(QUE) Real life facts

[gouldjg]

Hi all

I need the help of some history buffs here. (I don't do books )

1. How long did Co2 take to reach danger levels in real life
2. What would be a realistic max speed irl taking into account supercharging etc (surfaced and submerged)
3. What was the average gun reload time irl
4. What was the best top reloading time irl
5. What was max food supply in average e.g 100 days or 300 days
6. Same with dive depth = Max irl please
7.

[mookiemookie]

Just a couple of thoughts:

1. I don't think there's a cut and dried answer to that question, as there's many variables - number of men on board, if they're working or resting, when they started using the tauchretter breathing apparatus

2. The boats came from the factory with superchargers. Max speed listed is max speed.

3. Oh lord, don't start that fight again. Call it 15 to 20 seconds.

6. Many variables here too - quality of the steel, how many times it had been previously stressed by deep dives, the part of the ocean you're in

[gouldjg]

@3, I almost forgot that one ,

Yeah we better not go there,

I am really after the most realistic max speed such a u-boat would have reached as I have already reduced the effects of the abilities and still get a 20knot at lvl 2 which IMHO is rubbish.

You know, they could have made this system work a treat e.g. have scaled random effects in there e.g. hit button meant faster speed and more fuel consumption but they should have added a 1-15% chance for a failure to occur causing minor damage etc.

Aw well never mind

[Vandecker]

If I recall correctly in Das Boot they remained on the bottom for almost 2 days trying to pass through into the Mediterranean before they were finally forced to surface and re-air the boat.

It was not however fun, required special breathing equipment and very few of the men were fighting fit by the end of it.

Since the author of Das Boot says that he personally experienced at the very least similar events to the ones he wrote in the book I would have to guess that a U-boat could probably stay down at least 24 hours, maybe even up to 36.

If the sub was traveling at any speed at all however the battery would give up before the air (judging by Silent Hunter III) in Das Boot they were relying on the Mediterranean currents to carry them through the Gibraltar Straights rather than their engines allowing them to keep the ventialtion running.

[pythos]

In Das Boot, the boat was aerial bombed on it's attempt to make it through the strait, just like the actual U-96.

She went down to the bottom and stayed there for I think 16 hrs. But the air was contaminated by the crew frantically stopping leaks, and bucketing water from parts of the boat to the bilge. This was A LOT of breathing.

In total the boat stayed at the bottom for 16 hrs.

This time would probably be much higher had the boat made it safety under the waves and no frantic breathing had taken place.

Das Boot in this case is a poor choice to base the game off of.

There is a formula to get a rough estimate for the amount of increase of CO2 levels though.

[CCIP]

The CO2 problem is pretty complex because the biology behind it is complex, and because there are ways to partially help it - like the rebreathers/filters (you see those in Das Boot). And it's not something that suddenly runs out.

For example, some info dug up on Wiki:

1% can cause drowsiness with prolonged exposure.
At 2% it is mildly narcotic and causes increased blood pressure and pulse rate, and causes reduced hearing.
At about 5% it causes stimulation of the respiratory centre, dizziness, confusion and difficulty in breathing accompanied by headache and shortness of breath.. In addition at this concentration panic attacks may occur.
At about 8% it causes headache, sweating, dim vision, tremor and loss of consciousness after exposure for between five and ten minutes.

Adaptation to increased levels of CO2 occurs in humans. Continuous inhalation of CO2 can be tolerated at three percent inspired concentrations for at least one month and four percent inspired concentrations for over a week. It was suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a submarine) since the adaptation is physiological and reversible.

The average person, through the natural process of breathing, produces approximately 2.3 pounds (1 kg) of carbon dioxide per day. The actual amount depends strongly on the person’s activity level.

Density of CO2 = 770g/L

Therefore 45 people would, on average, produce about 2kg or 3L of CO2/hour. But how much air is in the U-boat? Someone can probably figure this out, but of course most of the pressure hull is probably NOT filled with air. But then in any case, it's a little bit hard to put a single figure on it since human activity really varies CO2 production/oxygen consumption. Then there is other stuff. Any fire would eat up oxygen at a massive rate, instantly. Chlorine gas in the air would probably reduce the life expectancy of the crew by a lot.

I will look it up, but I know that in fact some boats stayed down for a very long time. I think Jurgen Oesten mentioned an incident where a boat under his command stayed down for almost 40 hours. I think it was even possible for boats to stay longer.

By the way during this period, oxygen recycling equipment existed. It was not carried by U-boats however. For example when I toured the Russian D-2, I was told about how in 1936, the boat spent a full month on the bottom of the baltic with its full crew, testing the effectiveness of that equipment.

I think one reason Germans were not very interested in this type of thing is that batteries were by and far the greater limiting factor during this period. It was generally expected that, at least in open ocean, the sub would run out of battery long before it ran out of oxygen. At 40 hours, that's definitely something that would happen. I think the logic was that if a boat cannot surface after 30-40 hours, it probably can never surface at all. By and large that was true.

[Vandecker]

Originally Posted by pythos

In Das Boot, the boat was aerial bombed on it's attempt to make it through the strait, just like the actual U-96.

She went down to the bottom and stayed there for I think 16 hrs. But the air was contaminated by the crew frantically stopping leaks, and bucketing water from parts of the boat to the bilge. This was A LOT of breathing.

In total the boat stayed at the bottom for 16 hrs.

This time would probably be much higher had the boat made it safety under the waves and no frantic breathing had taken place.

Das Boot in this case is a poor choice to base the game off of.

There is a formula to get a rough estimate for the amount of increase of CO2 levels though.

I don't have the book on me so I can't check but I'm sure that the boat stayed down the bottom for at least a full day and a night.

The first night they attempted cross Gibraltar they were attacked on the surface at night by aircraft equipped with RADAR not too long after they surfaced and were forced to dive with considerable damage. They were unable to surface the rest of the night due to warships being close by when they came to periscope depth so they dived once more and had to wait a full day for the next night before they could finally surface.

I'm definately wrong about the 36 hours figure but I'm also sure that they stayed at the bottom close to or over 24 hours.

If anyone has the book handy please correct me where I'm wrong, I hate to think that I'm misquoting such a well written book.

[Sailor Steve]

One of the problems with maximum speed is that there is an optimum max to any hull design, and once you reach it you will need to double the horsepower for an increase of half the speed, and doubling it again gets you half of that.

I used to have a Ford Escort wagon that could make 90 mpg on 88 horsepower. A Grand Prix car with 800 horsepower barely makes 200 mph.

The North Carolina Class battleships made 28 knots on 120,000 horsepower, at a full-load displacement of 46,000 tons. The South Dakota class increased that power to 130,000 on the same displacement, and gained one knot for a max speed of 28. The Iowa class had a massive jump to 212,000 horspower, and this gave them 33 knots. On the downside their full-load displacement was much higher at 57,000 tons; but on the other hand they were more than 100 feet longer which gave them a better fineness ratio. The exact effect is arguable, but you can see the point.

And the point is that a Type VIIa u-boat without supercharging displaced 626 tons and made 2310 horsepower for 17 knots. A Type VIIb with supercharging displaced 753 tons and made 3200 hp for 17.9 knots. A Type VIIc with the same setup but an increase in displacement to 769 tons (an increase of 2%) reduced the speed to 7.7 knots.

To get even 18 knots out of a VIIc is going to take a lot more than just a little tweaking by the LI.

On the other hand the speed should increase slightly as the patrol goes on, due to the reduction in weight from using both fuel and food.

[Jimbuna]

The answer to Q7 is 42

[PortoFerro]

On the other hand the speed should increase slightly as the patrol goes on, due to the reduction in weight from using both fuel and food.

Only little weight change on fuel, tanks are seawater filled, oil on top.
Maybe not approved by greenpeace, but saves the need for higher volume ballast tanks.