Speed of laying a minefield in enemy waters

[Fatboy Coxy]

Hi all

I’m interested in knowing how quickly a minefield could be laid in enemy waters. During WW2, not only did the British use the Abdiel class minelayers, but also were able, thanks to relatively quick modifications, able to use fleet destroyers for the task. Minefields were laid in Norwegian waters, along the Dutch/German coast, and in the Mediterranean, at night, requiring a fast passage in and out of the area to be mined, unnoticed by the enemy.

Obviously, apart from the high speeds required in transit, there would be a need to lay the mines quickly, and this is the bit that interests me. What kind of speed were mines laid, one a minute, quicker or slower than this, what speed might a ship do while laying their mines, and what sort of sea states could this happen in

Regards
Fatboy Coxy

[OpanaPointer]

https://en.wikipedia.org/wiki/Minelayer

The references may give you more information.

[marcelo_malara]

I don´t see a ship releasing a mine at 30 knots. I think that the speed has to match the density of the minefield, for example if the mines are separated 50 m, at 30 kt a mine has to be released every 3 seconds.

[OpanaPointer]

How about 40 knots? https://en.wikipedia.org/wiki/Abdiel-class_minelayer

[marcelo_malara]

And they did lay mines at 40 kt...?

[OpanaPointer]

And they did lay mines at 40 kt...?

You lay mines in enemy waters. If you wish to dawdle while doing that be my guest, but leave me on the pier.

Swarm in, lay mines, depart. While you're in range of the enemy coastal guns you're in danger. You have an unreasonably large amount of go-bangs for your size. "T'were best done quickly." Sending a squadron of minelayers usually meant the enemy now has problems with sortieing. It's not "how many" mines, it's "how many do the enemy have to worry about".

[marcelo_malara]

[OpanaPointer]

Yep.

[Byron Angel]

I absolutely KNOW I have data on mine-laying methods (at least circa WW1) but I am d*mned if I can find it. They did not lay mines at 40 knots; the mine-laying process was a very carefully conducted timed exercise. Maintaining correct orientation, pattern and interval spacing was important. It was also extremely important to precisely fix the location and boundaries of the mine-field. If not done correctly, the field became nearly as much of a threat to friends as to enemies.

Keep in mind also that every one of those things you were rolling off the stern carried 300-500 lbs of Guncotton, TNT, Amatol or Hexanite (WW1-era). One little mistake could ruin your whole day.

Byron

[marcelo_malara]

Well Byron, we are speaking of offensive (ie in enemy waters) mine laying, friendly ships would not be supposed to be around. Anyway I agree, 40 knots is about 20 m/s, surely a bottom mine would have no problem being tossed at such a speed, but a moored mine is out of the question, the water is like concrete at that speed.

Regards

[OpanaPointer]

the mine-laying process was a very carefully conducted timed exercise. Maintaining correct orientation, pattern and interval spacing was important.

The enemy would certainly love predictable patterns, they would have to hunt so hard.

[Byron Angel]

Well Byron, we are speaking of offensive (ie in enemy waters) mine laying, friendly ships would not be supposed to be around. Anyway I agree, 40 knots is about 20 m/s, surely a bottom mine would have no problem being tossed at such a speed, but a moored mine is out of the question, the water is like concrete at that speed.

Regards

Hi Marcelo,
I've never laid naval mines as a profession, so what follows may not necessarily be "spot on" in every detail -

I'm fairly confident that accurate charting of the location of any new minefield, whether defensive of offensive, would have been carried out as a matter of due diligence. In the latter part of WW1, after sufficient stocks of modern mines were finally available, the British undertook a campaign of laying successive "layers" of mine-fields further and further out from the Heligoland Bight, which forced German mine-sweeping efforts to venture further and further out in order to maintain swept channels for the German fleet. Not knowing exactly where the previous fields were laid would have posed British minelayers venturing into nearby waters to lay the next field. In WW2, the USN was laying tactical offensive minefields in the Blackett Strait in an attempt to disrupt IJN efforts to deliver supplies by sea to Japanese Army forces defending Bougainville; but Blackett Strait was, at the same time, still regularly being transited by Allied warships on anti-ship sweeps, shore bombardment and their own supply missions.

Re the physical laying of the mines, if a minelayer intends to plant a line of, say, fifty mines at 100 yard intervals while travelling at 40 knots, she will need to drop ~13 mines per minute (one every 4-5 seconds if fitted with a single mine rail), or 6-7 mines per minute per rail if fitted with two rails (one mine per rail every 8-10 seconds). Either way, it sounds awfully fast to me.

I will make an effort to dredge up that information.

B

[Byron Angel]

the mine-laying process was a very carefully conducted timed exercise. Maintaining correct orientation, pattern and interval spacing was important.

The enemy would certainly love predictable patterns, they would have to hunt so hard.

Hi OpanaPointer,
I'm guessing you meant to write - "The enemy would certainly love predictable patterns, they wouldn't have to hunt so hard."

I just did manage to locate one of my references, "Endless Story - Being an Account of the Work of the Destroyers, Flotilla-Leaders, Torpedo-Boats and Patrol Boats in the Great War" by Captain Taprell Dorling, RN. Chapter XXIV - "The Twentieth Flotilla" covers his service in said Flotilla as captain of HMS Telemachus . 20th Flotilla was often employed in the last year of the war on mine-laying expeditions in the German Bight. Telemachus could carry 40 x "H mines". She was capable of 30+ knots, but mine-laying speed was 12 knots. The mission described in the a/m book referenced laying interval of "150 ft" (50 yards).

With a laying speed of 12 knots, an interval of 50 yards between successive mines and assuming two launching rails at work, the time interval between the dropping of each mine would work out to about four mines per minute per launching rail and eight mines per minute overall.

The mission Taprell describes involved a division of four destoyers cooperatively laying a field of 160 mines. Each destroyer dropped her mines in a very broad "V", with 20 mines in each leg. The first leg of each destroyer's "V" was in direct longitudinal alignment with those of its division mates, but the second leg of each ship's "V" alternated in direction - port/starboard/port/starboard. This, according to the author, was done to hinder sweeping efforts.

Hope this helps.

Byron

[marcelo_malara]

Thanks for your data Byron. Yes, it seems logical to chart accurately a mine field, nobody knows when an own force has to pass thru it. Anyway, did not mines have a life time? Did not the war treaties oblige its adherents to set their mines so they would become harmless after a set time?

Regards

[wadinga]

Hi All,

Byron has provided excellent information as always. Peter C Smith's 2005 "Into the Minefields" leans heavily on Taffrail's WWI book and then carries the story onto and through WWII. He has lots of detailed information, but the laying technique re 10-12 knots etc . seems similar to that of WWI as described. They could be dropped at faster speeds but any hang up moving the mines along the deck meant spoiled spacing.

Mines might be deployed with soluble plugs which caused them to sink after a pre-set period and equally with delayed action wire spools which stopped them floating up to their set depth until after an area had been swept and was imagined safe.

Navigationally, deployment accuracy was sometimes ensured by using "tautwire" equipment where a heavy weight on one end was dropped near a buoy, lightship or other known location and piano wire payed out off a drum to measure distance run precisely.

I know fatboy Coxy is always interested in South East Asia activities. Smith has details of operations off Singapore and Hong Kong. Old destroyers Scout and Tenedos were tasked with laying 3 defensive minefields for Singapore. Installation to lay mines started in Singapore dockyard and between 4th September 1939 and 8th they laid 544 mines in 15 separate lines. Many more mines were laid in the period until December 1941, by vessels including Thanet, Thracian, Mao Lee, Redstart and Man Yeung.

All the best

wadinga