Real Submarine Technology & History Q&A

[Rockin Robbins]

Good. I'll lead off with a question that you might not be able to completely answer. In Clear the Bridge, Dick O'Kane mentions setting up the PK and when he's happy with the solution, he sets up for a constant bearing attack. He points the scope at the shoot bearing and turns the bearing crank backwards to stop the bearing. However the AoB keeps updating and the speed of course, remains the same. This way he can shoot as juicy parts of the target cross the wire.

All this implies that there was a direct connection between the periscope bearing and the TDC, such as modeled in the U-Boat for SH3 and SH4. In addition, Nisgeis has reported that such an automatic TDC input from the periscope did exist.

What do you know about all that? And do you know if it was there in WWII?

[ReallyDedPoet]

Nice idea for a thread Thanks for doing this.



Always great to hear from folks who are doing, or did this in real life, look forward to seeing
this thread progress. I am sure I'll have a question or two to ask at some point.


RDP

[DaveyJ576]

Originally Posted by reallydedpoet

Nice idea for a thread Thanks for doing this.



Always great to hear from folks who are doing, or did this in real life, look forward to seeing
this thread progress. I am sure I'll have a question or two to ask at some point.


RDP

I love this shot of the ol' Darter Maru. This one was taken not long after I left the boat. She is pulling into the Maebata Ordnance Facility in Sasebo, Japan were we were homeported. Notice that the forward torpedo loading skid is rigged up on the forward deck

Dave

[DaveyJ576]

Ric Hedman is the webmaster of our site www.pigboats.com. A third co-founder, Rick Larson passed away last year. Ric also has a tremendous companion site called Through the Looking Glass: A Photo Essay of Submarines 1900-1940, a link for which is on the right side of the main page. Check it out as well.

Both sites are non-profit and ad free.

Surf back to them often. New material is added as often as we create it!

Dave

[CDR Resser]

Thanks Dave. Looks like a great site. Can't wait to go through it in more detail.

Respectfully Submitted;
CDR Resser

[ReallyDedPoet]

Originally Posted by DaveyJ576

Ric Hedman is the webmaster of our site www.pigboats.com. A third co-founder, Rick Larson passed away last year. Ric also has a tremendous companion site called Through the Looking Glass: A Photo Essay of Submarines 1900-1940, a link for which is on the right side of the main page. Check it out as well.

Both sites are non-profit and ad free.

Surf back to them often. New material is added as often as we create it!

Dave

Those are some great links, thanks


RDP

[dangerclose]

Originally Posted by reallydedpoet

Whoa, nostalgia alert. I used to ride my bike up that mountain in the background. Well, at least to that lodge on the right side.

[DaveyJ576]

Great. A hard one to start off with! Thanks!

Anyway, you are correct. Based on electronic input from the gyro compass, there was an automatic input to the TDC from the scope. A dial on the TDC showed the bearing the scope was on.

Pre-war doctrine for torpedo spreads called for a seemingly unusual tactic. One fish would be aimed to slightly miss forward. One would be aimed to miss slightly aft, and one (or two depending on the size of the target) would be aimed to hit amidships. Why? Well, one of the hardest things to estimate, but extremely important to the firing solution is target speed. If your target is going faster than what you estimate, the fish will miss astern. If it is going slower than estimate, they will miss ahead. Aiming one a little forward an one a little aft eliminates uncertainty in target speed, virtually guaranteeing at least two hits out of three. But it also virtually guarantees that at least one, and maybe two of the fish will miss! Kind of a wasteful practice if you ask me. One way of reducing the uncertainty was repeated observations of the target so that your solution could be smoothed. The flip side to this (there is always a flip side!) is that you have to expose your scope more and thus have more chances to be sighted.

As training intensified after the war started, our skippers got better and better at estimating target speed by observing the bow wave generated by the target, and the sonar operators got better at counting propeller revolutions for speed estitmates. Dick O'Kane and his crew were masters at this and he aimed all his fish to hit. His constant bearing method was part of this firing doctrine.

Dave

[AVGWarhawk]

Originally Posted by DaveyJ576

Great. A hard one to start off with! Thanks!

Anyway, you are correct. Based on electronic input from the gyro compass, there was an automatic input to the TDC from the scope. A dial on the TDC showed the bearing the scope was on.

Pre-war doctrine for torpedo spreads called for a seemingly unusual tactic. One fish would be aimed to slightly miss forward. One would be aimed to miss slightly aft, and one (or two depending on the size of the target) would be aimed to hit amidships. Why? Well, one of the hardest things to estimate, but extremely important to the firing solution is target speed. If your target is going faster than what you estimate, the fish will miss astern. If it is going slower than estimate, they will miss ahead. Aiming one a little forward an one a little aft eliminates uncertainty in target speed, virtually guaranteeing at least two hits out of three. But it also virtually guarantees that at least one, and maybe two of the fish will miss! Kind of a wasteful practice if you ask me. One way of reducing the uncertainty was repeated observations of the target so that your solution could be smoothed. The flip side to this (there is always a flip side!) is that you have to expose your scope more and thus have more chances to be sighted.

As training intensified after the war started, our skippers got better and better at estimating target speed by observing the bow wave generated by the target, and the sonar operators got better at counting propeller revolutions for speed estitmates. Dick O'Kane and his crew were masters at this and he aimed all his fish to hit. His constant bearing method was part of this firing doctrine.

Dave

There was button (not provided in game) on the TBT and scope that could be pressed to up date the bearing correct?

[DaveyJ576]

Originally Posted by AVGWarhawk

There was button (not provided in game) on the TBT and scope that could be pressed to up date the bearing correct?

Correct

[LukeFF]

Dave,

In the "Through the Looking Glass" section of the website, there is a picture of what is said to be the S-42 fitted with what is obviously the slotted antenna of SJ-1 radar. Flanking it are what appears to be to S-18 subs, also with the SJ-1 radar antenna. Do you or your cohorts know when that pic was taken? I've pored through the patrol reports for the S boats and can't find any mention of SJ-1.

The pic in question is this one:

http://www.pigboats.com/subs/s42conn.jpg

[DaveyJ576]

Originally Posted by LukeFF

Dave,

In the "Through the Looking Glass" section of the website, there is a picture of what is said to be the S-42 fitted with what is obviously the slotted antenna of SJ-1 radar. Flanking it are what appears to be to S-18 subs, also with the SJ-1 radar antenna. Do you or your cohorts know when that pic was taken? I've pored through the patrol reports for the S boats and can't find any mention of SJ-1.

The pic in question is this one:

http://www.pigboats.com/subs/s42conn.jpg

You have stumbled across a rare photo! I missed this one myself! The advanced age and limited capabilities of the S-boats relegated them mostly to training and secondary patrol duties after 1943. Because of this, they received a much lower priority for receiving advanced gear like the SJ-1. Most of the S-boats didn't receive any radar at all until 1943! This is what leads me to believe that this photo was taken later in the war, probably late '44 or early '45. By that time, enough of the SJ-1 sets would have been available to warrant their installation in the S-boats. S-42 received her last major overhaul in Brisbane in October, 1944 and this is when this radar set may have been installed, but it is possible that she got it as early as March '44 in Pearl Harbor.

[DaveyJ576]

Silent Hunter IV is pretty accurate historically. For a game developed in Europe, I have been impressed with all the things they got right, especially in some of the minor details. But one thing they really goofed on is Midway Island.

Every time I have run a SHIV patrol out of Midway or stopped off for fuel, there have been dozens of warships present, including carriers and battleships. Sometimes the number of ships present exceeds that of Pearl Harbor! NEVER, at any time during the war, was Midway a major fleet anchorage or base. It is only 2.4 square miles in size and has no source of fresh water. None of the three islands of the atoll are large enough to support a major fuel facility or repair yard. Only a major construction project enabled the basing of submarines there, and even then the repair "facilities" only consisted of submarine tenders, floating drydocks, and a few tugs. Having 3 or 4 subs in port for refit along with the tender crews almost overwhelmed the atoll's meager facilities.

Despite these limitations, Midway proved to be a valuable advance base for our submarines. It was 1,300 miles closer to the patrol areas off Japan and thus saved our boats valuable transit time and fuel, allowing longer patrols in Empire areas.

[LukeFF]

Originally Posted by DaveyJ576

You have stumbled across a rare photo! I missed this one myself! The advanced age and limited capabilities of the S-boats relegated them mostly to training and secondary patrol duties after 1943. Because of this, they received a much lower priority for receiving advanced gear like the SJ-1. Most of the S-boats didn't receive any radar at all until 1943! This is what leads me to believe that this photo was taken later in the war, probably late '44 or early '45. By that time, enough of the SJ-1 sets would have been available to warrant their installation in the S-boats. S-42 received her last major overhaul in Brisbane in October, 1944 and this is when this radar set may have been installed, but it is possible that she got it as early as March '44 in Pearl Harbor.

Thanks, Dave. My detective work says that it would have been sometime in late 1943-early 1944. Given that the caption says the photo was taken at Dutch Harbor, I came to that date range based on the following info we do know:

• The presence of the 3"/50 gun: the patrol report covering its last 1943 patrol (ending in early October) mentions that the 4"/50 was still installed.
• The conning tower configuration was first used on the above-mentioned September-October 1943 patrol.

Additionally, we can extract the following info:

• The boat to the left is an S-18 class boat, probably S-35.
• The boat to the right of S-42 is a mystery. It looks to have a 3"/50 gun in addition to SJ-1. My guess is it's either S-30 or S-41.

Whatever the case, it's a very fascinating photo and the only one I've seen of S boats fitted with SJ-1 radar.

[hunter301]

This question may have already been asked but I don't have time tonight to read thru 5 pages of threads so here it is.....

From what I read in NAVPERS on the fleet type submarine the periscope was slaved to the gyro angle of the torpedo. So when they raised the periscope and gave the command "Bearing-Mark!" and lower the scope to fire how is the bearing transferred to all of the torpedoes when they switch from tube to tube to do a multiple torpedo attack?