Let's Build! A WW2 Japanese escort.

The Japanese merchant marine suffered heavily from submarine attacks during WW2, partly because they were largely unescorted. In addition to holding back as many ships as possible for the decisive battle, the IJN designed ships which were poorly suited to being ASW escorts and didn't think much of the job in general. As others have remarked this is strange for an island nation which depends on overseas trade, especially since they had been Allied with the UK in WW1 and presumably heard something about the U-boat offensive and it's effects.

So let's say there is a hardworking group of officers tucked away in the back of IJN HQ who are at least aware of the potential issue and decide to do what they can about it. They can't change naval policy very much or decide the construction of many ships - the decisive battle is very important, after all. But they can try to come up with a design that can be built in civilian yards and is suitable for escorting merchant ships, thus releasing destroyers and cruisers for real warrior's work. They can probably get a few examples built, and start working out how to employ them.

What might they come up with?
 
For starters, a new leadership...

Coming up with a ship design is easy. The problem will be funding. And that comes from the brass. Who wouldn't even hear of it...
 
For starters, a new leadership...

Coming up with a ship design is easy. The problem will be funding. And that comes from the brass. Who wouldn't even hear of it...

"It takes three years for a navy to build a new ship, and three hundred to build a new tradition."
 

TFSmith121

Banned
Japan designed and built ASW escorts in the interwar era, like all the major powers, with the goal of emergency production as an element of mobilization. The first standard design was the Shimushu class sloops, of which four were built under the 1937 program and commissioned in 1940-41. These were 1,000-ton sloops, 19 knots, with 3 4.7 inch guns and capable of use as escorts or minesweepers. Including the older destroyers, the IJN had ~75 ocean-going escorts of various types in 1941, not including minelayers and minesweepers or conversions. They needed better organization and doctrine as much as numbers.

Best,
 
Yes, of course. There's no likelihood that these designs will be built in numbers before the outbreak of war. These officers are likely aware of that. But if they are fairly small and cheap and don't take valuable yard-space away from "real" fighting ships, a few might get built... and once Japan realises they need them, we might see a few more. Or a lot more.

In any case, the focus of this thread isn't really intended to be on the factional blinkers of IJN HQ. I'm more interested in the technical aspects - starting in 1937, what could have the IJN come up with along these lines?
 
Japan designed and built ASW escorts in the interwar era, like all the major powers, with the goal of emergency production as an element of mobilization. The first standard design was the Shimushu class sloops, of which four were built under the 1937 program and commissioned in 1940-41. These were 1,000-ton sloops, 19 knots, with 3 4.7 inch guns and capable of use as escorts or minesweepers. Including the older destroyers, the IJN had ~75 ocean-going escorts of various types in 1941, not including minelayers and minesweepers or conversions. They needed better organization and doctrine as much as numbers.

Best,

Excellent, thank you. The Shimushu class look pretty promising, but only four were built. Their successors look much more like ASW ships. Is there some way they could have been improved early on?
 

TFSmith121

Banned
Well, the designs they did build, from destroyers on down, were effective enough; they were poorly organized and coordinated poorly with the IJAAF. They could have built roughly another 70 sloops for one Yamato, of course.
 
Build a clone of the River or Castle-class ships the RN built, with modifications to allow for longer range.
 
What the Japanese needed was an ASW advocate. A Genda for ASW or maybe even a salty old sailor who was willing to sacrifice his career by placing priority on such an unglamorous area of naval warfare. Somebody like this guy https://en.wikipedia.org/wiki/Frederic_John_Walker.

There was only one Johnny Walker - a true sailor.

Would the Japanese have needed one though (hear me out) - after all unlike the British and Americans who had a very vexing experience of it they had not been subjected to unrestricted Submarine Warfare and while they no doubt had knowledge of it etc, during the 30s would the Japanese realistically have expected the home islands to come under a Submarine Blockade?
 
Ooops, I posted that before seeing those posts... my bad... delayed reading! :oops:

But yes, the basics are the same: 20-25 knots top speed, 2-4 3-5" main guns medium range AAA/ASuW, as much light AAA as can be crammed and multiple ASW weapons, all this in a simplified, easy-to-build hull. The japanese have the added problem (as the US) of needing longer endurance, to work in the Pacific.
 
The IJN participated in the Mediterranean campaign during WW 1, so they were aware of the need for ships to be escorted to prevent submarine attacks. There are also strong organisational connections with the RN into the 30s, so their poor showing is still surprising.

I have always thought that a possible solution for the IJN was to have the Convoy Escorts be constructed and crewed primarily by Taiwanese and Koreans.
 
There was only one Johnny Walker - a true sailor.

Would the Japanese have needed one though (hear me out) - after all unlike the British and Americans who had a very vexing experience of it they had not been subjected to unrestricted Submarine Warfare and while they no doubt had knowledge of it etc, during the 30s would the Japanese realistically have expected the home islands to come under a Submarine Blockade?

I actually have his book at home, great read and spurred my interest in ASW during my time in the Navy.

The IJN conducted an exercise with their submarine arm in the late 30's or in 1940 IIRC simulating a submarine blockade, which replicated the results of the USN submarine campaign in 1944 / 1945. So IMO they had the knowledge to improve their organisational structure, but chose not to.
 
Here's two Light DD's I designed long ago for NavWeapons forum in response to a request for designs. The quintuple 24-inch TT's were requested as part of the design. Personally I think 150 rpg is low and needs to be increased...

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Suyukaze, IJN Light Destroyer laid down 1937 (Engine 1945)

Displacement:
1,389 t light; 1,432 t standard; 1,576 t normal; 1,692 t full load

Dimensions: Length overall / water x beam x draught
286.70 ft / 280.00 ft x 29.00 ft x 15.00 ft (normal load)
87.39 m / 85.34 m x 8.84 m x 4.57 m

Armament:
4 - 3.94" / 100 mm guns (2x2 guns), 30.58lbs / 13.87kg shells, 1937 Model
Dual purpose guns in turrets (on barbettes)
on centreline ends, evenly spread
18 - 0.98" / 25.0 mm guns (6x3 guns), 0.48lbs / 0.22kg shells, 1937 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
4 - 0.52" / 13.2 mm guns (2x2 guns), 0.07lbs / 0.03kg shells, 1937 Model
Machine guns in deck mounts
on centreline, all forward, all raised mounts - superfiring
Weight of broadside 131 lbs / 60 kg
Shells per gun, main battery: 150
4 - 24.0" / 609.6 mm above water torpedoes

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.50" / 38 mm 1.00" / 25 mm 1.50" / 38 mm

- Conning tower: 1.50" / 38 mm

Machinery:
Oil fired boilers, steam turbines,
Direct drive, 2 shafts, 24,243 shp / 18,085 Kw = 30.00 kts
Range 4,000nm at 15.00 kts
Bunker at max displacement = 260 tons

Complement:
124 - 162

Cost:
£0.808 million / $3.231 million

Distribution of weights at normal displacement:
Armament: 16 tons, 1.0 %
Armour: 30 tons, 1.9 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 26 tons, 1.6 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 4 tons, 0.3 %
Machinery: 612 tons, 38.8 %
Hull, fittings & equipment: 650 tons, 41.2 %
Fuel, ammunition & stores: 188 tons, 11.9 %
Miscellaneous weights: 80 tons, 5.1 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
982 lbs / 445 Kg = 32.1 x 3.9 " / 100 mm shells or 0.4 torpedoes
Stability (Unstable if below 1.00): 1.03
Metacentric height 0.8 ft / 0.3 m
Roll period: 13.4 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.40
Seaboat quality (Average = 1.00): 1.01

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.453
Length to Beam Ratio: 9.66 : 1
'Natural speed' for length: 19.26 kts
Power going to wave formation at top speed: 70 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 18.41 ft / 5.61 m
- Forecastle (20 %): 16.71 ft / 5.09 m
- Mid (50 %): 14.71 ft / 4.48 m
- Quarterdeck (15 %): 11.71 ft / 3.57 m
- Stern: 11.71 ft / 3.57 m
- Average freeboard: 14.57 ft / 4.44 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 139.3 %
- Above water (accommodation/working, high = better): 66.2 %
Waterplane Area: 5,394 Square feet or 501 Square metres
Displacement factor (Displacement / loading): 108 %
Structure weight / hull surface area: 51 lbs/sq ft or 249 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.82
- Longitudinal: 5.69
- Overall: 0.99
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is cramped

*****************

Suyukaze II, IJN Light Destroyer laid down 1937 (Engine 1945)

Displacement:
1,371 t light; 1,410 t standard; 1,553 t normal; 1,668 t full load

Dimensions: Length overall / water x beam x draught
296.73 ft / 290.00 ft x 29.00 ft x 15.00 ft (normal load)
90.44 m / 88.39 m x 8.84 m x 4.57 m

Armament:
3 - 3.94" / 100 mm guns in single mounts, 30.58lbs / 13.87kg shells, 1937 Model
Dual purpose guns in deck mounts with hoists
on centreline ends, majority aft, 1 raised mount aft
12 - 0.98" / 25.0 mm guns (4x3 guns), 0.48lbs / 0.22kg shells, 1937 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
4 - 0.51" / 13.0 mm guns (2x2 guns), 0.07lbs / 0.03kg shells, 1937 Model
Machine guns in deck mounts
on centreline, all forward, all raised mounts - superfiring
Weight of broadside 98 lbs / 44 kg
Shells per gun, main battery: 150
5 - 24.0" / 609.6 mm above water torpedoes

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.50" / 13 mm - -

- Conning tower: 1.50" / 38 mm

Machinery:
Oil fired boilers, steam turbines,
Direct drive, 2 shafts, 23,202 shp / 17,309 Kw = 30.00 kts
Range 4,000nm at 15.00 kts
Bunker at max displacement = 258 tons

Complement:
123 - 160

Cost:
£0.765 million / $3.060 million

Distribution of weights at normal displacement:
Armament: 12 tons, 0.8 %
Armour: 8 tons, 0.5 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 3 tons, 0.2 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 4 tons, 0.3 %
Machinery: 586 tons, 37.7 %
Hull, fittings & equipment: 685 tons, 44.1 %
Fuel, ammunition & stores: 183 tons, 11.8 %
Miscellaneous weights: 80 tons, 5.1 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,019 lbs / 462 Kg = 33.3 x 3.9 " / 100 mm shells or 0.4 torpedoes
Stability (Unstable if below 1.00): 1.03
Metacentric height 0.8 ft / 0.3 m
Roll period: 13.3 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.30
Seaboat quality (Average = 1.00): 1.01

Hull form characteristics:
Hull has raised forecastle
and transom stern
Block coefficient: 0.431
Length to Beam Ratio: 10.00 : 1
'Natural speed' for length: 19.61 kts
Power going to wave formation at top speed: 67 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 18.50 ft / 5.64 m
- Forecastle (20 %): 16.50 ft / 5.03 m (10.50 ft / 3.20 m aft of break)
- Mid (50 %): 14.50 ft / 4.42 m
- Quarterdeck (15 %): 12.50 ft / 3.81 m
- Stern: 10.50 ft / 3.20 m
- Average freeboard: 13.66 ft / 4.16 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 133.9 %
- Above water (accommodation/working, high = better): 51.5 %
Waterplane Area: 5,488 Square feet or 510 Square metres
Displacement factor (Displacement / loading): 114 %
Structure weight / hull surface area: 55 lbs/sq ft or 270 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.94
- Longitudinal: 5.09
- Overall: 1.12
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is cramped
 
A modified version where the IJN, realizing the 25mm AA gun is worthless, builds the KM 37mm under license. Note the quintuple 24-inch TT is now a quad while the Main Battery now has 300 rpg...

************

Suyukaze III, IJN Light Destroyer laid down 1942 (Engine 1945)

Displacement:
1,464 t light; 1,531 t standard; 2,099 t normal; 2,553 t full load

Dimensions: Length overall / water x beam x draught
321.70 ft / 315.00 ft x 36.00 ft x 17.00 ft (normal load)
98.05 m / 96.01 m x 10.97 m x 5.18 m

Armament:
4 - 3.94" / 100 mm guns (2x2 guns), 30.58lbs / 13.87kg shells, 1942 Model
Dual purpose guns in turrets (on barbettes)
on centreline ends, evenly spread
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.55lbs / 0.70kg shells, 1942 Model
Anti-aircraft guns in deck mounts
on centreline ends, evenly spread, all raised mounts
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.55lbs / 0.70kg shells, 1942 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
6 - 0.98" / 25.0 mm guns in single mounts, 0.48lbs / 0.22kg shells, 1942 Model
Anti-aircraft guns in deck mounts
on side, evenly spread
Weight of broadside 138 lbs / 62 kg
Shells per gun, main battery: 300
4 - 24.0" / 609.6 mm above water torpedoes

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 2.00" / 51 mm 1.00" / 25 mm 2.00" / 51 mm

- Conning tower: 1.00" / 25 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 29,829 shp / 22,253 Kw = 31.00 kts
Range 9,000nm at 18.00 kts
Bunker at max displacement = 1,022 tons

Complement:
154 - 201

Cost:
£1.089 million / $4.356 million

Distribution of weights at normal displacement:
Armament: 17 tons, 0.8 %
Armour: 36 tons, 1.7 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 32 tons, 1.5 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 4 tons, 0.2 %
Machinery: 753 tons, 35.9 %
Hull, fittings & equipment: 558 tons, 26.6 %
Fuel, ammunition & stores: 635 tons, 30.3 %
Miscellaneous weights: 100 tons, 4.8 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,144 lbs / 519 Kg = 37.4 x 3.9 " / 100 mm shells or 0.5 torpedoes
Stability (Unstable if below 1.00): 1.30
Metacentric height 1.7 ft / 0.5 m
Roll period: 11.5 seconds
Steadiness - As gun platform (Average = 50 %): 54 %
- Recoil effect (Restricted arc if above 1.00): 0.16
Seaboat quality (Average = 1.00): 1.00

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.381
Length to Beam Ratio: 8.75 : 1
'Natural speed' for length: 20.84 kts
Power going to wave formation at top speed: 67 %
Trim (Max stability = 0, Max steadiness = 100): 54
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 18.41 ft / 5.61 m
- Forecastle (20 %): 16.71 ft / 5.09 m
- Mid (50 %): 14.71 ft / 4.48 m
- Quarterdeck (15 %): 11.71 ft / 3.57 m
- Stern: 11.71 ft / 3.57 m
- Average freeboard: 14.57 ft / 4.44 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 128.6 %
- Above water (accommodation/working, high = better): 87.0 %
Waterplane Area: 7,176 Square feet or 667 Square metres
Displacement factor (Displacement / loading): 118 %
Structure weight / hull surface area: 39 lbs/sq ft or 192 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.56
- Longitudinal: 2.59
- Overall: 0.66
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is cramped
 
A design by Joshua Kintner...

***************

Kato, IJN ASW Sloop laid down 1942

Displacement:
602 t light; 620 t standard; 765 t normal; 881 t full load

Dimensions: Length overall / water x beam x draught
250.00 ft / 250.00 ft x 35.00 ft x 10.00 ft (normal load)
76.20 m / 76.20 m x 10.67 m x 3.05 m

Armament:
1 - 3.94" / 100 mm guns in single mounts, 30.00lbs / 13.61kg shells, 1942 Model
Dual purpose gun in deck mount
on centreline forward
3 - 0.98" / 25.0 mm guns (1x3 guns), 0.50lbs / 0.23kg shells, 1942 Model
Anti-aircraft guns in deck mount
on centreline aft
Weight of broadside 32 lbs / 14 kg
Shells per gun, main battery: 150

Machinery:
Diesel Internal combustion generators,
Electric motors, 1 shaft, 7,218 shp / 5,384 Kw = 24.00 kts
Range 10,000nm at 12.00 kts
Bunker at max displacement = 261 tons

Complement:
72 - 94

Cost:
£0.323 million / $1.294 million

Distribution of weights at normal displacement:
Armament: 4 tons, 0.5 %
Machinery: 189 tons, 24.6 %
Hull, fittings & equipment: 360 tons, 47.0 %
Fuel, ammunition & stores: 163 tons, 21.3 %
Miscellaneous weights: 50 tons, 6.5 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,571 lbs / 712 Kg = 51.5 x 3.9 " / 100 mm shells or 0.7 torpedoes
Stability (Unstable if below 1.00): 1.40
Metacentric height 1.9 ft / 0.6 m
Roll period: 10.8 seconds
Steadiness - As gun platform (Average = 50 %): 51 %
- Recoil effect (Restricted arc if above 1.00): 0.02
Seaboat quality (Average = 1.00): 1.27

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.306
Length to Beam Ratio: 7.14 : 1
'Natural speed' for length: 15.81 kts
Power going to wave formation at top speed: 58 %
Trim (Max stability = 0, Max steadiness = 100): 40
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 17.39 ft / 5.30 m
- Forecastle (20 %): 11.07 ft / 3.37 m
- Mid (50 %): 11.07 ft / 3.37 m
- Quarterdeck (15 %): 11.07 ft / 3.37 m
- Stern: 11.07 ft / 3.37 m
- Average freeboard: 11.58 ft / 3.53 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 91.7 %
- Above water (accommodation/working, high = better): 154.3 %
Waterplane Area: 5,270 Square feet or 490 Square metres
Displacement factor (Displacement / loading): 167 %
Structure weight / hull surface area: 45 lbs/sq ft or 219 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.89
- Longitudinal: 2.96
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Good seaboat, rides out heavy weather easily
 
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