real mistake the Admiral Hipper class and destroyers?

[thaddeus_c]

was the real mistake the Admiral Hipper class and destroyers?

leave aside unfinished carriers and how many u-boats to build.

five modern cruisers and 40 (+/-) modern destroyers WERE built , all to no great effect

fail to see where the Admiral Hipper class fit in the fleet.

what was rationale for not using diesel engines in the destroyers since the "pocket battleships" had used them earlier?

fuel was always a concern with no network of overseas bases but that would seem to argue for common fuel with u-boats not against?

how would a fleet of (?) 48 diesel destroyers (maybe scrap the torpedo boats and build another 6-12 destroyers), (?) 90-100 u-boats , 3 PBs, 3 Scharnhorst class, 3 Bismarck class BBs compare to what was built.

[mescal]

The heavy cruisers & destroyers were built with France & Poland as opponents in mind.
For example, the initial requirement for the Hipper was to be at least a match for Algerie and faster than Dunkerque.

Moreover, cruisers and destroyers are an important part of any balanced fleet.

In the end, the real mistake was that the building plan of the Kriegsmarine was not integrated within the global national strategy - if such thing actually existed.

Note however that 10 of the 40 destroyer were not laid down before the loss of 12 destroyers in the first 4 months of 1940.

what was rationale for not using diesel engines in the destroyers since the "pocket battleships" had used them earlier?

Diesel propulosion was envisionned for the Hipper class, but high pressure superheated turbine were finally chosen, mainly for high speed performance reasons - they wanted the ships to be faster than the 29 knots Dunkerque, a feat the inital Deutschland class could not achieve.
As for destroyers, you could not by that time give them diesel engines without making unacceptable cuts in performance :
Diesel engines had significantly lower output for a given weight. Meaning that, to get a high to speed, you needed bulky and heavy engines which could not fit in a destroyer-sized hull.

Basically overall, the difference between diesel engines and turbine systems are that the first ones give you high endurance and high reliability at cruising speed, while the latter gives you better performance at high regime.
And in the 30s, nobody wanted a "slow" speed destroyer.

[thaddeus_c]

Note however that 10 of the 40 destroyer were not laid down before the loss of 12 destroyers in the first 4 months of 1940.

what was rationale for not using diesel engines in the destroyers since the "pocket battleships" had used them earlier?

Diesel propulosion was envisionned for the Hipper class, but high pressure superheated turbine were finally chosen, mainly for high speed performance reasons - they wanted the ships to be faster than the 29 knots Dunkerque, a feat the inital Deutschland class could not achieve.
As for destroyers, you could not by that time give them diesel engines without making unacceptable cuts in performance :
Diesel engines had significantly lower output for a given weight. Meaning that, to get a high to speed, you needed bulky and heavy engines which could not fit in a destroyer-sized hull.

Basically overall, the difference between diesel engines and turbine systems are that the first ones give you high endurance and high reliability at cruising speed, while the latter gives you better performance at high regime.
And in the 30s, nobody wanted a "slow" speed destroyer.

was the hybrid system only proposed? and the diesel in 1942 destroyer an "evolution" not available in the early '30s?

the layman's conception is a surface vessel working somewhat like a submarine with two propulsion systems, even if armor and armaments have to suffer somewhat to achieve range and speed.

the strategy is to go in two directions, long range destroyers to work in concert with u-boats and 9 - 12 large ships able to menace Brits while staying close to home (thus having air support without building carriers.) build out the rest of the fleet for "balance" later.

[Urmel]

What's the point of a long-range destroyer when the most likely opponent is using 6" cruisers to patrol the sea lanes around the world? The long-range destroyers would be outrun and outgunned. Every encounter would end like the Falklands 1914 did for the German side.

[mescal]

was the hybrid system only proposed?

The K-class and the Leipzig & Nürnberg had a hybrid propulsion plant.
The problems related to the twin machinery were that the bunkerage was too small and thus their radius was far too small, and that the boiler rooms + engine rooms + diesel rooms took far too much space belowdeck - more than 50% of the overall length.
Above all this, all those ships were structurally suspect and actually not blue-water capable.

It was proposed for the M-class cruisers and the so-called Spähkreuzers.
Those Spähkreuzer were sometimes considered as large destroyers, but the 1938 design displaced 5,700 tons, and the later 1940 design no less than 7,000 tons, which clearly put them in the cruiser category.

This displacement growth shows clearly that one cannot put all the requirements of a raider in a destroyer hull.

Note also that the hybrid system led to compromises which decreased survivability : for example, to fit the two propulsion plants within the hull, the Kriegsmarine had to eschew the unit principle - and in the M-class plans, the two turbines were in only one compartment, meaning that a single hit could prevent her escape.
And their protection was extremely light, with a 25mm belt, which imply that even destroyer guns could get penetrating hits.

The price of the compromises implied by the twin propulsion plant can be seen through a comparison with an Arethusa-class cruiser.
On a broadly similar displacement, with a similar armament, the British were able to fit an armor belt twice as thick, and a bunkerage 50% larger.
This last point is interesting : to get more economical machinery for cruising, the Germans had to cut everything they could, and notably the bunkerage.

One Spähkreuzer ("SP1") was laid down in 1941, but work was suspended in 1942.
I guess that the rationale was that, once the US Navy entered the war, there was little hope remaining for surface raiding.


Diesel destroyers were planned, with Z51 laid down in 1943 as a prototype. She was sunk before completion.
She was rated at 57,000 shp, for a top speed of 35+ knots.
I'm no engineer and may be mistaken, but given what I know of the diesel technology of the period, it looks like one another project where the Germans were pushing the limits on the learning curve, and I expect she would have been full of bugs.

[thaddeus_c]

was the hybrid system only proposed?

The K-class and the Leipzig & Nürnberg had a hybrid propulsion plant.
The problems related to the twin machinery were that the bunkerage was too small and thus their radius was far too small, and that the boiler rooms + engine rooms + diesel rooms took far too much space belowdeck - more than 50% of the overall length.
Above all this, all those ships were structurally suspect and actually not blue-water capable.

thanks, had read about that system at some point but couldn't remember which ship/prototype used it.


Diesel destroyers were planned, with Z51 laid down in 1943 as a prototype. She was sunk before completion.
She was rated at 57,000 shp, for a top speed of 35+ knots.
I'm no engineer and may be mistaken, but given what I know of the diesel technology of the period, it looks like one another project where the Germans were pushing the limits on the learning curve, and I expect she would have been full of bugs.

still think they should have gone with diesel from the time of the pocket battleships, invented a class of ship if necessary, something that could work in concert with u-boats and converted merchant ships.

pocket cruiser if you will or puffed-up torpedo boat (IIRC the latter class of torpedo boats was mooted to be ocean going?) open up the south atlantic to raiding, as well as the indian ocean.

[LWD]

Why? Hitler didn't plan on fighting the British at least until much later than actually happened. In any case the Germans simply weren't going to be able to match the RN in the near future. Thus their navy was aimed as mescal stated at France and Polan and perhaps at the Soviets. As it is they pushed things in a number of feilds so far that they had problems. Inovation is expensive and time consuming, especially if pushed to the "bleeding edge". Given that Germany was focused on the land battle where is the strategic need?

[Urmel]

still think they should have gone with diesel from the time of the pocket battleships, invented a class of ship if necessary, something that could work in concert with u-boats and converted merchant ships.

Sure, but why stop there? I think they should have invented magical levitation capabilities, stealth cloaks, and remote-operated drones, and a sub-species of Nazi mind-controlled sharks with friggin' laser beams on their heads. I mean, the Allies would have been in so much trouble.

You can't just 'invent' a class of ships. You work with the technology you have. The Germans tried to push the limit of the propulsion technology on their destroyers and paid for it by having a class of sleek-looking, well-armed harbour queens. Is there any proof that the mid-1920s Diesel technology (which is when the Panzerschiffe were designed) was up to powering a destroyer with acceptable speed? If so, I'd like to see it.

pocket cruiser if you will or puffed-up torpedo boat (IIRC the latter class of torpedo boats was mooted to be ocean going?) open up the south atlantic to raiding, as well as the indian ocean.

Which of the myriad of problems the KM was facing would this have solved?

[Urmel]

Diesel destroyers were planned, with Z51 laid down in 1943 as a prototype. She was sunk before completion.
She was rated at 57,000 shp, for a top speed of 35+ knots.
I'm no engineer and may be mistaken, but given what I know of the diesel technology of the period, it looks like one another project where the Germans were pushing the limits on the learning curve, and I expect she would have been full of bugs.

Whitley is a bit confusing, having Z51 both as the last ship of Type 41 and the first of Type 42. For the type 42 the following information is given:

Yard: Deschimag, Bremen
Key dates: Ordered 25 Nov 42, Launched 1944, sunk while fitting out at Bremen, 21 March 1945
Displacement 2,084/2,328/? (standard/normal/loaded)
Length: 108m
Beam: 11m
Draught: ?
Engines (design) 6x 10,000HP (rated)/9,500HP (actual) MAN Type 12 Z32/44 diesel engines with superchargers (abandoned for the follow-on types).
Engines (actual) 4x 10,000HP (rated)/9,500HP (actual) MAN Type 12 Z32/44 diesel engines geared on centre shaft, the remaining two to be installed on wing shafts when ready.
Electricity: 8x Diesel generators in two circuits, total 320kW
Shafts: 3
Horsepower: 57,000 - 60,000 (actual/rated)
Speed: ? (but the larger and bigger 42A was expected to go 35.9 knots)
Range at 19 knots: 5,200nm
Armament: 4x12.7cm (single), 8x 3.7cm (twin), 12x2cm (quad), 6x53.3cm TT

It is noteworthy that the final German destroyer design, Type 45, abandoned Diesel again in favour of steam turbines. Not that it mattered a hill of beans.

It is also noteworthy that for a similar output, Diesel engines weighed 200 tons more than steam turbines, demonstrating that there was no free lunch here. How far could a destroyer steam on 200 tons of fuel?

[mescal]

something that could work in concert with u-boats and converted merchant ships.

And we get to the usual problems of the strategy-making at OKM & higher level.

If they choose a "Mahanian" (or "Tirpitzian") strategy, they cannot deal with the Royal Navy in any foreseeable future.
Therefore they have to restrict their putative opponents to France, Poland and USSR.
Therefore they can stick to more or less what they actually built in the late 20s and 30s.

If they choose a "guerre de course" emphasis for the Kriegsmarine, they are still bottled up in the North Sea.
Therefore they must first build a fleet to gain control of the passages to the open Atlantic, and it's back to square 1.
Or find a way to use stealth to get to the open ocean - which they did through U-boat & auxiliary cruisers.
But if you intend to send squadron of diesel-powered destroyers .... well, you must first defeat the British cruisers which would intercept them.
Which imply that you'll have to buff your escort groups with heavy cruisers, which in turn means that the RN will have heavy units, and therefore you'll need a battle fleet ... to open the way to small inefficient raiders.

It's certainly oversimplistic, but here are the roots of the strategic dilemma faced by the Kriegsmarine between the wars.

Note also that such a "guerre de course" can only be waged with a non-zero hope of success if GB is actually without allies - a situation which did actually happen from July 40 to Dec. 41, but which was actually difficult to foresee.

And finally, the nature of the convoy system imply that your "destroyer" raiders will have to come to their preys. And those preys were not undefended, and as I stated previously, even the guns of the British destroyers escorting convoys were a significant threat to such lightweight raiders.

open up the south atlantic to raiding, as well as the indian ocean.

Brest to Cape Town is 5,700 nm.
The SP1 Spähkreuzer had a range of ~8,000 nm at cruising speed. Which means that you'll need some kind of logistic network afloat, which will be highly vulnerable.

And the North Atlantic line was by far more important.

[mescal]

It is noteworthy that the final German destroyer design, Type 45, abandoned Diesel again in favour of steam turbines

That's also in my opinion symptomatic that diesel destroyers in the 30s and 40s weren't that good.

My guess is that to make a diesel useful for a destroyer-type ship, you need to overcome the lack of high speed.
Therefore you need superchargers for your diesel, but those were still in their infancy by that time.

[Urmel]

It is also noteworthy that for a similar output, Diesel engines weighed 200 tons more than steam turbines, demonstrating that there was no free lunch here. How far could a destroyer steam on 200 tons of fuel?

Answering my own question here:

http://forum.axishistory.com/viewtopic. ... 2&start=15

So it appears 200 metric tons could take a Type 36a destroyer about 550 nautical miles. With the lessons learned on hull design, and the considerably smaller size and lower horsepower, 200 tons in Z51 would presumably have been worth considerably more than that.

What's the benefit in fuel consumption of Diesel over steam in a 1940s engine?

[thaddeus_c]

still think they should have gone with diesel from the time of the pocket battleships, invented a class of ship if necessary, something that could work in concert with u-boats and converted merchant ships.

Sure, but why stop there? I think they should have invented magical levitation capabilities, stealth cloaks, and remote-operated drones, and a sub-species of Nazi mind-controlled sharks with friggin' laser beams on their heads. I mean, the Allies would have been in so much trouble.

You can't just 'invent' a class of ships. You work with the technology you have. The Germans tried to push the limit of the propulsion technology on their destroyers and paid for it by having a class of sleek-looking, well-armed harbour queens. Is there any proof that the mid-1920s Diesel technology (which is when the Panzerschiffe were designed) was up to powering a destroyer with acceptable speed? If so, I'd like to see it.

pocket cruiser if you will or puffed-up torpedo boat (IIRC the latter class of torpedo boats was mooted to be ocean going?) open up the south atlantic to raiding, as well as the indian ocean.

Which of the myriad of problems the KM was facing would this have solved?

didn't they kind of invent a class of ship with the pocket battleship, an amalgam of "the technology you have?"

my point was that some of the follow-on ships were as you described "sleek-looking, well armed harbor queens."

leave aside the Bismarck-class and carriers, especially since so many threads already discuss those, IMO the Adm Hipper-class and destroyers were the real waste.

in the complete novice viewpoint, 45 ships laid down and NOTHING to show for it?

if switching to diesel was a poor choice (IIRC the reason they DIDN'T use them was they anticipated a shortage of diesel not technical reasons?) and the turbine system was also "pushing the limit of propulsion technology" what would be the alternative?

what changes to size and armaments would help?

[Urmel]

didn't they kind of invent a class of ship with the pocket battleship, an amalgam of "the technology you have?"

Yes, but the point here is that the technology didn't exist for the destroyers to make them capable of what destroyers are expected to achieve.

my point was that some of the follow-on ships were as you described "sleek-looking, well armed harbor queens."

And the reason for that was that they pushed technology too far.

leave aside the Bismarck-class and carriers, especially since so many threads already discuss those, IMO the Adm Hipper-class and destroyers were the real waste.

I find it hard to look at any major KM surface unit and not consider it a waste.

if switching to diesel was a poor choice (IIRC the reason they DIDN'T use them was they anticipated a shortage of diesel not technical reasons?) and the turbine system was also "pushing the limit of propulsion technology" what would be the alternative?

Use a proven system. Other navies didn't seem to have these issues.

[LWD]

One thing that puzzles me is that I seem to recall that one of the reasons the S-boats were considered so good was ther diesel engine and they certainly were capable of good speeds for their type. What am I missing here? Lack of armor and light weapons?