Commerce Raider designs from a 1920 German point of view?

You mentioned:
- Commerce Raider designs from a 1920 German point of view
- POD taking place right after WWI ends as historically

Given the Versailles treaty restrictions that would rule out for now cruisers, over-sized destroyers and submarines?
6 light cruisers, 6 destroyers and 12 torpedo boats - all with limited tonnage - don´t sound like a real raider force?

So for now (early 1920s) armed merchant raiders would be the focus of the German navy. If the federal budget allows it, offer German shipping companies some subsidies to build certain new merchant ships (certain minimum speed, certain minimum size) with conversion to armed merchant raider already in mind. If the money isn´t there try to appeal to their patriotism. :)
It would make conversion easier. And maybe wouldn´t be that expensive?
(Right now the design of a new merchant ship just would have to include thoughts on where to install guns and torpedo tubes. And on larger ships where to house a float plane? Plus where to store more fuel, house a larger crew etc.)

Fast passenger ships are out. Too expensive and too easily recognized. Ordinary merchant ships - which can blend in - are chosen.

In the early 1920s that would probably be coal fired ships. The early German naval diesel engines (except for the U-boat diesels up to 1,000-2,000 hp) weren´t quite that reliable.
That changes around 1924/1925. Several new inventions / improvements were made that raised the reliability of larger diesel engines (That´s when design work for the "Panzerschiffe" started in our TL.).
German merchant ships after that date increasingly used diesel engines. So after that the German focus might be on armed merchant raiders with diesel engines.

That doesn´t mean that the navy won´t design proper warships for the role of a merchant raider. And such a design probably will change a lot between 1920 and 1928 for example. But as long as Germany is bound by the Versailles treaty such designs can´t be build in sufficient numbers by Germany.

And even after getting rid of (some) restrictions (our TL Anglo-German Naval Agreement) Germany can´t hope to build enough warships suitable for merchant raiding. So the concept of (dedicated) armed merchant raiders developed over years will still be valuable.
 

BlondieBC

Banned
1. A warship that can fight enemy cruisers. Should be between a Deutchland and a Scharnhorst. A remake of the Derfflingers would work too. At the time the French have nothing that can fight it, and the British only have 3 battle cruisers.

2. A long range submarine. Somewhat untested in 1920, but well on the way. Proved to be very successful.

3. A Merchant, standard design. 20 kph speed, very long range. A few Turn-of-the-century 6'' guns, a couple of torpedoes, anti-aircraft guns and a float plane hidden in boxes on the deck, 100 mines, small arms and a pair machine guns for the crew. Flags from all plausible nations, paint and spare parts.

The auxiliary cruisers of both WWI and WWII were much cheaper and more successful than the true warships when it came to raiding.

Either you go for something that can fight enemy warships, or you go for something cheap. You get a hundred of these for the same price as a battle cruiser.

There's absolutely no point in building a purpose built raider with only 6x6'' guns as it can't even fight with a light cruiser. Too expensive for no utility. A merchant cruiser like the above could do anything that it could do, but for a fraction of the prize.

If you want some more fighting power, go for something that can actually fight the 50 or so cruisers out there, like a Deutchland.

1) I can see #1.

2) Germany had longer range U-boats in WW1 than WW2.

3) AMC are great too.

You have some additional points.

My CL + U-boat TEAM can defeat any single ship in the RN. It is too heavy for destroyers, and the U-boats kills cruisers and larger. With a U-boat with 25,000 mile range, It has near around the world ability if the surface ships can be refueled from neutral ports. When the German CL makes a run, and a CL or larger chases the German, it can't zigzag, which makes it easy for the U-boat.

And the CL + U-boat is a fraction of the costs of UK CA and above. Yes there is an answer, but he UK has to build customs ships to deal with the issue. The POD in this thread seems to have either a cold peace after WW1 or a vastly different ToV.
 
Uh, look at Kormoran: she fought a light cruiser (HMAS Sydney). Though both ships were sunk in the engagement, it proved that a disguised raider, in the right hands, could be lethal against a warship. And Thor had three fights with British AMCs: she damaged two (Alacantra and Carnavaron Castle) and sank one (Voltaire). And the German raiders sank or captured 890,000 tons of shipping in the process from 1940-43. Compare that with the Japanese result: they only sent two raiders out into shipping lanes-one cruise into the Hawaii-Australia route (two ships sunk) and two into the IO (three ships sunk or captured), before Hokoku Maru and Aiokoku Maru (10,437 GRT, each had 6 5.5", several 25-mm AAA, four TTs w/Long Lance and two E7K Dave Seaplanes) ran into the Dutch Tanker Oneida (one 4") and the Indian minesweeper Bengal (one 3"). One shot from the Dutchman's four-incher landed in the torpedo reload spaces of Hokoku Maru-sending her and 76 of her 354 men down, including her captain, who was in tactical command of both raiders. Her consort, Aiokoku Maru, broke off the fight to pick up survivors when she should've finished off both Allied ships before doing so.
 
from what i understand, in ww1 the germans preferred converted refrigeration ship, because they were fast.
I concur with the conclusion that a liquid fuel is preferable because not only less bulky, but also much easier to refuel at sea. I don't think they would go with a diesel though, oil fired steam would be more likely.

as for armament, the later it gets converted the more likely it will have heavier AA, but i would expect 37mm or 40mm twin mounts and 20mm ones.

the 2 seaplanes also sound logical, although them having a kolibri (Fl-282) on board would be cool, or maybe a Fa330 (more likely)
 

BlondieBC

Banned
Uh, look at Kormoran: she fought a light cruiser (HMAS Sydney). Though both ships were sunk in the engagement, it proved that a disguised raider, in the right hands, could be lethal against a warship. And Thor had three fights with British AMCs: she damaged two (Alacantra and Carnavaron Castle) and sank one (Voltaire). And the German raiders sank or captured 890,000 tons of shipping in the process from 1940-43. Compare that with the Japanese result: they only sent two raiders out into shipping lanes-one cruise into the Hawaii-Australia route (two ships sunk) and two into the IO (three ships sunk or captured), before Hokoku Maru and Aiokoku Maru (10,437 GRT, each had 6 5.5", several 25-mm AAA, four TTs w/Long Lance and two E7K Dave Seaplanes) ran into the Dutch Tanker Oneida (one 4") and the Indian minesweeper Bengal (one 3"). One shot from the Dutchman's four-incher landed in the torpedo reload spaces of Hokoku Maru-sending her and 76 of her 354 men down, including her captain, who was in tactical command of both raiders. Her consort, Aiokoku Maru, broke off the fight to pick up survivors when she should've finished off both Allied ships before doing so.

I am not against AMC, in fact, I think they are a valuable part of the triad of AMC, U-boat, and surface warship. I just don't think they are they only solution. A well planned German AMC program can probably reach numbers of 50-100 by 1939, and since they are using freighters, don't overlap the surface fleet budget or treaty limits. So there is a second question of what to do with the surface tonnage.

I have not looked at the WW2 AMC in details, but I have looked at the WW1. Most of the kills are on a few highly successful ships, and lifespans of 6-15 weeks are not uncommon. So the fact Japan lost two raiders is not a surprise. If Germany had only sent out two raiders in WW1 instead of mid-teens, these two ships might have also accomplished nothing.
 
I don't think they would go with a diesel though, oil fired steam would be more likely.
The Germans had rotten luck with their boilers throughout the war, so I'd personally go for diesels. Besides, reciprocating steam is utter crap speedwise (at best, I'd stick them on AMCs), while turbines are very fuel hungry.

As for the ship itself, I favour a light, clean design like the Condottieri-class. 8 6-inchers, 8 105-mm DP + 10 37-mm and 16 20-mm 3xA (numbers to be raised accordingly due to wartime air defence needs).
 
The Italians were worse: only a single raider put to sea from Italian territory (Massawa). Ramb I lasted less than a week: she sailed into the IO, and right into the waiting guns of a British cruiser.....
 
The Germans had rotten luck with their boilers throughout the war, so I'd personally go for diesels. Besides, reciprocating steam is utter crap speedwise (at best, I'd stick them on AMCs), while turbines are very fuel hungry.

As for the ship itself, I favour a light, clean design like the Condottieri-class. 8 6-inchers, 8 105-mm DP + 10 37-mm and 16 20-mm 3xA (numbers to be raised accordingly due to wartime air defence needs).

The basic problem with WW2 German steam plants was that in order to meet the overambitious power/volume/weight requirements set by their ship designers, the engine designers went to some extremely high-pressure & temperature operating conditions, and ended up pushing the technological & metallurgical envelope too far; in fact when the USN went to similar operating conditions in the steam plants used in the surface combatants of the 1960s, such as the Knox, Leahy, & Belknap classes, even with a lot more experience in engine design & a bunch of technological improvements, those steam plants were so problematic in service that the engineering people recommended reverting back to WW2-era steam conditions in the interests of reliability & serviceability, even though that would have meant a bigger, heavier, & thirstier plant- as that would have contradicted the rest of the design requirements, it's what led to the USN turning to gas-turbines in the 1970s.

As for fuel consumption & steam turbines, the original direct drive turbines were inefficient because of the incompatibility between the fast speeds a turbine is happy at & the slower speeds a screw can turn at without creating major cavitation problems, forcing naval engineers to adopt large, slow-turning & inefficient turbines. During WW1, experiments in how to deal with this situation lead to 2 basic means of allowing for turbines to spin as fast as they wanted for efficiency while allowing the screws to turn at an acceptable speed.

The first was the use of reduction gearing, which, once the bugs were work out, was a pretty efficient & relatively compact means of doing this, & was pretty much standard on ships so long as steam plants driving turbines was the most common means of propulsion.

The other was turbo-electric drive, where the turbines are hooked up to big generators which provide electricity for both big electric motors that drive the screws & ship's service. The USN favored it because it offered better fuel economy at cruising speeds, allowed for better subdivision, & one could get full power in reverse as well without putting undue stress on the powerplant. The drawbacks were that they were more vulnerable to shock & flooding (see USS Saratoga's experiences with Japanese torpedoes), and that a TE plant was considerably bulkier & heavier than a geared turbine plant of similar output- one late 1920s USN design study for a new battleship mentioned in Friedman's had a ~50,000 ish SHP TE powerplant that weighed ~2100 tons; the contemporary geared turbine plant that was used in USN treaty cruisers produced 107,000 SHP on the same weight- which led to their abandonment in most combatants, as given the size & displacement constraints set by treaty limits, designers simply couldn't afford the volume & weight penalty a TE powerplant imposed & still have enough left to play with to meet the other operational requirements in a design.

Reciprocating engines are also very maintenance-intensive, with their primary advantages being that they're cheap, easier to train people to use, & in a mobilization context, represent a source of engines for merchant hulls & low-end escorts & auxiliaries that's not otherwise in demand for warship construction.

In the time-frame the OP's talking about, marine diesels as a means to power large ships are still a somewhat immature technology that could be potentially unreliable, especially if high speed is desired- that was an issue with the OTL panzerschiffe.

If one's thinking about building a warship to act as a surface raider, as everyone's pointed out, the most practical option would be a number of cheap, fast CLs with good range & seakeeping (though if practical to do so while keeping the ship cheap & small enough to suit the requirements, I'd go with 8 guns & protection against destroyer gunfire, which, assuming a 4.7-5" HE round would mean about 1.5-2" armor over what's to be protected on the assumption a HE shell will penetrate about a quarter-caliber thickness of armor), & to do that on a treaty limited hull pretty much means geared turbines in this time period.

However, the best bang for the buck with surface raiders were armed merchant cruisers converted from fast freighters, and if I was coming up with designs for fast freighters intended for conversion into raiders upon mobilization in the early 1920s, I'd be looking at turbo-electric drive, as it'll be a better part of the decade before diesels are sufficiently mature for consideration as such.
 
An often overlooked issue is the need to incorporate oversized damage control systems (to be installed when the ship is converted from a freighter into a raider) into the basic design. While most damage control systems present on raiders were perfectly adequate for a civilian ship, the rigours of warfare found them quite subpar. Kormoran was lost following her battle with HMAS Sydney due to a runaway oil tank fire forcing Captain Detmers to sound evacuation.
 
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DD951 is right on this...

...I fear that going for anything but an Armed Merchant Cruiser (HSK in Reichsmarine parlance) would be pointless. Reasoning as follows:-
  • A fast modern merchant fleet of 100 - 200 vessels would be useful for international trade and influence;
  • Old and apparently obsolescent guns can be used to arm these vessels in a crisis, even being stored aboard as 'ballast';
  • Former Kaiserliche Marine seamen could be employed and covertly assured of an active role;
  • German shipyards could avoid recession with a building boom;
  • The merchant fleet would (perfectly legitimately) be used to those areas it would operate in during wartime. Acclimatisation problems (and deployment problems) could therefore be minimised.
  • Even when the Royal Navy knew what was going on, the armed merchant fleet would be the very devil to track and deal with. A warship with turrets is visibly a warship. A 'Q' ship can disguise itself as another innocent trader.
  • As floating U-boat bases, the HSK were in OTL of considerable value. In this context they would be a serious threat to the British, Dutch and French Empires.
 
Alternative options

Having invented the ideal commerce raider in WW1 in the form of the large "cruiser" submarine, the KM was forbidden to develop that path and had to watch while the French built the Surcouf and the IJN perfected the long range sub with its KD series.
OTL they tried to modernize the old Armoured Cruiser concepr, and hit the problem of having an artificial tonnage limit compromize the design.
A possible alternative would have been a fast hybrid cruiser/seaplane carrier ship. Such a vessel could use its aircraft to scout, and eventualy torpedo targets, retain enough surface fighting power to engage unescorted preys, and would be ideal to cooperate with submarines.
The much later Oyodo gives an idea of what could have been done.

oyodo01.jpg
 
Good...but expensive...

A warship of this kind reminds me more of the 'Graf Spee' crossed with a seaplane carrier, or a cross between 'HMS Manxman' and 'HMS Pegasus'.

Commerce raiding needs to be done by stealth or by using large numbers of expendable cheap raiders. Somali or Pearl River pirates on the grand scale. Have you considered Schnellboote (E-boats) based at friendly harbours and with HSK 'depot ships' to support them?
 
Just how useful is a smoke screen at sea? Can a good one mask a torpedo attack? Can a good smoke screen allow a raider to evad a slower persuer long enough to get out of range undamaged?
 
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How about a hybrid crusier carrier?

17,000 tons, fight deck, catapults and hangar forward capable of handling up to 5 floatplanes for recon and launching several wheeled fighters (which ditch upon return) that serve as emergency defense against enemy recon planes.

Several torpedo mounts and secondary 5-inch mounts, and 20mm AA ordinance on main deck aft of flight deck.

All main battery guns mounted aft. A triple 11" turret with a superfiring twin 8" turret.

Armor designed to defeat 8" guns over vitals

Speed 30 kts.
 
How about a hybrid crusier carrier?

17,000 tons, fight deck, catapults and hangar forward capable of handling up to 5 floatplanes for recon and launching several wheeled fighters (which ditch upon return) that serve as emergency defense against enemy recon planes.

Several torpedo mounts and secondary 5-inch mounts, and 20mm AA ordinance on main deck aft of flight deck.

All main battery guns mounted aft. A triple 11" turret with a superfiring twin 8" turret.

Armor designed to defeat 8" guns over vitals

Speed 30 kts.

Does it run towards or away from the enemy?

While it in theory could handle a lot of situations, plans for ships like these were all crapped in favour of real cruisers and real light carriers, both which performs better.

Also, can't mix 8'' and 11'' guns as its too hard to tell the difference from splashes from them, meaning you can't reliably aim both together (That was the point with the Dreadnaughts). Better to go with more heavier and more lighter guns.

Last, the general rule is that 8 main guns (4x2 mounts) provide the most accurate fire (while 3x3 being more efficient in layout and +1 gun), and 6 main guns is the minimum required for actually having a reasonable chance to score a hit.
 
For the TL outline I am working on, the Germans will have many 'Q' ships, and one of the buterflies of my interwar years will make tracking them down much harder for the allies this time round.

For the primary (Surface) force, I am leanig towards an ocean going raider fleet, that are cheap and fast to build, as well as being able to be built in large numbers.

For a surface vessal, I am focusing upon a vessal purpose built to 'run away' from an enemy combatant using a smoke screen/torpedo attack, and perhaps having a towed lighter-than-air spotting craft. With the main armament concentrated in the stern, this allowes the raider to break contact (using speed/smoke), while still bringing a good weight of firepower to bear until out of range.

Any thoughts?
 
Have you considered Schnellboote (E-boats) based at friendly harbours and with HSK 'depot ships' to support them?

Historically some German raiders carried a single small Leichte Schnellboote.

http://www.german-navy.de/kriegsmarine/ships/fastattack/ls/index.html

However, there could have possibly been more opportunities to use them. Principally in minelaying and raiding party delivery roles. Torpedo attack role is probably superfluous.

Another possibility which might have been used would have been to use one or two whaling factory ships as flying boat tenders. Flying boats or heavy floatplanes (He-115, Do-22) might have been used for scouting, attack and mining duties with far more efficiency than Ar-196.
 
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