Sinking the Shinano 11-29-1944

[ancient46]

From the Official Patrol #5 Log of the SS Archerfish CDR Joseph F Enright commanding, to COMSUBPAC. Source: www.ussarcherfish.com

November 28, 1944
1718 Surfaced.
2034 Sighted Inamba Shima. Distance about 12 miles but no radar contact.
2048 Radar contact 24,700 yards, 028° T. Started tracking from ahead. Ship
Contact #4.
2140 Identified target as aircraft carrier, base course 210, speed 20. It appeared he only had one escort. With sky overcast, and dark horizon to north, started surface approach on starboard flank.
2230 Escort on starboard beam sighted. Not possible to make surface approach on this side. Changed course back to his base course.
2250 Target group closing and we are off the track too far to submerge. Carrier turned on red truck light for about 10 seconds, then off for 20, and on again for 10. Range to closest escort 6100 yards and to carrier 15,000. Sent lookouts below and watched for gun flashes or splashes. Escort continued to ignore us - Called lookouts back.
2300 Enemy group now determined to consist of large carrier and 4 escorts. One on either beam, one ahead and one astern.
2330 Sent contact message.
2340 Looks like big zig in our direction.
2400 Probably a base course change to the west. We are now on his port flank further off the track than before. Changed our course to 270 and coaxed a few more turns from the already overloaded motors.



November 29, 1944 From here on it was a mad race for a possible firing position. His speed was about one knot in excess of our best, but his zig plan allowed us to pull ahead very slowly.
0241 Sent second contact message when it appeared he planned to stay on 275 and not much chance of us reaching a firing position.
0300 Looks like another change of base course or big zig to southward. Range closing rapidly and we are ahead.
0305 Changed course to 100 and submerged. Range to carrier 11,700 yards. Sighted carrier in periscope at 7000 yards. Changed course 10° to left to keep from closing track too much. A small starboard angle on the bow and range 3500. Escort closed carrier to receive blinker message. This caused him to pass nicely ahead of us at 400 yards.
O316 Carrier zigged away about 30°. Picture improves. Good positIon, 70 starboard track, 1400 yards. Gyro shots necessary due to late favorable zig.
0317 Started firing all bow tubes, MK 14 torpedoes, set depth 10 feet - First gyro 28° right, track 100, spread from cards, aft to forward.
0317-47 Heard and observed first hit just inside stern near props and rudder. Large ball of fire climbed his side.
0317-57 Second hit observed and heard. This was about 50 yards forward of the first.
With hits seen, a destroyer about 500 yards on our quarter, and wakes visible, started deep.
Four more properly timed hits on our way down. The time corresponded to the firing interval and sounded the same as the two that were observed. The six hits with a spread can be explained by considering the data as correct, the overall spread from the card for 600 foot target is 10° and our target, 750 feet long is 10½° at 1400 yards.
The six hits are certain.
Breaking up noises started immediately.
With the bright moonlight the identification is quite accurate. The carrier appeared to be similar to the Hayntaka class except it is believed to had a raked stern. Perhaps our recco plane over Yokohama has a picture to further identify this one.
0325 Started receiving a total of 14 depth charges. Closest one was perhaps 300 yards away.
0345 Last depth charge. The hissing, sputtering, and breaking noises continued. At one time they covered 90° of scale on the sound receiver.
0405 Last breaking up noise. Our starboard sound head training gear damaged by a broken roller and a holding down lug. Either from depth charge or pressure. Both training motors grounded out by bilge water as it was necessary to use a 10° up angle. Credit is claimed for a sinking because of these items:
(a) Six certain hits. (2 observed)
(b) Heavy screws stopped and did not restart.
(c) Loud breaking up noises for 47 minutes.
(d) Escorts give us slight attention and closed carrier, probably picking up
survivors.
0610 Daylight and first periscope observation. Nothing in sight.


Does anyone have copies of the spread cards used for this historic sinking? Are they adaptable for use in SH4? I found a formula for calculating spreads in the Torpedo Firing Manual that could be used to construct the cards but not the cards Enright mentioned.

[Nunya]

What I find ironic is that the Shinano was only a few hours into it's maiden voyage when sunk and that this was the only ship that CDR Enright sunk during the war.

[Nisgeis]

Originally Posted by ancient46

Does anyone have copies of the spread cards used for this historic sinking? Are they adaptable for use in SH4? I found a formula for calculating spreads in the Torpedo Firing Manual that could be used to construct the cards but not the cards Enright mentioned.

I'm working on a version of a spread card for SH4. I'm not sure if this was a standard issue, or whether it was something made up by the crew. As the TDC could not generate spread angles, it was up to the crew to calculate them, using simplified maths, or matching by hand the bearings on the TDC, as used by Dick O'Kane, or by calculating gizmos that they made up. There is a spread angle calculator card in the USS Torsk that is a graphical means of calculating the spread required at variable torpedo tracks and at variable torpedo run length for variable target lengths. It's a recreation of this that I'm working on.

[Raptor1]

What are these spread cards anyway?

Shinano shared a very similar fate to the Taiho, which was sunk 3 months (IIRC) after it left port during the Battle of the Philippine Sea, both were sunk because of hits that should not have been critical (bulge deficiency with Shinano and idiotic damage control with Taiho) and together they were the largest IJN carriers of the war (Taiho was the biggest fleet carrier as Shinano technically wasn't a fleet carrier at all)

[Rockin Robbins]

All this is VERY interesting. I still wonder why the TDC had an input for target length if it didn't calculate spread. I think we're missing something here and the TDC did exactly that. However my research can't seem to absolutely confirm that, although I have access to both the Torpedo Fire Control Manual and Torpedo Data Computer Mark 3 Manual. It has been most frustrating.

[ancient46]

Thanks for the reply Nisgeis. I was going to try to calculate and make up my own cards but one based on a historical card is much better. With all of us poking around in the historical records the game keeps getting better all the time.

What really got me was that Enright got a firing solution on the carrier and used a card to select a spread that made six hits on a carrier sailing at 20 knots. Also that the spread produced two observed hits about 50 yards apart. Since I am lousy at setting spreads that all hit, this got my interest. Maybe the info on the cards could help me out. The admiral sent me several times to remedial sub school for dummies but I still have not mastered spreads.I still sink ships but a lot of expensive ordinance sails off to nowhere. Unless of course it hits a ship behind my target!

[Nisgeis]

Originally Posted by Rockin Robbins

All this is VERY interesting. I still wonder why the TDC had an input for target length if it didn't calculate spread. I think we're missing something here and the TDC did exactly that. However my research can't seem to absolutely confirm that, although I have access to both the Torpedo Fire Control Manual and Torpedo Data Computer Mark 3 Manual. It has been most frustrating.

Rockin Robbins,

The functional diagram you posted in the other thread of the PK and SBC showed what the target length was for. If you have a close look at it, you will see that the input for target length is labelled 2P2 and is indexed against SR/1000. Basically, the input is twice half the target length indexed against SR/1000. The input is graduated in steps of twice the value entered as a means of multiplying the input by two, without having additional gearing. You can also see that the index is against SR/1000, which is target speed multiplied by target range, divided by 1000. For a target at 4,000 yds at a speed of 20 knots, SR/1000 would be 80. For a target length of 400 feet, you'd turn the 2P2 dial so that 400 was against 80.

This information is fed into the TDC and the SBC part (the Sound Bearing Converter) takes into account your own course, the target's course, the position of the sonar head (indicated as P1 in the functional diagram, which is the sound head paralax and is set when the TDC is installed) and the range, the SBC will work out the change in bearing from the sonar and convert it into LOS (Line of sight - a point between the two periscopes). It will also take into account the time it would take sound from a target, at the position the PK says it is in, would take to travel to the sonar head and compensate for the distance that the target would have travelled in that time (the sound bearing would lag behind actual bearing). The periscopes can take instantaneous bearing readings, as light travels so fast as to be almost instant, whereas the speed of sound underwater can introduce noticable differences in sound bearing and target bearing. Think of a jet flying past at high speed - you hear it after it has passed you. The same is true of underwater bearings, you are listening to where the target was, not where it is now. It's more noticable at higher ranges and if the target is steaming accross your bow or stern.

The SBC works out the bearing that the sound contact is on, does its magic and then takes into account the target length and AoB and things like that and works out the actual bearing of the screws and then works out the bearing of the middle of the target (hence half the target length being an input). This is so that all bearings on the TDC point to the MOT (as listed on the gyro angle solver). Periscope bearings are taken from the MOT, so the SBC works out the equivalent for sound bearings. MOT stands for Middle Of Target. As you can see, the target length is essential to work out where the centre of a ship is, when you can only hear the screws.

[CaptHawkeye]

Too bad Shinano would have been completely useless even if it did survive. Despite being a 70,000 ton monster it could only carry like 40 planes. Pre-war carriers could do better than that.

[Nunya]

Originally Posted by CaptHawkeye

Too bad Shinano would have been completely useless even if it did survive. Despite being a 70,000 ton monster it could only carry like 40 planes. Pre-war carriers could do better than that.

IIRC, it could store 120 planes, but only 47 planes if used as a CV and not as a replenisher.

[Raptor1]

Like I said, Shinano was never meant to be a Fleet Carrier

[Nisgeis]

Here's another account of the Shinano sinking. It seems to disagree somewhat with the patrol report.

http://www.fischer-tropsch.org/prima...t%20S-06-2.pdf

[CaptHawkeye]

Originally Posted by Raptor1

Like I said, Shinano was never meant to be a Fleet Carrier

On paper it won't really matter what it was meant to be anyway. By 1944 the IJN is just an organization of moving target vessels.

[Sailor Steve]

Originally Posted by Nisgeis

Here's another account of the Shinano sinking. It seems to disagree somewhat with the patrol report.

http://www.fischer-tropsch.org/prima...t%20S-06-2.pdf

What a great find! Another keeper.

Yes, it does differ quite a bit from the report, and I had wondered about that, since I have a copy of Enright's book. Unfortunately it's in storage so I couldn't look it up, but I thought I remembered him talking about the time delay between the torpedoeing and the sinking, as well as the armor weakness and other details, and that postwar report confirms it.

I have just recently seen the Silent Service episode on Enright's patrol, and way back then in the TV show Joe Enright was played by DeForrest Kelly, Star Trek's Doctor McCoy!

[Christopher Snow]

Wow. Now that's a real bit of trivia for you.

"He's dead, Jim! Really dead! He must be, because I hit him six times!"


CS

[Kamikaze Krazy]

Here is some additional info on the Shinano:

http://www.subsim.com/radioroom/showthread.php?t=130044

She was on her maiden voyage when she got torpedoed.

"Like I said, Shinano was never meant to be a Fleet Carrier."-Raptor1

Very true sir! Like it says in the book, it stated that it was a Carrier Group Support Carrier, NOT a Fleet Carrier.


Also as an extra bonus perk, when it got sunk, it was carrying 50 Ohka bombs on board. It spooks me because each of them could have destroyed an Allied ship. The Ohkas where VERY destructive, each being able to carry about 2,700 pounds of high explosive. The casualties caused by those where bad enough, but can anyone imagine how many more thousands of sailors would die if the U.S.S. Archerfish did NOT sink the Shinano?