German Battleships and convoy hunting.

[Glider]

I certainly agree about swapping the 5.9 for additional 4.1 and 37mm, as I have never been a fan of 6in secondary weapons. Personally have yet to find an example of them hitting anything.
I am less confident about increasing the engine output. These were amongst the first large diesels used at sea and to double the output on what was already a highly advanced design could be asking for trouble on the reliability front. They had their fair share of teething problems as it was.
Extra deck protection is never wasted but I think that is as far as I would have taken it.

[delcyros]

I do personnaly dislike 5.9" as well but I can understand those who say they have their own advantage: better range, more punch (a lot more AP-capabilities).
While the RN was advantageous in introducing 5.25" dual purpose (to be fair it must be said that this gun is of very doubtful use against aircrafts if any), the KM stayed with specialised guns, the more powerful 5.9"/55 against ships (which also was used against low level flying torpedo bombers by Bismarck, Scharnhorst and Gneisenau) and the high velocity, rapid firing 4.1"/65 against aircrafts (which regulerly was used against unarmored sea targets).
I do know of some succesful 5.9" uses against Exeter, Jervis Bay, Achates, Acasta, Glowworm and some transports as well.
Rodneys 6" secondarys did well against Bismarck as did Warspites secondarys against the (harboured) german destroyers in Narvik.
However, the focus on 5.9" even for destroyers is a clear disadvantage in the german design philosophy, no doubt. The 4.1" had only a slightly inferior range, almost the same AP-capabilities at close and very long ranges, a better ballistics and a 50% increased cyclic firing rate beside of the advantage of dual purpose service.
Diesel wasn´t really new, the High sea fleet had designed and build some large Diesels for Sachsen, Großer Kurfürst and Markgraf beside of their use in submarines. Next to the Deutschland class, the Bismarck should originally get Diesels as well and the uncompleted Hindenburgs also had Diesel engines. The H-class Diesel powerplant design was closed in 38, each unit made 14.500 SHP (instead of 6.000 SHP in case of Graf Spee), so there is a lot of power redundance for a power output doubling. The O-class BC had a unit of similar poweroutput but lighter and shorter as well as broader than the "H" -class ones.
It is questionable, if these designs would have been avaiable for these "P" class designs of 1937/38. These designs were much heavier ships (22.000 t.) with a proposed speed of 35 kts (I expect to encompany thecarriers?) and 3 or 4 screw design with 15.000 miles range.

[Glider]

Thanks for this. I knew that the Bismark was originally due to get diesel engines and admit I put the fact they were not fitted down to problems with the engine. A case I am afraid of putting two and two together and coming up with five.

I knew the High Seas Fleet had some but considering the fact that they were dropped would indicat that there were some problems with them. These days of course its hard to find a large merchant tanker/ ore ship whatever without one.

Thanks again

[syscom3]

Didnt those diesel engines emit huge clouds of smoke when they went to full throttle? Makes them easier to find I would imagine.

Just curious though, if they're running diesels, wouldnt they need diesel fuel, which is far more flammable than bunker oil.

[delcyros]

In opposition to what you might expect, the Diesels have some benfits:
Smoke. Under full power, the Deisel engine can operate completely smoke free (unlike steam), this was demonstrated by Scheer a few times in the indic ocean, when the ship prevented beeing spotted by full power smoke free cruise. The Panzerschiffe had a special device to prevent smoking by heating the exhaust gazes (and therefore burn parzicles), similar but more effective than those used on submarines.
Another advantage is the high efficiancy and economics of those powerplants (Lutzow was the ship with greates operational range: 20.000 nautic miles / 13 kts.).
Diesel fuel is a bit more flammable than oil but not by that much, indeed a temperature is needed, which at all would inflame oil as well. The burning is not that intensive compared to gazoline, avgas and so on.
The spacial dimensions of Diesel engines are also smaller than boiler and turbines, but nethertheless they are heavier (compared to the amount of HP created by them).
The full run from zero is possible in within a minute, unlike turbines which require some 5-13 minutes to do so, fuel is not needed if the powerplant is brought to zero.
The complement can also be reduced, since operating Diesels require far less personal than operating turbines.
Not the least, the ship is more immune, since the great danger of boiler hits (which usually were critical, since they had the potential to rip the ship ) is banned. If a engine room is hit, than ok-you loose power, but the ship cannot blew up (or take further damage due to steam bursts).
Of course there are negative aspects as well:
The Diesels were heavy units compared for their poweroutput,
While beeing much shorter and narrower they require more height than turbines (this was the very reason to skip them from the Bismarck design, because they would need to place the armor deck a level higher (reduced stability, reduced immunity from very close distances, no two deck deep zitadell = much thicker armor thicknesses needed) as they did in case of Lutzwo, Scheer and Graf Spee.
Unlike turbines, the Diesels cannot be overrewed (enforced power) that much (Iowa had 20% design overrew!).
The vibrations and sounds caused by those units were uncomfortable.
The Battleships of the High Sea fleet indeed had some problems with the tech, only two of them eventually had mixed propulsion (Diesel for the middle screw, turbines for the two others), some other already produced units were used in large submarines, but statisfyingly. Concernes were that there were no records how the engine would work under battle circumstances (impacts).

[delcyros]

Sidestep:
I also digged some more on Okun. His major armor penetration formula is based generally on empirical US tests. The only exception are german armor, for them he refused US results (which were better) and instead used german datas known to him (which had lower figures). The comparability of these results is matter of discussion:

Using Scharnhorsts 11"/55 gun on four armor types I can show the difference (hypothetical impact at 30.000yrds distance)-all datas from Okun´s database on AP-capabilitys of KM armor:

1.) on US class"B" deck armor: 3.1"
2.) on german Wh deck armor: 3.8"

This result would imply a superiority of 22.6% in impact resistance for the US class "B" homogenious armor. Indeed if we check his datas, both armor have the same quality (1.00), the US "B" a better elongation but less Brinell hardeness. Now we take italian, japanese and british armor
into consideration:

3.)on italian homogenious: 3.4"
4.) on japanese homogen.: 3.3"

Concluding these datas, the Wh has the worst resistance of all involved homogenious armor. Datas from Okun imply that italian has a quality factor of 1.0, while the japanese one is somehow less resistant with 0.95. Now if we take US tests into consideration at no time there was a significant advantage of US"B" over german KC new. Under the same circumstances they were rated at about equal in resistance, just giving the US "B" an advantage in less fragmentation. This fits with all I read. And a difference in 20% would imply an advantage comparable to those pre ww1 armors to some late ww2 armors! Hell, this datas are wrong.
Had he used the comparable US results 3.1" would be the estimation in AP-capabilities for this gun and this range on Wh, this fits.
Why is that important? Because if using Bismarcks 15"/52 on Wh deck armor the distance at which penetration may occur shifts further into the 30 Kyrds region....

[DerAdlerIstGelandet]

Originally Posted by delcyros

In opposition to what you might expect, the Diesels have some benfits:
Smoke. Under full power, the Deisel engine can operate completely smoke free (unlike steam), this was demonstrated by Scheer a few times in the indic ocean, when the ship prevented beeing spotted by full power smoke free cruise. The Panzerschiffe had a special device to prevent smoking by heating the exhaust gazes (and therefore burn parzicles)

Cool, that I did not know. I thought the same as sys up there on that. Pretty cool, learn something new every day.

[syscom3]

I thought the Scharnhorst was found due to the bellowing diesel exhaust when it went to full throttle.

[delcyros]

Scharnhost did not had Diesel powerplants. So it could be discovered by her smoke. Her powerplant was the high pressure steam turbine powerplant used on many contemporary warships (including Iowa, North Carolina, South Dakota, Yamato, KGV and Richelieu). This powerplant has a more benefitable hp to weight relation and quite a good efficiancy, so it was choosed for the Scharnhorsts (as well as Bismarcks). Unfortunately the tech was somehow new in case of Scharnhorst, so both ships had quite a lot of problems to deal with their engines up to 1940. If we compare the teething problems of Diesel and HPT powerplants I would choose Diesels, anyway. The HPT tech reached eventually maturity in the Bismarck design stage, so we donot have reported problems by Tirpitz or Bismarck considering their powerplants.
All in all Diesels would be a wiser choice esspeccially for the US BB designs, which also depended on a good range but I doubt that this tech was avaiable for them in the necessary development stage.

[syscom3]

The US capital ships built in the late 30's and in the 40's were using (the then revolutionary and advanced) super heated steam turbines which gave them a very good power to weight ratio. The use of diesels would have been a step backwards.

[delcyros]

Super heated steam turbine = high pressure steam turbine (HPT)
Agreed, by its arrival this tech was revolutionary compared to the old low pressure trubine.
But Diesel by far isn´t a step back. Esspeccially for US purposes:
As we know, the US soon went to the all or nothing raft body armor sheme after ww1. Diesel engines really fit more to this specification than would HPT.
The only real disadvantage is that they were heavy.
I will calculate an example with roughly some estimations based on the original 1939 North Carolina BB design(sorry for using metrics):
The NC´s were the first true US BB to be builded after ww1 (Lexington BC turned into CVA and South Dakota fell victim to the Washington treaty), let´s compare the design with a proposed Diesel design:

displacement: 42.000 t. (actually 46.770 deeply loaden)
length(waterline): 214,6m
beam: 33 m
length/beam relation: 6.5
speed (trial):28,5 kts @ 125.000 hp (enforced) and 43.500 t.
armor weight: 13.976 t.
main armor length: 111,3m
propulsion: HPT, 4 shafts, 8 Babcock boilers, 121.000 hp (at 100%)
propulsion length (biolers + turbines): 59, 5m
engine weight: 1.881 t. (+ 845 t. auxilary and systems)
fuel complement: 6.592 t.
range: ? according to the datas from Iowa, which had a comparable hull shape, but beeing larger and having more powerful and efficient engines (as well as more fuel complement) I estimate around 10.000 miles /12 kts. It should be noted that the ship benefits a lot by the low weight HPT engine, which spared some weight.
Now I replace the HPT with a german Diesel engine (Graf Spee), and since Graf Spee had 8 engines and 2 srews and NC has four I (just for gaming) calculate with the exact doubling (which would result in 108.000 hp), by arranging the 16 engines in the same way (4 on each shaft):
What would change?
engine weight: 3.302 tons (+ 650 auxilary and systems)
propulsion length (gears and Diesels 54 m
fuel complement: 2.814t.
range: approx. 18.000 nm at 12 kts.
= if we calculate engine weight with fuel complement together, the Diesel driven NC propulsion weights 6.772 t (compare, the executed design is 9.318 t., that are 2.5 Ktons safed in the end for a nearly doubled range, not bad is you ask me). Now what happens with the speed?
at 41.500 tons (reduced trial) 108.000 hp could still drive the ship to 28,3 kts, no significant speed drop. (Variant A)
But it even goes further: Lets assume the 5 m shorter engine dep. would led to a shorter ship design, which probably would happen. Then another 2 (at least) Ktons could be safed due to the shorter vital armor box as well! Less deck armor zone, less main armor belt in spacial dimensions (important for the AON sheme), but all has the same thickness. In the end such a modified NC would only weight around 43.000 tons (deeply loaded), be a bit shorter, having a reduced beam-length relation (~6.3 instead of 6.5) and therefor a reduced speed (27.7 kts deeply loaden). In their appearenc ethis ship would look like a modified South Dakota(Variant B)
Another possibility is to keep the weight and take a reduced speed (26.8 kts) for 3.000 tons of additional armor. Less probable. (Variant C)
A last one (my favourite) could use the space for additional Diesels, one on each screw and a larger internally protected fuel bunker. This variant (D) would have little larger spacial dimensions like the original one due to 4 m increased length and therefor beeing 2 Ktons heavier (larger armor dimensions):
Displacement: ~48.000 t. deeply loaden
length:~ 218 m (waterline)
beam: 33m
length-beam relation: 6.6
engine weight: 4.127 tons (+~ 850 t. auxiliarys)
fuel complement: 4.221 tons
range: approx. 26.000 nm/12 kts
Engine power: 135.000 SHP
estimated peed: 29,02 kts at 135.000SHP and 45.600 tons
Compared to the original design this variant would more than double the range and a slightly increased speed as well as slightly less engine weight (9.200 t. instead of 9.318 t.)
Concluded some positives:
A shorter construction time due to reduced displacement (except Varian D)
A better TDS because of more void cells instead of oil filled cells
A much longer range
A reduced crew complement
Better Seakeeping because of higher freeboard
Some tactical advantages (smoke free)
And a reduced vulnarability because of impossibility of boiler hits.
The disadvantages would be as following:
uncomfortable vibrations, high degree of produced sound
higher engine height (neglectable, since the US BB design already placed the main armor deck one level higher, so the engines fit into the spacial subdivision)
Keep in mind that we calculated with old 1927/28 designed Diesel systems! Now explain me why it would be kind of step back?

[delcyros]

No comment?
Well, I agree that this was gaming, only. The Diesel tech of this sizeclass simply weren´t avaiable in the North Carolina design stage in the US. And I also have to underline that the HPT-tech advanced even further (take the South Dakotas and it simply doesn´t work anymore with Graf Spees Diesel, agreed).
Now I am close to finishing my critics on combinedfleet.com, jumping to tactical factors. I still have not all Datas for the Iowas but I can show mistakes for the South Dakotas and Bismarcks regarding the range figures:
The authow gives South Dakota and Iowa a 10 compared to the 8 for Bismarck. The superior range of Iowa/SD never was matter of discussion but I have reasons to question this. The author´s numbers would imply a 20% range advantage of South Dakota compared to the Bismarck class (at 12 kts). That´s partly wrong.
Why?
At first the fuel complement of Bismarck and Tirpitz differs:
Bismarck: 7.775 tons
Tirpitz: 8.641 tons
So in particular comparison with Bismarck it is both, true (ragarding the lower fuel complemet of Bismarck) and false (the bunker volume of Bismarck and Tirpitz are nearly identical, Bismarck simply wasn´t that deeply loaded, but it could have...), regarding Tirpitz it truly is false.
But lets discuss South Dakota first:
Fuel complement: 6.950 t. (also Massachusetts, but Indiana and Alabama: 7.340 t.)
At 12 kts the range of SD indeed is 16% superior to that of Bismarck (not Tirpitz!), but is 12 kts really a serious cruise speed? In a ship vs ship comparison (which is the intended purpose of the website) not necessarely. If Bismarck comes into play it would rarely cruise under 25 kts, this would force SD to this speed as well: range at 25 kts: 6.650 nm; Bismarck: 5.850 nm ( Tirpitz: 6.720 nm). Normal cruise speed for Bismarck in it´s historical first part (prior to damagings) of "Rheinübung" was 28 kts (range: 4.528 nm), while those of SD would be extrapolated to 4.400 nm (at 138.000 SHP enforced). Result:
With increased cruise speed the range gap between SD and Bismarck closes, while Tirpitz HAS MORE OPERATIONAL RANGE than South Dakota or Alabama. Keep in mind that the author prefers the most favourable cruise speed for his comparison.
I am not intending to reduce the excellent range performance of SD/Alabama nor the high economy efficiancy of their powerplants, just outlining one more point where statistics are bended in favour to the US ships. I would like to see some statistics for Iowa also but I suspect that the 7.073 t. fuel complement of Iowa (resp. 7.251 t. of BB62-BB65) serve them as well.

[DerAdlerIstGelandet]

I did not having anything to comment about, my knowledge on WW2 Naval Warfare is not extensie eneogh, I just mostly read and learn.

[Gnomey]

So do I. On the topic of the German surface fleet the Graf Spee's Eagle has been raised from the bottom of the River Plate almost intact.

http://news.bbc.co.uk/1/hi/world/americas/4702832.stm

[delcyros]

Its quite interesting how many tools they will recover from GS. Wether or not all ship remains will be lifted remains unclear, I suspect they have not enough financial background to do so. Inteesting on Graf Spee in particular is that the ship was the first to be equipped with radar for limited fire controll (alike Washington in Guadacanal with their MK 3 FC radar) und also the first to use fc radar during surface engagements.