18in Type 91 Torpedo Evolution

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All Forums >> [New Releases from Matrix Games] >> War in the Pacific: Admiral's Edition >> Scenario Design and Modding >> 18in Type 91 Torpedo Evolution

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18in Type 91 Torpedo Evolution - 7/25/2019 3:54:38 AM

engineer

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The current 18in Type 91 torpedo is a reasonable compromise. The penetration matches the warhead weight in High Explosive.

The data represents the Mod 3 torpedo that got out the fleet in early 1942 and was used through 1943. The Improved Mod 3 came along in 1943 that
increased the launch speed of the aircraft to 300 knots, and then the Mod 3 Strong in 1944 that increased launch speed to 350 knots.

The Mod 7 came along in late 1944 that had a great increase in payload to 926 lbs without sacrificing launch speed.

However at Pearl Harbor and the first few months of the war, the Japanese were using the Mod 2 that only had 452 lbs of HE.

My question is whether AE allows an upgrade path for ordnance, e.g. a Type 91 Mod 2 until 2/42, then Mod 3 through 11/44, and then Mod 7 for the balance of the game?

< Message edited by engineer -- 7/25/2019 3:57:44 AM >

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RE: 18in Type 91 Torpedo Evolution - 7/25/2019 10:05:19 AM

Rising-Sun

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That is interesting, be sure to post this under my threads, so I can go over it. Maybe I can figure out how to do this, if the sources are correct.

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RE: 18in Type 91 Torpedo Evolution - 7/25/2019 12:47:11 PM

inqistor

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quote:

ORIGINAL: engineer

The current 18in Type 91 torpedo is a reasonable compromise. The penetration matches the warhead weight in High Explosive.

The data represents the Mod 3 torpedo that got out the fleet in early 1942 and was used through 1943. The Improved Mod 3 came along in 1943 that
increased the launch speed of the aircraft to 300 knots, and then the Mod 3 Strong in 1944 that increased launch speed to 350 knots.

The Mod 7 came along in late 1944 that had a great increase in payload to 926 lbs without sacrificing launch speed.

However at Pearl Harbor and the first few months of the war, the Japanese were using the Mod 2 that only had 452 lbs of HE.

My question is whether AE allows an upgrade path for ordnance, e.g. a Type 91 Mod 2 until 2/42, then Mod 3 through 11/44, and then Mod 7 for the balance of the game?

Yup, that is doable. Check my MOD.
Actually, those larger later torpedoes could only be carried by BETTY. And there is similar issue with US torpedoes, as smaller warhead was used at the beginning of war.
If you check database, all those torpedoes were actually implemented in earlier version, but are not used in AE.

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RE: 18in Type 91 Torpedo Evolution - 7/25/2019 5:03:05 PM

engineer

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According to NavWeapons http://navweaps.com/Weapons/WTJAP_WWII.php the Mod 3 torpedo was 1872 lbs so the improved and strong models mostly let faster TB's and LB's (Jill, Grace, Francis) carry the Mod 3 without creating the need for an increasing dud rate due to the torpedoes being rendered inoperable when dropped into the ocean or making the bombers slow down and become more vulnerable to flak to sustain the historical dud rate. Here is a happy example where history neatly aligns to eliminate the need to choose between historical abstraction or a bunch of special purpose code. You're right about the Mod 7, however, The extra warhead comes with a hefty weight penalty (now 2319 lbs)

From this site the length of the torpedoes is given as 18' for mod 2, 17'4" for all flavors of Mod 3 and 18'9" on the Mod 7. So clearly, the next level of research is a pretty easy check of aircraft payload capacity and a more complicated check of bomb bay length on level bombers that carry the torpedo internally. If the torpedo engineers had any sense the mounting hardware would remain the same from version to version so the question would be clearance (mostly on the front end of the torpedo I suspect) for the extra length associated with the warhead.

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RE: 18in Type 91 Torpedo Evolution - 7/25/2019 5:29:47 PM

engineer

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I took a quick dive into the US Mark 13 page at Navweapons, and it looks like it takes the trophy for "Most Improved Torpedo of WW2". It fits in the general "everything gets more lethal" trend of 41-45. At least here there is good evidence that Avengers could carry the extra 265 pounds of weight that came with the improvements. The late 42 change from TNT to TPX in the warhead is probably significant, but most of the improvements are about decreasing the dud rate that should already be coded into the game (need to re-read the manual on that point).

Of course, the same exercise is due diligence on RN torpedoes.

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RE: 18in Type 91 Torpedo Evolution - 7/26/2019 9:51:23 PM

inqistor

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Yeah, reduction of dud rate is hard coded, so no reason to worry about this.

However, it would be nice if someone have found dates of introduction of those torpedo improvements. Explosives in Mark's 13 warhead increased from 400 to 600 lbs, so that is serious increase in damage. Were there some smaller changes between those values?

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RE: 18in Type 91 Torpedo Evolution - 7/26/2019 11:26:25 PM

engineer

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Well, firing up DuckDuckGo, the San Francisco Maritime Museum has an original Navy Mk 13 detailed description https://maritime.org/doc/torpedomk13/torp009.htmon line that is dated from June 1942 and still lists the warhead as 400 lbs of TNT. So that would be the warhead through summer of 1942.

At the Navweapons site I noted above, there is a cover article on US torpedoes that discusses various topics on US torpedoes. According to that in late 1942, the US introduced TPX as a warhead explosive. The TPX was a blend of TNT, RDX and powdered aluminum. The RDX increased the explosive power relative to pure TNT and the powdered aluminum burned a little slower so the bubble of the expanding gas of the explosion would last a little longer. Empirical testing indicated that this would increase the damage of detonation by about 50%. The bad bit about TPX was that it was not as stable as TNT, but there was a war on.

The main Mk 13 page talks about the poor running performance extending into 1943 but everything getting sorted out by the Leyte Gulf, fall of '44. It's not clear when along the way, the warhead size was increased to 600 lbs.

The most complete text appears to be in an official history from the Bureau of Ordnance. See http://www.ibiblio.org/hyperwar/USN/Admin-Hist/BuOrd/BuOrd-6.html. This is by far the most complete discussion. The Mark 13 material is after a long detailed discussion on the submarine torpedo fiasco and fixes. Much of the other sources' text seems to paraphrase the language here.

Performance slightly improved in 1943 (only 70% dud rate) from even more abysmal values in 1942, but the incremental improvements (mostly with the shroud ring/pickle barrel) started to reach the fleet in 1944. Those worked spectacularly well so the Model 10 was standardized with the bigger TPX charge and shroud ring assemblies were manufactured and shipped out to the fleet so the older torpedoes in inventory could be retrofitted to Model 10 standards.

So if I was king, the most detail I include is:
- Model 1, 90% dud rate at start, 404 lb TNT warhead.
- Model 2: 70% dud rate July, 42, 404 lb TNT warhead.
- Model 2A 70% dud rate, October, 42, 404 lb TPX warhead (606 value)
- Model 10, 10% dud rate, September 44, 606 lb TPX warhead, (909 value)

One thing I don't know is if upgrades on ordnance pass through to torpedoes afloat in magazines. My reading of the source material is autumn is broadly operational timing so moving that intro date up a month to give carriers a chance to resupply with torpedoes might be appropriate.

Since the dud rates are hard coded, you can drop the Model 2 at no loss. If there was a good source to justify quicker implementation of the bigger warhead that might included, but it is pretty clear that the Model 10 is where the bulk of the improvements had been achieved. Increasing the drop height of the torpedoes from 100 feet to 5000 feet might be well documented historically, but I don't know how to get that into AE.

BTW, I agree that the IJN TB should be restricted to the Type 91 Mod 3, but I think the heavier Mod 7 should be available to the Francis and Peggy as well as the Betty.

< Message edited by engineer -- 7/27/2019 12:44:01 AM >

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RE: 18in Type 91 Torpedo Evolution - 7/27/2019 5:52:08 PM

jmolyson

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It's unfortunate that so many Americans were lost while attempting to deliver crappy torpedoes in U.S. aircraft, ships and subs.

The admirals who ran the naval ordnance organization should have been court marshalled for failing to adequately test the weapons they provided to the operating forces.

Ditto for providing the 1.1 inch anti-aircraft guns that failed to adequately defend the Lexington (Coral Sea), Yorktown (Midway) and Hornet (Santa Cruz) during the 1942 carrier battles.

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