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Old 03-20-2019, 11:08 AM   #1
AS
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Default Diving system seems weird

Hi all,

I made a couple of test divings, the results seem strange if not unrealistic.

As much as I appreciate that the Dev considers hull/ water pressure, the compressed air - dive tank Ratio seems totally wrong (or broken). Now here goes:

Negative tank is EMPTY

Dive/ Ballast tanks are full

I am at 50m statically (engines stopped).

Now I blow the Ballast tanks. Compressed air is completely EMPTY with the ballst tanks still half filled!

Although I should have positive buyoncy right now, the boat takes ages to get back to surface. (Getting back to Surface also takes way too Long using the engines and neutral buyoncy)

Now there are at least two things wrong here I guess: compressed air is empty way too far (if 50m is such a problem, what would they have done in 220m???)

The effect of blowing the Ballast tanks should be way stronger, the U-Boat would raise way faster and not crawling meter for meter.

The effect of the dive planes at low and normal speed should be stronger especially when surfacing.


Batteries:


2 and half Hours of going slow Speed takes About 70% (!) of battery power. Charging on the other Hand doesn´t affect top Speed (which is 18 with or without charging) and is way too fast: after a couple of minutes (!) the battery was already fully charged. If that was possible in 1940, why doesn´t Tesla make use of this? ;-)



So please don´t get me wrong, I do LOVE this sim so far, but there are inconistencies in realism that cannot be ignored.


Cheers, AS
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Old 03-20-2019, 01:26 PM   #2
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Interesting points.

I'll just add that i noticed that at full speed the battery lasted only about 20 minutes at full charge. Whether that's accurate or not i don't know, but just throwing that out there.

maybe because we're only simulating one convoy attack, the discharge and recharge of the batteries are artificially accelerated so that they become a factor. Otherwise we'd never have to recharge them, and if we did have to it would take longer than the mission itself.
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Old 03-20-2019, 02:11 PM   #3
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I only use the negative tank and dive planes for depth control (thats why there are 2 wheels for blowing and flooding the negative tank without having to blow the main tanks) . I only blow the main tanks if i want to completely surface . So as soon as i get to the surface i flood the negative tank for when i need to crash dive . If i want to dive i flood the main tank and when i have reached the desired depth i blow the negative tank . If i need to dive quickly i will flood the negative tank again and then blow the negative tank when i have reached the desired depth .
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Old 03-20-2019, 02:22 PM   #4
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I just took the time for crash dive exercise (note that I played alone):

10m (Tower disappears in the water): 28-30 Sec. (this is absolutely accurate historically)

50m: About 1:10

100m: About 1:58

150m: 2:48

With an EMPTY negative tank (German: Untertriebszelle) it takes about 1min and 40 seconds to dive at all! So the negative tank MUST be filled when on Surface!

At greater depths the boat realistically takes on water, so you must take this into account when moving slowly: the boat will tend to sink bit by bit. I will try and blow the main Ballast tanks A TINY BIT before going real Deep to compensate for flooding. (Trying all these things is so much fun I cannot believe a "game" actually let´s me do all this fancy "U-Boat stuff". So far I didn´t fire a single Torpedo, I just love to OPERATE "Das Boot"!)

Maybe the compressed air-behavior is correct, considering the fact that you only Need to get rid of SOME water to make the boat raise. However, the surfacing Speed is way to slow I´m sure.
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Old 03-20-2019, 02:34 PM   #5
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Quote:
Originally Posted by sober View Post
I only use the negative tank and dive planes for depth control
In reality they had so called trimming and adjusting tanks ("Regelzellen" in German) which were used to compensate for weight changes due to food and fuel-consumption, torpedoes etc. That´s why they had to "balance and Level" the boat every day. The negative tank (German: Untertriebszelle) was just there to speed up diving. It was blown (=emptied) fairly quickly after diving.

Physically interesting fact: When they went Deep, they FILLED the negative tank a little bit to KEEP the U-Boat ballanced. The reason for this: the deeper a Sub dives, the more it is "squeezed" so it loses volume. Less volume means less water replacement. This will Change the raise-sink tendency. So they had to make the boat heavier in great depths to compensate for that.

Another effect, which has similar physics: in very calm weather they could "hang" the U-Boat at periscope Depth without engines (=fully stopped). Certainly, a ZERO balance is not possible, but the periscope shaft itself changed the U-Boat´s replacement when it went a bit deeper or raised a bit, so this tiny little bit was enough to "keep" the Sub stable at periscope Depth if it was really well balanced by the L.I.

Quote from the novel "Das Boot" (losely translated): "You see, there´s a lot of physics and chemistry going to sea with a U-Boat!"
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Old 03-20-2019, 04:16 PM   #6
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What would you do different gameplay wise ?
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Old 03-21-2019, 02:36 PM   #7
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Quote:
Originally Posted by sober View Post
What would you do different gameplay wise ?

As I implied above: make blowing ballast tanks way more effective, making depths changes (especially going UP) faster, re-considering the amount of compressed air that is used in greater depths.

Later in war it was common practice to crash dive very deep (150-200m), and then they operated the submerged U-Boat for many hours. In "Wolfpack" that would hardly be possible or way too dangerous because of the (too) limited compressed air.


Cheers, AS
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