it can exert steering effort through a very long "lever" against the tendency of the hull to go straight ahead. I expect this is why Torsten would like to know whether two tiddlers could have overcome any problems with the main rudder.

All the best

wadinga

For whatever it’s worth, The Soviet project 23 sovietskii class battleships had a three shaft arrangement like Bismarck, and were originally intended to have a three rudder arrangement similar to littorio, with a centerline main rudder, and an auxiliary rudder considerably farther forward behind each wing propellers. The Soviets did extensive model tank tests and determined the auxiliary rudders can’t overcome a jammed main rudder, but if the main rudder is not there, the auxiliary rudders by themselves were able to provide the ship with adequate turning circle. Because the auxiliary rudders were located considerable farther forward then the center propeller, they were separated from each other by the deadwood, so they are unlikely to be disabled by a single hit. So soviets deleted the main rudder, leaving projekt 23 with just the two auxiliary rudders. The center propeller looks lonesome with no rudder behind it.

[chuckfan3@gmail.com]

Rather than assuming a kind of redesign that deviates substantially from German design practice, such as a wide transom stern, I think a much more plausible design improvement intended to lessen the ship’s vulnerability to rudder damage is the installation of one or two Voith Schneider propellers under the keel forward of the citadel. The Germans included two voith Schneider propellers in the Graf Zeppelin. Voith Schneider propeller spins about a vertical axis and, like a helicopter rotor, is able to deliver thrust in any desired direction by varying the pitch of the vertical blades cyclically.

A Voith Schneider prop forwards would be able to deliver lateral thrust to generate the turning moments to counteract a jammed main rudder, and it could vary the magnitude and direction of the thrust quickly by changing the cyclic pitch, without needing to constantly fine tuning the RPM as steering with main engine would.

[StanS]

I'm thinking about optimizing the design in terms of scaling it down.

I looked at some machinery plans for Deutschland, and came to the conclusion that a unit of 4 MAN M12Z 42/58s, together with the Vulcan gearbox between them should need about 35 x 5.8 x 6.2 m of space (L x W x H). In addition, a new room with a length of about 11 m would be necessary for 2 MAN M6Z 42/58 auxiliary engines, electric generators, and other equipment.

( A lot of interesting drawings here: https://drive.google.com/drive/folders/ ... uCxWLS9HXW )

So, a power-plant of 4 such units side by side should need only 46 x 23.2 x 6.2 m. I think this should allow 4 15" twin turrets to be fitted in a shorter citadel and ship (well, placing all units side by side may not be the brightest idea, but they can be spread over, let's say 60 m). If we scale Bismarck down to 93%, we get a 232.5 x 33.5 m ship, about as long as Scharnhorst, but 3.5 m wider.

This thread https://forum-marinearchiv.de/smf/index ... ic=30661.0 suggests a ship ~220 m long, 32.76 m wide, with side height 13.65 m. The ship has 4 x 2 380/50, 6 x 2 150/55, 6 x 2 105/65. Standard displacement is 31 830 t, design ~35,500 t, with a draft of 8.75 m. The full displacement is 39175 t, with a draft of 9.51 m. The ship has an immunity zone between 13,750 m (15,000 yds) and 22,750 m (25,000 yds) with some compromises compared to Bismarck's protection (the author tried to fit in within 30000 t standard displacement). The power-plant is steam turbines, 93000 hp, and speed is 27 kt. The bunker capacity is around 7,026 cbm, enough for 9760 NM at 19 kts. I would guess that a diesel power-plant would increase the standard displacement to about 35000 t, and the full to ~42000 t with a draft of 10 m. This particular version would have too low free-board, and not be very suitable for action in the North Atlantic.

However, the overall idea of getting a ship in-between Bismarck and Scharnhorst, to replace them both looks appealing to me, especially if she can be armed with 4 x 2 380/52, and 12 x 2 127/45 in DP mounts. I think that such a design could get 30+ knots out of the 144000 hp diesel power-plant, have a great range, be lower in price, easier to build, we get 4 ships armed with 15" guns instead of two, easier logistics, etc.

[wadinga]

Hi All,

Breyer describes the proposed power plants for the H class behemoths: mainly employing MAN diesels for cruising/endurance, with steam turbines for extra tactical speed. After an earlier aborted cruiser design, there were no more pure diesel-driven proposals, based presumably on the pocket battleships' difficulties and experience.

H-41, the last battleship seriously considered for production had eight MAN diesels totalling 165,000shp, four each driving two outer shafts and either a single or in later A and B designs 55-75,000shp two turbine driven props. As size ballooned in H-44 so did the power requirement, H-42 requiring 280,000 shp from a four screw design again with diesels on the outer screws and turbines for the inner.

Nelsol and Rodol which were the nicknames for HMS Nelson and Rodney, based on their silhouettes' resemblance to humble RFA oilers, were indeed considered a handful when manoeuvring slowly in adverse winds, due to windage on their massive, aft mounted superstructures.

Which brings us to the Voith Schneider propellers on Graf Zeppelin. These are primarily low speed manoeuvring aids employed on tugs or cross harbour ferries. I personally believe these were only considered for the afore-mentioned problem of getting a carrier alongside in adverse winds, and would have been useless vulnerable drag at anything higher than dead slow speeds and almost certainly would have been retracted into the hull once harbour was left behind. A fleet carrier needs something like 30 knots to get suitable wind over the deck, and I'm not sure a projecting V-S prop would take that kind of treatment. In the Korean War novel "The Bridges at Toko-Ri" James Michener describes the horror of prop-aircraft pilots that a lazy carrier captain used their strapped-down planes on deck to provide sideways thrust, potentially damaging engines by overheating and thus endangering their lives for subsequent missions.

Today, most big vessels employ tunnel thrusters, conventional props mounted athwartships in a tunnel going from one side of the hull at bow and stern to the other in order to give lateral thrust when going alongside. However as those cruise-ship crunches attest, windage can sometimes overpower even these aids to low speed manoeuvring.

All the best

wadinga

[hans zurbriggen]

Hello,
H-39 class battleships (six of them were actually ordered in summer 1939 by KM and two of them were even laid out, before works were cancelled at war start) were last fully designed and detailed KM BB's, AFAIK. They had a pure Diesel propulsion plant for 29-30 knots speed (12 MAN M9Z 65/95 from 1938 design, 4 on each of 3 shafts, for 13.750 hp each and 165.000 hp total), despite unfortunate interruption in MAN researches from 1933 till 1938.

At class H-39 design time, Panzerschiffe engines had already proved to be reliable, performing and easy to maintain, after initial problems (due mainly to foundation weakness, not much to engine problems) and Admiral Scheer successful cruise (1940/41) would have definitely confirmed that Diesel were much better than steam turbines for commerce raiders, giving class H-39 only 1 knot less top speed than Bismarcks vs much higher range.

I don't know why, after 1940, KM came back to steam (in just a 'draft' design for class H-41 and later only in very high-level, unlikely sketches, never approved); I suspect that steam lobby was still very powerful inside different KM branches. Mixed Diesel/turbines solution would have been more difficult to manage and to maintain aboard, while rapid evolution of MAN engines (see V12Z 32/58, 15.600 hp each from 1939 and later turbocharged V12Z 32/44, very small, 16.000 hp) would have guaranteed speed too.

hans

[wadinga]

Hi All,

The bitter conflict between diesel and steam enthusiasts in the Kriegsmarine was at a crescendo when the H-39 design was underway. Reading Koop and Schmolke's Pocket Battleships of the Deutschland class it is suggested their diesels were bedevilled by excessive demands for low weight and installation on flimsy foundations. MAN were no longer in receipt of Kriegsmarine support from 1933 onwards but were free to develop what they wanted.

The book Plan Z (David Wragg) says Plan Z envisaged the heavy battleships, not as ocean raiders themselves, but as a powerful escort to protect the 12 diesel powered P-class Panzerschiffe/ heavy cruisers past the RN's blockade and out into the world's oceans, avoiding the High Seas Fleets' WWI problem of the geographical trap of the North Sea.

A previous thread here from 2007 said:

Based on these, a V-Version (type VZ 42/58) was developed and build. This engine made a 200 hour endurance run at 10000 hp in 1939.

Some engines for the H-class battleships were also build. Some parts like a piston with connecting rod are on display in museums. Each shaft should have been driven by four 9-cylinder (Type MZ 65/95) motors with a combined power of 50000 to 55000 shp. Therefore a single engine produced between 13400 and 15000 hp (without gearing losses).

A different engine was build [sic] and tested during WW2. It's a 24-cylinder-V-engine (type ZV 32/44) producing 10000 hp (endurance), 12600 hp (max) and 15000 hp with an exhaust-turbo-charger which allowed a weight to power ratio of 4 kg/hp. Six of these engine were planned to power the destroyer Z51. One engine is at display at Sinsheim.

These engines for H-39 would have meant a doubling of individual output compared with the Panzerschiffe types, and thus surely represent something of a major engineering gamble. K & S mention Lutzow being operationally unavailable because of unreliable diesels in July 1943, having to rely for harbour power supply from Dithmarschen or other ships. They say after the successful cruise Scheer spent April 1941 through July in dockyard hands and after working-up and a truncated deployment to Norway, the ship was back in Hamburg by September for urgent engine repairs.

K & S quote Konteradmiral Fuchs (writing IMHO with considerable hindsight) "The tragedy in German warship construction was the return to high pressure steam turbines for the large warships....." As it was the H-39s were scrapped on the slipways after a few thousand tons of steel had been assembled and the diesel powered P-class heavy cruisers never made it off the drawing board.

All the best

wadinga

[hans zurbriggen]

Hello Mr. Wadinga,
you are right when you say that "MAN were no longer in receipt of Kriegsmarine support from 1933 onwards but were free to develop what they wanted", however they were not funded to develop what they possibly wanted. Researches at MAN were seriously slowed till 1938, if not interrupted at all, concentrating only on small torpedo-boat engines.

Regarding what you describe as "major engineering gamble":
- Panzerschiff engine (M9Z 42/58) was a 9-cylinder that displaced 1,382 liter. Each engine produced max 7,100 hp @ 450 rpm (weight 110 tons).
- Class "H" engine (M9Z 65/95) was a 9-cylinder that displaced 5,423 liter. Each engine produced max 13,750 hp @ 265 rpm (weight 248 tons).
Both engines were very similar in design, I see no technological jump, just an up-scaling, with a much larger engine, turning slower and weighting less (compared to displacement), being less exasperated. Weight per hp was therefore comparable too.

Technological jump came with V-24 engine (V12Z 42/58), developed in 1939, after KM had started again to fund MAN researches, for class "O" battlecruisers (3,686 liter , 15,600 hp @ 450 rpm, weight 150 tons), with a larger, more powerful and comparatively lighter, fast turning engine, followed by its destroyer smaller and faster version (V12Z 32/44 also called V24Z 32/44, 1,623 liter, 56 tons for 10,000 hp @ 600 rpm). Another jump came with former engine turbo-charged version (66 tons for 16.000 hp) designed in 1940 that would have provided an exceptional power for a very limited weight.

hans

[wadinga]

Hello Hans,

To me the Kriegsmarine situation vis-a-vis diesels vs turbines for large ships is similar to the steam reciprocating vs steam turbines that the RN faced at the beginning of the 20th century. The civilian Turbinia had embarrassed the RN at Queen Victoria's Fleet Review by outrunning the fastest warships sent to catch her, but the RN let turbine developers install their upscaled engines in larger liners to see what they could do in service before wholly committing to them for Dreadnought, putting her propulsion-wise far ahead of foreign designs which stuck to inferior reciprocating engines.

If giant high power diesels had been as easy an option as you suggest, then the commercial market for high speed liners built in Germany like Europa and Bremen and later vessels would have been an ideal proving ground. The Nazi regime was quite happy to support technology advances in civilian activities which would offer a long term military benefit (eg Heinkel and Dornier bombers). However German shipbuilders mainly stuck to steam turbines. As it was the Reichsmarine, and later Kriegsmarine, experience of diesels in their larger ships, including the Panzerschiffe and Bremse was not wholly positive with vibration problems so bad gunnery optics had to be redesigned. Even K & S who are generally positive to the diesel argument say

The medium/fast-running MAN large sip diesels were naturally not without their faults, and these were not fully ironed out until 1941.

before continuing to extol their overwhelming virtues for long range commerce raiders. Bizarrely, K & S suggest Kriegsmarine policy makers were more influenced by negative foreign press reports on the Panzerschiffe performance than by their own experience.

I stand by my suggestion than a totally diesel driven H-39 was a big technological gamble. Evidently those responsible for the later hybrid propulsion variants thought so too. The diesel driven destroyer, for instance, never materialised. Promised, extrapolated performance is no guarantee of reliable delivery.

The smaller diesels developed for submarines and S-Boats were peerless in performance, no argument. However the Panzerschiffe engines were the biggest and most powerful in service and suggesting doubling their size and output would be a trivial matter minimizes the difficulties such "up-scaling" often involves.

All the best

wadinga

[wadinga]

Hi All,
Before I am shot down, Z-51 did get off the drawing board but only as an unfinished hulk with no propulsion installed, after a lengthy, chaotic design process see Wikipedia.

Promised, extrapolated performance is no guarantee of reliable delivery.

As for the long distance commerce raiding role, Hilfskreuser and the WW1 cruiser raiders could "live off the land", capturing and transferring coal or fuel oil from their victims. There weren't that many motor ships at sea in WW2 so a Panzerschiffe needed an attendant oiler with the correct fuel even with its extended range.

BTW I have heard suggestions that it was irreparable damage to a fuel processing installation that made Langsdorff's decision to scuttle Graf Spee inevitable as she couldn't effectively use the fuel she had aboard for escape. Does any other contributor know anything about this?

All the best

wadinga

[hans zurbriggen]

Hello Mr. Wadinga,
possibly I was unclear: I don't say that doubling output for H-39 would have been a trivial matter for MAN (despite their design was almost same as Panzerschiffe engines), but I say that final decision had already been taken by KM. Orders for 48 of these engines for 4 H-39 BB's were actually issued to MAN before being cancelled by war start. One of such engines was actually built and successfully tested in 1940 (later it was destroyed during an Allied air raid). Apparently, having evaluated benefits of Diesel propulsion (quick to switch on from zero to full power, better maneuverability (due to Vulcan gears), extremely larger range at cruise speed, ease to maintain at sea) vs problems (noise and vibrations) KM had taken definitive decision vs turbines for her 6 new approved battleships already in 1938.

What I cannot understand is the following return-back to turbines in following projects (H-41 and later), once doubts about reliability of Diesel power plants had been already superseded in 1938 (5 years after Deutschland was commissioned and was successfully tested, correcting initial issues): I suspect that even H-41 only detailed design was just a draft and that, looking at what would have been available in 1941 at MAN, final decision would have been for Diesels only.

hans


Re. Admiral Graf Spee damage to fuel oil processing system, I'm afraid I know nothing more. Was this damage among the ones repaired in 72 hours in Montevideo ? Is any further detail available regarding this hit and damage ?