Real Submarine Technology & History Q&A

[Platapus]

Ok, now I am going to ask the stupidest submarine question.

Good thing I am a landlubber so I can have some excuse.

Given all the technology we have these days, why are not modern submarines constructed without sails?

Everything could be in a very streamlined "whale" shape. Now that Periscopes do not need a direct optical path as they are more sensors than a periscope, why is there still a need for a sail on a submarine?

What is the use of the sail on a modern nuclear submarine that spends 99% of its time underwater tryin to be sneaky?

[DaveyJ576]

Originally Posted by LukeFF

The WWII patrol reports mention the use of what is called a "bubble sextant" for navigation. Many commanders also mention how it was sometimes difficult to use this device. How did this new type of sextant differ from the "old" style sextant, and what made it so more difficult to use?

When using a standard sextant, the angle to a celestial object is determined by sighting it, then bringing the reflected image of the object down to horizon level by moving the index arm along the semi-circular arc scale at the bottom of the sextant. Obviously, in order to do this, you have to be able to see the horizon. See the following link:

http://www.tpub.com/content/administ.../14220_230.htm

If for some reason you are unable to see the horizon, you would need to find a substitute. In a bubble sextant, the visual horizon is replaced by a regular alcohol bubble level. The reflected image of the celestial object would be brought down to the artificial horizon created by the bubble and the angle read off of the arc scale as normal. See this link:

http://www.users.bigpond.com/bgroble...t/sextant.html

Not being able to see the horizon was usually a problem for aviators flying at night. A shipboard navigator usually takes his sights at morning twilight, when it is still dark enough to see the stars, but when it is light enough to drown out the minor stars, making the major navigational stars easier to distinguish and the horizon visible. Aviators flying night missions may not always have this luxury of choosing the time of their sightings. At night and at altitude it would be very difficult, if not virtually impossible to see the horizon.

I have never used a bubble sextant and therefore can not directly comment on its ease of use. However, it is probably quite difficult to keep the bubble level enough to take an accurate sight on the pitching and rolling bridge of a fleet boat. Why didn't they just use a normal sextant? Well, it would give them the advantage of getting a fix at any time during the night, not just at morning twilight. The more fixes you get, the better your navigational situation will be.

[Platapus]

How long would it take for an average navigator to take the sightings he or she needs using a sextant?

[DaveyJ576]

Originally Posted by Platapus

Given all the technology we have these days, why are not modern submarines constructed without sails?

This is not a dumb question at all. In fact, several leading naval architects have asked the same question. They really wanted to eliminate the sail as it is a major source of hydrodynamic drag.

The main purpose of the sail was to provide a streamlined housing for the masts. These masts have to be a certain length in order to be able to penetrate the surface while at the same time keeping the boat at a deep enough depth to maintain control. This made for a fairly long mast. In order to house the mast completely when retracted, the hull of the boat would have had to be huge in cross section. This is impractical so the compromise is the sail.

The other important feature of the sail is the bridge. A partially sheltered, raised bridge is vital to safe navigation once the boat is on the surface entering or leaving port. It has to be some distance above the hull in order for the OOD and lookouts to be able to see anything.

On two separate occasions in the 1950's and 1960's the proposal to eliminate the sail was seriously put forth. However, each time the designers ran afoul of the problems that I described above. They tried one more time in 1968 during the CONFORM project, which was the first attempt at designing a follow on to the Permit and Sturgeon class SSN's. A scale model of the proposed design was built that had no sail at all. The masts and periscopes folded flush with the hull, similar to the way the snorkel mast folded on the late war German U-boats. The CONFORM design even featured a small folding bridge structure. This project would have produced a radically new and different submarine if it had been built. However, Admiral Rickover was adamantly opposed to these radical changes and championed the more "conservative" SSN-688 design. Rickover's forceful protestations eventually won out. CONFORM died and his design eventually became the Los Angeles class.

Realistically, we are only just now coming into a technology level that will permit the removal of the sail structure. CONFORM would have stretched the state of the art to its limits, and ultimately may not have been practical. Our newest submarines of the Virginia (SSN-774) class have non penetrating masts (i.e. they don't retract into or penetrate the pressure hull). This would allow a serious reduction in sail size. See this link for an artists impression of a proposed sail design for later Virginia class boats:

http://www.navsource.org/archives/08/0877413.jpg

[DaveyJ576]

Originally Posted by Platapus

How long would it take for an average navigator to take the sightings he or she needs using a sextant?

The actual taking of the sights doesn't take long at all, maybe 3-5 minutes depending on conditions. It is the prep and post sighting work that eats all your time. From start of work to plotting the posit on the chart, probably an hour for the average navigator, a little less for a really good one.

[Platapus]

As always, thanks for the clear answers.

[DaveyJ576]

There is currently a debate going on in the Submarine Trivia thread concerning the reliability of author Norman Friedman's book U.S. Submarines Through 1945: An Illustratred Design History. This book, while I consider it to be a authoritative reference work, has to be read and absorbed with a certain degree of caution. I can not emphasize this enough: this is not a book for a novice, or even average, reader. He wrote it for an experienced reader with a naval history or engineering background.

Mr. Friedman's writing style is not the best in the world. It is very academic in nature, with a choppy and broken paragraph structure. He will frequently drop interesting morsels like "The Electric Boat S-boats had to be rebuilt", then utterly fail to explain or expand on that statement. He also frequently refers to an extensive notes section, often leaving very important and illuminating information to a section in the back of the book, forcing the reader to constantly flip from the page you are reading to the notes section. This serves to break up your line of thought and makes his material hard to understand, and very easy to take out of context. I have also occasionally found some minor typos. Whoever his editor was did a poor job of keeping him on task and writing a well formulated and readable book.

I have a feeling that when he took on this project he didn't realize what a massive and detail loaded work it would become. A well intentioned attempt to cram as much detail as he could into the book backfired and the result was a sometimes confusing mass of data.

That is not to say that he is unreliable. Rarely have I found an out-and-out error in his works and in general he gets it right. He primarily works from original sources, i.e. Department of the Navy planning and construction documents, construction plans, materiel vendor documents, etc. Therefore, I consider him to be an authoritative and reliable author. But this also puts him at the mercy of the very material he uses. Planning documents will sometimes contradict the construction orders. Construction orders and plans are sometimes changed on the fly as needed to get the job done. These changes were sometimes not properly documented and this leads to contradictions from one document to the other. As the years have passed, some of the original documents have been lost and some destroyed, leaving gaps in the knowledge base and this leads to further confusion and contradictions.

My background has given me the experience necessary to "read between the lines" so to speak and interpret what Mr. Friedman writes. Even still, I have to read his works very carefully in order to understand what he intended.

For the average or novice reader, Mr. Friedman's book should only be used as a backup resource. The book that I can highly recommend is John D. Alden's The Fleet Submarine in the U.S. Navy. In this book, Mr. Alden hit solid gold. He has a well formulated and very readable writing style. It flows well and he makes this sometimes arcane subject easy to understand. I have never caught Mr. Alden in a mistake and his material has always checked out as accurate against other sources. I have refered to my copy of this book (which I have had for about 27 years) so many times it has become a little dog eared and worn. I consider it a true treasure and it is my prime source of info on the fleet boats. Unfortunately, I believe that this book is out of print so it may be a little difficult to find.

[Lt.Fillipidis]

DaveyJ576
I have a question here that has to do with the hull toughness on a VII or IX.
Ill just repost the question i posted on the SH3 forum.

A week ago i've got my hands on "The Curious Case of Benjamin Button" film.
At some point of this ridiculously long film, a tug boat rams a german u-boat which looked like an IX to me. The tug boat collides with the boat and pierces the bow armor, causes the torpedoes to explode and the uboat sinks.
As far as im concerned, the mere tug boat is too light and its bow not pointy enough to do such damage but i would like a second opinion on that...

Thanks!

[Sailor Steve]

Originally Posted by DaveyJ576

Mr. Friedman's writing style is not the best in the world. It is very academic in nature, with a choppy and broken paragraph structure.

I was reading his book on the history of U.S. destroyers, and was pleasantly surprised to find out that naval history came to him as a sideline. His original professionwas teaching physics at the Naval War College. That explained a lot to me I didn't understand about his writing.

Of course even he didn't give me the one piece of information I was looking for, which was the hull plate thickness of the 1890s torpedo boat destroyers.

[DaveyJ576]

Originally Posted by Lt.Fillipidis

A week ago i've got my hands on "The Curious Case of Benjamin Button" film.
At some point of this ridiculously long film, a tug boat rams a german u-boat which looked like an IX to me. The tug boat collides with the boat and pierces the bow armor, causes the torpedoes to explode and the uboat sinks.
As far as im concerned, the mere tug boat is too light and its bow not pointy enough to do such damage but i would like a second opinion on that...

It has taken me a while to respond because the Navy and my family have kept me busy!

I am not an expert on the German boats, so someone correct me if I am wrong here.

I believe the Type VII and Type IX boats were of single hull construction. That means that most, if not all, of the ballast tanks were internal to the pressure hull. The Type IX probably had external fuel tanks, called saddle tanks, on the outside of the hull, but all the ballast tanks were internal. Why is that important to this issue? Well, on a single hull submarine, the pressure hull is always directly exposed to the sea, unprotected by external ballast tanks, all along the length of the hull. This makes the pressure hull somewhat more vulnerable to damage, especially from ramming. The USN fleet boats were of a partial double hull construction, having ballast and fuel tanks wrapped around the pressure hull, protecting it to a degree. The pressure hull is only exposed at the extreme ends, at the foreward and after torpedo rooms.

On a single hull boat, any blow to the outside of the boat will be directly on the pressure hull. If it is breached in any way, you will get massed quantities of water in the "People Tank" and that will make for a very bad day.

Now, as to whether or not a small or medium size tug boat could breach the pressure hull of a submarine by ramming, that is very hard to say. There are a lot of variables involved. My gut feeling would be probably not. I think it would have a tendency to ride up and over the hull, causing damage to the superstructure and the topside equipment, but not to the pressure hull. This is all conjecture, though. If it was my submarine, I would avoid getting rammed by anything larger than a canoe at all costs.

You would have to have a very unusual set of circumstances occur to have the torpedoes explode from ramming. It is just not likely to happen. Torpedo explosive like Torpex is quite stable by nature. It has to be in order for the torpedoes to stand up to depth charging. Only a very hot fire or an explosion from another source would set off the warheads accidentally. If you get rammed you get a hole in the hull, water rushes in, your boat sinks, and you die. The torpedoes, though, should be safe!

[Stormende]

Davey, I have more questions for you that I hope you can answer, plz.

If the American torpedoes were that bad at the beginning of the war, how come the kill ratio between surface vs submerged vessels favored the subs?

How often did the submarines use their deck guns and how effective they were?

Were the English torpedoes better (reliable) than the Americans ?

Well that will be all for now, thankx in advance!

[DaveyJ576]

Originally Posted by Stormende

If the American torpedoes were that bad at the beginning of the war, how come the kill ratio between surface vs submerged vessels favored the subs?

You have to remember that for most of the first year of the war, submarines were the only contingent of our armed forces that were effectively carrying the hurt to the enemy. Everything else was sidelined or distracted into defensive actions. Submarines were out there making offensive patrols, seeking out and engaging enemy vessels from day one and didn't stop until the last day of the war. Our surface forces (destroyers, cruisers, and battleships) didn't enter into combat against other ships until the Guadacanal campaign in August 1942, and even then when boiled down to pure numbers, we lost more ships than the Japanese did in the Solomons. The surface forces were tasked with seeking out and destroying the relatively sparse IJN fleet units, leaving submarines and the air forces to engage the more numerous merchant vessels. They simply had more targets to shoot at and therefore the kill ratio favored the boats.

Yes, our torpedoes sucked initially, but they did work some of the time, often enough for aggressive and skilled skippers like Chester Smith, Mush Morton, and Creed Burlingame to put some ships on the bottom.

Originally Posted by Stormende

How often did the submarines use their deck guns and how effective they were?

There is a rather romantic vision in many people's minds of submarines engaging in heated gun battles with merchant vessels. From the American side at least, this actually was pretty rare. The 3" and 4" guns that were carried by the boats in the first two years of the war lacked sufficient punch to dispose of a merchant vessel quickly enough to warrant the danger of exposing the boat to counter attack. Therefore their usage quickly evolved to finishing off cripples (even this was fairly uncommon) and destroying sampans and small coastal luggers. It wasn't until the appearance of the 5"/25 cal gun in the last year of the war that the boats had an effective and fairly powerful gun. However, by this time the torpedo problems had been solved and there was even less incentive to risk your boat in a surface gun battle.

Without a stable element and centralized fire control, accuracy from the pitching and heaving deck of a submarine was poor even under good conditions. You ended up expending a lot of rounds (when misses were figured in) to sink a decent sized vessel, and this took too much time for most skippers.

Submarines are not tolerant of holes in the pressure hull. One small hole and assuming you don't sink, your patrol is over right there and you head home. It is fairly easy to punch a hole in a submarine and disable it, but even a moderate size merchant ship with all its reserve buoyancy can absorb a comparitively large amount of damage and not sink. Therefore the odds favor the merchant ship in a gun battle.

Originally Posted by Stormende

Were the English torpedoes better (reliable) than the Americans ?

Comparitively speaking, British torpedoes were mechanically more reliable than their American or German counterparts. The RN conducted an exhaustive series of firing trials on the China station prior to the war and were thus able to work out most of the bugs. However, the RN also fell prey to the siren-song lure of the magnetic influence exploder. Theirs didn't work any better than the ones used by the USN and the Kriegsmarine and the last of them were not discarded until late 1944.

[Stormende]

Thankx again for the answers, Davey.

[Mikeb213]

Hey guys, I am new here but have been reading through this amazing set of posts. I had an idea and wanted to see what you guys would think of this. I am really interested in comparing the sub tech between the major players in wwII both before and after the war. I really want to see the specs of German, Jap, and American subs to see where they all were and what they ended up with by the end of the war. Do you guys have any ideas where we could get the specs for the best boats they had at the start of the war, and the best by the end?

Thanks!
Mike

[Sensekhmet]

That would be a pretty simplistic comparison, don't you think? For example, the XXI would probably come out on top as 'the best' but in reality it saw little to no action, and its impact on the conflict was according.