The technology of the 1940's was not capable of creating a ballast control system precise enough to enable a fleet boat to hover. Achieving perfect neutral buoyancy is very difficult even with today's computerized systems. There are dozens of factors that have to be constantly monitored and adjusted for in order to maintain the desired level of buoyancy. As an example, one crewman that moves from the crew's mess to the forward torpedo room will make the boat heavy forward. Water will have to be pumped from the forward trim tank to the after trim tank to compensate. Other factors that effect buoyancy are temperature and salinity of the water, currents, surface wave action, fresh water production, fuel useage, loading torpedoes, leaking shaft seals, battle damage, etc. The diving officer and the trim & drain manifold operator have to constantly monitor all these factors and compensate for them.

Everything on these boats was done by hand. To pump water from forward trim to after trim for example, the manifold operator opened the valve for the fwd trim tank using a large T-shaped wrench. He then pushed a button to start the trim pump. Once a suction on the tank was achieved, he would transfer the wrench to the valve for the after trim tank and open it. His eyes would then be glued to a flow gauge that was calibrated in pounds of sea water and would call out to the diving officer as each 100 pounds was transferred. Once the diving officer was satisfied with the amount transferred he would have the manifold operator secure the system. Neither the flow gauge nor the trim pump was sensitive enough to move amounts less than about 100 pounds.

Even if you were able to achieve perfect neutral buoyancy you would not be able to maintain it for very long due to the factors that I mentioned above. Strange as it may sound, these boats were not 100% watertight 100% of the time and that effected your ability to maintain neutral buoyancy. For safety purposes most diving officers trimmed their boats slightly light and used plane action to maintain depth.

Also, since the trim and drain pumps made noise, they were used only when absolutely necessary during battle. Most diving officers waited until the planesmen had trouble maintaining depth before they used them.

So, to sum up, the trim and drain pumps were not constantly in use and perfect neutral buoyancy was very difficult to achieve and maintain. If a boat came to all stop while submerged, it would usually either rise or sink depending on its' state of buoyancy at that time.

Excellent reply as always, thanks!

Yep, the Fleet Sub manual makes mention of the fact (in the trim and drain pump section) of all the different areas where water could and did leak into the boat.

A revised version of "A Visual Guide to the U.S. Fleet Submarines Part One: Gato Class" has been posted on Navsource.

http://www.navsource.org/archives/08/10idx.htm

I reformatted the article for better readability and added some new information. Based on the inputs from readers, I added a new mod, the Mod 1A. I also updated the Mod 2 and Mod 3 sections, and added information that I found concerning a one off variation to the Gato herself. This is probably the final version for this particular article, but if previously unknown info turns up, who knows?

Awesome stuff! I've looked at those from time to time, and never realized that was you. Thanks for that great site! :salute::rock:

Thanks for the update. This is tremendously interesting and helpful information you have published for all of us. Thank you.

Not really sure if this has been posted yet, but this site includes PDF versions of 16 sets of general plans for American submarines ranging from the USS Holland (SS-1) to USS Growler (SSG-557). The Tang contract plans are worth checking out if you're seriously interested in submarine design and construction.

HNSA - Booklet of General Plans

Sub Plans
 

I looked over with a great deal of interest the webpage that Subnuts referenced above. In particular the plans for the Guppy boats Catfish & Dogfish (Guppy II), and Razorback (Guppy IIA) caught my eye. The plans for the Guppy II boats had a discrepancy that I initially could not explain.

The Guppy II boats were basically a Guppy I with a snorkel. To get the extra power needed for the greatly desired higher submerged speeds, both batteries were expanded to four sets of 126 cells each. The existing forward and after battery wells were too small to accomodate this new arrangement so a new smaller battery cell was developed. Even this measure was not enough so the after battery was extended into the now superfluous ammo magazines under the crew's mess and the forward battery was expanded into the pump room under the control room. This presented a problem as the drain pump, air conditioner plants, and air compressors located there were still vitally needed machinery. The solution was to remove the unneeded auxiliary diesel from its' location below the deck plates in the after engine room and relocate this gear there. This proved to be a very cramped arrangement and proper maintenance of this gear was very difficult. The Guppy II boats retained all four of their main propulsion diesels.

The greatly expanded and modernized sonar gear for these boats simply would not fit in the already crowded conning tower or control room. The solution was to build a new sonar room in the aft port corner of the forward torpedo room. Unfortunately, this arrangement meant that only shorter ASW torpedoes like the Mk-37 could be carried in the port stowage racks, effectively reducing the amount of the big torpedoes (Mk-14 and Mk-16) that could be carried. The Guppy II conversion was also quite expensive and the Navy wanted to find a way to cut costs so that more of the fleet boats could be converted.

One of the solutions was the Guppy IIA. The major difference was in the battery. In a timely development a much more powerful (and cheaper) battery cell design using the same size of the original came into service and this allowed a power output similar to the Guppy II battery without having to expand the size of the battery wells. This development, along with the desire to regain the lost space in the forward torpedo room led the designers to move the sonar room to the forward half of the pump room. Once again, the A/C, air compressors, and drain pump had to be moved. The cramped arrangement of the Guppy II's in this regard led to the radical solution of removing #2 main propulsion diesel from the forward engine room and placing the machinery from the pump room in its' place. This obviously had the effect of lowering the surface speed, but since these boats were going to be spending a lot more time submerged than in the past, the loss of approximately 4-5 knots in surface speed was not considered critical.

As I was looking over the plans shown for the two Guppy II boats, I noticed that both showed that #2 main engine had been removed with the displaced pump room gear relocated in its' place. This ran contrary to all the listed specs for these boats in my reference materials. I scratched my head on this one for a while until I came across a paragraph in Norman Friedman's book U.S. Submarines since 1945.

By the mid 1960's, the need to increase the effectiveness of the sonar systems on the Guppies to counter the rising Soviet threats led to some measures to silence these fairly noisy boats. Own ship generated noise made it hard for the sonar operators to hear anything, especially when snorkeling. The solution was the Masker system. It bled air from small ports in the hull forward of the engine rooms and along the bilge keel. These small bubbles mostly masked the noise from the engine rooms from the sonar gear located forward. The propellers also generated noise and another system called Prairie forced air through tiny holes in the propeller blades and this greatly reduced their noise output. The large compressors needed for these systems had to go somewhere and in a manner similar to the Guppy IIA's, #2 main engine was removed from the Guppy II's and the compressors placed there. This also led to the happy move of the gear previously displaced from the pump room to this location as well, greatly easing the maintenance problems encountered in the after engine room.

John Alden's book The Fleet Submarine in the U.S. Navy made no reference to this and Friedman's book only had one small obscure paragraph that I had previously missed. None of my other references mentioned this 1960's modification to the Guppy II's either. But if you look at the plans closely, you can see the Prairie/Masker compressors labled in the forward engine room. I didn't realize that this was a later addition to the Guppy II's

The history of the development of the Guppy modifications is quite interesting and well worth a read. I would recommend either of the two books I listed above.

Some technical questions regarding WWII torps.
 

Hello I'm in designing phase for a WWII sub game I wish to do. At the momment I'm taking care of the game's UI (using windows controls only). I am in great need of understanding some aspects of WWII u-boats related to torpedoes.

1 - The torpedo loading sequence.
How long to load a torpedo? How many crew members were involved in such task?

2- The torpedo's setting for bearing, speed and depth.
Does this requires the torpedo to be out of the tube?

3 - The torpedo firing sequence.
What happens once the inner door is closed? Is the torpedo flooded when opening the outer door? How long does it take to flood the tube?

4 - Unloading a torpedo which was already flooded.
How long to empty a flooded tube?

Thank you.

PS: if someone is interested in the project, please do let me know. I will gladly describe what I intend to do.

Keep in mind that all answers that I give will be related to operations aboard the USN fleet submarines. Specific procedures will vary somewhat in other navies, although in principal it will be very similar.

This is a factor that will vary greatly depending on the level of proficiency of the torpedo room crew. Using a system of ropes and pulleys (block and tackle) a well trained crew of about 4-6 Torpedomen will be able to load a tube in approximately 5-8 minutes. A USN Mk-14 torpedo weighs a little over 3,000 lbs! Whenever possible, the Diving Officer will order the planesmen to hold a slight down angle (or up angle if it is the stern tubes) to assist the Torpedomen in their efforts.

Once the torpedo was loaded in the tube, setting spindles were engaged to ports on the weapon. The Torpedo Data Computer, which constantly tracked the target's course, speed, range, and angle on the bow set the gyro angle on the weapon and automatically updated it right up to the moment of firing. Other spindles set the running depth and speed of the weapon, although the low speed feature of the Mk-14 was rarely used. These spindles are disengaged as part of the firing sequence. This ability to automatically and remotely set these parameters was a tremendous advance in capability for the USN.

Once the weapon is in the tube and the spindles engaged, the inner (breech) door is shut and locked. Water is flooded into the tube from the Water 'Round Torpedo (WRT) tank with the remaining air in the tube vented into the room. An equalizing valve is then opened to ensure the interior of the tube is at the same water pressure as the outside of the boat. The outer (muzzle) door of the tube can then be opened. A good Torpedoman takes pride in how fast he can make the tube ready to fire, the process to this point will take approximately 30-45 seconds.

To fire the tube, a shot of high pressure air is fired into the aft part of the tube behind the weapon, pushing it out of the tube. Before the air bubble can escape the tube and give away the boats' position, a poppet valve opens which vents the air back into the room, this process is assisted by the water which floods back into the tube from outside. The muzzle door is then shut. The water in the tube is then drained back into the WRT tank with the excess volume going into the forward trim tank. This compensates for the loss of the weight of the torpedo. Once drained, air pressure in the tube is equalized with that of the torpedo room and the breech door is opened. An interlock system prevents the breech door and the muzzle door from being opened at the same time.

Draining the tube after firing takes a little longer than flooding it, approximately 45 seconds to one minute. If you didn't fire the weapon and had to unload it from the tube, just reverse the procedure that I described above. It will take a similar amount of time.

Did I answer all of your questions? I will defer to someone else on the specific procedures for U-boats. They did differ somewhat from the USN.

Great topic, with lots of useful info indeed!:up:
Regarding the transfer of torpedoes from aft to forward as discussed on page 11, it is perhaps interesting to note how HMS "E-11" recovered torpedoes that had missed their target during her first patrol in the Dardanelles/Sea of Marmora in 1915. Torpedoes were set to float when their fuel was expended if they missed; when the coast was clear, the sub would surface and search for the torpedo. When found, a brave chap would dive overboard, swim to the torpedo and unscrew the firing pistol. On the first occasion the torpedo was hoisted on deck, the warhead removed and warhead and torpedo body then lowered into the boat separately through the fore hatch in the usual manner. On the next occasion, however, the boat was trimmed until the aft tube was awash; the outer door was opened and the torpedo guided warhead first into the tube, the outer door closed; then the inner door was opened, revealing the warhead. After that it was "simply" a matter of transporting the torpedo to the bow torpedo space- presumably, the internal arrangement of "E-11" did not make this too difficult. See "Dardanelles Patrol" by Peter Shankland and Anthony Hunter.
Of course, Turkish anti-submarine capabilities were nowhere near even those of the Japanese- one can hardly imagine any Allied sub being able to do this off the coast of Honshu or in Malacca Strait and get away with it...........

Man.. thank you so very much! Though I understand that this info is USN related, I does let me get the general picture of such aspects. Having also in count that the player will be able to play to the USN side, the information you shared with me is indeed double perfect!

Can I ask you about the math formula used to compute the path of a torpedo torwards a target? I know I need speed, distance and angle of the target relative to the player's sub position and bearing. It is too complicated?

Thanks again!

There are several excellent threads on this forum concerning game related torpedo fire control. Rockin Robbins in particular has a very good handle on this issue. Take a look at those threads and you will find all that you need.

Well didn't managed to find anything. Anyway this will be addressed later on. It is not important at the moment.

Thanks anyway.

Try this: http://www.subsim.com/radioroom/showthread.php?t=146795

It should have just about everything you want to know.

Davey, I have a mechanical question. Did the WW2 fleet boats use gears, a transmission system like in cars? Or was it just more fuel means more speed. Submerged I'd guess that it was just more electricity means a faster screw speed.