The photo in Jan Kyster's post above is interesting. It shows a Gato class boat with a Mod 4 fairwater (low bridge, covered wagon ribs exposed, SJ radar mast forward of the shears). I can't see the limber hole pattern in the superstructure, but based on the angle of the trailing edge of the fairwater, this boat looks like a Government built version (Portsmouth or Mare Island.) This picture was probably taken in early to mid 1944. She has a 4"/50 cal deck gun in the forward position, a 20 mm mount on the forward fairwater gun deck, and a 40 mm on the cigarette deck. The interesting thing here is that on the aft deck gun position she has an additional 20 mm mount. This was sometimes done to gain additional firepower. Note that on both 20 mm mounts, the gun itself is missing. The Mk 10 Oerlikon 20 mm automatic cannon did not hold up well with repeated dunkings in saltwater, so the guns were removed from their mounts and taken below when not in use.

Jan, which boat is this?

Not even close, man! Photo was taken 21 August 1944! :smug:

It is USS Silversides (SS-236) outside Mare Island after an upgrade... sweet, isn't she? Buildt there too, btw.

Well I guess that depends on how you define "mid 1944"! I got really close! :D Much later than this date and most boats received a 5"/25 gun, although it appears Silversides finished the war with a 4"/50. That is unusual.

I did nail that it was a Government built boat, though! :smug:

Thanks for answer Dave! I got continuation question about radar. In SH4 vanilla version all fleet boats have rotating (radar?) antenna in port side of their fore deck. What this is?

I looked at the picture and said "Yep, that's a submarine all right!"
:rotfl2:

That's the JP-1 sonar head.

Yup, on that note, Ptiy we can't make the FM sonar head work like its supposed to. :cry:

Late war Japanese radar operated on the same frequency that US radar did, so radar equipped Japanese escorts were able to detect what bearing US submarines were on and were able to alter course away from them as a result (they would both receive interference on their scopes from the other's radar). The whole thing became a game of cat and mouse, with each side using their radar sparingly and the US radar operators 'keying' their radar sparingly. Each time the US sub used their radar, the Japanese convoy would alter course accordingly. Each time the Japanese used their radar, the US sub would get a bearing on their new position. When a correctly defended convoy operated like this, the convoy turned away and an escort came down the bearing of the radar. This coupled with the late war coast crawlers caused significant problems for US submarines.

Dave,

I don't know how familiar you are with Bauer and Roberts's Register of Ships of the U.S. Navy (very good book, BTW), but some info in there on the fleet subs has me curious. Namely, he lists the later fleet sub types (Gato, Balao, and Tench) as having a top submerged speed of 10 knots. Every other source I've ever seen lists a top speed of 9 knots. Do you know where that 10-knot speed possibly comes from?

http://btobsearch.barnesandnoble.com...of+the+us+navy

Rounding up????


:hmmm:

Possibly.

Dave, while we're at it, I've come across a pic of an S-18 class submarine I've never seen before. I found it at the U.S. Navy and Marine Corps Museum Photo Archive, and it depicts an S-18 class sub at Dutch Harbor:

http://img.photobucket.com/albums/v2...BoatAlaska.jpg

Any guess as to which boat it might be? The only 3 S-18s I know of that got a AA gun platform are S-28, S-31, and S-35. Also note the spray shield mounted on the bridge. Not something I've seen on any other S Class pics!

That site is really fascinating, showing some pics of American subs I've never seen before. Really worth checking out!

In this post Nisgeis is referencing a very interesting entry in the 4th war patrol report of the USS Baya (SS-318). See this link:

http://www.ussbaya.com/patrol4.html

The convoy commander in this incident was a very skilled operator and was able to take advantage of every tool at his disposal. Probably based on past experience, he was using interference on his radar screens to detect the prowling Baya and reroute his charges away. Most importantly, he took his job of Anti-Submarine Warfare (ASW) seriously. Unfortunately for the Japanese (and fortunately for the USN!) naval officers of his skill and temperament were few and far between. While it is documented that incidents like this did happen, they were fairly rare and for the most part, USN submarines could use their surface search radar with near impunity.

It is sometimes quoted that almost half of the late war IJN escorts had radar. While this somewhat murky statistic has some truth to it, one thing that must be considered is what type of radar they carried. There were three major types of radar at this point: surface search, air search, and gun fire control. Air search and gun fire control made up the majority of the radars installed on IJN ships and they operated on frequencies and possesed mechanical and operational limitations that made them very ill-suited (at best) or useless for detecting other ships. See this link and take a close look at the purpose and the installed platforms listed for each type:

http://www.combinedfleet.com/radar.htm

As you can see, very few of the dedicated surface search radars made it onto ASW ships. When they did, few officers and enlisted men had any knowledge or patience with the newfangled gadget and therefore the successful employment of this incredibly useful tool was limited at best.

I should have been clearer in my original post. There was indeed a strong suspicion that Japanese aircraft were detecting (probably through interference on their radios and own radars) the emissions of the SD air search radar used by our subs. Towards the end of the war, USN sub skippers began to use the SD on a limited basis for this reason. The surface search SJ, operating on different frequncies, seems to not have had the same issues.

Good writeup there on Japanese radar, Dave. The other thing to keep in mind was that, in general, Japanese radar was far less reliable than American types. The postwar technical research conducted by the Americans shows that, for instance, the Type 22 surface search radar was reliable only 80% of the time.

Actually, Diopos' answer to this question is probably correct. The authors of this book rounded up.

The two most authoritative authors, John D. Alden and Norman Friedman, list the max speed of these boats as 8.75 knots. Remember, this is the designed speed. Under real world combat situations, this speed was probably less. Most boats probably topped out at 8 knots. I have seen a few sources list the speed as high as 9.5 knots. The authors of the book in question probably saw this listed somewhere and for simplicity sake rounded up.

If you guys come across something on the technical side that sounds goofy, always refer to Alden and Friedman (with emphasis on Alden) for a quick fact double check.

Thanks, Dave. I've been meaning to pick up Alden's book, so I just placed an order for a copy on Amazon.