Das Boot surface attack at flank speed - how?

[commandosolo2009]

A few remarks..

1- Charging in, surfaced, or merely decks awash in the presence of a destroyer is pretty unrealistic, unless it's darks enough, but the moon fading into the sky doesn't necessarily mean that the boat is in 'stealth' mode.

2- The captain was desperate and if you watched the full movie, they had a transmission of a convoy which they couldn't round to. capt. was supposed to make it steady into any of those conditions.

3- About the full speed firing, the torpedos had more speed than the boat even at low setting, and additionally get an air induction on their way out. So I don't see why not charge at full speed.

4- they moved to the forward room to quick dive. Imagine there were slots at the game for that.

[Sailor Steve]

No, not much of Das Boot was accurate, at least in the operational sense. The interiors were great, but the crew's reactions were overstated and the portrayal of actual operations was limited and in some cases flat-out wrong.

Originally Posted by commandosolo2009

1- Charging in, surfaced, or merely decks awash in the presence of a destroyer is pretty unrealistic, unless it's darks enough, but the moon fading into the sky doesn't necessarily mean that the boat is in 'stealth' mode.

Agreed. Night surface attacks were conducted at low speeds, often using electric motors to keep noise and smoke down.

2- The captain was desperate and if you watched the full movie, they had a transmission of a convoy which they couldn't round to. capt. was supposed to make it steady into any of those conditions.

Even more in the book than in the movie the captain is far from perfect, and makes several mistakes.

3- About the full speed firing, the torpedos had more speed than the boat even at low setting, and additionally get an air induction on their way out. So I don't see why not charge at full speed.

Themrwho's question was whether the outer doors could open and that speed, not how fast the torpedoes were. I also wonder if the outer doors could open at 15+ knots.

4- they moved to the forward room to quick dive. Imagine there were slots at the game for that.

That's something that's always bothered me. I've read that they really did that, but I wonder why, given that the diving tanks were capable of transferring up to 20 tons of water between fore and aft trim tanks, many times the weight of the entire crew.

[Herr-Berbunch]

Originally Posted by Sailor Steve

That's something that's always bothered me. I've read that they really did that, but I wonder why, given that the diving tanks were capable of transferring up to 20 tons of water between fore and aft trim tanks, many times the weight of the entire crew.

Every little helps, but maybe it was more psychological - if the crew get there fast they think they'll live, and if not...

[mookiemookie]

Movies are just that - movies. They're not real life.

[Sailor Steve]

Originally Posted by Herr-Berbunch

Every little helps, but maybe it was more psychological - if the crew get there fast they think they'll live, and if not...

Could be. It also would help give the off-duty crew something to do besides sit and wait.

[Jan Kyster]

Originally Posted by Sailor Steve

I also wonder if the outer doors could open at 15+ knots...

They're hinged at the front... the problem would rather be closing them...

[Sailor Steve]

Originally Posted by Jan Kyster

They're hinged at the front... the problem would rather be closing them...

I didn't mean the hull doors, but the front doors of the tubes themselves. They open outward, partly because they act as caps and can't go inward, and partly to make sure they seal under pressure.
http://www.maritime.org/fleetsub/tubes/chap3.htm

[Rockin Robbins]

Originally Posted by Sailor Steve

That's something that's always bothered me. I've read that they really did that, but I wonder why, given that the diving tanks were capable of transferring up to 20 tons of water between fore and aft trim tanks, many times the weight of the entire crew.

Steve, the U-Boats did that because they were an older design than the US Submarines. American subs had fore and aft trim tanks to perform weight adjustments, U-Boats did not.

So they used the ballast they had--the crew. Their boats were smaller than the US boats and the crew forward trick did a great job of pitching the sub down for a quicker dive without all the plumbing and pumps the American boats had. Well, maybe it wasn't so great, but it was the best they had and they could dive mightily quick.

[Sailor Steve]

Fair enough. Thanks.

[SuperEtendard]

Even with the modern plumbing, plumbs and trim tanks. The US subs crash dived in twice the time that the U-boats did .... But im comparing VII against Gato/Balao. Maybe a fair comparision would be with the IX. but i dont know it s crash dive time.

Once the tanks were filled with water, they starting pitching down the sub, and it takes some time, the crew reaches the forward edge earlier than the water filled the tanks, and the planes got into position, so i think its an important help for the sub to sink faster. it s true that the crew weight is nothing compared to water s, but with the forward balance of weigth , it pitched down the sub and sinked, just like an airplane, with "inclined speed" more than heavier weight, later the tanks gets filled and the sub can gain depth without the use of speed.

[senjorlossi]

Hi Guys,

just a little detail in the scene: The captain orders "both engines slow ahead" just before opening the tubes. So he doesen´t go with the tubes open at flank speed.

From my point of view, it is not so unrealistic: The captain uses a moment where there are no escorts around and the moon is behind some clouds to reduce the distance to the target. So there is a good chance that nobody sees the speeding submarine. The attack itself is done at slow speed.

Greetings,
Stefan.

[Rockin Robbins]

The U-Boats were little boats. Of course they were a bit more nimble than the larger American subs. The Type IX had comparable dive times and comparable size to the American submarines. When you're talking much less mass, you need less buoyancy to keep her up on the surface safely, which means less water to take on to get to neutral.

The crew is a much higher percentage of the weight of the submarine, so their positions within the boat influence the pitch angle much more than they would in a larger American boat. One thing you give up with larger size is nimbleness. But you gain the ability to take enough firepower to win a sub war. The Germans needed a lot more subs to have a chance. And they didn't have enough manpower to run the subs even if they had enough of them.

That was a major part of their problem getting the Type XXI to war. Nobody could run them on a war footing and they couldn't spare the crews from active duty to train them.