Slitherine

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I am trying to find additional information on a late-war modification made to some Yugomo class DDs. It was performed on ships that had already had #2 twin 5/40 removed and replaced with 25mm. According to Conway the #3 5/50 and the 25mm AA in the old #2 gun location were removed and replaced with a twin 5/40 mount. Watts agrees but says a twin 4.7in mount.

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ORIGINAL: Don Bowen

Thanks - that site is on my favorites list. It has a lot of data - where else can you find concise service histories - but nothing to support late war upgrades.

I have a confusing mass of data on the Yugumo, much of it contradictory. I may just use best guess/best feel and move on.

Yammas from The Apo-Tiki Lounge. Future site of WITP AE benders! And then the s--t hit the fan

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ORIGINAL: Don Bowen

I am trying to find additional information on a late-war modification made to some Yugomo class DDs. It was performed on ships that had already had #2 twin 5/40 removed and replaced with 25mm. According to Conway the #3 5/50 and the 25mm AA in the old #2 gun location were removed and replaced with a twin 5/40 mount. Watts agrees but says a twin 4.7in mount.

To confuse it even more: http://www.combinedfleet.com/yugumo_n.htm

Does anyone have anything on this??

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ORIGINAL: AlaskanWarrior

Has anyone looked at an upgrade path for the various Japanese Minelayers? Most, if not all of them were designed to be converted over to escort work, and indeed many of the surviving ones were. If needed I can give specs on these.

RM

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ORIGINAL: Don Bowen

I have this data from Watts but would appreciate anything else you might have. MLs do upgrade to escorts in our scenario. Also, Ron and Justin have proved that non-escort vessels can drop DC so the MLs that retained minelaying capability when DC were added will be implemented that way - ML with depth charges.

I could use endurance figures for these ships, both before and after conversion.

Don

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ORIGINAL: Herrbear

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ORIGINAL: Don Bowen

I have this data from Watts but would appreciate anything else you might have. MLs do upgrade to escorts in our scenario. Also, Ron and Justin have proved that non-escort vessels can drop DC so the MLs that retained minelaying capability when DC were added will be implemented that way - ML with depth charges.

I could use endurance figures for these ships, both before and after conversion.

Don

Is this a design decision by you guys in order to aid the Japanese (AI). In Watts and Gordon, "The Imperial Japanese Navy" indicate that many (not all) minesweepers and minelayers had these abilities deleted and added depth charges as conversion to ASW vessels. Is this information refuted in other sources?

MWS 1 thru 4: Towards the end of the war these vessels were used mainly as escorts and the minesweeping gear was removed and replaced by 36 DCs.

MWS 5 & 6: ...then in 1944 being modified for escort work, having the minesweeping gear removed and replaced by 36 DCs.

MWS 13 thru 16: The minesweeping gear was replaced by 36 DCs...

MWS 7 thru 12: ...By 1944...the "X" 4.7 and the minesweeping gear removed and replaced by ... 7 25mm guns and 36 DCs to make them into escort vessels.

MWS 19 thru 88 (about 1/2 cancelled): ...while in 1944...their minesweeping gear was removed...fitted with DC throwers and 36 DCs. (By the way, endurance for these and "7 class above was doubled, "making them most effective escorts")

ML[ Shirataka: During the later stages of the war, she was adapted as an escort and carried 36 DCs together with rails and throwers at the expense of her minelaying equipment.

ML Kamome & Tsubame: ...in 1943-44 they were adapted for use as escorts on local convoys, the ML gear being removed and 36 DCs being fitted.

ML Yaeyam: ...refitted towards the end of 1943 as an escort, the mine gear being removed and 36 DCs being carried.

ML Natsushima class: In 1943-44 she was fitted to cary 36 DCs at the expense of her ML rails...

As I said above, a number had both capabilities, but many had the MSW or ML capability removed as Japan needed more escorts. I think this should be a choice./color]

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ORIGINAL: Herrbear


Is this a design decision by you guys in order to aid the Japanese (AI). In Watts and Gordon, "The Imperial Japanese Navy" indicate that many (not all) minesweepers and minelayers had these abilities deleted and added depth charges as conversion to ASW vessels. Is this information refuted in other sources?

MWS 19 thru 88 (about 1/2 cancelled): ...while in 1944...their minesweeping gear was removed...fitted with DC throwers and 36 DCs. (By the way, endurance for these and "7 class above was doubled, "making them most effective escorts")

(snipped)

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ORIGINAL: Don Bowen

I am trying to find additional information on a late-war modification made to some Yugomo class DDs. It was performed on ships that had already had #2 twin 5/40 removed and replaced with 25mm. According to Conway the #3 5/50 and the 25mm AA in the old #2 gun location were removed and replaced with a twin 5/40 mount. Watts agrees but says a twin 4.7in mount.

To confuse it even more: http://www.combinedfleet.com/yugumo_n.htm

Does anyone have anything on this??

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ORIGINAL: Subchaser
I think none of Naganami’s refits should be modeled in the game.

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ORIGINAL: Don Bowen


I have only two sources on Japanese Minesweepers: Japanese Warships of WWII by Watts and Conway's All The World's Fighting Ships series. Both of these generally agree with most of your data. There are two things on which I need more information (or advice).

1. I can find no reference to support the inclusion of Depth Charges on the 12/41 versions of any of the "W" series minesweepers. Matrix has included them (classses 124-126). I do have documentation for DC on the "WA 1" class. Also, major U.S. classes of Minesweeper also carried DC. Should I delete the Depth Charges from the "W" series until they are refitted mid-war?

I would not equip them with DCs until they were refitted for escort work except where known.

2. I also can not find any data for endurance increases on the W 19 or any other classes. Do you have details?

Watts and Gordon says MWS #7-12 radius 2000m @ 14knts and indicates by 1944 when the MS gear was removed "The radius of action was increased to 4000m at 14knts by using some of the ballast tanks for fuel oil.

For the MSW 19 class they show the initial radius the same as in the #7 class and state that "as in the #7 class their radius was doubled up to 4000 miles making them most effective escorts.

That is all the information I have abount expanding their radius of action.

Don

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ORIGINAL: Don Bowen

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ORIGINAL: Subchaser
I think none of Naganami’s refits should be modeled in the game.

Thanks and will do. What is the source of this excellent information??

Don

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Fubuki - Increase of the 6/44 refit to 6-10 13mm.

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Akatsuki - Show the 4/43 and 4/44 refits with 4x13mm and the 1/45 refit increase to 10x13mm.

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Shiratsuyu - I am not sure if the initial configuration didn't carry the 4x13mm. I did not see that they were deleted during the 6/43 nor 5/44 refit.

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Asashio, Kageo and Yugumo - While the 22x25mm is within the range my sources indicate up to 28x25mm. That would be a significant increase. Also, I show that the 5/44 refit should include 4x13mm.

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Shimakaze - Not sure that the 11/44 refit is needed as this class only has one ship. Make the 11/44 in the 6/44 refit figure. Source say by mid 44 or in 1944...Also include 4x13mm.

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ORIGINAL: Andrew Brown

There are spare nationality slots in the data, but I have no idea if they would be treated as Axis or Allied.

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ORIGINAL: mikemike

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ORIGINAL: Andrew Brown

There are spare nationality slots in the data, but I have no idea if they would be treated as Axis or Allied.

I just tested that under 1.40, for a similar reason. I´d done that already under 1.21, but the results are subtly different. There are three unassigned nationalities, N3, N17 and N19. I assigned those nationalities to several LCU´s with random leaders. Using N19 will crash the game as it loads the data. N17 is Communist Chinese; appropriate leaders will be assigned. N3, under 1.21, seems to have been neutral, at least its units were colored yellow, and the leaders were all WO´s with names that sounded Hungarian. Now, under 1.4, N3 units are red (Japanese) and have Staff Officers as leaders. The nationality is simply omitted in all texts (Nationality name is a Null string). Hope this helps.

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ORIGINAL: Don Bowen

Did not find anything on the definition of Allied or Japan, probably a range check something like ">3 = allied else japanese".

Note however that N17 is defined, as Communist China

These are the actual values from the program (the ... represent nulls). They are in reverse order:

Canada..Communist China.Philippines.Commonwealth....Indian..Soviet..Chinese.Dutch...French..British.New Zealand.Australian..US Marines..US Army.US Navy.IJ Navy.IJ Army.

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ORIGINAL: Subchaser

My previous notes posted several months ago, I deleted everything that was already fixed/added.

IJN submarines.

Type KD6A/B (Kaidai 6a/b)

- Submarines I-171 - I-175 should have 4,7in/45 3YT gun instead of 3,9in/50 type 88.
- Submarines I-168 – I-173 should have 1 x 2x13,2mm type 93 AA mg, and I-174 – I-175 subs should have 2 x 2x13,2mm mgs.

Type KD7 (Kaidai 7)

- These subs had twin 25mm mount not single.

Type J1 (Junsen 1)

I-5, I-6 were the first Japanese submarines designed to carry an aircraft and if aircraft containers on I-5 were removed and additional gun was mounted in 1940, I-6 entered pacific war duly equipped for air reconnaissance missions.

- I-6 should have 1 aircraft capacity and 1 Glen float plane, 4 forward tubes with 3 ammo, 2 aft tubes with 3 ammo and one 4,7in/45 3YT gun.
- Subs I-2, I-4 and I-6 had one 13,2mm type 93 AA mg mount

Type J3 (Junsen 3)

- In game these subs have two twin 13,2mm mounts and one single 13,2mm mg, this should be changed to one twin 25mm mount, one twin and one single 13,2mm mgs mounts.

Type KRS (Kirai-sen)

- Durability should be changed from 20 to 24.

Maneuverability of the following types should be changed
Type STo – 51,
Type AM – 52,
Type A2 – 54,
Type A1 – 56,
Type B3/4 – 57,
Type B2 – 58,
Type B1 – 58,
Type C3/4 – 57,
Type C2 – 59,
Type C1 – 59,
Type KD7 – 63,
Type KD6A/B – 64,
Type KD5 – 65,
Type J3 – 58,
Type J1 – 63,
Type KRS – 59,
Type ST – 92,
Type STS – 95,
Type L4 – 73. .

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Type C2 (Kaidai Hei-Gate C2)

I-49, I-50, I-51 - these are the phantom subs, none was even laid down. Order for them was really placed in 1941, under fleet replacement program, but it was canceled in may 1943. However these are in the game, this supposes that in game I-48 will be laid down in september ’43, I-50 in july ’43 and I-51 in february ’44. If these subs were included to beef up IJN submarine force in 1945, when it probably will be already mauled, then I must admit that this is strange choice. May be it would better to give player submarines which were really laid down and by spring ’45 were almost ready. I-404 was 95% ready when she was sunk by US carrier planes in Kure on 28 july ’45; I-1 (type AM) 70% ready; I-15 (type AM) 90% ready; I-204 90% ready; I-205 -80% ready; I-206 was 85% ready in march ’45 etc. Or to launch more perspective boats from the canceled order list than these kaidais in late 43, there were so many plans… any ideas?

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Where is japanese transport submarine fleet?

28 IJN transport submarines are missing, (since IJA vessels are completely ignored there is no wonder why 26 army transport submarines also weren’t included).

The number of transport submarines Japanese built during the war and the number of subs converted ito undersea transports actually deserves additional ship type – SST, transport submarine.

Type Sen-Ho (2 subs - I-351, I-352)
Max Speed - 16
Cruise Speed - 10
Mvr - 59
Dur- 34
End- 27 500
Fuel- 750
Cap - 365 tons (FUEL)
Torps - 4x 21in type 95 –F (1)
AA guns - 2 x 3x25mm type 96 + 1 x 1x25mm type 96

Type Sen-Yuso-Sho (12 subs - Ha-101 – Ha-112)
Max Speed - 10
Cruise Speed - 8
Mvr- 61
Dur - 31
End - 3 500
Fuel - 75
Cap - 60
AA guns - 1 x 25mm type 96

26 army sub transports (12 of Yu-1 type and 14 of Yu-1001 type).

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Part 2. Minelayers

OOB corrections

Ikitsushima

Wrong refit. 3in/40 type 88 guns were replaced with 2 x 2x25mm AA guns before the war actually, not in 44. In 1944 ship was refitted in order to enlarge her mines holds, that was the main goal of the refit, in 1944 number mines was increased from 300 to 400, besides that 3 x 2x13,2mm AA mgs were added.

Ma-1

Mines type 4 (1944 design) should be replaced with type 93 mines.

Hatsutaka

Cruise speed should be 10 instead of 15. In 1943-44 must be refitted as escorts, mine laying equipment should be dismounted and 2 DCT should be installed (36 depth charges type 2)

Hirashima

Wrong refit. There should be no DCT in original minelayer configuration. And after refit 9/43 ships should have no minelaying capabilities, their endurance must be increased up to 5000 nm (with 55 fuel) 2x DCT (36 depth charges type 2) must be added.

Sokuten

Hirashima, Sokuten and Ajiro types were in fact one ML class – Sokuten. In wartime Japanese classification table they were all listed as Sokuten class ships (different replacement programs 3,4,5), multipurpose kaidai auxiliaries, capable to lay mines and nets of all types. If Hirashima class vessels are supposed to be refitted in game, why Sokuten class refit is not modeled? Sokutens were refitted in the same time as Hirashima class. In 9/43 configuration these ships should not have mines and instead should be equipped with 2 DTC (36 depth charges type 2).

Toshima

These ships represented in their 1944 configuration but without DTCs. In 1941 they should have 1x 3in/40 type 88 gun and 60 mines type 93, after refit in 1944 they should have 1x 3in/40 type 88 gun, 120 mines type 4, 4 DTC (18 depth charges type 2) and one twin 13,2mm AA mg.

Natsushima

Amalgamation of 3 ML classes - Nasami, Tsubame and Sarushima. Because of that, correct refit cannot be modeled. Kamome, Tsubame and Sarushima lost their mine laying equipment in 1944 and were refitted as escort vessels with 2 DTC (36 depth charges type 2).

Yaeyama

This ML was also converted in 1944. Mines hardware was removed and 2 DTC (36 depth charges type 2) installed.

Shirataka

If all previous types really were minelayers during the war, this ship became a patrol gunboat already in 1940. This ship should have only one 120mm gun and 6 DTC (54 depth charges type 95).

Katsuriki

Since 1936 Katsuriki was in service as an oceanographic vessel of navy department W, in january ’42 was refitted again, this time as an rescue ship. Probably should not be modeled at all.

Missing types

Hatsushima Class

These were probably not included because this type was designed as a cable layer type, but in fact these 4 ships were multipurpose and were capable to lay mines as well. The only problem was their awfully small mine holds, which were enlarged only in 1943-44.

Hatsushima – commissioned 10/1940, Kawasaki, Kobe
Tsurushima – commissioned 03/1941, Kawasaki, Kobe
Odate – commissioned 07/1941, Harima SB
Tateishi - commissioned 08/1941, Harima SB

1940-1943 (originally cable layers)
1564 / 1670 tons, 2 boilers x 2300 hp, 14 knots,
1 x 76mm/40 gun, 1 x 2x13,2mm MG, 12 mines

1943-1944 (converted to minelayers)
1 x 76mm/40 gun, 6 x 25mm AA cannons, 2 x DTC 36 depth charges type 2, 120 mines type 93.

Tateishi – 09/1943
Odate – 11/1943
Hatsushima – 2/1944
Tsurushima – 3/1944

Kamishima Class

Simplified version of Ajiro/Sakuten type, only 1 was built, order for 18 additional ships under 43/44 replacement program, was canceled.

Kamishima – commissioned 06/12/1945, Sasebo Arsenal K

766 / 787 tons, 2 x 1900 hp diesel. 16,5 knots
2x 40mm/40 guns, 3 x 3x25mm AA cannons, 4 x DTCs (36 depth charges type 2), 120 mines type 93.

Ajiro Class

One Sakuten class ML is missing. I guess it was not included since Ajiro never was a minelayer, when all other Sakutens were converted to escorts Ajiro was still under construction and it was decided to complete this unit as escort vessel also.

Ajiro – commissioned 7/1943, Hitachi, Innoshima

717 / 733 tons, 2 x 3600 hp diesel, 21 knots, fuel - 35 tons; endurance 2550 miles at 14 knots; Crew – 100; 1 x 76mm/40 gun; 2 x 3x25mm AA cannons; 2 x DTC (36 depth charges type 2.)

Transport-minelayers

Two standard transports completed as minelayers.

Eijo - (2-DRS class conversion) - commissioned 3/45, Kiangnan Dock, Shanghai
Mino - (2-DT class conversion) - commissioned 8/45, Naniwa Dock, Osaka

3224 / 5118 tons, 12 knots, 1 x 120mm/40 gun, 14 x 25mm AA cannons; 380 mines type 93.

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Amphibious and Landing Crafts

122 crafts of this type are missing… or better to say ignored.

T-1 Class (1st Class Fast Transports)
EDIT: Added

Type SS-1 Landing craft

22+5 units: SS-1 – SS-22 (commissioned 2/43 – 7/44) + 5 unfinished units

Japanese analog of LCM craft (even looked very much the same). Type was designed for Army, but all ships were under navy control.

Displacement – 933 tons, Dimensions – 63 x 9,6 x 2,8 meters. Power unit – 2 diesels 1800hp. Max Speed – 13,5 knots, cruise –12; Endurance – 2000 miles (12 knots). Armament – 1 x 76mm/40 gun + 1 mortar + 2 x 2x25mm. Load (project specification) – 4 x 15tons tanks + 1 transport vehicle + 150 men.

Type SB/SBD/SBT Landing craft

73 units: SBD type – 6 units commissioned in 1944, SBT type – 47 units commissioned 4/1944 – 3/1945, SB type – 20 units commissioned 5/1944 – 9/1944

Designed in late 1943 as SS-1 replacement type. By design and conception they were very close to LST-2 vessels, but a bit smaller and faster. Last letter in designation goes to type of the power unit, D for diesel and T for turbine. SB version ships were initially built for army but were transferred to navy in October 1944.

(SBT subtype) Displacement – 970/1004 tons, Dimensions – 80,5 x 9,1 x 2,9 meters. Power unit – 1 turbine, 2 boilers at 2500hp. Max Speed – 16 knots, cruise –14; Endurance – 2500 miles (14 knots). Armament – 1 x 76mm/40 gun + 2 x triple 25mm mount. Load – 218 tons of supplies, or 320 men, or 7 x 15tons tanks or 67 tons of cargo and 120 men.

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Shinshu Maru

1 unit - commissioned in 1934.

First Japanese vessel designed for landing operations. Ship is in the game, but modeled as ordinary sAK. In fact she was designed as mothership vessel for smaller landing craft and as floatplane tender in the same time.

Displacement – 9000/11810 tons, Dimensions – 156 x 22 x 9 meters. 2 x turbines 8000hp, Max Speed – 19 knots, cruise – 12, Endurance – 16000 (at 9 knots) Armament – 8 x 76mm/40 gun + 3 x twin 25mm mount + 12 x 13,2mm AA mgs. 20 floatplanes (Shinshu Maru Daitai (!)), 2 catapults. Load – 29 Daihatsu landing barges and 2200 men.

Japanese thought that Shinshu Maru concept was quite successful and converted several standard transports into amphibious operations support ships, 7 ships total. 4 of these are in the game (as ordinary transports) Mayasan Maru, Tamatsu Maru, Hyuga Maru, Takatsu Maru, and 3 more are missing - Tokitsu Maru, Kibitsu Maru, Setsu Maru

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ORIGINAL: Subchaser

Type J1 (Junsen 1)

I-5, I-6 were the first Japanese submarines designed to carry an aircraft and if aircraft containers on I-5 were removed and additional gun was mounted in 1940, I-6 entered pacific war duly equipped for air reconnaissance missions.

- I-6 should have 1 aircraft capacity and 1 Glen float plane, 4 forward tubes with 3 ammo, 2 aft tubes with 3 ammo and one 4,7in/45 3YT gun.
- Subs I-2, I-4 and I-6 had one 13,2mm type 93 AA mg mount