Real Submarine Technology & History Q&A

[Pacific_Ace]

Great thread idea!
Im wondering about the effectiveness of ww2 passive sonar vs the speed of the destroyer using it. Currently Im replaying a situation I saved that placed me almost dead ahead of a TF containing 8 AS ships, 3 to a side, one ea front and back, the QE and the Hood .
Im inside the screens line of travel waiting for my juicy targets and Im at 1 kt and they are traveling at 19 kts. At this point Im tracking by sonar, yet they still detect me somehow and go active. Im just having a really hard time believing British sonar in late 39 is this good. Any idea whats going on here?

[Stormende]

Hey Davey, I have another question for you. It might seem dumb but remember I am just a virtual sailor so, how was the life inside a sub? With a bunch of people canned inside such a small place, did they get into fights or were strong bonded? Was the odor bad - I know the modern subs have some fancy ventilation system but what about the WWII era ones? Showers, WC? How did the crew ate? I do not think they had a mess room like the nuclear powered ones, right?

Well thankx in advance and keep up the good work!

I love this thread.

[Pacific_Ace]

Stormende, while I am not Davey and never served in subs, I suggest this link that I found. Lots of stories from people who served in the 'smokeboats'.
http://www.olgoat.com/
You have to click on 'Afterbattery' to get to the stories.

[Stormende]

In the meantime I get the answer from Davey, I will check this site.

Thankx Pacific Ace!

[DaveyJ576]

Originally Posted by Stormende

Hey Davey, I have another question for you. It might seem dumb but remember I am just a virtual sailor so, how was the life inside a sub? With a bunch of people canned inside such a small place, did they get into fights or were strong bonded? Was the odor bad - I know the modern subs have some fancy ventilation system but what about the WWII era ones? Showers, WC? How did the crew ate? I do not think they had a mess room like the nuclear powered ones, right?

Hey guys!

Sorry about the extended time away. The Navy has kept me busy.

There were several great technical advances for USN submarines in the 1930's, several of which directly contributed to improving the habitability of the boats.

Air conditioning was originally intended for reducing the humidity levels inside the boat and thus greatly reduced the number of condensation induced electrical fires. It had the happy side effect of cooling the air as well. The increased endurance of the crew combined with the reduction of electrical fires enabled the completion of 60+ day patrols in the warm waters of the Pacific Ocean.

Refrigeration allowed the preservation of food for much greater periods of time. It enabled a greater variety and quality of food to be carried, which made the crew happier and healthier, once again increasing their endurance. The scene from Das Boot in which the crew was sitting around the table cutting mold off a chunk of cheese will give you a good indication of what it was like in the days before refrigeration.

Kleinschmidt stills allowed a vastly increased production of fresh water over what was possible from the older evaporators. Better food could be prepared, the crew could stay cleaner, and sanitary conditions increased.

All of these advances greatly improved the quality of life aboard the USN fleet boats. By keeping the crew healthier and happier the boat's ability to carry out its mission improved as well. Other navys often scoffed at these "unneeded luxuries", but the fact remains that the USN was able to work in these new technologies without compromising the fighting ability or mechanical reliability of the boat. If that is the case, then why not do it?

Make no mistake, though, that life on a diesel submarine was some sort of pleasure cruise. It was not.

Even with A/C it was always hot in the boat. It was entirely normal to have interior temps in the 80's F., and temps in the engine room would routinely reach 100 deg and higher. Enginemen would come forward to crew's mess for a drink of water and would start shivering, even though the temp in crew's mess was 85 deg.! The 20 deg difference between the engine room and crew's mess was all it took.

The Kleinschmidt stills were a great advance, but they tended to be a bit cranky. Fresh water production usually fell behind and with most of it going to the batteries and for drinking by the crew, the crew was often restricted in how often you could take a shower. The interval frequently stretched to a week or more. This made for some smelly bodies.

The sanitary tanks that the toilets emptied into were emptied by pressurizing them with air and blowing the contents through a valve and overboard. The crewman conducting this evolution had to follow the procedure to the letter or contents of the tank would force themselves up in a rather forceful manner through sink drains and the toilets and into the interior of the boat. This situation, to put it mildly, is very unpleasant and if it happens makes for a bad day. Even with a successful and proper blowing of the sanitary tanks, before the toilets can be put back into operation, the residual air pressure has to be vented from the tank. If you are on the surface, no problem, it gets vented overboard. But if you are submerged the tank gets vented into the interior of the boat, and this once again is not very pleasant.

Smoke from the engines, incessant noise from ventilation fans and other machinery, zero personal space, and a myriad of unpleasant smells all tended to make life aboard a diesel submarine difficult and trying. Yet despite this, or perhaps because of it, a bond stronger than any other developed amongst the crew. A brotherhood born of shared adversity develops and serious disputes and fights amongst the crew are extraordinarily rare.

I highly encourage you to surf over to the link that Pacific Ace provided above. The stories there by Dex Armstrong give an accurate picture of life aboard a diesel boat. Although written during the Cold War, they still accurately depict the conditions that were faced during WWII. Dex is also an extraordinary writer and his stories are hugely entertaining and sometimes outrageously funny.

[DaveyJ576]

Originally Posted by Pacific_Ace

Im wondering about the effectiveness of ww2 passive sonar vs the speed of the destroyer using it. Currently Im replaying a situation I saved that placed me almost dead ahead of a TF containing 8 AS ships, 3 to a side, one ea front and back, the QE and the Hood .
Im inside the screens line of travel waiting for my juicy targets and Im at 1 kt and they are traveling at 19 kts. At this point Im tracking by sonar, yet they still detect me somehow and go active. Im just having a really hard time believing British sonar in late 39 is this good. Any idea whats going on here?

The effectiveness of any sonar system, surface ship or submarine, is inversely proportional to the speed of the platform using it. In other words, the faster you go, the worse your passive (listening) sonar gets. There are two main reasons behind this.

As you increase in speed, water flow over the sonar array increases, producing ambient noise. Think of driving in your car, listening to the radio with the window down. If you are at 5 mph the wind noise generated by the car moving is very slight and you can hear the radio with ease. As you increase in speed the wind noise also increases and you are forced to continuously increase the volume of the radio in order to hear it clearly. A similar principle applies to sonar. However, with sonar, at a certain point own ship's speed can render passive sonar completely ineffective (this point varies with the system) and you won't be able to hear a freight train coming at you, much less a quiet submarine.

The other factor is own ship generated noise. As you increase speed, your propulsion plant increases its noise output. The engines, fuel pumps, lube oil pumps, coolant pumps, bearings, reduction gears, and propellers all get noisier as you go faster. This increased noise output from your own ship will make your passive sonar much less effective.

Active (pinging) sonar is much less effected by speed and thus is the type most often used by surface ships while conducting generalized searches. Submarines, however, contrary to what is shown in the movies rarely use active sonar because the ping put into the water will easily reveal it presence to the enemy and allow them to locate you.

I do not have the figures for WWII British sonar systems, but an educated guess would be that at 19 knots a destroyer's passive sonar system would be borderline effective at best. If this is what is happening in the game, it would be my opinion that the destroyer's sonar is modeled incorrectly.

[Fluffysheap]

Another thing to consider is that if there is more than one destroyer, they can cooperate. One can move quietly and listen, and radio bearings to the other one which can move quickly to intercept. I believe this behavior is modeled in both SH3 and SH4.

[donut]

If Mass+Speed= Inertia, shouldn't A sub be able to turn inside A DE of similar length due to slower speed ? Seems not to be modeled in game correctly, the turning radius/speed seems way to tight for DD's ? I do recall man overboard drills, It took almost .5Kn to turn 300Ft DE around at cruise speed to all stop,& lower boat at hard rudder.

[Wilcke]

The stock DD's are agile as cats, turn on a dime and accelerate like drag boats.

jrex53 tackled this issue earlier in the year.

FYI this thread http://forum.kickinbak.com/viewtopic.php?f=11&t=1720

[vickers03]

don't forget the already finished maneuver mod
by webster
http://www.subsim.com/radioroom/down...do=file&id=942

[Sailor Steve]

Originally Posted by donut

If Mass+Speed= Inertia, shouldn't A sub be able to turn inside A DE of similar length due to slower speed ? Seems not to be modeled in game correctly, the turning radius/speed seems way to tight for DD's ? I do recall man overboard drills, It took almost .5Kn to turn 300Ft DE around at cruise speed to all stop,& lower boat at hard rudder.

I'm sorry I wasn't around when this was posted, because I've done a lot of research on how ships turn, and the surprise is that unlike cars and planes, a ship doesn't go fast enough to force a wider turn radius, and since at 40 knots or less the action on the rudder is dependent on the speed, the faster a ship goes the tighter it turns.

Specific numbers I have include the trials of the battleship HMS Dreadnought. At 12 knots it took her more than a minute to turn her first 45 degrees, while at 21 knots it took 40 seconds. After that she accelerated into the turn and was turning about 135 degrees per minute at 21 knots. Of course a ship that size creates a lot of drag, and she lost about 3 knots per minute doing that.

Most destroyers' listed tactical diameters give their best turning at around 20 knots, but you can bet a DD at 12 knots is indeed going to outturn a submarine going 8. And lose a lot less speed doing it.

[Sensekhmet]

So can a ship/boat actually turn 'too fast'? And what would the consequences be?
I know what happens to cars and bikes (I'm an amateur racer and a certified motorsport marshal), I can even imagine what happens to tracked vehicles but imagination fails me when 'floaters' are concerned.
For a few years now my town hosts one of the inshore European speedboat championship races*. Everytime I'm surprised to see those boats not slowing at all for a tight switchback around a buoy and still make the turn. I see it but I don't understand it. The only problem these guys seem to have is hitting the wake of a competitor and nosing down into the water. That stops them pretty damn fast.

* Here's a picture of one of the fastest classes, O-700 I think:
http://upload.wikimedia.org/wikipedi...tila_Havas.jpg

[Sailor Steve]

If by "too fast" you mean fast enough to lose control, then no. They use what is called a "discplacement hull", which means they sit in the water, and when they turn they tend to heel outward. This can seem to be fairly extreme, but under normal circumstances they just can't go fast enough to get into trouble.




And:



A boat on the other hand uses a "planing hull", which sits on top of the water. This lets them achieve much higher speeds, and when they turn they lean into the turn. This includes PT boats, which in WW2 weight upwards of 50 tons. They also weren't fast enough to lose their grip, but a high-speed racing boat certainly can. In even a slight chop one of those is sometimes bouncing completely out of the water, and in a turn can do exactly what a car does - get just a little too tight into the turn, lose its grip and flip right over. And over, and over, and over.