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Japanese torpedoes and Amendment 1


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#1 Dave Franklin

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Posted 05 December 2008 - 07:31 AM

Doing the Wake Island Sweep scenario this weekend, and have a question about the IJN torpedo ranges.It appears obvious the ranges to the right of the Ammendment 1 IJN Torpedo CRT are for the Type 93 torpedo.Are the ranges under the "Standard" label for the "conventional 24" torpedo"?Assuming that's the case, what are the ranges for the IJN 21" torpedo (e.g. on the Kamikaze class DDs)?Is it the 4500 and 9500 yards from the original chart?

#2 Coastal

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Posted 05 December 2008 - 08:45 AM

Are the ranges under the "Standard" label for the "conventional 24" torpedo"?Assuming that's the case, what are the ranges for the IJN 21" torpedo (e.g. on the Kamikaze class DDs)?Is it the 4500 and 9500 yards from the original chart?

Yes. The older 24" and 21" torpedoes would use the same scale (the 'Standard' scale to the left). The performance of the two types (there were several within each size) were, in game terms, generally similar.

#3 Dave Franklin

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Posted 08 December 2008 - 03:31 PM

I found the other, similar thread on the forum. If I understand correctly, the "official" position is:1. Type 93 (Long Lance) 24" torpedoes (i.e. red on the SDS) use the so labeled range scale on the right of the Amendment 1 IJN Torpedo CRT, and as noted on all of the Mine and Torpedo Damage Tables, if the roll is even you take an extra hull hit.2. Non-Type 93 24" torpedoes (black open circle on the SDS) use the "Standard" labeled range scale on the left of the Amendment 1 IJN Torpedo CRT, and their damage is normal.3. IJN 21" torpedoes (white in solid black circle on the SDS) use the "Standard" labeled range scale on the left of the Amendment 1 IJN Torpedo CRT, and their hull damage on the Mine and Torpedo Damage Table is halved.Is that right?Now, I'm not sure I buy the "in game terms, generally similar" line. Amendment 1's torpedo ranges/speeds are slightly different for the Germans (to the tune of 300 yards shorter, or 3cm for their long range setting), the Italians (100 yds or 1cm, then 200 yards or 2 cm shorter/2 knots slower in the first two bands of their long range setting; the Standard is significantly different), and the Japanese (Type 93 is 300 yards or 3cm longer/3 knots faster in the first two range bands, 400 yards or 4cm longer/4 knots faster on the third range band, and 200 yards or 2cm longer in the last range band; the 21" or Standard is significantly different). So, assuming the changes to Amendment 1 were for data that wasn't "in game terms, generally similar", that must be anywhere less than from 100 yards or 1 cm/knot to 400 yards or 4cm/knots per turn. I've seen references to the Type 90 24" torpedo that have it capable of 46 knots to 7000m and 42 knots to 10000m, compared to 37-38 knots to 10000m for the Type 8 24" torpedo and 35-36 knots to 7000m for the Type 6 21" torpedo. These seem to me not to fit the "in game terms, generally similar" definition.

#4 Lonnie Gill

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Posted 09 December 2008 - 06:53 PM

Co diver,Yes, you’ve the Amendment 1 torpedo application correct.Given the space limitations on the chart, the “Standard” range scale is a composite for the 21” Type 6, the 24” Type 8 and the 24” Type 90 – all of which were employed in WWII by IJN ships that did not carry the Type 93. There are many range settings that could have been employed as a check of www.NavWeaps.com or Campbell’s Naval Weapons of World War Two will show.The medium/long range setting was selected as being applicable to the widest range of tactical situations for the torpedoes using the “Standard” scale. These all had the same range of 10,900 yds, hence they were grouped into the same scale. Like any compromise, this simplification is handy, but does not reflect all details. The torpedo speeds at this range setting varied by type. For those who would like to reflect this additional detail, here are the speeds by type:Type 6 (21”) 10,900 yds @ 32 ktsType 8, No 1 (24”) 10,900 yds @ 37 ktsType 8, No 2 (24”) 10,900 yds @ 38 ktsType 90 (24”) 10,900 yds @ 42 ktsYou can agree on an option before beginning a scenario to employ these detailed range/speed scales in place of the compromise scale listed on the Amendment 1 IJN chart. Range bands for each Game Turn would be multiples of the torpedo speed. A Type 6 spread would have a range band of 1 – 3,200 yds fore the first Game Turn, 3,300 – 6,400 yds for Game Turn two and so on. Just list the individual range bands for each type on a 3 x 5 card for handy reference during a scenario and you’re ready to go.While ships equipped with the 21” Type 6 are clearly identified on the IJN Ship Logs, it is often not clear which of the conventional 24” torpedo types was carried by a particular ship at a given point in time. Not all were upgraded to the Type 90 and, like other navies, a ship probably got what was in stock or available when she drew her torpedoes. If you are fortunate enough to find the type data for a historical engagement being simulated, use it. Otherwise, you’ll need to agree on which type of 24” to employ in the scenario.This will enable you to include additional detail in your Wake Island Sweep scenario this weekend. Looking forward to an After Action Report.LONNIE

#5 Dave Franklin

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Posted 10 December 2008 - 05:22 AM

Since you mention it, the IJN "Standard" torpedo amalgamation has a little bit of a problem I just noticed: 32 knots gives you 3200 yards for the first range band, and 6400 yards for the second - as is on the table. However, they apparently accelerate to 45 knots the third turn to get out to 10900 yards range...I guess if you really want it to be an amalgamation of the torpedoes you listed, it would be better if it was 3700 - 7400 - 10900 or 3800 - 7600 -10900.We played the game last Saturday the 6th. The following is what I posted on the Yahoo group:Sunday being December 7, we decided to play GQ3 on Saturday, and Idecided to run the Wake Island Sweep scenario from the GQ3 site.We rolled up day time visibility of 27000 yards, just under the average.Played as a day time scenario, this is a tough go for the IJN. Theyhave 4 old CAs that only have CL(CS) armor, so the USN CAs canpenetrate them at any range. The USN is fortunate to have 3 latertreaty cruisers with CA(CA) armor. The IJN has to either stay outsideof 24000 yards to penetrate them with plunging fire, or close to within15000 yards. Of course they have to close even further to have adecent chance to utilize their torpedoes effectively.The scenario is balanced in that initially both sides throw the samenumber of 8" dice. However, I would recommend anyone playing thescenario use the 1.5.13 Not Engaged optional rule (which for somereason was left off the Amendment 1 charts, even though 1.5.10 InitialSalvos and 1.5.11 Evasive Action are on there). Otherwise, assumingthe CAs are engaging each other, two of the IJN CAs will be penalizedfor concentrating on the same target.In our game the USN out shot the IJN, both due to the issues mentionedabove, and by just rolling better. Aoba absorbed 2 fires (1 an FP thatalso caused a hull box, the other from having Type 93 torps) and abulkhead hit in one turn. Tough to repair all of that before you runout of hull boxes... They also had lost 2 Mutsuki class DDs, andYubari was about to go down when we called the game. The USN hadn'tlost any ships; in fact only one of their CAs had lost an 8" turret,and I think the worst hull damage to any USN ship was 2 boxes.There were no torpedo hits in the game (we used the basic 1/2" widetorpedo track rules). The one time the USN had a chance, they rolledlow enough, but it was even, so it was a dud. The IJN never managed tohave a torpedo track intersect a USN ship.

#6 Lonnie Gill

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Posted 16 December 2008 - 11:15 AM

Co diver,As you noted, the first two range bands are weighted toward the Type 6 21” torpedo to avoid providing an unrealistic advantage, while the third range band (at lower hit probabilities) was for the 24”, all of which could reach 10,900 yds in three Game Turns.That said, a composite range scale remains a compromise, not exactly representing either the 21” or the 24” torpedo performance. Accordingly, I went back and took a look at some reformatting and have been able to find room to add separate range scales for both the 21” and the conventional 24” torpedo. I selected the Type 90 for the 24” as this 1930s vintage torpedo would be the preferred load for an IJN captain when available.We will post the revised Chart 7 C in the Amendment 1 section of the Bonus Files in the next week for download. Thanks to the download feature, we can continue to work together to evolve GQ III to provide a better simulation.Thanks also for the report on the Wake Island Sweep. In a daytime engagement, the USN cruisers are a bit stronger and likely to do well. But, the airpower in the area would probably make for a different outcome in the aftermath. The Wake Island Ship Log files also include the carriers for both sides so you can simulate that aspect as well. It would be interesting to run a follow on scenario using the carriers to simulate the consequences of the engagement you recently concluded.LONNIE

#7 Dave Franklin

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Posted 18 December 2008 - 12:37 PM

Cool Lonnie! I'll be eagerly awaiting the new chart! I'd just as soon reduce the number of times I have to make up new torpedo range sticks...My take is, based on the data for the 21" Type 6 on navweaps.com you referenced, it would take 4 turns for it to reach 10900 yards at 32 knots: 3200 - 6400 - 9600 - 10900.I agree with the choice of the Type 90 over the Type 8. So it sounds like you're looking at 4200 - 8400 - 10900?Regarding "In a daytime engagement, the USN cruisers are a bit stronger and likely to do well. But, the airpower in the area would probably make for a different outcome in the aftermath.": what, you don't think those F2A-3 Buffalos on Lexington and Saratoga would have turned the tide!?OK, never mind...;)

#8 Lonnie Gill

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Posted 19 December 2008 - 12:41 PM

Yep, you've got the range bands right. The new chart should be posted for download in the next few days.Careful or Jim will remind us that the F2A has gotten a bad rap. BUt, I think that refers to the early F2As. By the F2A-3, the airframe was so loaded down with armor and additions that performance was sadly degraded. Still, it would be interesting to see how they tangle with the A6Ms near Wake in December 1941.LONNIE

#9 Jim O'Neil

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Posted 19 December 2008 - 05:16 PM

Hey, they are great in a dive ... second only to the P-47 ... it's only when they try to pull out and fly that they have problems ...




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