VLR B-24 Liberators and the Mid-Atlantic Gap (3 Viewers)

[Reluctant Poster]

But they did not stop more than 10% of the supplies, even though the ships they sank were capable of more than one trip. Read Hitler's U-Boat War by Clay Blair; he explains this. We did react to the U-boat success, built ships faster than they could sink them, and in 1944 were sinking something like 10 times the tonnage in U-boats that they were sinking in our ships. The Germans lost 500 U-boats in WWII, 10 times as many as the USN.

The idea that America won the war simply by building ships faster than the enemy could sink them is an argument with several large holes in it;
1. In addition to losing ships you are losing cargo which must be replaced. In some instances the cargo is virtually irreplaceable. For example the planned expansion of the enormous refinery at Abadan was delayed on two separate occasions, each time by several months due to a U-boat sinking the ship carrying the equipment.
2. There was a world wide shortage of shipping throughout the entire was. If all you're new builds are going into the lifeline to Britain the other theaters are going without. The Bengal famine which claimed 2 to 3 million lives was blamed in part on the prioritization of shipping for war materials.
3. There was a shortage of tankers. Tankers are much harder to build than cargo ships. The Germans knew this and made them priority targets. Admiral King stupidly lost 50 priceless tankers in the first 6 months of the war which was 10% of the allied fleet. After that tankers were always in short supply. Without oil the whole show grinds to a halt.
4. When the Royal Navy defeated the U Boats in May 1943 the USN was able to cancel a large portion of their destroyer escort program. This freed shipyard capacity to build landing craft. The was a shortage of landing craft through the war. without the additional landing craft operations would have had to be postponed. I would guess that the advance thru the Pacific would have suffered.
5. People. War is actually fought by humans. Any organization consistently losing 10% of its strength falls to pieces pretty quickly. Everyone is a rookie. Efficiency plummets. Serving in the Merchant Marine was one of the most dangerous jobs in the war. I think only bomber crews and, ironically, U-boat crews had a higher mortality rate. Approximately 30,000 mariners died terrible deaths, blown to bits when you're ammunition cargo goes up, trapped below deck when your ore carrier sinks within a minute of being torpedoed, burned to death when your gasoline tanker catches fire, scalded by steam in the boiler room or simply freezing to death in the Atlantic watching the other ships sailing off because they can't stop for fear of suffering the same fate. I'm amazed that morale didn't crack as it was, but if the loss rate had continued I doubt you would find anyone willing to go on a suicide mission.

 

[Shortround6]

Unless I am adding things up wrong the U-boats were sinking ships faster than they could be built in 1940 and 1941. The shipbuilders beat the U boats by about 17% in 1942 and it is probably true that it was in the last few months? Things may have been a bit on the iffy side at the end of 1942. Things looking better for the allies but not out of the woods yet, If Germans can get back to earlier success rates (or even close) then the surplus goes away.

The Allied introduction of new sensors and weapons means they keep the tactical initiative and the increase number of escorts just push that further.

The Germans failed to keep up the technical pace fell and behind quickly. A few extra AA guns or 20 tons more fuel oil is not really changing things by very much. They sat on the schnorkel for several years. They failed to enlarge the internal size of the boats for far too long and used those ridiculous deck storage tubes for reloads, which were pretty much useless in the North Atlantic, especially in winter. They kept a rather slow submerged speed, Under 8kts for the Type VII while the British T and U/V could make 9 and the S class could do 10kts. In a given amount of time (say 15 minutes) a boat that can do 10 kts has over 50% more "area" to disappear into than an 8 kt boat.

Please note I am not talking about new hull forms or type XXI subs.

The outcome of the Battle of the Atlantic was a lot harder to call in 1941 and most of 1942. Nov 1942 being a high point for the U-boats with 126 ships (802,160 tons) sunk. the next month saw the sinkings drop to about 1/2.

There is a difference between what we know now and what they knew then. Just a few really bad months in row would have meant real trouble but the Germans were not able to put 3 or more (or even two?) high scoring months together.

 

[DO335]

Why didn't the British bomb the U boat pens while they were being built on West Coast of France? If they had bombed around the time the cement was poured it would have destroyed them.

 

[syscom3]

Why didn't the British bomb the U boat pens while they were being built on West Coast of France? If they had bombed around the time the cement was poured it would have destroyed them.

Not enough bombers. And not enough time

 

[pinehilljoe]

Not enough bombers. And not enough time

The Pens are also as indestructible as a structure made by Man can be with 1940s bombing technology. They are still there in Lorient, too expensive to break up.

 

[SaparotRob]

The idea that America won the war simply by building ships faster than the enemy could sink them is an argument with several large holes in it;
1. In addition to losing ships you are losing cargo which must be replaced. In some instances the cargo is virtually irreplaceable. For example the planned expansion of the enormous refinery at Abadan was delayed on two separate occasions, each time by several months due to a U-boat sinking the ship carrying the equipment.
2. There was a world wide shortage of shipping throughout the entire was. If all you're new builds are going into the lifeline to Britain the other theaters are going without. The Bengal famine which claimed 2 to 3 million lives was blamed in part on the prioritization of shipping for war materials.
3. There was a shortage of tankers. Tankers are much harder to build than cargo ships. The Germans knew this and made them priority targets. Admiral King stupidly lost 50 priceless tankers in the first 6 months of the war which was 10% of the allied fleet. After that tankers were always in short supply. Without oil the whole show grinds to a halt.
4. When the Royal Navy defeated the U Boats in May 1943 the USN was able to cancel a large portion of their destroyer escort program. This freed shipyard capacity to build landing craft. The was a shortage of landing craft through the war. without the additional landing craft operations would have had to be postponed. I would guess that the advance thru the Pacific would have suffered.
5. People. War is actually fought by humans. Any organization consistently losing 10% of its strength falls to pieces pretty quickly. Everyone is a rookie. Efficiency plummets. Serving in the Merchant Marine was one of the most dangerous jobs in the war. I think only bomber crews and, ironically, U-boat crews had a higher mortality rate. Approximately 30,000 mariners died terrible deaths, blown to bits when you're ammunition cargo goes up, trapped below deck when your ore carrier sinks within a minute of being torpedoed, burned to death when your gasoline tanker catches fire, scalded by steam in the boiler room or simply freezing to death in the Atlantic watching the other ships sailing off because they can't stop for fear of suffering the same fate. I'm amazed that morale didn't crack as it was, but if the loss rate had continued I doubt you would find anyone willing to go on a suicide mission.

 

[SaparotRob]

Why didn't the British bomb the U boat pens while they were being built on West Coast of France? If they had bombed around the time the cement was poured it would have destroyed them.

I believe the "turncoat" Frenchman who was in charge of the facility was assassinated by the Resistance. It turned out he was working for British intelligence.

 

[DO335]

The Pens are also as indestructible as a structure made by Man can be with 1940s bombing technology. They are still there in Lorient, too expensive to break up.

I've visited one in France, I agree they appear indestructible.

 

[Elan Vital]

Why didn't the British bomb the U boat pens while they were being built on West Coast of France? If they had bombed around the time the cement was poured it would have destroyed them.

They did, but with such a small payload and so little subsequent bombing during construction that they didn't prevent their completion and after that there simply never was the consistent and focused effort to take them out/disrupt operations for good. The surrounding cities and civilian population took a heavy beating instead.

 

[pinehilljoe]

Base de Sous-Marins · 56100 Lorient, France

âââââ · Museum

www.google.com

Interesting to look at the street view on google maps. Next best thing to being there.

 

[EwenS]

These bunkers were built in incredibly short periods of time when you consider the volumes of concrete that were poured. Work at these sites went on day and night, under floodlights when necessary, only stopping for air raids. Even after they were completed, additional works were carried out to make them even more bomb proof by adding more concrete to some of the roofs, spaced from the first layer, along with concrete bomb traps to explode bombs before they hit the roof proper. Not all these works had been completed by the time that the U-boats were withdrawn from France in Aug 1944. And all these sites were well protected with flak guns and balloons.

Lorient
First air raid on 27 Sept 1940 showed the vulnerability of U-boats in the open harbour and triggered the design of the concrete pens.

2x "Dom" bunkers built to protect existing slipways in the shipyard
Scorff bunker (2 wet docks with 4 berths) completed Aug 1941.
Then:-
Keroman I (5 boats + protected slipway) work started Feb 1941 completed Sept 1941
Keroman II (7 boats + garage to protect the transporters) work started May 1941
The Keroman complex was designed to lift U-boats completely out of the water and repair them ashore. The first U-boat was brought ashore at the Keroman complex in Aug 1941 and the whole complex, with its transporter system to move U-boats around, was officially handed over to the KM on 20 Dec 1941.

Keroman III with 7 pens (4 designed with pumping equipment as dry docks) to hold 12 U-boats, saw work start in Oct 1941, with parts being used from early 1943 before it was completed in May or July 1943.

In Jan/Feb 1943 the Allies bombed Lorient town in an effort to cut off the supply routes to the U-boat bunkers. In doing so they flattened 90% of the town

Late summer 1943 work began on Keroman IVa & IVb, but never progressed beyond some foundation work.

Brest
Construction started Jan 1941 and the first pen was ready for use in Sept. 15 pens (10 dry dock & 5 wet)

Saint-Nazaire
Built from Feb 1941, with the first pens available for use in June that year. It was fully completed in Oct 1942. 8 dry and 6 wet docks. Following Operation Chariot a new protected lock to the basin in which the U-boat pen sat, was designed and built 1943/44, but it doesn't ever seem to have been used in WW2.

La Pallice / La Rochelle
Work started April 1941. The first phase (2 dry and 5 wet docks for a total of 9 U-boats) was completed in Nov. In April 1942 work began on a second phase of 3 pens (2 dry & 1 wet for another 4 U-boats). A protected lock was also built from July 1942.

Bordeaux
Construction began Sept 1941 and it became operational in Jan 1943. 11 pens (4 wet & 7 dry docks)

All these bunkers were targets during the construction phase but that was at a time when Bomber Command wasn't very strong, so damage was limited. By the time they became a priority after the beginning of 1943 at a time when Bomber Command was much stronger and the 8th AF was beginning to become available, most were complete. Instead the towns and cities around them were laid waste with significant French civilian casualties.

On 5 Aug 1944, 617 squadron dropped 14 12,000lb Tallboys on the Brest bunker. 6 hit the roof. Two penetrated the 18ft of concrete. Two others left craters 8ft deep. Brest was revisted on the 12th Aug. 3 hits were obtained completely penetrating the roof. Another raid on the 13th may have added another penetrating hit as well as causing other damage.

On 6 Aug it was the turn of Lorient. 3 Tallboys hit the roof of Keroman III but failed to make a complete penetration, although one hit did cause some crumbling, to thethickest part of the roof.

On 9 Aug 617 visited La Pallice. Again a number of hits were obtained causing craters or, in one case penetrating the top layer of concrete roof. Another visit was made on the 18th August. several non penetrating hits were obtained.

By 22nd Aug it was becoming clear that these structures were sufficiently stoutly constructed that neither direct Tallboy hits nor near misses to undermine the foundations would have the desired effect of destroying these targets. Tallboy did however prove effective against the more lightly built E-boat pens at places like Boulogne.

 

[EwenS]

Unless I am adding things up wrong the U-boats were sinking ships faster than they could be built in 1940 and 1941. The shipbuilders beat the U boats by about 17% in 1942 and it is probably true that it was in the last few months? Things may have been a bit on the iffy side at the end of 1942. Things looking better for the allies but not out of the woods yet, If Germans can get back to earlier success rates (or even close) then the surplus goes away.

The Allied introduction of new sensors and weapons means they keep the tactical initiative and the increase number of escorts just push that further.

The Germans failed to keep up the technical pace fell and behind quickly. A few extra AA guns or 20 tons more fuel oil is not really changing things by very much. They sat on the schnorkel for several years. They failed to enlarge the internal size of the boats for far too long and used those ridiculous deck storage tubes for reloads, which were pretty much useless in the North Atlantic, especially in winter. They kept a rather slow submerged speed, Under 8kts for the Type VII while the British T and U/V could make 9 and the S class could do 10kts. In a given amount of time (say 15 minutes) a boat that can do 10 kts has over 50% more "area" to disappear into than an 8 kt boat.

Please note I am not talking about new hull forms or type XXI subs.

The outcome of the Battle of the Atlantic was a lot harder to call in 1941 and most of 1942. Nov 1942 being a high point for the U-boats with 126 ships (802,160 tons) sunk. the next month saw the sinkings drop to about 1/2.

There is a difference between what we know now and what they knew then. Just a few really bad months in row would have meant real trouble but the Germans were not able to put 3 or more (or even two?) high scoring months together.

Schnorkel
The Germans weren't the only ones to sit on the Schnorkel and do nothing. Britain knew about it from at least late 1941 when the Dutch subs started to operate from Singapore and then Ceylon under British Command (see O-19 & O-20), if not from May 1940 when Dutch forces started arring in Britain. And the RN had apparently studied "underwater battery charging" pre-war. It was raised again in late 1942 when the A class were being designed. It was dropped on the ground that "submerged dieseling" had no operational value to British submarines "presumably because neither the German nor the Jpanese had effective airborne sea search radars to threaten submarines at night. Late in the war the the idea was revived, and plans were made for depot ships in the Far East to fit snorkels ('snorts' in British parlance) if necessary." (Friedman "British Submarines in Two World Wars")

And the Schnorkel had a major problem - it slowed the deployment speed of a U-boat from a decent surface cruising speed to a 6 knot at most crawl. So U-boats could spend less time in the operational area.

The Schnorchel - Technical pages - German U-boats of WWII - Kriegsmarine - uboat.net

The U-boat War in World War Two (Kriegsmarine, 1939-1945) and World War One (Kaiserliche Marine, 1914-1918) and the Allied efforts to counter the threat. Over 40.000 pages on the officers, the boats, technology and the Allied efforts to counter the U-boat threat.

www.uboat.net

Underwater speed
First a correction. The only British S class with an underwater speed of 10 knots were the 12 pre-war built subs, completed 1934-38. The wartime boats of this class, ordered from Jan 1940 and completed from March 1942) could only do 9 knots submerged. And they could only run at that speed for 1.25 hours which only gets you about 11 miles away from your target before you have to surface to recharge your batteries, thereby making yourself a sitting target. And that assumes that you had a fully charged battery to begin with, which was unlikely given a submerged approach if the attack is in daylight. The RN were however happy to see that underwater speed reduced to 8 knots in the A class of 1943.


S class submerged endurance 120 nm @ 3 knots.
T class (1943 spec) 126 nm @2.25 knots
U class 120 nm @ 2 knots.
A US Gato could run underwater for 48 hours on a full battery charge. But that was at a speed of only 2 knots = 96 nm

Underwater speed was not nearly as important in WW2 as you seem to believe. All navies preferred to sneak away at low speed and increasing depth if necessary to remain undetected. That way they might be able to come back for a second bite at the cherry. A dived sub could not generally outrun a surface escort in most sea conditions. One reason why the RN escort classes had a minimum speed of 16 knots at the start of WW2, increasing later. Also a sub of that era travelling fast underwater generated a lot of noise, rendering it more detectable on ASDIC / Sonar. And running at high underwater speeds burned through the available battery power VERY fast (see above for the S class).

Type XXI
The purpose of the latger battery capacity and higher underwater speed of a Type XXI as the Germans saw it when it was being developed, was not to increase the max speed to allow escape after an attack, but to increase the underwater cruising speed, so reducing the transit times to the operating areas, and only surfacing if the weather was too bad to Schnorkel. Some comparitive date from Showell's "Hitler's 'Wonder' Boats". Type IXC v Type XXI Speed / range

Surface fast - 18.3knots / 5000 nautical miles v 15.6 knots / 5,100nm
Surface cruising - 10 knots / 13,450 nm v 10 knots / 15,500 nm
Submerged max - 7.3 knots v 17 knots
Submerged fast - 4 knots / 63 nm v 10 knots / 110 nm
Submerged cruising - 2 knots / 128nm v 5 knots / 340 nm.

This way they reckoned a Type XXI could travel 160 nm submerged each day at 7 knots with 4 hours schnorkelling and runnning the diesels burning just 2 tons of fuel while crossing the really dangerous Bay of Biscay. It could then cruise at 10 knots burning just 3.5 tons per day.

A Type IXC would need 12 days to travel submerged from Lorient 720 nm to 20 degrees west and 38 days on the surface to travel the 3,800 miles from 20 degrees west to Panama. A Type XXI would reduce that to 5 and 23 days respectively.