Sinking WW1 Submarines By Depth Charge.

[PhilB]

There seem to have been a few films shown recently about WW2 submarine warfare. Luckily, depth charge damage was usually fixed by a man with a spanner turning a nut on a pipe! I read that, in WW2, it required a depth charge to detonate within 14ft of a submarine to cause serious hull damage. How close would that need to be in WW1 with the explosives and hulls of that time?

[michaeldr]

From Jellicoe's The Crisis of the Naval War

"Many people held very exaggerated ideas on this subject, even to the extent of supposing that a depth charge would destroy a submarine if dropped within several hundred yards of her. This is, unfortunately, very far indeed from being the case; it is, on the contrary, necessary to explode the charge near the submarine in order to effect destruction. Taking the depth charge with 300 lb. weight of explosive, ordinarily supplied to destroyers in 1917, it was necessary to explode it within fourteen feet of a submarine to ensure destruction; at distances up to about twenty-eight feet from the hull the depth charge might be expected to disable a submarine to the extent of forcing her to the surface, when she could be sunk by gun-fire or rammed, and at distances up to sixty feet the moral effect on the crew would be considerable and might force the submarine to the surface."

 

[michaeldr]

From the same source

It is not possible to give exact information as to the particular means by which the various German submarines were disposed of, but it is believed that of the 186 vessels mentioned as having been lost by the Germans at least thirty-five fell victims to the depth charge, large orders for which had been placed by the Admiralty in 1917, … … …

[Michael Lowrey]

I’m working on a book which reassess all 184 U-boats sunk or interned during the war based upon the latest evidence, including wreck discoveries. All loss causes besides mines and operational/accidental loss are overstated in the British wartime assessments.

A more accurate estimate of German U-boat losses involving depth charge is around two dozen with a few cases still uncertain or hard to discern the actual cause of loss.

[PhilB]

Would heavier explosive weight depth charges be an option or would that have endangered the destroyers?  

 

[PhilB]

It`s estimated that some 16,500 depth charges were dropped in WW1. For, say, 35 U boats sunk, that`s 1 per 471 dropped.  That ratio would look better though if damaged U boats were included in some way.

[healdav]

On 08/04/2024 at 16:32, PhilB said:

It`s estimated that some 16,500 depth charges were dropped in WW1. For, say, 35 U boats sunk, that`s 1 per 471 dropped.  That ratio would look better though if damaged U boats were included in some way.

Its a miracle that so few were dropped for so many destroyed. There was no SONAR at the time, and all they had were (latterly) hydrophones which gave no real idea of depth of the sub or distance.

It was really a case of hearing a sub and tossing a few charges over for luck. In fact, even the hdyrostatic fuse on the charges only came in from the end of 1917. Up until then it was all timing fuses, which wasn't much use when you didn't know how long the charge would take to get to the depth of the sub or far surpass it.

 

[PhilB]

The list of U-boat losses shows an interesting spread of causes:-

Boats lost in action - Fates - German and Austrian U-boats of World War One - Kaiserliche Marine - uboat.net

[Michael Lowrey]

20 hours ago, PhilB said:

The list of U-boat losses shows an interesting spread of causes:-

Boats lost in action - Fates - German and Austrian U-boats of World War One - Kaiserliche Marine - uboat.net

Glad you like the list. I'm also the one that does most of the WWI side of uboat.net, including the loss information.

Sinking a submarine by depth charge during the Great War is different than during World War II. In World War I, there aren't very many (if any) extended hunts for a submarine that results in its destruction. The technology is too primitive.

What you do see are sudden, reactive sinkings of U-boats by depth charge. German submarines generally attacked targets by torpedo at 1,000 meters or less. Sometimes, their periscope would get sighted and a destroyer/sloop/armed trawler etc. would proceed to the site and drop depth charges, sinking the U-boat. Other times, a U-boat would get surprised on the surface by a destroyer or sloop, and be able to get deep enough fast enough, and get sunk by depth charges.

As an example, the High Seas Fleet U-boat losses involving depth charges:

U 68, to a Q-ship depth charge, after a very short-range gun action.

U 58, periscope sighted then depth charged.

U 87, periscope sighted then depth charged.

U 110, dived before destroyers, which dropped depth charges where the destroyers estimated the U-boat had dived 5 minutes earlier…

UB 82, periscope sighted then depth charged.

U 104, sighted on surface at night by sloop, fatally depth charged before the submarine got deep enough.

Depth charge attacks against minelaying U-boats previous sunk on their own mines: UC 41, UC 42.

Discredited sinking claims: U 61 (attack actually against UC 56, which survived), boat now listed as missing, possible operational loss; UB 63 (DC attack location not consistent with U-boat's operating area, another possible operational loss)

[rolt968]

I wonder if there are any statistics covering submarines which were damaged by depth charges, forced to surface and were then destroyed by gun fire or torpedo (another classic from some WW2 films?).

RM

[Michael Lowrey]

7 minutes ago, rolt968 said:

I wonder if there are any statistics covering submarines which were damaged by depth charges, forced to surface and were then destroyed by gun fire or torpedo (another classic from some WW2 films?).

RM

There are detailed description of virtually all WWI ASW actions, so you can get information on that. A damaged submarine will try to come to the surface (they don't always succeed) and attempt to make an escape, but the situation is desperate (or worse) if warships are in the area. (Yes, the surfacing sub will attract a lot of gun fire.) Typically, the commander will have a look around when the U-boat surfaces and order the boat scuttled and abandoned.

The closest cases in WWI of some sort of actual combat happening after major damage were:

U 48, after running aground on the Goodwin Sands and exchange fire with British light patrol forces before scuttling.

UC 75, had its periscope sighted while attacking a convoy and was then rammed by a small steamer. UC 75 surfaced but was spotted by the old destroyer Fairy, with both vessels then opening fire and trying to ram each other. Both vessels are ultimately sunk.

[healdav]

On 10/04/2024 at 16:10, Michael Lowrey said:

German submarines generally attacked targets by torpedo at 1,000 meters or less.

Distance, not depth!

[KizmeRD]

Just for information, some of you may be interested in reading Standing Orders for depth charge attacks (as applicable to Otranto barrage)…

11. When depth charges are dropped ahead of a wake or of a recently sighted periscope, the tendency is always to drop them too far astern of the submarine. Officers should make a point of dropping their charges well ahead. For instance, a submarine’s periscope is sighted by a vessel who then takes one minute before she is in position ahead of a submarine. If the submarine was going five knots and the depth charge was set to 150 feet, the dropping position should be 700 feet ahead of the position where the periscope was last sighted.

 12. Depth Charges are on no account to be saved for future use, and every charge available is to be dropped on any occasion of probable value.

 13. Unless local conditions indicate otherwise, charges should be dropped in accordance with the following rules:-

  (a) Set to a depth of at least 150 feet by day and 100 feet by night. Until Mark IV pistols are received, pistols are to be set at maximum depth.

  (b) Dropped at 20 second intervals by an 8 knot vessel, at 17-second intervals by a 10-knot vessel and at 10-second intervals by a 15-knot vessel.

  (c) If other vessels are in company, the ground covered by the charges is to be marked with a Calcium or other float at each end.

  (d) Charges must not be dropped within 100 feet of one another as they are liable to be countermined if less than 100 feet apart.

 MB

Edited 12 April by KizmeRD