- Yes
- No
Gunboat Daihatsu (Buso Daiahtsu / 武装大発)
7.7mm Type 92 HMG with AA sight on the bow of Daihatsu
Historical Background
Daihatsu-class landing craft (Daihatsu is shorten of Large Motorboat in Japanese) developed by Japanese army since 1920s.
Originally it was designed for land troops, tanks and munitions to enemy coast but due to its high convenient to use it was also used for auxiliary gunboat.
In South Pacific, US torpedo boat’s raiding was very serious problem for Japanese army’s sea lane. However in that time Japanese army had only Soko-Tei (AB), Kousoku-Tei Ko (HB-K) or Kousoku-Tei Otsu (HB-O) but all of them had serious problems:
Soko-Tei have good weapons but its too slow, Kosoku-Tei Ko have very good speed (faster naval fast craft) but did not had weapon, and Otsu had only 7.7mm single MG. Furthermore, there aren’t enough number of such boats.
Therefore, for temporary stopgap they used weaponized landing craft to hunt PT-boats.
Specification was extremally inferior to PT-boats but according to frontline’s report some of them sunk PT-boats, and captain was called “Tiger of the Solomon”.
This article is generally basis on manual of Japanese army of weaponize Daihatsu and attack PT-boats.
Design
There were multiple layouts of the gun, but generally speaking IJA’s one had three weapons:
- Bow: Heavy weapons (20 mm autocannon or 37 mm AT cannon)
- Midship: Autocannon (13.2 mm single MG)
- Stern: Heavy machine gun (7.7 mm single MG)
20mm Autocannon
40mm/37mm QF gun
(IJN also used weaponized Daihatsu but normally weapon was one 13mm or 7.7mm MG. Also, they build crew cabin in midship.)
Crew layout for 20mm autocannon and 40mm cannon
This layout scheme seems to have been improved based on actual battles.
According to battle report attached in document, equipment patterns were below:
- 1x 7.7mm MG
- 2x 7.7mm MG
- 1x 13.2mm MA
- 1x 13.2mm MA + 2x 7.7mm MG
- 2x 13.2mm MA + 1x 7.7mm MG
- 1x 20mm MA
- 1x 37mm TA
- 1x 37mm TA + 1x 7.7mm MG
- 1x 75mm BA
- 1x 75mm BA + 1x 7.7mm MG
Battle reports:
Spoiler
July 21, 1943 near Huon Peninsula, New Guinea
| Type | Weapon |
|---|---|
| Soukou-Tei | 1x TKG, 2x Turret MG |
| Command boat | 1x MA, 2x MG |
| 2nd/3rd boat | 2x MG |
| note: MA will be 13.2mm autocannon. MG will be 7.7mm heavy machine gun. | |
| In this battle, MA and MG did not had protection so gunners were killed immediately. Only Soukou-Tei was survived. |
July 29, 1943, Dampier Strait
| Type | Weapon |
|---|---|
| Command boat | 1x MA (20mm) |
| 2nd boat | 1x MA (20mm) |
| 3rd, 5th boat | 1x MG |
| 4th boat | 1x MA (13mm) |
| “Lesson: Do NOT use luminous signal” |
December 10, 1943, Cape Hardenberg (Bismark?)
| Type | Weapon |
|---|---|
| Command boat | 1x TA, 1x MG |
| 2nd boat | 2x MA, 1x MG |
| 3rd boat | 1x TA, 1x MG |
| 4th boat | 2x MA |
| They sunk one PT boat. |
September 10, 1943
| Type | Weapon |
|---|---|
| Command boat | 1x BA, 1x MG |
| 2nd boat | 1x BA, 1x MG |
| 3rd boat | 1x BA |
| 4th boat | 1x TA |
| They sunk one PT boat and damaged one, but two troops were killed. |
October 9, 1943
| Type | Weapon |
|---|---|
| Command, 2~4th boat | 1x TA, 1x MG |
| lesson: If they had hand grenades, they could damage enemy ship when charge to enemy |
Hull design
It had stable “W-shape” bottom bow and protected screws.
Engine room is stern of the ship, and steering post is roof of engine room.
Displacement: 9.5 Tons
Length: 14.8m
Width: 3.30m
Draught: 0.8m
Carry Capacity: 11 Tons
Propulsion:
1 x Diesel engine
1 shafts, 60 shp
Speed: 9 knots (16 km/h)
Endurance: 100 nautical miles @ 7.5 knots
Complement: 8-12-70 (Varies by source and purpose)
lines of Daihatsu Model D (LB-D)
Drawing of Daihatsu Model D (LB-D)
Drawing of 60HP Diesel engine for Daihatsu
Weapons
Type 92 Heavy Machine Gun / 九二式重機関銃
A standard Japanese HMG during WW2.
- Caliber: 7.7mm
- Feeding system: 30 rounds strip
- Rate of Fire: 450 rounds/min
- Muzzle Velocity: 732 m/s
Type 93 13mm machine gun / 九三式十三粍機銃
Japanese Navy popular 13mm autocannon.
Its naval weapon, but sometimes army unit received it from navy to use on Daihatsu.
- Caliber: 13.2mm
- Feeding system: 30 rounds magazine
- Muzzle Velocity: 800 m/s
Type 98 AA Autocannon / 九八式高射機関砲
Familiar Japanese Army’s standard AA gun.
- Caliber: 20mm
- Feeding system: 20 rounds magazine
- Rate of Fire: 300 rounds/min
- Muzzle Velocity: 950 m/s
Type 94 37mm Gun / 九四式三十七粍砲
Japanese popular anti-tank gun used during WW2.
- Caliber: 37mm
- Muzzle Velocity: 700 m/s
Type 94 Mountain Gun / 九四式山砲
Japanese standard mountain gun to replace old Type 41 mountain gun during WW2.
- Caliber: 75mm
- Muzzle Velocity: 392 m/s
References:
Author: Matsubara Shigeo, Edit: Endo Akira (1996) “Army Ship War: Ship is lifeline of island country Japan even now and then”, Senshi Kanko-kai, pp.50-61, 234-239
Okumoto Gou (2016) “Boats and Ships of Japanese Army: For Landing, Transporting, Escort, Attack and special ships”, Dai-Nippon Kaiga publishers,pp.6-15
JACAR ref.C14020226400 “線図” (Lines of Daihatsu model D)
JAcAR Ref.C19010111700 “Anti-torpedo boat combat for Daihatsu, January 1, 1944”