[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