Diesel Kriegsmarine

[thaddeus]

I guessed as much, but did you find more info on the OTL german plans for these ships?
Obviously particularly important considering the instability claims of Europa.

thought it was simply case of becoming top heavy? and high fuel usage doomed project.

my speculative scenario is always to convert the Dithmarschen-class to carry seaplanes, they were already fast, not sure if another diesel engine could have been added?

 

[PSL]

thought it was simply case of becoming top heavy? and high fuel usage doomed project.

my speculative scenario is always to convert the Dithmarschen-class to carry seaplanes, they were already fast, not sure if another diesel engine could have been added?

It would be difficult to back fit additional diesels to the Dithmarschen but building them with better diesels in the first place should be doable. Historically they had 4 x 5500hp nine cylinder diesels, while the V 12 cylinder diesels should manage 12,500hp , increasing hp too 50,000hp. not sure what could happen.

http://www.german-navy.de/kriegsmarine/ships/auxships/dithmarschen/index.html

DITHMARSCHEN, Germany tanker laid down 1935



Displacement:

10,275 t light; 10,699 t standard; 17,539 t normal; 23,011 t full load

DITHMARSCHEN

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)

(595.19 ft / 574.15 ft) x 72.18 ft x (22.97 / 28.78 ft)

(181.41 m / 175.00 m) x 22.00 m x (7.00 / 8.77 m)



Armament:

8 - 4.13" / 105 mm 65.0 cal guns - 39.16lbs / 17.76kg shells, 400 per gun

Breech loading guns in deck mounts, 1935 Model

4 x 2-gun mounts on centreline ends, evenly spread

12 - 0.79" / 20.0 mm 65.0 cal guns - 0.27lbs / 0.12kg shells, 2,000 per gun

Breech loading guns in deck mounts, 1935 Model

6 x 2-gun mounts on sides, evenly spread

6 raised mounts

Weight of broadside 317 lbs / 144 kg



Armour:

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)

Main: 0.39" / 10 mm - -



Machinery:

Diesel Internal combustion motors,

Geared drive, 2 shafts, 50,436 shp / 37,625 Kw = 26.00 kts

Range 12,000nm at 25.00 kts

Bunker at max displacement = 12,311 tons



Complement:

761 - 990



Cost:

£2.966 million / $11.865 million



Distribution of weights at normal displacement:

Armament: 72 tons, 0.4 %

Armour: 4 tons, 0.0 %

- Armament: 4 tons, 0.0 %

Machinery: 1,433 tons, 8.2 %

Hull, fittings & equipment: 7,646 tons, 43.6 %

Fuel, ammunition & stores: 7,264 tons, 41.4 %

Miscellaneous weights: 1,120 tons, 6.4 %

- Hull below water: 60 tons

- Hull above water: 30 tons

- On freeboard deck: 1,000 tons

- Above deck: 30 tons



Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship):

76,634 lbs / 34,761 Kg = 2,169.6 x 4.1 " / 105 mm shells or 8.5 torpedoes

Stability (Unstable if below 1.00): 1.40

Metacentric height 5.5 ft / 1.7 m

Roll period: 12.9 seconds

Steadiness - As gun platform (Average = 50 %): 77 %

- Recoil effect (Restricted arc if above 1.00): 0.02

Seaboat quality (Average = 1.00): 1.55



Hull form characteristics:

Hull has a flush deck,

an extended bulbous bow and large transom stern

Block coefficient (normal/deep): 0.645 / 0.675

Length to Beam Ratio: 7.95 : 1

'Natural speed' for length: 27.43 kts

Power going to wave formation at top speed: 53 %

Trim (Max stability = 0, Max steadiness = 100): 50

Bow angle (Positive = bow angles forward): 26.00 degrees

Stern overhang: 9.84 ft / 3.00 m

Freeboard (% = length of deck as a percentage of waterline length):

Fore end, Aft end

- Forecastle: 20.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m

- Forward deck: 30.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m

- Aft deck: 35.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m

- Quarter deck: 15.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m

- Average freeboard: 22.97 ft / 7.00 m

Ship tends to be wet forward



Ship space, strength and comments:

Space - Hull below water (magazines/engines, low = better): 30.2 %

- Above water (accommodation/working, high = better): 189.5 %

Waterplane Area: 32,966 Square feet or 3,063 Square metres

Displacement factor (Displacement / loading): 417 %

Structure weight / hull surface area: 159 lbs/sq ft or 775 Kg/sq metre

Hull strength (Relative):

- Cross-sectional: 1.59

- Longitudinal: 2.39

- Overall: 1.66

Hull space for machinery, storage, compartmentation is excellent

Room for accommodation and workspaces is excellent

Ship has slow, easy roll, a good, steady gun platform

Excellent seaboat, comfortable, can fire her guns in the heaviest weather



dithmarschen tanker completed as a CVE TANKER

 

[sitalkes]

I copy the selection from Excel into MS Paint and then save as PNG.

Michael

Paint has some idiosyncrasies that you may prefer not to deal with: another way is to use Snipit. Snipit (Snipping Tool) is part of Windows, you will find it in the Windows Accessories group near Paint. All you have to do is start Snipit, select the area you want copied, then Snipit will offer the choice of saving it as a file (jpg or png).

 

[sitalkes]

Operation Rheinübung Part 2, The Battle of Denmark Straights (May 24th, 1941)

....
At the same time as the battle with the British cruisers was reaching its height the hydrophone station on board Prinz Eugen reported the following, “Noise of three fast-moving turbine ships at 280° relative bearing.”....

***

Why didn't the Germans use their radar? That's what they did historically, to good effect

 

[sitalkes]

There's a very simple answer to that - the German economy was being run pretty much to the limit from the late-1930s onwards, the British economy wasn't: if London wants to spend more on the navy, they can just increase their borrowing a bit and build it. If the Germans want to do the same, they need to cut something else of roughly the same value to do so unless they're willing to heavily cut into the civilian economy which they weren't until the war started going very badly for them in OTL.
That situation changed later on - once the war started the UK very rapidly hit full utilisation of the economy and used rationing to limit civilian consumption while heavily using female labour, which took Germany several years.

As for the RN being well aware of what the Germans were up to, Germany was the #1 threat to the RN and had been for a long time. Keeping tabs on what the Germans were up to was a very high priority for them, so it would be very surprising if they didn't know what was going on.

"Yet the financial allocations, great as they were compared with the normal peacetime expenditure on the armed forces, turned out to be inadequate in relation to their objects. They were cramping to the men in charge of rearmament and proved to be insufficient for the very purposes for which the country was rearming. The supplies they bought were not large enough either to deter the aggressor or fully to prepare this country for war.

The financial arguments employed were not in any way new. All governments, and especially all British Governments, are bound to resist additions to expenditure, and Treasury control had always been a powerful and, on the whole, a salutary brake on military extravagance. If in the early thirties the Government appeared to use the brake with great vigour, it could claim for this every theoretical and political justification. It was still engaged in fighting the great depression, and although its way of doing so might not be approved by present-day economist, it was not subject to much critical doubt in the official circles of 1935. The days of Keynes' General Theory' were not yet, and the prevalent view was the crisis had been aggravated, if not caused, by Government extravagance and could only be remedied by a drastic curtailment of Government expenditure and taxation. This was indeed the main argument against Mr. MacDonald's Labour Government and became the programme of Mr. MacDonald's National Government. And as long as these arguments prevailed new and great additions to expenditure appeared to be too dangerous for this country to adopt.

Indeed the financial dangers of excessive expenditure on rearmament continued to figure in official discussions almost to the eve of the war. As late as 1938 the Chancellor of the Exchequer, in resisting further claims of the Services, found it necessary to stress that expenditure could reach a limit beyond which it might defeat the very purpose of rearmament. Finance, he argued, was one of Britain's military resources: something in the nature of a fourth arm. Britain could not hope to match an aggressor in a lightning war, and her chances of victory rested on her ability to withstand the financial stresses of a long war. To overtax her financial resources and to undermine her financial stability for the sake of military preparedness might jeopardise her very ability to wage war.

Hence, the continuous rearguard action which the Chancellors of the Exchequer fought against the ever-rising demands of the Services. Within limits they had to give way, and the financial allocations constantly grew, but limits there always were, and for at least three years after the first rearmament programmes these limits continued to circumscribe the supply of arms for the Forces as well as the preparation of industry for the production of munitions in time of war."

History of the Second World War, Michael Postan http://www.ibiblio.org/hyperwar/UN/UK/UK-Civil-WarProduction/UK-Civil-WarProduction-2.html

 

[Gudestein]

It would be difficult to back fit additional diesels to the Dithmarschen but building them with better diesels in the first place should be doable. Historically they had 4 x 5500hp nine cylinder diesels, while the V 12 cylinder diesels should manage 12,500hp , increasing hp too 50,000hp. not sure what could happen.

http://www.german-navy.de/kriegsmarine/ships/auxships/dithmarschen/index.html

Its a very nice design, but to go for 26 knots, wouldn’t you want to do what it takes to go to 30?
How many planes would it carry?

 

[sitalkes]

Define success? The ship will be horribly vulnerable when taking damage because its not built to military spec but its available sooner rather than later. Its a question of trade offs. The British light fleet carriers built to civilian standards had very successful post war careers.

Going off Japanese examples if any of the German conversion see service and take damage expect horrible fire / explosion to follow. Now that could just be the japanese fuel / munitions handling as even their military designs proved very vulnerable to fire.

The german super liners also suffered really badly from fires, which could not be stopped once started and the ships were burnt to the water line even though they were in port.

 

[sitalkes]

You mentioned that the German torpedo problem was fixed, that would have resulted in major British losses in Norway (by the way the problem was detected during the Spanish Civil War but pooh-poohed by the man responsible). You could also have the U-boats equipped with schnorkels (they were in Dutch submarines in 1940) and have far better co-operation with the Luftwaffe making it easier to find the RN ships as well as making life harder for allied shipping in the Atlantic. Remember it was only one squadron of aircraft that Churchill named the "scourge of the Atlantic". Maybe the armed merchant ships should have an easier time while the RN was concentrating on the heavy ships of the Kriegsmarine. You could also have a more concentrated magnetic mine operation.

 

[sonofpegasus]

So a carrier based on the Dithmarschen would basically be like a Sangamon capable of 25knots. Should carry about 25/30 aircraft. A very useful carrier but the comparably low speed of 25knots (when compared to 30knt+ for the major fleet units) could hamstring a raiding force.

 

[takerma]

I am very curious to see what effect on war in USSR will shutting down north convoys will have. In fact would British even risk North convoys with the situation as it is? Same with any force in the far east, it would get sent back home as things are getting really bad.

Great TL very interesting read

 

[weasel_airlift]

Its really only duke of York that Can do the job if not the carriers. What did the British CAG’s look like at this time if we play the game that nothing has changed?

As per what carriers available, there are 9. Of those, Illustrious is just shaking down after extensive repairs, Indomitable is only just finished, and probably not really ready for action, and Argus, Hermes, and Eagle aren't fast enough. Furious is in the yards in the US for a much-needed refit, and Formidable is in the yards repairing damage received in the Med.

I assume Victorious and Ark Royal are repaired, so they are the only fast carriers available. Per planes, Sea Hurricanes are available, but in low numbers. Mostly it will be Fulmars and Swordfish still.

 

[Gudestein]

As per what carriers available, there are 9. Of those, Illustrious is just shaking down after extensive repairs, Indomitable is only just finished, and probably not really ready for action, and Argus, Hermes, and Eagle aren't fast enough. Furious is in the yards in the US for a much-needed refit, and Formidable is in the yards repairing damage received in the Med.

I assume Victorious and Ark Royal are repaired, so they are the only fast carriers available. Per planes, Sea Hurricanes are available, but in low numbers. Mostly it will be Fulmars and Swordfish still.

Dangerous indeed. Britain Can only rally one battlegroup that is fast enough to cover the Atlantic ocean. And Germany read the British codes.

 

[weasel_airlift]

Dangerous indeed. Britain Can only rally one battlegroup that is fast enough to cover the Atlantic ocean. And Germany read the British codes.

Right, if they want a fast battle group, then it is Duke of York, Ark Royal and Victorious, and Renown if feeling completely insane. That is obviously not enough to even think about standing up the German battlegroup, so I suspect that they'll have all of the available Queens and Nelson as a secondary slow force. Have the carriers slow the group, then the slow group and Duke comes to pummel them into submission.

If the Queens, Nelson and DoY are in the Atlantic, then that leaves the R class and Renown to staff the Med

 

[PSL]

Its a very nice design, but to go for 26 knots, wouldn’t you want to do what it takes to go to 30?
How many planes would it carry?

Sure but I was running with Thaddeus original idea of modifying the Dithmarschen line of support ships. There were 6 laid down, with 3 completed prewar and the fourth in 1940, with the fifth completed in 1943 and the sixth never completed.

An improved design seems unlikely until they prove there worth in the war. certainly the last two could be completed to an improved design with 3 pairs of the improved diesels to 75,000 hp

could look like following

DITHMARSCHEN II, GERMANY tanker laid down 1935

Displacement: 11,936 t light; 12,348 t standard; 16,968 t normal; 20,664 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(599.14 ft / 574.15 ft) x 72.18 ft x (22.97 / 26.97 ft)
(182.62 m / 175.00 m) x 22.00 m x (7.00 / 8.22 m)

Armament:

8 - 4.13" / 105 mm 65.0 cal guns - 39.16lbs / 17.76kg shells, 400 per gun
Breech loading guns in deck mounts, 1935 Model
4 x 2-gun mounts on centreline ends, evenly spread
12 - 0.79" / 20.0 mm 65.0 cal guns - 0.27lbs / 0.12kg shells, 2,000 per gun
Breech loading guns in deck mounts, 1935 Model
6 x 2-gun mounts on sides, evenly spread
6 raised mounts
Weight of broadside 317 lbs / 144 kg

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.39" / 10 mm - -

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 74,913 shp / 55,885 Kw = 29.00 kts
Range 10,000nm at 23.00 kts
Bunker at max displacement = 8,315 tons

Complement: 743 - 966
Cost: £3.758 million / $15.031 million

Distribution of weights at normal displacement:

Armament: 72 tons, 0.4 %
Armour: 4 tons, 0.0 %
- Armament: 4 tons, 0.0 %
Machinery: 2,128 tons, 12.5 %
Hull, fittings & equipment: 8,611 tons, 50.7 %
Fuel, ammunition & stores: 5,032 tons, 29.7 %
Miscellaneous weights: 1,120 tons, 6.6 %
- Hull below water: 60 tons
- Hull above water: 30 tons
- On freeboard deck: 1,000 tons
- Above deck: 30 tons



Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship):
49,315 lbs / 22,369 Kg = 1,396.2 x 4.1 " / 105 mm shells or 5.3 torpedoes
Stability (Unstable if below 1.00): 1.31
Metacentric height 4.9 ft / 1.5 m
Roll period: 13.6 seconds
Steadiness - As gun platform (Average = 50 %): 59 %
- Recoil effect (Restricted arc if above 1.00): 0.02
Seaboat quality (Average = 1.00): 1.19



Hull form characteristics:
Hull has a flush deck,
an extended bulbous bow and large transom stern
Block coefficient (normal/deep): 0.624 / 0.647
Length to Beam Ratio: 7.95 : 1

'Natural speed' for length: 27.48 kts

Power going to wave formation at top speed: 59 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 9.84 ft / 3.00 m

Freeboard (% = length of deck as a percentage of waterline length):

Fore end, Aft end
- Forecastle: 20.00 %, 26.25 ft / 8.00 m, 22.97 ft / 7.00 m
- Forward deck: 30.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m
- Aft deck: 35.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m
- Quarter deck: 15.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m
- Average freeboard: 23.23 ft / 7.08 m

Ship tends to be wet forward



Ship space, strength and comments:

Space - Hull below water (magazines/engines, low = better): 44.3 %
- Above water (accommodation/working, high = better): 190.3 %
Waterplane Area: 32,319 Square feet or 3,003 Square metres
Displacement factor (Displacement / loading): 303 %
Structure weight / hull surface area: 181 lbs/sq ft or 883 Kg/sq metre

Hull strength (Relative):

- Cross-sectional: 1.79
- Longitudinal: 2.81
- Overall: 1.87

Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent



IMPROVED Dithmarschen tanker finished as a faster CVE/TANKER. The cruise of 10,000nm @ 23 knots was needed to simulate the REDUCED oil tanker to proved more space for another pair of V12 cylinder diesels. reducing the combinded ship own bunkerage plus tankerage..

 

[Gudestein]

Sure but I was running with Thaddeus original idea of modifying the Dithmarschen line of support ships. There were 6 laid down, with 3 completed prewar and the fourth in 1940, with the fifth completed in 1943 and the sixth never completed.

An improved design seems unlikely until they prove there worth in the war. certainly the last two could be completed to an improved design with 3 pairs of the improved diesels to 75,000 hp

could look like following

That is a small fleet carrier indeed.

 

[miketr]

Why didn't the Germans use their radar? That's what they did historically, to good effect

British were beyound visual horizion so Radar couldn’t see them.

You mentioned that the German torpedo problem was fixed, that would have resulted in major British losses in Norway (by the way the problem was detected during the Spanish Civil War but pooh-poohed by the man responsible). You could also have the U-boats equipped with schnorkels (they were in Dutch submarines in 1940) and have far better co-operation with the Luftwaffe making it easier to find the RN ships as well as making life harder for allied shipping in the Atlantic. Remember it was only one squadron of aircraft that Churchill named the "scourge of the Atlantic". Maybe the armed merchant ships should have an easier time while the RN was concentrating on the heavy ships of the Kriegsmarine. You could also have a more concentrated magnetic mine operation.

I have decided deliberately to avoid diving too deep into exactly the impact of better torpedos. I am aware that some major ships could have been lost; especially off Norway. For now its enough that the torps work.

Welcom to the thread!

 

[Tom_B]

I had wondered about that as well at the time but figured that you wanted to avoid butterflies that could have a major impact on the war in the Med.

 

[PSL]

That is a small fleet carrier indeed.

Yes- further reduced by fact that such a design could only fit hanger of maybe 120m x 22m . Given deck space of 175m^2 per A/C , that limits you to maybe 15 planes in the heavy stormy seas of the North Atlantic. Battle experience may well demand deck parking for a flight or two for emergency CAP, thus raising the numbers by 6-8 more planes.

 

[thaddeus]

my speculative scenario is always to convert the Dithmarschen-class to carry seaplanes, they were already fast, not sure if another diesel engine could have been added?

It would be difficult to back fit additional diesels to the Dithmarschen but building them with better diesels in the first place should be doable. Historically they had 4 x 5500hp nine cylinder diesels, while the V 12 cylinder diesels should manage 12,500hp , increasing hp too 50,000hp. not sure what could happen.

Its a very nice design, but to go for 26 knots, wouldn’t you want to do what it takes to go to 30?
How many planes would it carry?

So a carrier based on the Dithmarschen would basically be like a Sangamon capable of 25knots. Should carry about 25/30 aircraft. A very useful carrier but the comparably low speed of 25knots (when compared to 30knt+ for the major fleet units) could hamstring a raiding force.

while a likely candidate for conversion to CVE, my speculation was to use them as seaplane carriers, to quickly supplement their limited number of carriers.

(MY scenario would develop the HE-119, as it could manage 300mph in seaplane version and had long range, and was smaller than some of the planes they handled pre-war on Atlantic crossings)

 

[PSL]

while a likely candidate for conversion to CVE, my speculation was to use them as seaplane carriers, to quickly supplement their limited number of carriers.

(MY scenario would develop the HE-119, as it could manage 300mph in seaplane version and had long range, and was smaller than some of the planes they handled pre-war on Atlantic crossings)

HE-119 had potential but was dependent on the troubled DB-606 engine, which meant it could suffer from the over heating problems of the HE-177 BOMBER and also could not be available until 1942 to prototype such a plane. Since the main propeller shaft went right though the cockpit , it could mean trouble for the crew.

https://en.wikipedia.org/wiki/Heinkel_He_119