A few new ideas

[Bilge_Rat]

Originally Posted by Fidd

12. Interval between ASDIC acquisition if DC's are dropped.

I can't provide any evidence for this, and I'm no expert, but from what I've read early decoys operated by making clouds of bubbles when they reacted with sea-water, with this design arising because it was already clear to both sides that ASDIC produced very muddled return signals, or failed to work at all, if the water-column above the boat was aerated by the DC explosion. This is useful, as this feature could be used to help make DC attacks more prolonged but less lethal, especially in shallower-water.

Actually, British Sonar was very effective from the very beginning. There were 4 encounters between U-Boats and DDs in September 1939. All 4 U-Boats were found and held on Sonar, were depth charged and damaged and 2 were sunk.

Current behaviour seems about right in game. Ship/U-Boat damage review is already on the roadmap, so no doubt this will be tweaked further.

[Fidd]

Originally Posted by Bilge_Rat

Actually, British Sonar was very effective from the very beginning. There were 4 encounters between U-Boats and DDs in September 1939. All 4 U-Boats were found and held on Sonar, were depth charged and damaged and 2 were sunk.

Current behaviour seems about right in game. Ship/U-Boat damage review is already on the roadmap, so no doubt this will be tweaked further.

Based on memoires of surviving submariners from WW2, DC's seem to be very much too effective, with a very brief period in which the escort persists with hunting and attacks. Boats often reported 50-100 DC's being expended on a single u-boat plus 2-4 barrages with Hedge-hogs. The effect of DC's was fairly often a loss of depth control, as even-though the misses were far enough away to only cause minor damage, the effects on the u-boat's bouyancy at any given instant could be profound, especially with charges that exploded above or below the u-boats depth. This "dynamic-instabilty", ie instability caused by movement of the boat, magnifying tbe effect of any brief changes to the water-pressure or aeration of the water-column above the boat, could result in either the boat passing or approaching crush-depth or accidentally broaching the surface.

So, IMHO, DC attacks (as opposed to pinging, should be far more numerous but far less effective. This would also allow for progressive damage to be fixed by the crew when more detailed damage models follow.

Self evidently, we cannot have escorts prosecuting attacks for hours, so there's a balance to be struck. Personally I think DC attacks should last for 30-40 minutes.

[Bilge_Rat]

Originally Posted by Fidd

Based on memoires of surviving submariners from WW2, DC's seem to be very much too effective, with a very brief period in which the escort persists with hunting and attacks. Boats often reported 50-100 DC's being expended on a single u-boat plus 2-4 barrages with Hedge-hogs. The effect of DC's was fairly often a loss of depth control, as even-though the misses were far enough away to only cause minor damage, the effects on the u-boat's bouyancy at any given instant could be profound, especially with charges that exploded above or below the u-boats depth. This "dynamic-instabilty", ie instability caused by movement of the boat, magnifying tbe effect of any brief changes to the water-pressure or aeration of the water-column above the boat, could result in either the boat passing or approaching crush-depth or accidentally broaching the surface.

So, IMHO, DC attacks (as opposed to pinging, should be far more numerous but far less effective. This would also allow for progressive damage to be fixed by the crew when more detailed damage models follow.

Self evidently, we cannot have escorts prosecuting attacks for hours, so there's a balance to be struck. Personally I think DC attacks should last for 30-40 minutes.

well that is an oversimplification, the reality was a lot more complex.

for example:

1. sept. 14, 1939: 2 DDs working as a team find and attack U-30. Sonar conditions were good. Attacks were delivered over 6 hours. U-30 received extensive damage, 2 torpedo tubes, engine room valve, 1 diesel engine out and the other heavily damaged, flooding took the boat down to 472 feet. U-30 escaped;

2. sept. 14, 1939: 3 DDs working as a team find and attack U-39. Sonar conditions were good. 12 depth charges were dropped in 3 attacks at depths of 100 to 500 feet. Batteries were damaged, lighting was knocked out, valves were cracked, chlorine gas was released when sea water entered the batteries, electric motor was knocked out, U-39 surfaced and scuttled. Attack lasted 20 minutes;

3. sept. 17, 1939: 2 DDs attack U-29 over 4 hours expending all their DCs. U-29 was damaged, but escaped;

4. sept. 20, 1939: 4 DDs hunt U-27 over a period of 2 hours at night losing and regaining contact several times. U-27 goes "deep" to 393 feet and orders silent running. 5 attacks are done dropping 25? DCs at depths of 100 to 250 feet. U-27 suffers extensive damage over the course of these attacks: bent propeller shaft, "series flooding". After 2 hours, U-27 tries to escape on the surface, but is caught and scuttles;

5. oct. 13, 1939: 2 DDs hunt U-42. U-42 goes to 361 feet. The 1st DC attack ruptures the aft ballast tank, the U-boat starts sinking backwards at a 45 degree angle. Crew is obliged to surface and scuttle;

6. oct. 14, 1939: 4 DDs hunt and attack U-45 which is sunk with no survivors;

7. nov. 29, 1939: 3 DDs hunt U-35. U-35 goes "deep" to 229 feet. 3 DC attacks are carried out with DCs at 250 feet. U-35 diving planes are jammed, aft ballast tanks and fuel line are ruptured, Boat is at a steep up angle and unable to regain control. U-35 surfaces and scuttles;

8. nov. 12?, 1939: 2 DDs attack U-49 delivering a "punishing depth-charge attack". The boat is driven down to 557 feet, periscope and all 4 forward torpedo tubes suffer unrepairable damage, but U-49 escapes. Note that this occur in weather which was "hideous",i.e. a storm;

9 and 10. nov ?, 1939: DDs (number unknown), escorts of convoy Sierra Leone 7 attack U-41 and U-43. U-41 is held down for 20 hours, but escapes with light damage. U-43 is "severely damaged", but also escapes;

11. dec. ?, 1939: DDs (number unknown) attack U-47, but attack is "desultory" and U-47 escapes undamaged;

so first 11 attacks of the war, 5 U-boats sunk, 3 heavily damaged, 2 w. light damage and only one undamaged.

[Fidd]

Originally Posted by Bilge_Rat

well that is an oversimplification, the reality was a lot more complex. [SNIP]

That's a lot more detailed, but it's broadly in agreement with what I stated, namely that DC attacks went on for much longer than is typical in game, and often cause involuntary surfacing, either because of non-lethal cumulative damage, or because of loss of depth control due same.

[Bilge_Rat]

Originally Posted by Fidd

That's a lot more detailed, but it's broadly in agreement with what I stated, namely that DC attacks went on for much longer than is typical in game, and often cause involuntary surfacing, either because of non-lethal cumulative damage, or because of loss of depth control due same.

Hi, note there was no involuntary surfacing, in the 3 examples above, the skipper ordered the boat to surface.

Again, based on the data, most DC attacks were dangerous, in the 11 examples I cited above 8 U-Boats were sunk or heavily damaged.

Another way to look at this is U-47 under Prien was depth charged 4 times in 39-41 and was sunk the 4th time. The U-99 under Kretschmer and U-100 under Schepke were each depth charged 3 times and sunk the 3rd time. U-567 under Endrass was sunk the 1st time it was depth charged. These were all U-Boat aces who knew how to handle their boats.

The reality is that escorts with well trained crews and working as a team generally had no problem holding a sub on sonar under good sound conditions and could generally inflict serious damage to the sub. When you see an attack stretching out for hours, it is usually because the escort is having trouble finding the U-boat because of poor sound conditions, poorly trained crews, escorts working alone, etc which would have been the case during the "Happy Times" in last six months of 1940.

When you look at the careers of most successful U-Boat aces, you see they managed to survive a long time by sinking unescorted ships and staying well away from the escorts when they attacked convoys.

Now in game, yes, there should be a good chance that an escort can heavily damage/sink the boat if it finds you and attacks you. That is realistic and makes the game more interesting. Note that current behaviour is still early access since revisiting U-boat damage is on the development roadmap.

[Fidd]

Originally Posted by Bilge_Rat

Hi, note there was no involuntary surfacing, in the 3 examples above, the skipper ordered the boat to surface.

If the boat has suffered damage where the boat has to surface, then whether the captain orders the precise moment or manner of it's doing so is besides the point. That is an involuntary surfacing. The same applies to one forced to surface for want of oxygen, one with chlorine spreading from the battery compartments and so forth. As RN destroyers (and aircraft) attacked until a particular u-boat was demonstrably sunk, or it's ammunition was expended, this was not uncommon.

My general point here is that a contact was not captured once, depth-charged once and then assumed to be sunk with the escort then returning to the convoy; which is what currently happens in game. If a u-boat did go down to 185m, it would become very difficult to hit, because of the interval in time between the asdic contact being lost, and the escort firing the charges, and for those charges reaching the u-boats depth, if indeed they were fused as far down as that depth. On the other hand, even a near miss at that depth would potentially much more damage as a much shallower DC.

[Fidd]

20. Reworking of attenuation. I think attenuation within a metal-hulled u-boat is overdone currently. It should be like farting in church - loud and heard over considerable distance, given the acoustics of such an environment. I really like the the idea of attenuation, but for example, it's over done in the case of say the conning tower to the control room where intervening hatches are open. Naturally if doors or hatches are closed, then that's a completely different situation. So I think that voices should carry well to the adjacent compartment unless if no intervening hatch is open, likewise louder sounds: the e-motor, torpedo reloading winches (one day) the diesels should be heard more or less throughout the boat, if all the hatches/doors are open.

EDIT: To clarify, what I meant here is that the attenuation (reduction of volume with distance/intervening bulkheads etc) is basically fine, but the reverberation is massively overdone.