mgb IJA Type 4 mod.2 Kuchikutei "Ka-Ro"

[aizenns 3,591]

四式二型駆逐艇 (カロ艇第二型式)

Type 4 mod.2 Kuchikutei (Ka-Ro mod.2)

Blueprint of Ka-Ro mod.2 from research report

This boat muss-produced and deployed to Okinawa and Taiwan, but there aren't any photo.

 

 

About Ka-Ro

In 1941 Imperial Army start to research submarine chaser to defend fleet under landing operation.

But middle of Pacific war they start to transporting by Daihatsu-class landing craft because Japan lost air control of south pacific so large cargo-ships cannot replenish front line troops. These Daihatsu equip machine gun and 37mm guns but it is difficult to defend itself from US PT-boats.

For this reason IJA change objective of this boat to fight against PT-boats.

First prototype of Ka-Ro built August 1943. It enough performance (37 knots), but IJA reinforce its arms. Second prototype built December, and it have very good performance. After that that boat named mod.1 (Type 4 mod.1)

In parallel they build Ka-Ro with air-cooled aircraft engine in July. Engine of this boat is weaker than for mod.1 and need to use 18% of its power for cooling so it have only 25.7 knots but it adopted and named mod.2 (Type 4 mod.2)

These boats were send to Okinawa and Taiwan, and used by "Maritime Destroyer Battalion"(海上駆逐大隊) and "Maritime Mobile Brigade" (海上機動旅団).

Surprisingly, IJN Type Otsu Torpedo boat is based this boat!

 

For game, this boat will be early tiers MGB. Compared to rival of this: PT-boats, this is slow, small, and have week weapons.

37mm gun is based Type 98, 37mm tank gun so it fire is not same as PT's 37mm, and there are only 2x 650hp engines.

But "Army's MGB" is very interesting for the naval tree!

Quote

This is a off-topic: Japanese vessels that have speed same as PT-boats were only IJN Shimakaze-class DD and JMSDF PT-11 class. (There speed is 40 knots)

 

Specification

(Material: Wood)

Length between perpendiculars		18.000 m
Max width		4.300 m
Depth		2.000 m
Displacement and draft		Displacement	Draft (average)
Light-load		16.798 t	0.590 m
Normal-load		21.214 t	0.669 m
Full-load		21.961 t	0.9681 m
Cruise range		About 200 miles
Speed	Max	25.7 knots
	Normal	21.0 knots
	Lower	9.0 knots
Main Engine	Type	Type 97, 650 HP air-cooled aircraft engine
	Number	2
	Max power	930 HP (trial)
Rotate per Minute	Max	2200 rpm (trial)
	Normal	1800 rpm
	Lower	800 rpm
Propeller	Number	2
	Diameter	0.610 m
	Pitch	0.730 m
	Area	0.2200 m2
	Rotate per min	1650 rpm
Weapon		Type 4 37mm ship gun		1
		Type 98, 20mm AA		1
		depth charge dropper		2
		Ship radio Ko		1 set
		Ra-Go sonar		1

 

Type 4, 37mm ship gun (四式三十七粍舟艇砲) was based Type 98, 37mm tank gun.

 

Blueprints

Quote

 

Floor plans of Ka-Ro

This is Army boat so did not rise rising sun flag.

 

 

Quote

Lines of Ka-Ro

 

 

Camouflage

According to JACAR ref.C14020257100, standard paint before March 1944 is Grayish blue. (灰青色)

 

 

Spoiler

In JACAR ref.C14020256700 there are sample of camouflage but it color faded.

According to Okumoto, horizontal face is Ultramarine (群青), and side is mixed paint of blue and white. (He guess it will be Ultramarine : White = 5 : 1)

Spoiler

According to specification document of this boat, outside paint of this boat is "White-Green"(白緑色).

Inside of the ship is lower than chine is rust, and upper than chine is no-paint. (maybe plane wood)

 

Quote

Sources

(original documents of JACAR is in National Institute for Defense Studies, Japan Ministry of Defense)

about Camouflage

JACAR ref.C14020257100

陸兵政本審報第１９４号　迷彩（船舶）審査終了報告   (Report of complete of camouflage (Vessels) research)

JACAR ref.C14020256700

三技研報第１３６号　迷彩（船舶）研究報告 (Camouflage (vessels) research report)

 

Okumoto Gou (2016) "Boats and Ships of Japanese Army: For Landing, Transporting, Escort, Attack and special ships", Dai-Nippon Kaiga publishers, pp.56-58

ISBN978-4-499-23177-0 C0076

 

about Ka-Ro mod.2

JACAR ref.C14010850800

駆逐艇第２型式研究報告 (Kuchikutei mod.2 Research report)

 

JACAR ref.C14011003600

整理番号１０技研仕第１号　昭和１９年１１月６日　４式２型駆逐艇仕様書（案） (Type 4 mod.2 Kuchikutei Specification document (draft), November 6, 1944)

 

JACAR ref.C14020254500

カロ艇　線図 (Ka-Ro tei Lines)

 

JACAR ref.C14020254400

第２図　駆逐艇（カロ艇）線図　（被板外）  (Kuchikutei (Ka-Ro tei) lines (Outside))

 

Okumoto Gou (2016) "Boats and Ships of Japanese Army: For Landing, Transporting, Escort, Attack and special ships", Dai-Nippon Kaiga publishers, pp.86-87

 

translation of JACAR ref.C14010850800 by me

Spoiler

On 03/09/2016 at 21:25, aizenns said:

[Military secret] Rules Article 72 applied. After a done deal, need incinerate.
Reference number 34-1
1944 September 4
No.10 Army Technical Research & Development Institute

Kuchiku-tei Type 2 Research Report
 
Kuchiku-tei type2 research report

　　　　I, Research reason
By the 「兵政技密」Order No.39 (January 13, 1944), start research of Kuchiku-tei type2 with 
air-cooled aircraft engine.

    II, Evaluation to research result and Future prospects
1, Evaluation
　Structure and function of Kuchiku-tei Type 2 is good and it suits actual fighting.
2, Future prospects
  1, It's necessary to prepare manual for maintenance.
  2, Technical guidance for maintenance is performed as the need arises.

    III, Overview of the course of research
　1, Start of research

 
  End of January 1944
　2, About design
  The basic design was completed in 1944 February, and the details of the design was 
completed in 1944 March.

　3, Trial production
1, The factory which build a prototype
  Mitsubishi Heavy Industries, Nagasaki Shipyard
2, Passage of an experimental production
   Laying of a keel: April 10 1944
   The launch: June 22 1944
   Experimental production completion: July 20 1944

　4, Test sailing
Test duration: July 24 ~ 27
　At Nagasaki city Mie offing, do a completion test with continuous sailing test, speed test, 
steering and the turning test.
　Result of test is mostly good, but necessary to refurbishment a part of detail.

　5, Refurbishment
  After the test sailing, we start refurbishment and in August 10 1944 it was completed.
Result of re-test is fit as expectation performance, so we ended a research.
 

    IV, Overview of Kuchiku-tei Type 2
1, Intended use
  Mainly use for anti-submarine and anti-torpedo boat battle at coast.
2, Overview of Structural function
  This is wooden high-speed boat and it have an illustrated placement in attached chart.
  The difference between Kuchiku-tei Type 1 is use air-cooled engine, mount more strong 
weapons, and do refurbishment of structure.
(1)    The hull part
1, Hull form
  This boat is a V-bottom semi-drainage type and have a back board in edge.
2, Structure

 A, 
 Keel is made of Zelkova [*1], and keel is structured adjust the upper and lower timber, and 
place a rib made of Oak or Masaki [*2]. Spacing of ribs are 600mm, but Bow part is 400mm.
　[*1] In Japan, Zelkova is called Keyaki (ケヤキ,欅).
　[*2] 柾(Masa, Masaki)has a two meaning: if this kanji pronounced Masa, it mean wood of a 
straight grain, and if this pronounced Masaki, it mean one of a low tree Masaki.(It always used for 
hedge.) In this sentence, this kanji used in this word:”柾樹”. “樹”mean tree, so I think this mean 
Masaki.
　
 B, 
 Shell and Deck is veneer made of birch or Pine [*3] (This veneer must use Urea system 
synthetic resin adhesive), and its thickness is 12mm (Two 6mm boards) at deck and side board, 
and bottom board is 18mm (Three 6mm boards)
[*3] Print unclear, so I’m unconfident about this kanji is “松”
 
Place □□□ [*4] on shell and deck, and place two or four stringer on bottom and deck.
 C, 
 Main engine structure is obstructed round wind tunnel radially iron structure, and its upper be 
iron ceiling of machine room.
 And, exhaust port (two) place upside and Air inlet place backside of exhaust port.

3, Rooms placing
 A,
 Wheelhouse is placed center of deck, and warehouse, troops chamber/munitions depot, wireless 
room, Ra-gou [*4] room, machine room, and munitions depot/oil tank room are placed under 
the deck.
[*4] Ra-gou system is mine detect sonar developed by Japanese Army. Strangely, IJA advanced 
about sonar from IJN.
 B,
 Wheelhouse is superstructure made of veneer, window is on front and backside, door is on 
backside, 遮属板is placed upper-back , and there are command post in wheelhouse with required 
communication contact equipment. Wheelhouse have steering container, compass, the rate [*5] 
and communication equipment.
[*5]I can’t understand what mean “速力通信機器”.
 C,
Bow warehouse stock ship equipment.
 D,
Troops chamber/munitions depot has a chair and ammo box (for 37mm cannon).
 E,
Troops chamber is for crew’s resting, and in this room there are chairs and Drinking water tank 
(200 m3) [*6]
[*6] In original text didn’t show unit clearly. (“二〇〇立入”)
 F,
Wireless system and Ra-gou room has a radio and Ra-gou gauge.
 G,
In machine room, there are main-engine, sub-engine, shaft and any machines necessary for 
sailing.
 
 H,
Munitions depot stock 20mm AAgun ammo and depth charges.
 I,
Stern fuel tank room has two oblong shape 50 m3 tanks, and wheelhouse down-back oil tank 
room has one round shape 950 m3 tank.

4, Rudder
 Rudder is one and it placed center downside of stern.

5, Others
 A,
Tow apparatus and Mooring equipment (“Bit”, “Fair-leader”, “Creed”) are placed on deck.
 B, 
Built a mast on front of wheelhouse and backward of machine room, and put the antenna.

(2)    Engines
1, Main engine
 Main engine is two air-cooled radial aircraft engine, and surround it wind tunnel.
Inhale air from the intake port placed on deck backward of machine room, and cool engine with 
fan directly connected to main shaft.
 The direction of rotation of each engine is counterclockwise.

2, Shafts
 Shafting arrangement are composed a countershaft, reverse machine, “Clutch”, main shaft, and 
stern tube, etc.
 Reverse machine and clutch through countershaft (it has a 6hp starter electric motor.) and 
connect each engine and Transmitting the power to main shaft.
 Main shaft (these has a 爪shape stopper) one end is connected reverse machine or clutch and 
through stern tube and its another end projects into an underside outside the boat and connect to 
screw.

3, Screw
 Screw is two and it have 3 wings.

4, Pomp
 This boat has: Hand pump for fuel transfer, Hand pump for lubricating oil transfer, Hand pump 
for seawater priming water, Hand pump for Biruchi [*6]
[*6]I can’t guess what mean “ビルチ”.

5, Oil tanks
 
This boat has: two fuel tank (750 m3), one fuel tank (950 m3), one Fuel collecting tank (10 m3), 
one lubricating oil tank (160 m3), two Lubricating oil recycle tank (40 m3)

6, Other
 In a required part, a lubricating oil refrigerator, several meters, some 管濾機[*7] , a valve and 
cook kinds are equipped.
[*7] I think it is for Filtration…?

(3) Electric equipment
1, Power supply
24V 180AH Storage battery for engine start and lighting and contacting supply at machine room.
24V 120AH Storage battery for radio and Ra-gou machine at each room. These battery charge 
from 24V 1KW Generator connect to starboard engine by belt.

2, Electric machine
Mainly for two 24V 6hp starter motor, Lighting systems, radio connecting machines.

(4) Weapons
 

1, 37mm boats cannon
 Equip on bow deck.

2, Type 98 20mm AAG
 Equip on backward of machine room deck.

3, Depth charge drop machine
 Equip on stern each side. Each machine stock four Type 3 depth charge.

4, Depth charge
 8 depth charges on drop machine and 4 depth charges stock in Munitions depot.

6, Ra-gou machine
Handset are equipped on Starboard, its flame is on deck, operation board and other meters are in 
Ra-gou room.

 3, Main specification

The full length: 18.000m
Substantial: 4.300m
 
Depth: 2.000m

　　　　Displacement and draught
Light load condition
   Displacement: 16.799t
   Draught: 0.590m

Normal condition
   Displacement: 21.214t
   Draught: 0.699m

Loaded condition
   Displacement: 21.961t
   Draught: 0.681m

Cruising range: about 200 Nautical mile

    Speed
Max speed: 25.7kt (Official trial state)
Normal speed: 21.0kt
Lowest speed: 9.0kt

    Main engine
Form: Type 97 650hp air-cooled aircraft engine
Quantity: 2
 

Max axis horsepower: 930hp (Official trial state)

    Rotation per minute
Max: 2200 rpm
Normal: 1800 rpm
Lowest: 800 rpm

    Screw
Quantity: 2
Diameter: 0.610,
Pitch: 0.730m
Deployment area: 0.2200 m2
Rotation per minute: 1650 rpm

    Weapons
37mm boats cannon: 1
Type 98 20mm AAG: 1
Depth charge dropper: 2
Boats radio Ko: 1
 

Ra-gou machine: 1 (This is treated as 5th secret weapon)

Military Secret
No.6 research Person in charge
Chief: Army Lt. Col. Uchiyama Tetsuo
Manager: Army technical captain Sato Shigeru
Army technical Lt. Shimada Shigeyoshi
Army technical Lt. Shisen Masayoshi

Distribution destination
“兵政本”Heiseihonn(13) 
1st Institute (1)
3rd Institute (1)
4th Institute (1)
5th Institute (1)

 

 

Edited July 6, 2019 by aizenns

[Radom 4,245]

Open for discussion

[Nemrav 31]

Very good research, though one thing: what was the crew size?

Can't wait to see more of these very thorough suggestions! +1

[aizenns 3,591]

On 27/10/2018 at 05:23, Nemrav said:

Very good research, though one thing: what was the crew size?

Can't wait to see more of these very thorough suggestions! +1

Thank you very much!

But sorry, I can't find the crew data.

[Milocat 4,857]

+1 for this, would be a nice gunboat to see added.  

[Tasty95215 2,099]

The Ka-Ro has been added! However, it's listed as using the Type 94 37mm gun instead of the Type 4 ship gun (or Type 98 gun)

[aizenns 3,591]

1 hour ago, Tasty95215 said:

The Ka-Ro has been added! However, it's listed as using the Type 94 37mm gun instead of the Type 4 ship gun (or Type 98 gun)

Thanks, I write bug report on dev-server forum.

[Tasty95215 2,099]

8 hours ago, aizenns said:

Thanks, I write bug report on dev-server forum.

 

The muzzle velocity of the shells are incorrect too - it's only 574 m/s for the APHE and 583 m/s for the HE. But strangely, the penetration seems to be correct despite the muzzle velocity (38mm penetration compared to 32mm penetration of the Ha-Go's gun), so maybe Gaijin confused the Type 94 and Type 98? Either way, thank you for making the bug reports.

[leroyonly 4,311]

As the Type 4 mod.2 Kuchikutei "Ka-Ro" has been implemented in update 1.89,

 

Moved to Implemented Suggestions.