How would you build your merchant raider?

[Lucky13]

Let's say that it's early 30's, January '30, with what all that means, unrest in the world start to show etc., so you wan to build some 'merchant raiders or battlecruisers, just in case (I know). Being that I live in Glasgow, you're allowed to have the same size of your ship industry, capability, capacity etc., that they had here back then. Let's also say that you have a design ready in about a year, so the first ship of the line is laid down in mid to late '31, launched mid to late '32 and that they take about four years to complete and be commissioned in mid to late '36. Also, the Washington Treaty plays in here (your country wasn't involved in WWI, but just to make it interesting), which means capital ships (battleships and battlecruisers) were limited to 35,000 tons standard displacement and guns of no larger than 16-inch calibre. (Articles V and VI), but....I'm gonna limit the weight to 32,000 tons (about the same as Scharnhorst), still allowed anything up to 16-inch guns though, in three, four or whatever number of turrets you fancy, depending on size..
Also, you're allowed to use any technological advancements between being available between '31-'36, most modern aircraft etc., etc...
Another thing, your country will have the same kinda archipelago as Sweden and Stockholm, which means about 30,000 islands and islets, where these ships need to be able to operate...

Now, how would you design these ships for maximum hitting power, range, survivabilty and maneuverability, within these limits?

 

[DonL]

To my opinion 32000ts for a merchant raider is a total overkill.

I would choose a decent improved Panzerschiff.

1. lengthen the hull equal to the Hipper Class but stay at the same or near the same beam.
2. instead of the 8 x M9Z42/58 (7.100 PSe) Diesel engines choose the 8 x M12Z42/58 (9.500 PSe; available since 1934) Diesel engines (76000 WPS)
3. instead of the 6 × 28-cm-SK/28-L/52 choose 6 × 28-cm-SK/34-L/54 (SH Class, with the armour of the Deutschland Class)
4. instead of the 8 × 15-cm-SKC/28-L/55 single ordnance choose the 12.7 cm/45 SK C/34 with real DP turrets (elevation to 80 degree) or the 5"/38 (12.7 cm) Mark 12 as 5 x 2. One turret in centerline, two on the left and two on the right side.
5. instead of the 8 × 3,7-cm-SKC/30-L/83Fla-MK choose 8 x Bofors 4 cm/56 Flak 28 (40 mm/56.3 Bofors) as 4 x 2 AA guns
5. 10 x Flak 2 cm/65 (0.79") C/30 as 5 x 2 AA guns.

6. Admiral Graf Spee had 100mm inclined belt improved to 120mm inclined belt, weather deck was 18mm improved to 25mm, main deck was 40mm improved to 60mm.

Admiral Graf Spee had Standard 12.340ts, so we are talking here about something about 14000ts to 14500ts standard.

This is much cheaper then a 32000ts ship has much more endurance (same as the Deutschland Class) through the diesel engines and would be around 29kn fast. It could match with every 10000ts, 8 inch treaty cruiser and could send him to hell with the 28-cm-SK/34-L/54.

This ship is no BC or BB and not treaty conform through the 14500ts standard and the 11 inch guns but from the cost-benefit ratio to my opinion the optimal merchant raider.

 

[Shortround6]

Another thing, your country will have the same kinda archipelago as Sweden and Stockholm, which means about 30,000 islands and islets, where these ships need to be able to operate...

Now, how would you design these ships for maximum hitting power, range, survivabilty and maneuverability, within these limits?

That first sentence counter acts all the others. For a Swedish style archipelago you build a crap load of small destroyers/large steam torpedo boats and have at it. You don't need range, you don't need sea keeping. You need shallow draft, Ranges will usually be short sometimes well under a mile from island to island, engagements will also be short, minutes before one ship or another disappears behind an Island. Small size might actually allow you hide behind islands. A nightmare location for a big ship.

 

[Shortround6]

For a true merchant raider the working guns are the 6in or 15cm guns. Enough range for merchant ships and enough punch. Anything bigger is pretty much over kill against a merchant hull and is actually used for fighting the "merchant raider" CATCHERS.

Ammo storage is a problem for the bigger shells and higher performance guns are not always better. They often have shorter gun lives ( need re-barreling sooner) and shoot more erratically at longer ranges. They do make range finding at close range a bit easier though.

Smaller than 6in is workable but shell power falls of quickly, instead of the 88-112lb shells of the 6in class the 5 in class tend to be around 45-54 lbs per shell.

 

[DonL]

That first sentence counter acts all the others. For a Swedish style archipelago you build a crap load of small destroyers/large steam torpedo boats and have at it. You don't need range, you don't need sea keeping. You need shallow draft, Ranges will usually be short sometimes well under a mile from island to island, engagements will also be short, minutes before one ship or another disappears behind an Island. Small size might actually allow you hide behind islands. A nightmare location for a big ship.

Ok here I agree I haven't read this sentence and thought about a merchant raider in the wide ocean.

For a true merchant raider the working guns are the 6in or 15cm guns. Enough range for merchant ships and enough punch. Anything bigger is pretty much over kill against a merchant hull and is actually used for fighting the "merchant raider" CATCHERS.

Ammo storage is a problem for the bigger shells and higher performance guns are not always better. They often have shorter gun lives ( need re-barreling sooner) and shoot more erratically at longer ranges. They do make range finding at close range a bit easier though.

Smaller than 6in is workable but shell power falls of quickly, instead of the 88-112lb shells of the 6in class the 5 in class tend to be around 45-54 lbs per shell.

Here I disagree fundamental because a merchant raider is a lonesome wolf and must be able to first attack escorts of merchant ships and second shoot his way through hunting groups if necessary. (for example La Plata).

I think also the 5 inch gun is enough for a merchant ships so here i would perhaps add a sixth turret 5 inch guns a second one in centerline, so the merchant raider had 8 x 5 inch guns to one broadsight. Admiral Graf Spee carried 3400 shells for the 6 inch and 4 inch guns so 3000 shells for 12 x 5 inch guns seems adequate. The german 5 inch shell had 62 lbs.

Also the 11 inch SK34 L54 was one of the best german naval guns from barrel life (250 shots per gun) and dispersion (same or better then the 15 inch SK 34 from Bismarck class). Admiral Graf Spee caried 120 shells per gun.

To my opinion for a lonesome merchant raider it is fundamental to have more firepower then a treaty cruiser with 8 inch guns, elsewise you are in need of a ship which was at least 34kn fast and that is till 1940 impossible with diesel engines. With steam turbines you haven't the endurance for a merchant raider.

 

[Lucky13]

I was thinking, when I added about the archipelago, was that the Captain should have a good knowledge about the ship handling etc., that he could go out, do what he and the ship was expected to do at the time, when done, break off and sneak away and hide as to speak...
Just said up to 32,000 tons, these could be 25-27,000 or so..
Much like Admiral Graf Spee, she sank, what was it, 14 ships?

 

[Shortround6]

A big problem with "merchant raiders" as understood in the late 20s-early 30s is that they were intended to roam the oceans and take out lone freighters. Not try to bust up convoys. This is what bothered the British so much about the Graf Spee and sisters. One raider could tie up 1/2 dozen to a dozen cruisers searching for it.

Tying the ship to a specific area, even the size of the Swedish archipelago, makes it much easier to deal with. It also allows the use of small ships like destroyers in the hunt/kill unlike the high seas were the destroyers don't have the range/endurance to go "looking" for raiders. It allows the use of escorts only in the danger area instead of having to use them over thousands of miles.

Convoys helped as they reduced the number of stray ships cruising around. It is much harder to find one convoy than to run across on of 2 dozen ships sailing independently.
If the convoy escort is strong enough it can cripple the raider as well as fix it's location. Not all independent ships got off a radio signal. A convoy will. No raider really wants to tangle with destroyers. While an individual destroyer ( or pair or trio) can be blasted by a Graf Spee or battle cruiser in good weather, in bad weather there is too much chance of a destroyer getting lucky with a torpedo. It doesn't have to wreck rudders like the Bismark. The simple loss/contamination of hundreds of tons of fuel oil when thousands of miles from a friendly port can mean the eventual end of the raider.

 

[davebender]

1930s merchant ship costs about $2 million.

KM Bismarck cost RM 197 million ($78.8 million). You must sink 40 merchant ships just to break even.

KM Hipper cost RM 85.8 million ($34.32 million). You must sink 17 merchant ships just to break even.

KM Königsberg cost RM 38 million ($15.2 million). You must sink 8 merchant ships just to break even.
.....Light cruiser displacing about 7,000 tons.

Long range Gato class submarine costs about $2.7 million. Sink two merchant ships and the submarine has paid for itself.

Short range Type VII U boat costs about RM 2.5 million ($1 million). Sink a single merchant ship and the submarine has paid for itself twice over.

RLM paid RM 280,000 ($112,000) for a Fw-200. You can lose 18 aircraft while sinking a single merchant ship and still break even. Such aircraft also provide recon information.

Unless your nation is made out of money I recommend submarines and long range maritime attack aircraft for commerce interdiction. Surface commerce raiders rarely pay for themselves and they cannot hide from recon aircraft.

If you are determined to purchase surface commerce raiders I recommend a small mine laying light cruiser. Something like the WWI era Brummer class but with greater endurance and two seaplanes for recon.

KM Brummer. Laid down 1915.
about 5,000 standard tons.
4 x 15cm main guns plus 400 mines.
28 knots. 5,800 miles @ 12 knots.

 

[davebender]

KM Bummer, Germany CL Minelayer laid down 1930

Displacement:
3,826 t light; 3,971 t standard; 5,385 t normal; 6,495 t full load
Loading submergence 349 tons/feet

Dimensions:
460.63 ft x 43.31 ft x 19.69 ft (normal load)
140.40 m x 13.20 m x 6.00 m

Armament:
4 - 5.91" / 150 mm guns (4 Main turrets x 1 guns, 1 superfiring turret)
Superfiring turret is aft
2 - 3.46" / 88 mm AA guns
Weight of broadside 453 lbs / 206 kg
2 - 21.0" / 533.4 mm above water torpedoes

Armour:
Belt 1.50" / 38 mm, ends unarmoured
Belts cover 110 % of normal area
Main turrets 1.97" / 50 mm
Armour deck 0.63" / 16 mm, Conning tower 3.94" / 100 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 36,741 shp / 27,409 Kw = 28.00 kts
Range 26,000nm at 12.00 kts

Complement:
314 - 408

Cost:
£1.411 million / $5.643 million

Distribution of weights at normal displacement:
Armament: 57 tons, 1.1 %
Armour: 410 tons, 7.6 %
Belts: 159 tons, 2.9 %, Armament: 84 tons, 1.6 %, Armour Deck: 142 tons, 2.6 %
Conning Tower: 26 tons, 0.5 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 1,113 tons, 20.7 %
Hull, fittings equipment: 1,745 tons, 32.4 %
Fuel, ammunition stores: 1,560 tons, 29.0 %
Miscellaneous weights: 500 tons, 9.3 %

Metacentric height 2.0

Remarks:
Hull space for machinery, storage compartmentation is adequate
Room for accommodation workspaces is adequate
Good seaboat, rides out heavy weather easily

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.20
Shellfire needed to sink: 7,073 lbs / 3,208 Kg = 68.7 x 5.9 " / 150 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 1.3
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 54 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.29
Relative quality as seaboat: 1.39

Hull form characteristics:
Block coefficient: 0.480
Sharpness coefficient: 0.32
Hull speed coefficient 'M': 8.03
'Natural speed' for length: 21.46 kts
Power going to wave formation at top speed: 54 %
Trim: 39
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics strength:
Underwater volume absorbed by magazines and engineering spaces: 85.9 %
Relative accommodation and working space: 113.0 %
(Average = 100%)
Displacement factor: 150 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 0.95
(Structure weight / hull surface area: 75 lbs / square foot or 365 Kg / square metre)
Relative longitudinal hull strength: 1.61
(for 16.40 ft / 5.00 m average freeboard, freeboard adjustment 3.02 ft)
Relative composite hull strength: 1.00

WWI era Brummer class cruiser mine layers were considered good sea boats and highly maneuverable. No need to change a good thing.

KM Bummer hull dimensions, armament, armor and max speed identical to SMS Brummer. I have replaced the steam turbines with diesel engines and used every available bit of free hull space for additional fuel. 500 tons of misc. weight is for 400 mines plus two seaplanes.

 

[DonL]

@ davebender

Once detected it is near dead meat with this armament.

A big problem with "merchant raiders" as understood in the late 20s-early 30s is that they were intended to roam the oceans and take out lone freighters. Not try to bust up convoys. This is what bothered the British so much about the Graf Spee and sisters. One raider could tie up 1/2 dozen to a dozen cruisers searching for it.

Agreed.

Also Admiral Scheer attacked successfully a convoy escorted by auxiliary cruisers. So the germans did attack escorted convoys.
Convoy HX-84, auxiliary cruiser HMS Jervis Bay was sunk till 20 minutes

 

[davebender]

A 28 knot ship with almost unlimited endurance is tough to catch. You can always lay your mines elsewhere.

 

[davebender]

If you have merchant ships they should be incorporated into naval war plans.

Germany is poster child for letting your merchant marine go to waste. No realistic pre-war plans or preparation. Consequently WWII Germany didn't get their first merchant raider (Atlantis) into the sea lanes until April 1940. Germany also failed to use available ocean liners for amphibious operations to Norway.

WWI Germany did even worse. Second largest merchant fleet in the world. Dozens (perhaps hundreds) of Hapag and North German Lloyd merchant ships sat in neutral ports contributing absolutely nothing to the German war effort.

 

[Shortround6]

There wasn't much the German Merchant Marine could contribute to the war effort in either war. The Much larger British navy could pretty much blockade the North Sea ( and did) preventing any meaning full over seas trade.

Auxiliary Cruisers like HMS Jervis Bay don't last long in combat with real warships, especially by WW II. Sticking a bunch of 5-6 in guns on a medium sized liner or fast freighter does not turn them into real cruisers. The don't have real cruiser fire control, they don't have the needed shell hoists to keep up a good rate of fire, they have little or no armor, The have much less compartmentation compared to a warship. In WW I many ships were powered by reciprocating steam engines, in war ships care was taken that the engines did not rise above the armored deck or in cases the water the line, in some cases the engines were laid over on their sides ( horizontal) to accomplish this. Again in some cases the engines had to be staggered to fit them in this way, Merchant ships were under no such constraints and in fact strived to make the engine spaces as short as possible. Tall engines were common ( they kept the rpm down) but exposed them to gunfire if shot at.

A few armed merchant raiders at at time do all that is required. Large numbers get diminishing returns. The effect of raiders is not only in ships sunk but the disruption of shipping. Instead of single sailings the ships are grouped into convoys and proceed at the slowest ships pace causing great inefficiencies in cargo movement. Large numbers of warships( again mostly cruisers) are chasing a handful of ships, doubling or tripling the number of raiders in an area will not double or triple the amount of sinkings but will increase the chances of one of the raiders being found. Finding guns and gun crews to arm large numbers of merchant ships is also a problem.
Trying to use them as clandestine mine layers only goes so far. A mine layer needs the proper speed and stern shape, more than one mine layer blew itself up when a mine got sucked back into the stern. Carting tons of mines around in the hold for months on the chance that war will break out any day isn't the safest thing to do either. Hopefully you can keep the mines concealed from customs inspectors or war might just break out sooner than expected.

Dying bravely in an under gunned under protected warship to save other ships is one thing, to send sailors out on such ships just so they can be doing "something" is wrong.

 

[davebender]

That misses the point.

Merchant raiders cost almost nothing as you are paying only for conversion from cargo configuration. Typically the crew consists of merchant sailors who are military reservists. A merchant raider whose minefields sink even a single ship has paid for itself. They shouldn't attempt to capture enemy merchant ships except to obtain resupply.

 

[Shortround6]

I think that you have rather missed the point. you were complaining that the German Merchant Marine didn't do much in WW II or in WW I. There wasn't much they could do from a practical stand point. Practical meaning actually accomplishing much except providing target practice for Allied warships. Many German Merchant ships, just like many other country's ships, spent only a minimal amount of time in home ports or waters. Foreign ports were NOT "awash" in 75mm-150mm guns and ammunition to be bought up and mounted when war broke out. Same goes for sea mines. Merchant crews were seldom of a single nationality. Mixed crews and changes of personnel (crew jumping ship), were actually the normal condition so the "security" of carrying a secret hold full of weapons wouldn't last long. Any ship that made more than a few cruises and kept a single nationality crew would be regarded as something out of the ordinary.
Any German merchant ships caught by the start of war outside German waters have a very, very restricted access to weapons, which rather limits their usefulness, unless you think they should try to ram other ships.

As for how many ships would actually prove useful, even if given weapons, see this list used by the German officer in WW I you started the second wave of raiders.

He went looking for his ship, with this list of criteria:-

1. Not too fast so that coal could be conserved.
2. Cargo space sufficient to cope with a large load of mines.
3. Decks sufficiently strong to bear the recoil and weight of guns with a 15cm. capacity.
4. A new ship would be ideal.
5. Speed fast enough to overtake the average British Tramp Steamer.

It had already been found out that Liners consumed coal ( or in WW II, oil) at too high a rate for a ship operating with scant support.

One German raider in WW I used the guns from a colonial gunboat/cruiser who's machinery was too worn out to undertake a raiding cruise itself. That source of weapons is obviously going to be rather limited.

Armed merchant ships can fall into a number of categories.

Auxiliary cruisers, of several types (jobs). More useful to the British than the Germans. The British needed ships to enforce the blockade, which means ships with good sea keeping and fair endurance that can patrol the North sea and stop and search ANY ship bound in or out for contraband. Neutral ships and/or ships bound to/from neutral ports are allowed to continue. The converted Merchants freed up regular warships.
Other auxiliary cruisers, suitably refitted, provided command ships for convoys or task forces (especially amphibious task forces). They could provide ships to run down enemy raiders. Shorter endurance is less of a problem for the chasers as they have more access to coaling, oiling facilities.

In both wars, although much was hoped for before the war from such ships ( especially by the treasury which was always attracted by cheap) in actual practice the number of suitable ships was a very small percentage of the total merchant fleet.

For the Germans the number of useful roles was rather limited. As was the number of weapons even in Germany to arm such ships in WW II. The Germans were not allowed to stockpile weapons pulled from the scrapped battleships and cruisers of WW I. While I am sure they managed to squirrel away some what more than they were supposed to I really doubt there were hundreds of guns sitting in store like the RN had.

 

[Glider]

I admit that I like the idea of a GS with some additions as outlined by DonL. She is more than capable of taking on a normal convoy. A handful of destroyers/sloops converted for anti sub warfare wouldn't stand a chance and they are not too large to risk losing. The only change to DonL's idea I am tempted by, is to lose the eight individual 5.9 in guns and have one triple 5.9 in turret mounted above and behind the rear 11in turret. I like the idea of having a turret that has an advantage againt a 4.5-5 in armed escort. The weight saving would still be considerable and allow for a significant increase in AA as well as dealing with two escorts at the same time.

 

[Shortround6]

Four guns is usually the minimum for long range firing using salvos. Since you are firing a "pattern" and trying to center the target in the pattern, 3 shells gives too much chance for error and 2 guns are scarcely better than one gun. If firing short range under local control it doesn't matter as much.

 

[delcyros]

Designing a raider is not a trivial task. It should be both, expandable and long ranged to cover long distances.

I suggest a freighter modified to carry four to six armed float planes stored in the central housing (preferably Do-22W). Size around 4000 to 6000ts, max speed 22.0 kts (Diesel propulsion, single shaft), range ca. 20000nm @ 14 kts. No armour except for splinter screens. The catapult on the foredeck (to be covered by day), some underwater TT and light AAA for self defense. Doesn´t need to get in physical detection range to other merchants and can be really nasty to pin down in the loose Atlantic.


Do-22W charackteristics:
First flight: 1935 (production models aviable from mid 1938 onwards)
crew: 3
MTOW: 4 to.
max flying range: 1240 nm
speed: 190kts
armament: 4 x lmg (2 fixed fwd firing, 2 flexible mounts in ventral and rear cockpit position, 1 x 800kg torpedo or bombs