AHC: Best possible German performance in the Battle of the Atlantic

Can you link the sub? The Hollands that come to my mind are pre-ww1 kerosene power subs.

Also, in 1940-1941 time frame when the war can be won, are these subs better than OTL submarines? Are they better than OTL subs with snorkles?
You got the right one. Its the right shape.
The hydrodynamic shape is nothing new. It was basically tried things going into the idea of a ship that was mostly underwater. Now, why was that idea so hard to come by
 
Easier. Yes, probably easier to increase AMC effectiveness than build fleet submarines. Easier still to build more AMC, or more specifically, have the ability to spam these things out via freighter conversions once the war starts.

to put a fine point on it, was not disagreeing about improvements to u-boats. my thought was there would just never be enough surface warships?

think the improvements you have already highlighted both more feasible and more likely? than increased speed

i.e. if AMC and u-boat(s) operating in tandem were pursued a slightly faster AMC might escape and improved u-boat might be able to remain submerged longer
 

BlondieBC

Banned
to put a fine point on it, was not disagreeing about improvements to u-boats. my thought was there would just never be enough surface warships?

think the improvements you have already highlighted both more feasible and more likely? than increased speed

i.e. if AMC and u-boat(s) operating in tandem were pursued a slightly faster AMC might escape and improved u-boat might be able to remain submerged longer

Yes, each surface ships go with a half squadron of subs if I remember Japanese doctrine correctly. So the 15 planned panzerschiffe would need 90 long range subs (Type IX). There will still be needs for subs to patrol the north sea. Still need for subs to hang around British ports. Still need for solo, long range patrols where surface ships do poorly.
 
Yes, each surface ships go with a half squadron of subs if I remember Japanese doctrine correctly. So the 15 planned Panzerschiffe would need 90 long range subs (Type IX). There will still be needs for subs to patrol the north sea. Still need for subs to hang around British ports. Still need for solo, long range patrols where surface ships do poorly.


Sounds good but replace the five U-Boats with a couple of wolf pacts and you have the potential of the KM situation with couple dozen surface raiders mid war. Don't forget from mid 1942 through early 1944 B-Dienst was detecting 1/2 of all Wallie convoys in the North Atlantic through code cracking. Less than 1/2 of those detected convoys were actually attacked, so leveraging up the number of search options was critical. B-Dienst reported during this period that they could estimate the position of these detected convoys with a days travel and 500-600nm north south. A 10 U-Boat wolf pact [spaced 10 miles apart] 'had a fair chance of sighting this convoy' with in 2 days sweep.

That's 10 x 10nm x 10 knots = 1000nm ^2 per hour and over a 48 hours time period that's 48,000nm^2. A days travel for the convoy is likely to be @ 7.5-9 knots x 24 hours or 180-220nm. So the area to be swept is roughly 90-130,000nm^2 . Perhaps a 'fair chance' for convoy detection was 50-50 over this two day period. To effect such an interception would require the massive Wolf Pact chatter that later would lead to Wallie interception of the Wolf Pact -while they were forming up. In addition Wallies also learned how to use this Wolf Pact chatter to divert the convoys away from the threatning Wolf Pacts.

Long range MPA would be critical here since it could act quickly on a B-Dienst direction baring and have a good chance of locating such a convoy and then broadcast this location to nearby wolf pacts . That in turn would minimise the Wolf Packs risk of interception and result in much higher chances of convoy interception. Likewise surface raiders could also exploit these detected convoy broadcasts.
 

Ian_W

Banned
Sounds good but replace the five U-Boats with a couple of wolf pacts and you have the potential of the KM situation with couple dozen surface raiders mid war. Don't forget from mid 1942 through early 1944 B-Dienst was detecting 1/2 of all Wallie convoys in the North Atlantic through code cracking. Less than 1/2 of those detected convoys were actually attacked, so leveraging up the number of search options was critical. B-Dienst reported during this period that they could estimate the position of these detected convoys with a days travel and 500-600nm north south. A 10 U-Boat wolf pact [spaced 10 miles apart] 'had a fair chance of sighting this convoy' with in 2 days sweep.

That's 10 x 10nm x 10 knots = 1000nm ^2 per hour and over a 48 hours time period that's 48,000nm^2. A days travel for the convoy is likely to be @ 7.5-9 knots x 24 hours or 180-220nm. So the area to be swept is roughly 90-130,000nm^2 . Perhaps a 'fair chance' for convoy detection was 50-50 over this two day period. To effect such an interception would require the massive Wolf Pact chatter that later would lead to Wallie interception of the Wolf Pact -while they were forming up. In addition Wallies also learned how to use this Wolf Pact chatter to divert the convoys away from the threatning Wolf Pacts.

Long range MPA would be critical here since it could act quickly on a B-Dienst direction baring and have a good chance of locating such a convoy and then broadcast this location to nearby wolf pacts . That in turn would minimise the Wolf Packs risk of interception and result in much higher chances of convoy interception. Likewise surface raiders could also exploit these detected convoy broadcasts.

Note that radio direction finding cuts both ways - you can use it to detect a convoy, or you can use it to detect a U-boat reporting a convoy.

Where aircraft become lethal to pack tactics is how they force u-boats to travel underwater during the day, thus slowing them to below the speed of the convoy.
 
Note that radio direction finding cuts both ways - you can use it to detect a convoy, or you can use it to detect a U-boat reporting a convoy.

Where aircraft become lethal to pack tactics is how they force u-boats to travel underwater during the day, thus slowing them to below the speed of the convoy.

Exactly ! Wolf Pacts had to minimise their radio traffic/chatter to avoid detection and it was part of prewar U-Boat doctrine to avoid such chatter.
 
Note that radio direction finding cuts both ways - you can use it to detect a convoy, or you can use it to detect a U-boat reporting a convoy.

Where aircraft become lethal to pack tactics is how they force u-boats to travel underwater during the day, thus slowing them to below the speed of the convoy.


U-boats are already slower than a convoy. Sure, 18 knots is faster than an 8 knot convoy, but you can't do that for long without emptying your tanks (a quick wiki suggests 10 knot for cruising speed for a Type-VII). The problem is when you have to chase a convoy. The geometry gets ugly. So once the convoy is past the picket line there is no point chasing.

Of course forcing a U-boat under slows them down to virtually immobile...

Really the Germans have to get away from using submarines for their spotters. Signals and aircraft are the way to go, but have their own special problems.
 

Ian_W

Banned
Exactly ! Wolf Pacts had to minimise their radio traffic/chatter to avoid detection and it was part of prewar U-Boat doctrine to avoid such chatter.

Yes, but concentrating u-boats so they could overwhelm a convoy's defenses needed that chatter to coordinate the u-boats.

Prewar doctrine would have had uboats attacking a convoy one at a time, and therefore probably being forced under by the escorts after a single kill.
 
This is how I would change the surface fleet with a POD of January 1933. I'll have to do a separate post about how if would affect the Battle of Atlantic (which the Germans still loose).

Aircraft Carriers

Don't build the Graff Zeppelin and Aircraft Carrier B. The shipyard workers and materials would instead be used to accelerate the building of the other ships.

Battleships

The 3 panzerschiffen are already built or building. Still build the Twins, Bismarck and Tirpitz. However, don't order the H class battleships and O class battle cruisers.

Cruisers

Normally I build an enlarged version of Leipzig instead of Nurnberg and the Hipper class. IOTL the Reischsmarine wanted to build Nurnberg as an 8,000 ton version of Leipzig to cure the faults in her and the K class. However, she had to be built as a repeat of Leipzig because the design team was busy with what became the Hipper class.

Instead a different heavy cruiser design was built, which to avoid confusion with the OTL Hipper class will be called the Moltke class. The ships were named Moltke (vice Hipper), Von der Tann (vice Blucher), Goeben vice (Prinz Eugen), Derfflinger (vice Seydlitz) and Roon (Lutzow). In common with OTL only 3 of the 5 ships were completed.

The Moltke class was essentially an enlargement of Leipzig armed with nine 8" guns in 3 triple turrets mounted in A, X and Y positions, with the same secondary, LAA and torpedo armaments as the OTL Hipper class. Its engines were more powerful versions of Leipzig's (low pressure) steam and diesel machinery so the Moltke class should have more reliable machinery than the Hipper class and greater range.

Large Destroyers

The first 22 Z-boats (Z-1 to Z-22) were built to the same designs as OTL. That is 4 Type 1934, 12 Type 1934A and 6 Type 1936.

However, the next 8 (Z-23 to Z-30) would have been ordered and built to the Type 1936B design armed with five 5" guns instead of the Type 1936A armed with five 5.9".

OTL the next 12 (Z-31 to Z-42) were originally ordered in the summer of 1939 to the Type 1938B design which was a smaller destroyer than Types 1934 and 1936. However, in September 1939 all were re-ordered as Type 1936A Z-boats. In the event 7 were completed to the Type 1936A design, 2 were completed to the Type 1936B design and 3 (Z-40 to Z-42) were cancelled and re-ordered as scout cruisers, which were not built. ITTL all 12 destroyers were ordered as Type 1936B ships in the first place and built to that design.

Subsequent large destroyers were built to the same designs as OTL, but only 3 (Z-43 to Z-45) were completed and it was too late for them to have any influence on the war.

Small Destroyers

12 small destroyers of Types 1923 and 1924 would still be built in the 1930s. However, 30 enlarged Type 1924s were built in the second half of the 1930s instead of the 10 F-boats and first 21 T-boats, which were failures. The enlargement to about 1,200 tons would be for improved endurance and seakeeping, although it would also allow for a fourth 4.1" gun to be carried.
 

perfectgeneral

Donor
Monthly Donor
This is the major issue that the strategy of more U Boats suffers from - by 1941 there was only a relatively small part of the North Atlantic called "The Black Gap" that was free from ASW air patrols and had Coastal command gotten their hands on more than a dozen or so VLR Liberators and had the US deployed theirs accordingly rather than everywhere the u boats were not then the losses suffered in 42 and early 43 would have been a lot less than OTL.

In such places where aircraft were operating (which would often be where the convoys were) submarines could only stay on the surface at night or in very bad weather

It was far easier for the allies to increase the number of LRMPA available for ASW patrols than it was for Germany to increase the number of U boats.
When did Liberators become operational? I would argue that a much more effective blockade in Sept '39 - March '41 would render them moot.
A best possible U-boat fleet would have air and exhaust snorkel. Training/coastal Baltic boats up to the AGNT limitation. A large fleet of Atlantic interdiction boats that rarely surface in daylight and can pursue convoys effectively while submerged. These are built from "sub" assemblies concealed before open aggression commences.
 
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Have we considered U-boat quality? Is there any good reason why an electroboote could not be designed from 1933?
Yes, ideas, doctrines, but technical?

The 'electroboote' is not new. This is the WW1 RN R Class conceived as anti-submarine submarines, hydronamically clean and high underwater speed:
1024px-R_class_submarine.svg.png


British_WWI_Submarine_HMS_R3.JPG


The problem for such boats is the batteries and the time taken to recharge them.
 

perfectgeneral

Donor
Monthly Donor
Axis tech from 1938: https://en.m.wikipedia.org/wiki/Submarine_No.71
Germany could have something ocean going and larger by 1938. Start production, in secret, away from the coast, as "boiler parts" or some such. Snorting eases the charging problems. Electroboot type VII being around 1,200 tons and the later refinement type XXI being twice that.
 
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Yes, but concentrating u-boats so they could overwhelm a convoy's defenses needed that chatter to coordinate the u-boats.

Prewar doctrine would have had uboats attacking a convoy one at a time, and therefore probably being forced under by the escorts after a single kill.

True but this was not black and white. They had been "concentrating U-boats" in the wolf pact attack since Donitz started the war, but it seemed the diverting of convoys and suppressing the PACTs didn't become a problem until mid war. The big difference must have the volume of traffic to control the Wolf-Pact sweeps and attacks. The reverse was true in tracking the convoys. It tool BdU until mid 1941 to accurately map out the bulk of the WALLIE convoy routes.
 
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The 'electroboote' is not new. This is the WW1 RN R Class conceived as anti-submarine submarines, hydronamically clean and high underwater speed:

The problem for such boats is the batteries and the time taken to recharge them.

What sonar did it use?
 
When did Liberators become operational? I would argue that a much more effective blockade in Sept '39 - March '41 would render them moot.
A best possible U-boat fleet would have air and exhaust snorkel. Training/coastal Baltic boats up to the AGNT limitation. A large fleet of Atlantic interdiction boats that rarely surface in daylight and can pursue convoys effectively while submerged. These are built from "sub" assemblies concealed before open aggression commences.

120 Squadron RAF was setup in July 41 - but the close blokade of the uk had already been defeated by Coastal Commands other shorter ranged aircraft - it was only the 'Black Gap' a fairly large area in mid Atlantic where land based MPAs could not cover where Uboats could operate with impunity and so that is where the battle moved - however 120 Squadon with a handful of VLR Liberators could cover much of this area but this remained the only unit thus equipped operating in the Black Gap until early 43. US Units thus equipped where carrying out ASW patrols everywhere the Uboats were not!

It was only when increasing numbers of U-Boats bagan to surge this area and losses increased in late 42/early 43 that more VLR Liberators where prised away from bomber command in March 1943 and those USAAF squadrons where assigned at the same time, that any further VLR Liberators where made available.

A mere 50 additional VLR Liberators by May 43 helped turn the tide (along with an alignment of additional escorts, the RCN and USN escort groups coming of age, improved tech and intellegence methods).

So an earlier upsurge of Uboat numbers and effectiveness is going to elicit an earlier and more robust response from the allies because they cannot lose the BotA and throwing aircraft at the problem is a relatively easy and effective response for them to make at the expense of a small % drop in heavy bombers reaching the Strategic Airforces.

Also snorkles while allowing a submarine to remain submerged while using the deisels are not the be all and end all to that particular problem

Firstly in anything but calm weather the snorkle can become swamped and when this happened the engines sucked air from the submarine - a highly unpleasent ear popping experiance for the crew

Secondly while submariners are tough and all that - travelling at periscope depth at speed for any period would be exhausting for the crew as the surface wave effect would be moving the boat all over the place in anything but calm conditions.

Thirdly unless designed as a underwater sub its hull form would be less efficient than motoring on the surface and so use up its fuel and speed was limited to about 6 knots anyway because anything faster would deform and damge the snorkle.

Lastly - you cannot see anything - visabile horizon from a perisope is 2-3 miles - although depending on speed of the boat and conditions hydrophones could probably hear further than that?

A surfaced boat would be able to travel faster and see further than a submerged one using a snorkle.

The snorkle only makes sense as an 'improvement' in improving a submarines ability to traverse an area where enemy ASW airpower is strong - so until that happens why bother?
 
Hydrophones. Submerged subs killing other submerged subs did not happen till 1944-45 a RN V class being the first to achieve a kill.
Yes but the KM used long range passive sonar to help locate convoys because the convoys were so noisy .
 
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