I'm not sure if it's modelled in SHIII but another good reason to open outer doors in advance is to avoid detection (assuming there are escorts nearby).

In real life, the opening of the tubes can be a noisy evolution. Not only do the tube doors make a metallic transient noise, but the tubes have to be equalized prior to the doors being opened and that makes a fairly significant noise while the water rushes in to fill the tube around the fish.

It makes sense to do this out of ear shot of the enemy, that way the first sound he hears is the cavitation from your fish closing in for the kill!:rock:

Openning the doors ahead of time will sometimes save you the headache of pre-detonation when using the magnetic detonators.. Not always, but the eels seem more stable in the warhead if you give them a couple minutes to equalize with the sea.

Grayling, the torps fit the tubes pretty tightly, as grease was used to get them to fit the tubes easier, and they were lauched with compressed air. Any gaps, and you won't launch anything, and wind up with a live eel stuck in the tube.

I assumed that the tubes worked basically the same as the tubes on the sub I was on. On a modern sub, there is an equalizing valve that is used to fill the space around the torpedo with sea water and to equalize the pressure between the inside of the tube and sea pressure.

Compressed air is used to launch the fish, but indirectly. It forces water out of a holding tank and into the tube and flushes the fish out. Then the outer doors are closed and the tubes drains into another tank.

Although I am sure that modern tubes are somewhat more sophisticated than those used in WWII, I imagine the basic concept is pretty similar.

Regarding acutal operations, the only thing i know for sure is that the compressed air used to eject the torpedo's was vented into the boat so as to not leave telltail bubbles coming up at the point of firing.

edit:
im pretty sure Grayling is correct. Im not familiar with the technical operations ,but from what ive read the outer doors are the primary doors. The inner doors cannot handle much sea pressure. The tubes are flooded first. Then the outer doors are opened. Compressed air is used to force a water jet that ejects the fish, and at that point the compressed O2 i beleive is vented into the boat.

I agree except that the inner (breach) door is still subject to sea pressure once the outer(muzzle) door is opened. Not only is the air vented inboard, but the water from the tube is drained to a holding tank to help compensate for the missing weight of the launched weapon in order to maintain trim.

Again, I don't have any experience on a U-boat (other than SHIII), but I have a considerable amount of experience on a 637 class US sub. The operation of the tubes may be different, but I'm pretty sure the overall function is pretty much the same.

I know off the point, but I remember in a high school speech class I did a speech on how to flush a toilet on a submarine with all the steps involved (with the toilet machinery) it was about 7 pages long, the report notes that is

My impressions on the inner door i get from the book "iron coffins". If its to believed as a credible source. In it two points stuck in my mind. It was said that they couldnt really go past 30 meters with the outer doors open. Hence why i said, that the inner doors couldn't handle much sea pressure.

Another intresting note was a passage that cited how while in harbor, an inner door fell off its hinges and fell flat on the torpe do room deck. Apparently bomb shock damage rattled the hinges or somehow caused its mountings to go faulty.

In a third passage, a stuck open outer door that could not close, effectively ended a patrol. Again, owing to the amount of seapressure that the inner door could handle, which from all accounts in this book, wasnt very much.

Interesting! I hadn't thought that much on it, but it makes sense. A U-Boat in WWII wouldn't be firing torpedoes very often (if ever) below periscope depth, because they primarily used visual contact to obtain a firing solution. Therefore the breach door wouldn't need to withstand sea pressure below about 30m.

On a modern sub, the entire solution may be based on sonar information only... and they have the capability to operate at much deeper depths...and to fire torpedoes from those depths...so their breach doors have to be tougher.

I'd like to pick up "Iron Coffins"...do you recommend it?

The only book I have read on the subject was "Operation Drumbeat", which I read while on deployment (to the Med I think). I thought it was excellent but that was quite a while ago.

The most important step was to pay attention to the sign..."Secured Blowing Sanitary Tanks"...If you happened to be wander to the head, half-asleep, and didn't notice the red sign...you'd be in for a rude awakening when you pull the valve handle and blow the not-at-all sanitary contents of the sanitary tank right in your face.:o :down:

Even worse, if you were the watch assigned to blow sanitaries and you forget to change one of the signs...in the CO/XO's head for instance. Nothing makes a captain grumpier than wearing his own crap because the watch forgot to change the sign.:nope:

Iron coffins, i think is a fairly good book. It's essentually a memior that tells about how he got into uboats, how he started in them, and follows his wartime career. Through his eyes you see how drastic the changes become. He starts as a midshipman, by war's end was a captain of his own boat.

The book has a foreward section in it by Edward Beach (http://www.fleetsubmarine.com/beach.html ) who apparently has endorse the book, and said that Herbert Werners career seems to mirrior his own.

Now how much of it is exaggerated or painted up i coudlnt tell you, but it seems like the real deal.

ANother book id recommend is "Steel boat, Iron hearts" by Hans Gruebler (spelling). As it gives both a crewmans perspective of the war, and that on the U-505 capture, since he was a crewmember of that boat throughout it's service. Not quite a "plank owner" but he saw every war patrol that boat ever did.