mtb IJN No. 10-class and No. 11-class Motor Torpedo Boats (T-51a and T-51b)

[tester188@psn 1,413]

No. 10-class Motor Torpedo Boat / No. 11-class Motor Torpedo Boat

第十号型魚雷艇 / 第十一号型魚雷艇

No. 14 motor torpedo boat (No. 11-class MTB) running trial in Cape Inubō, June 1944

 

No. 10-class MTB and No. 11-class MTB were motor torpedo boats built by the Imperial Japanese Navy. No. 10-class MTB and No. 11-class MTB are classified as model-Ko (A type) meaning large size, whereas the No. 538-class (T-14) MTB etc is classified as model-Otsu (B type) MTB which means small size. A-type MTB has two MTBs with different engine and armament. This suggestion treats them all together. 

 

History

The Imperial Japanese Navy learned that E-boat (S-boot), a large German motor torpedo boat, works effectively against the British Navy. In the production plan of 1941, four vessels from 1942 to 1943, 14 vessels from 1943 to 1944, temporary budget for producing a new large type motor torpedo boat were approved. 

 

Until now, the motor torpedo boat designed by IJN was 20 tons No. 1-class MTB, but the new type of motor torpedo boat has decided to enlarge to 80 tons. The design of the hull was a round ship bottom, made of iron framework and wood skin. The engine copied Italian Baglietto MAS motor torpedo boat. The engine was equipped with four 900 horsepower engines, each as a coupled engine, and made two 1800 horsepower engines. According to the plan, it was supposed to be able to demonstrate the maximum speed of more than 30 knots with a two-axis screw propeller. Armament was four 45 cm torpedoes. It is estimated that there was a twin 25 mm AA gun on the stern deck. There is a possibility that about 8 depth charges can be installed. However, there was a problem with the design. The German torpedo boat was made of light alloy, but in Japan it is necessary to save resources, the materials that the designers of the motor torpedo boats can choose are limited. Iron and wooden hulls increased weight, the coupled engine system also increased weight. The designer was obliged to reduce the weight of the hull, but it sacrificed the strength of the structure and vibration occurred. Finally the structure was strengthened to eliminate the vibration, but the weight increased more than the plan, which could not achieve the planned 30 knots. The project number of this motor torpedo boat was T-51a, but only one No. 10 motor torpedo boat was produced.

 

No. 10-class motor torpedo boat had problems with the design, so it was to be improved. The project number was T-51b. The difference in design was to eliminate the coupled engines, change to a 4-axis screw propeller. The armament was also changed, two torpedoes were reduced, and instead replaced by three 25 mm AA guns. It is estimated that a total of 8 to 18 depth charges could be installed on both sides of the stern. If torpedoes are all removed, it may be possible to increase depth charge to 18 perhaps. It suffered from delays in production plan due to lack of materials and technical problems, but a total of 7 vessels were built.

 

The US intelligence during the war reports No. 10-class and No. 11-class motor torpedo boats as follows based on the captured Japanese document.

Information of No. 10-class and No. 11-class seems to be mixed, but as far as I found it is almost the only primary source.

 

Diagram

No. 10-class (T-51a)

Spoiler

 

No. 11-class (T-51b)

Spoiler

 

Specification

• Type: motor torpedo boat
• Displacement: 86.0 t (full load) (No. 10-class: 89.4 to 89.6 t)
• Length: 32.40 m (overall)
• Beam: 5.00 m
• Draft: 1.166 m (maximum)
• Propulsion:
  • 4 × 920 hp Mark 71, Model 6, 18-cylinder gasoline engines (maximum power: 950 hp at 1,800 rpm)
  • 4 shafts (No. 10-class: 2 shafts)
• Speed: 29.0 knots maximum (No. 10-class: 29.86 knots)
• Endurance: 410 nml at 28 knots, 1,200 nml at 16 knots
• Complement: 18
• Armament: 
  • No. 10-class
    • 4 × torpedo dropping gears
    • 4 × 45 cm Type 44 or Type 91 torpedoes
    • 1 × twin 25 mm Type 96 AA gun mounted aft
    • 8 × depth charges (Remove torpedoes: 12 to 18)
  • No. 11-class
    • 2 × torpedo dropping gears
    • 2 × 45 cm Type 44 or Type 91 torpedoes
    • 3 × single 25 mm Type 96 AA guns, two forward, one aft
    • 8 × depth charges (Remove torpedoes: 12 to 18)

(Edited on 13th November 2018 based on the provided source.)

 

Armament

Regarding armaments, it differs slightly depending on the source, but there is a possibility that even the same class has been modified according to the time. 13 mm MG and 25 mm AA gun were equipped to many Japanese Navy small vessels in the second half of the war. Enemy aircraft and submarines were a serious threat. It was found that 25 mm AA gun is more likely to be equipped as standard with the provided source.

 

13.2 mm Type 93 MG

Spoiler

 

25 mm Type 96 AA gun

Spoiler

 

In War Thunder
Armament is relatively strong. It is unusual for IJN motor torpedo boats to have four torpedoes. Also 3 x 25 mm AA guns will be competitive. It will fit because the low tier motor torpedo boat is insufficient.

 

Photo

No. 17 motor torpedo boat (No. 11-class MTB) running trial in Tone River, October 1944

 

Sources

Historical documents:

Weekly Intelligence bulletins

Spoiler

(Vol. I, No. 1-17) Weekly Intelligence bulletins, Vol. I, Nos. 1 to 52, 14 July 1944 to 9 July 1945. Report No. 11-c(3), USSBS Index Section 6. Frame Number 256-262, 308, 309, 373.

http://dl.ndl.go.jp/info:ndljp/pid/4009857?itemId=info%3Andljp%2Fpid%2F4009857&__lang=en

 

(Vol. I, No. 18-35) Weekly Intelligence bulletins, Vol. I, Nos. 1 to 52, 14 July 1944 to 9 July 1945. Report No. 11-c(3), USSBS Index Section 6. Frame Number 51, 118, 166, 170, 233.

http://dl.ndl.go.jp/info:ndljp/pid/4009858?itemId=info%3Andljp%2Fpid%2F4009858&__lang=en

 

(Vol. I, No. 36-52) Weekly Intelligence bulletins, Vol. I, Nos. 1 to 52, 14 July 1944 to 9 July 1945. Report No. 11-c(3), USSBS Index Section 6. Frame Number 260.

http://dl.ndl.go.jp/info:ndljp/pid/4009859?itemId=info%3Andljp%2Fpid%2F4009859&__lang=en

 

Far-Eastern Small Craft, ONI 208-J, Sup 2, and Sup 3, 1945.

http://archive.hnsa.org/doc/id/oni208j-far-eastern-small-craft/pg009.htm

 

Book:

日本魚雷艇物語 (Japanese motor torpedo boat story). Written by Imamura Yoshinobu. May 2011. ISBN-13: 978-4769826910. pp. 16, 57-59, 81, 235.

昭和造船史 (Shōwa period Shipbuilding History). 日本造船学会 (Issued by Society of Naval Architects of Japan). 1981. ISBN-13: 978-4562003020. p. 597. (@aizenns provided, thx)

 

Websites:

http://www.ptboatworld.com/PT_Boat_Info/JapaneseMTBs.htm

http://www.navypedia.org/ships/japan/jap_aux_t51.htm

Edited November 13, 2018 by *tester188
The specification was corrected based on the provided source.

[leroyonly 4,311]

Open for discussion. 

[aizenns 3,591]

I really wated Suggestions about such a small vessels!!

 

I have a questions about machine guns. I your sources these boats had 13.2mm or 25mm, but books that I read it have only 7mm machine guns (No.10: 3x 7mm / No.11: 2x7mm)

 

I believe Japanese torpedo boat with 3x 25mm is Hayabusa-Tei (Falcon boat, torpedo boat that remove torpedoes.)

 

P.s. I upload scan of my source ASAP after I back to home

 

Sorry, I read 昭和造船史, but it says it have 25mm, too. (No.10: 25mm*2/ No.11: 25mm *3)

 

Add scan of page 897

Spoiler

 

Edited November 12, 2018 by aizenns

[tester188@psn 1,413]

2 hours ago, aizenns said:

Sorry, I read 昭和造船史, but it says it have 25mm, too. (No.10: 25mm*2/ No.11: 25mm *3)

Wow! Your post is always extraordinary! I was also confused because the claims of anti-aircraft guns are different for each source, but perhaps this is historically correct. Although it may have been 7.7 mm MG in the initial plan, the example of reinforcing the anti-aircraft gun and replacing it with 13 mm MG or 25 mm AA gun was often on other vessels. In the drawing of a #10-class posted in a Japanese book, I thought that it was twin 13 mm MG, but the possibility of twin 25 mm AA gun is high. I will correct the OP.

 

Thanks. 

[funkrockjock 30]

+1 to both!  Makes a good tier progression, one after the other. There are so many people that say "japan had no small combat boats, so that's why gaijin took so long to make the IJN happen". How ridiculous. All nations had small boats! I want all combat ships from all nations, but if we have to start somewhere then this is a good start

[Milocat 4,857]

Yes please, this would be a perfect small boat for Japan.  I'd like to see them both.  +2.

[Miki_Hoshii 2,449]

On 16/05/2019 at 01:03, funkrockjock said:

+1 to both!  Makes a good tier progression, one after the other. There are so many people that say "japan had no small combat boats, so that's why gaijin took so long to make the IJN happen". How ridiculous. All nations had small boats! I want all combat ships from all nations, but if we have to start somewhere then this is a good start

I dont believe that was the reasoning, it was that  "Information on small boats is hard to find for the IJN"

[tester188@psn 1,413]

Implemented in Update 1.89. However, T-51a and T-51b are mixed, and four torpedoes and 25 mm AA of triple mount are powerful. GJ seems to have sourced US intelligence reports. 

[jon_man1199 563]

5 hours ago, *tester188 said:

Implemented in Update 1.89. However, T-51a and T-51b are mixed, and four torpedoes and 25 mm AA of triple mount are powerful. GJ seems to have sourced US intelligence reports. 

Ouch, wonder if they would accept a bug report on it or something

[Tasty95215 2,099]

I'd love to see the true T-51B in game - the 25mm gun is surprisingly great, and having even more of them (in a non-awkward firing position) on a fast-ish torpedo boat sounds great. Having less torpedoes isn't that big of a deal IMO, since they're a bit situational and liable to getting detonated.

 

On another note, I've reached the current T-51B in the tech tree (it's technically the T-51A with one extra gun, but whatever). The rear facing triple 25mm's is powerful, but awkward to use, and the guns seem more inaccurate than the single. If the bug report for that ship is accepted (changing the name to T-51A and replacing the triple mount with a double mount) I'd like to see it move down to BR 2.0, and the T-51B (assuming it's added later) can be at BR 2.3 

Edited July 19, 2019 by Tasty95215

[aizenns 3,591]

I find rough history about each boats. I list them on here.

 

• Torpedo Boat No.10
  • After construction completed, deployed at Truk Islands. Sunk by air raid.
• Torpedo Boat No.12
  • Immediately after completion of construction, sparks from the electric motor caused an explosion of gasoline gas, and the hull was wrecked, burned, and sank at wharf of coastal defense unit.
• Torpedo Boat No.16
  • Equip only two engines. Left spaces for engines were used for hold, and this boat was used for Tender boat of Kawadana assault unit (川棚突撃隊, one of the coastal special attack unit with torpedo boats, suicide boats and suicide divers.)
• Others
  • Deployed at surface special attack units, but hardly ever fought.
  • Only one boat that deployed at Habu port of Izu Oshima attack enemy submarine.

Source: 海軍造船技術概要, pp.716-719

[Wiggly_Armed_Man 2,383]

Hopefully they fix the "T-51b" we have in-game, either by converting it to the T-51a or making it the T-51b, and adding the T-51a.  I would love to see them both in game but, hopefully, at a lower BR. The torpedoes aren't really an argument for their high BR considering they're more of a detriment than an advantage as torpedo kills are difficult to get and having four mounted on the majority of the hull provides a large ammo rack. So, hopefully they add the T-51b at 2.3 and move the T-51a/add the T-51a to 2.0.

[OKAZAQI 166]

+1

[leroyonly 4,311]

As the No. 11 class has been implemented previously,

 

Moved to Implemented Suggestions.