[REL] Real ASW Mod

[gap]

Originally Posted by schlechter pfennig

I'd meant "increased ASW"

http://www.subsim.com/radioroom/show...=increased+asw

(And yes, that's my old name)

So I have read the list of features of the increased ASW mod by our schlechter pfennig / Albrecht Von Hesse, and I have a few remarks about some of them. I wanted to post my comments directly in the mod thread, but then I realized that the mod itself is no longer available, and that the last post in its thread dates back to when I wasn't even aware of subsim or Silent Hunter games. After all, I think I will post my remarks here rather than risking to be called a thread necromancer

Here we go:

Originally Posted by Albrecht Von Hesse

1) setting all bombs so that they detonate when they impact the water, or just below.

That would be correct for most bombs, including the (remarkably uneffective) British A/S bombs, used during the early part of the conflict. Matter of factly those bombs were commonly fitted with impact fuzes/pistols which could be set for triggering an explosion immediately or with a short delay, usually in the order of a few tens of seconds. Nonetheless, it must be noted that the US 500-lb and 1000-lb GP bombs could be fitted with hydrostatic fuzes, thus behaving as a normal depth charge.

Sources:
US Bombs and Fuzes Pyrotechnics, ed. June 44, pp. 45, 47 and 171
US Bombs and Fuzes Pyrotechnics, ed. September 45, pp. 51, 53, 251 and 253

Originally Posted by Albrecht Von Hesse

2) setting the air depth charges to detonate at 9 meters (which isn't exactly historic, I'll admit; from what I've been able to research 7.9 meters seems to be the 'normal' depth setting, although I've only been able to find the tech details for British air depth charges so far).

According to John Campbell (Naval Weapons of World War Two, 1985, p. 94):

"The original pistol setting of 50ft (15m) was too deep for aircraft attack on a surfaced U-boat and it was reduced to 25ft (7.6m) in 1942"

This is referred to the British Mk. VII airborne DC, but it probably applies to other aircraft depth charges used ny the British. An user in navweaps' discussion board quotes another source (a link to is provided, but it is no longer available online):

"In the first two years of the war depth charges were mainly set for explosion at a depth of 30/45 metres [this figure having being set years ago and never altered since]. Analysis of pilot reports by ORS showed that in 40% of attacks the U-boat was either still visible or had been submerged less than 15 seconds (these are the U-boats that we would expect to have most chance of killing as we have a good idea of their position). Since the lethal radius of a depth charge was around 5-6 metres it was clear that a shallower setting was necessary.

Explosion at a depth of 15 metres was initiated and as new fuses became available at 10 metres and then 8 metres."

This is probably referred to US depth bombs. The two pamphlets by Navy Bomb Disposal School I mentioned above (dated summer 1944 and autumn 1945) specify for all the hydrostatic fuzes used with air ordnance depth settings in steps of 25ft, from 25ft (7.6m) to 125ft (38.1m), but I think only the 25ft setting was used in practice.

Originally Posted by Albrecht Von Hesse

3) setting the 'explosiveness' of air depth charges to match up to the weight of explosives they normally carried.

The 'explosiveness' of depth charges (and thus the damage they can cause at a given distance) should be roughly proportional to the cubic root of the weight of its explosive filling multiplied by its TNT equivalency factor. You can find the relevant formulas in any of the articles I linked towards the end of post #89 in this thread.

Originally Posted by Albrecht Von Hesse

4) setting the sink rate of air depth charges to match the historical sink rates.

I am curious to know your settings. Unfortunately I couldn't find much information on this respect, except for the British Mk VII air depth charge probably had a terminal velocity equal or similar to its surface counterpart (i.e. 9.9 fps, 3.02 mps, source: United Kingdom / Britain
ASW Weapons @ navweaps.com). Both navweaps.com and Campbell list the illogical figure of 600 fps (183 mps!) as terminal velocity of the streamlined Mark VIII 250-lb a/c depth charge, but I regard it as a typo. No information at all on the sinking speeds of US depth bombs.

Originally Posted by Albrecht Von Hesse

5) modified the Catalina, Sunderland, Wellington, select Liberator and select Fortress aircraft with ASW loadouts.

I think you forgot here the embarked bombers, fighters and scout planes, which also played an important role in WWII A/S warfare.

Originally Posted by Albrecht Von Hesse

Most British DDs and DEs begin carrying the Mark VII heavy depth charges starting September 1942. The Mark VII heavy had a somewhat improved sink rate from the addition of lead to the depth charge.

That's probably a bit too late. According to navweaps.com, the Mark VII heavy depth charge was introduced in service in 1940. This is in accordance with Cambell (op. cit, p. 89) who states the end of 1940 as time frame for its introduction.

Originally Posted by Albrecht Von Hesse

US DDs and DEs begin carrying the Mark 9 'fast sinker' depth charge starting June 1943. Designed to sink fast and detonate at up to 1000 feet, the Mark 9 was aerodynamically shaped, lead-weighted and finned.

There were two main versions of the Mark 9: the first version (depth charge Mk. 9 and Mk. 9 Mod. 1) had a terminal velocity of 14.5 fps (4.4 mps) and it entered service in spring 1943. The second version, called Mk. 9 Mod. 2, was further improved "by means of a finer setting of the tail and added lead". This came at the sacrifice of explosive power, but it resulted in a maximun sinking speed of 22.7 fps (6.9 mps). In a personal note, I have noted august 1943 as date for the introduction of this later version, though honestly I cannot find the source for it. For all the other information reported here, the sources are:

John Campbell, op. cit, p. 163
United States of America ASW Weapons @ navweaps.com
Depth Charge, Mark 9 and Modifications: Descriptinìon and instructions for Use, Bureau of Ordnance, February, 1944

[gap]

Originally Posted by gap

According to John Campbell (Naval Weapons of World War Two, 1985, p. 94):

"The original pistol setting of 50ft (15m) was too deep for aircraft attack on a surfaced U-boat and it was reduced to 25ft (7.6m) in 1942"

This is referred to the British Mk. VII airborne DC, but it probably applies to other aircraft depth charges used ny the British. An user in navweaps' discussion board quotes another source (a link to is provided, but it is no longer available online):

"In the first two years of the war depth charges were mainly set for explosion at a depth of 30/45 metres [this figure having being set years ago and never altered since]. Analysis of pilot reports by ORS showed that in 40% of attacks the U-boat was either still visible or had been submerged less than 15 seconds (these are the U-boats that we would expect to have most chance of killing as we have a good idea of their position). Since the lethal radius of a depth charge was around 5-6 metres it was clear that a shallower setting was necessary.

Explosion at a depth of 15 metres was initiated and as new fuses became available at 10 metres and then 8 metres."

This is probably referred to US depth bombs. The two pamphlets by Navy Bomb Disposal School I mentioned above (dated summer 1944 and autumn 1945) specify for all the hydrostatic fuzes used with air ordnance depth settings in steps of 25ft, from 25ft (7.6m) to 125ft (38.1m), but I think only the 25ft setting was used in practice.

Quick update from the USNBD Pamphlet "British Bombs and Fuzes, Pyrotechnics, Detonators", November, 1944 Ed.
Apparently, the hydrostatic pistols that could be used with British a/c depth charge were as follows:

Pistol Mk. X** (obsolete by the date of publication):
Depth settings: 50, 100 and 150 ft (15.2, 30.5 and 45.7 m respectively)
DC's used on: Mk. VII and VIII

Pistols Mk. XIV and XIV* (in service):
Fixed depth setting: 14-18 ft (4.3-5.5 m)
DC's used on: Mk. VII, VIII, XI and XI*

Pistols Mk. XVI and XVI* (in service):
Fixed depth setting: 20-24 ft (6.1-7.3 m)
DC's used on: as above

Pistol Mk. XIX (in service):
Fixed depth setting: 20-24 ft (6.1-7.3 m)
DC's used on: Mk. XI and XI* with Mk. IV tail

Pistol Mk. XX (in service):
Fixed depth setting: 14-18 ft (4.3-5.5 m)
DC's used on: as above

Summing up: after all, unlike stated by post-war sources, British a/c depth charges could be set to detonate at depths shallower than 25ft. Indeed, we don't know how reliable/effective were the shallowest pistols (Mk. XIV and XX, 14-18 ft), and how common they were.

Incidentally: happy Easter guys

[schlechter pfennig]

I have been unable to ressurrect my oldest HD, so I'm going to try replying "off-the-cuff" to these as best as I can.

Originally Posted by gap

That would be correct for most bombs, including the (remarkably uneffective) British A/S bombs, used during the early part of the conflict. Matter of factly those bombs were commonly fitted with impact fuzes/pistols which could be set for triggering an explosion immediately or with a short delay, usually in the order of a few tens of seconds. Nonetheless, it must be noted that the US 500-lb and 1000-lb GP bombs could be fitted with hydrostatic fuzes, thus behaving as a normal depth charge.

Sources:
US Bombs and Fuzes Pyrotechnics, ed. June 44, pp. 45, 47 and 171
US Bombs and Fuzes Pyrotechnics, ed. September 45, pp. 51, 53, 251 and 253

That is a really good point. The major problem that I'd experienced (and this applies to several of the following points as well) is that SH3 gives a limited "palette" of choices, so at times I had to maximize effects by making assumptions. So, for instance, in this case, aircraft had a loadout choice of either depth charge or bomb; I elected to assume that if the designer wished for the aircraft's armament to explode at depth (either as a depth charge or a hydrostatic fuze-set bomb), then they would select "depth charge", and if they wanted it to explode on the surface, they would select "bomb". Therefore, I decided to set all bombs as surface impact.

Originally Posted by gap

According to John Campbell (Naval Weapons of World War Two, 1985, p. 94):

"The original pistol setting of 50ft (15m) was too deep for aircraft attack on a surfaced U-boat and it was reduced to 25ft (7.6m) in 1942"

This is referred to the British Mk. VII airborne DC, but it probably applies to other aircraft depth charges used ny the British. An user in navweaps' discussion board quotes another source (a link to is provided, but it is no longer available online):

"In the first two years of the war depth charges were mainly set for explosion at a depth of 30/45 metres [this figure having being set years ago and never altered since]. Analysis of pilot reports by ORS showed that in 40% of attacks the U-boat was either still visible or had been submerged less than 15 seconds (these are the U-boats that we would expect to have most chance of killing as we have a good idea of their position). Since the lethal radius of a depth charge was around 5-6 metres it was clear that a shallower setting was necessary.

Explosion at a depth of 15 metres was initiated and as new fuses became available at 10 metres and then 8 metres."

This is probably referred to US depth bombs. The two pamphlets by Navy Bomb Disposal School I mentioned above (dated summer 1944 and autumn 1945) specify for all the hydrostatic fuzes used with air ordnance depth settings in steps of 25ft, from 25ft (7.6m) to 125ft (38.1m), but I think only the 25ft setting was used in practice.

This is extremely interesting. I hadn't encountered this information before, and had I known that I would have incorporated the depth setting change(s) for the applicable ordnance. I do know that I had used information I'd researched to decide on that setting, but it's obvious that here, as elsewhere, you'd done a lot more comprehensive research than I had.

Originally Posted by gap

The 'explosiveness' of depth charges (and thus the damage they can cause at a given distance) should be roughly proportional to the cubic root of the weight of its explosive filling multiplied by its TNT equivalency factor. You can find the relevant formulas in any of the articles I linked towards the end of post #89 in this thread.

I hadn't had access to that article, and honestly I forget how I'd calculated the 'explosiveness' factor. However, that article is perfect for doing exactly that!

Originally Posted by gap

I am curious to know your settings. Unfortunately I couldn't find much information on this respect, except for the British Mk VII air depth charge probably had a terminal velocity equal or similar to its surface counterpart (i.e. 9.9 fps, 3.02 mps, source: United Kingdom / Britain
ASW Weapons @ navweaps.com). Both navweaps.com and Campbell list the illogical figure of 600 fps (183 mps!) as terminal velocity of the streamlined Mark VIII 250-lb a/c depth charge, but I regard it as a typo. No information at all on the sinking speeds of US depth bombs.

I had found several articles (all of which are on my deceased HD) that dealt specifically with air depth charges. They detailed how pilots were trained to aim, target and drop them, their design features and revisions, etc. I used the information gleaned there to set the characteristics.

Originally Posted by gap

I think you forgot here the embarked bombers, fighters and scout planes, which also played an important role in WWII A/S warfare.

GWX just had so many different aircraft, and roles they were used in, that I probably did overlook that.

Originally Posted by gap

That's probably a bit too late. According to navweaps.com, the Mark VII heavy depth charge was introduced in service in 1940. This is in accordance with Cambell (op. cit, p. 89) who states the end of 1940 as time frame for its introduction.

I used the dates provided by the research materials that I had access to at the time, which doesn't seem to be as comprehensive as your sources are.

Originally Posted by gap

There were two main versions of the Mark 9: the first version (depth charge Mk. 9 and Mk. 9 Mod. 1) had a terminal velocity of 14.5 fps (4.4 mps) and it entered service in spring 1943. The second version, called Mk. 9 Mod. 2, was further improved "by means of a finer setting of the tail and added lead". This came at the sacrifice of explosive power, but it resulted in a maximun sinking speed of 22.7 fps (6.9 mps). In a personal note, I have noted august 1943 as date for the introduction of this later version, though honestly I cannot find the source for it. For all the other information reported here, the sources are:

John Campbell, op. cit, p. 163
United States of America ASW Weapons @ navweaps.com
Depth Charge, Mark 9 and Modifications: Descriptinìon and instructions for Use, Bureau of Ordnance, February, 1944

Again, it seems as if your research sources are more detailed and comprehensive as mine are/were.


In closing, I cannot argue or dispute any of your points, or reasonings and, in fact, would have incorporated those into my mod had I been aware of them.

[gap]

Sorry for the late feed-back guys, family problems have absorbed most of my time during the last month; now I am slowly getting back to normality. I am preparing my replies to your unaswered posts. Just stay tuned and keep patient a few more days

[padi]

Originally Posted by gap

Sorry for the late feed-back guys, family problems have absorbed most of my time during the last month; now I am slowly getting back to normality. I am preparing my replies to your unaswered posts. Just stay tuned and keep patient a few more days

No problem, I hope you will be fine soon.
I also was in holiday so I haven't made progress in the last month...
I think that it would take some time because I have personal problems since a few months and not that many time for research...

[Niume]

IS this mod compatible with wac 5.1?

[padi]

Originally Posted by Niume

IS this mod compatible with wac 5.1?

Sadly no because I have experienced positioning problems with the DC Racks which I'm not able to fix...
There is anything different with the Racks than in vanilla and the other mods and even changing them to vanilla doesn't fix that.

[Niume]

Originally Posted by padi

Sadly no because I have experienced positioning problems with the DC Racks which I'm not able to fix...
There is anything different with the Racks than in vanilla and the other mods and even changing them to vanilla doesn't fix that.

So the only problem is bad dc rack positioning