I'm rereading Invasion of England 1940 by Peter Schenck. It is considered the best source for the German side of the campaign.
He had a section on mining. It has 6 pages and includes s map of the proposed fields and a table on data on them. I am having an issue reconciling his text and his tables.
His text says field D2 was two rows of mines and two rows of decoys. The table says it is 16 3 nautical miles long and has mines spaced 55 meters apart for a total of 550 mines. This seems like only a single row. Would the rows be staggered so only 550 mines are needed or should it really require 1100 mines?
Question on German Minelaying
Re: Question on German Minelaying
550 is clearly the total number to be laid. 16.3 nautical miles is about 30,000 meters so it appears that with a double row there would be 110 meters between mines in each row.
It seems these planned mine barriers were more like trap lines than real barriers. D1 would be 5.4 nautical miles long (about 10,000 m) and consist of 250 standard EMC moored contact mines in four rows, so the distance between mines in each row would be about 160 m. On either side a double row of in total 300 explosive Sprengbojen (explosive charge 0.8 kg) and 100 Reissbojen (mechanical devices to damage minesweeping gear) would be laid to hamper sweeping, making one per 100 m in each row. With one mine per 160 m, even in four rows, a destroyer with a beam of 12 m, or even a cruiser with a beam of 20 m, might well sail right through them without noticing. Or to put it another way, sweeping a gap a mile wide through D1 would require the removal of only about fifty mines.
Another complication was that with a tidal range of up to twenty feet (6 m) on spring tides in the Channel, moored contact mines, such as the EMC mines planned for D1 and D2, which at low water would be just below the surface, would at other times be so deep under water that enemy vessels would pass over them unharmed. To solve this problem the Germans developed a moored "tidal mine" or Gezeitenmine (EMG), which was held at a constant depth below the surface by a small inconspicuous buoy above and a counterweight below. Of the 5,600 mines to be laid in the Seelöwe barriers, almost half would be of this type, if enough could be produced in time.
It seems these planned mine barriers were more like trap lines than real barriers. D1 would be 5.4 nautical miles long (about 10,000 m) and consist of 250 standard EMC moored contact mines in four rows, so the distance between mines in each row would be about 160 m. On either side a double row of in total 300 explosive Sprengbojen (explosive charge 0.8 kg) and 100 Reissbojen (mechanical devices to damage minesweeping gear) would be laid to hamper sweeping, making one per 100 m in each row. With one mine per 160 m, even in four rows, a destroyer with a beam of 12 m, or even a cruiser with a beam of 20 m, might well sail right through them without noticing. Or to put it another way, sweeping a gap a mile wide through D1 would require the removal of only about fifty mines.
Another complication was that with a tidal range of up to twenty feet (6 m) on spring tides in the Channel, moored contact mines, such as the EMC mines planned for D1 and D2, which at low water would be just below the surface, would at other times be so deep under water that enemy vessels would pass over them unharmed. To solve this problem the Germans developed a moored "tidal mine" or Gezeitenmine (EMG), which was held at a constant depth below the surface by a small inconspicuous buoy above and a counterweight below. Of the 5,600 mines to be laid in the Seelöwe barriers, almost half would be of this type, if enough could be produced in time.
"The true spirit of conversation consists in building on another man's observation, not overturning it." Edward George Bulwer-Lytton
Re: Question on German Minelaying
Thanks
How much space did the anti sweep devices take on a minelayer? If a minelayer could carry 60 mines were any anti sweeping devices in addition to them or part of that total? If they replace mines is it 1 for 1 or more or less? Since the inner and outer lines would have different types of devices would some ships carry mines while others carried anti sweeping devices?
How quickly could a vessel lay mines? How fast could it steam while doing so? How did the Germans ensure they knew the location of their minefields? The outer barriers were supposed to have gaps through which U-Boats could pass. How did an operation pass from one minelayer to the next when the first had exhausted its supply of devices? Would all lines be laid simultaneously or in sequence?
If a force laying mines was attacked were they to jettison their mines and fight, run for it with or without the mines or hope the escort force could keep them safe and continue with the field?
How vulnerable would a destroyer with a deck load of mines be to a catastrophic hit?
From the maps and timetables in Schenck the two furthest west sets of minefields look like they would be very risky to lay and unprotected once they are down. The British had lots of very active minesweepers and they were sweeping constantly. The A and B barrages would be hard pressed to not be breached. In addition the groups laying this fields might well run into Royal Navy surface forces, night flying Coastal Command or Fleet Air Arm patrol craft or even coastal batteries. Even if they trade 1 for 1 in ships sunk and damaged those are losses the Royal navy and afford and the KM cannot. The minelaying forces consist of almost half of the available Destroyers and Torpedo Boats available.
Does anyone have a map of the British minefields in these areas at this time?
How much space did the anti sweep devices take on a minelayer? If a minelayer could carry 60 mines were any anti sweeping devices in addition to them or part of that total? If they replace mines is it 1 for 1 or more or less? Since the inner and outer lines would have different types of devices would some ships carry mines while others carried anti sweeping devices?
How quickly could a vessel lay mines? How fast could it steam while doing so? How did the Germans ensure they knew the location of their minefields? The outer barriers were supposed to have gaps through which U-Boats could pass. How did an operation pass from one minelayer to the next when the first had exhausted its supply of devices? Would all lines be laid simultaneously or in sequence?
If a force laying mines was attacked were they to jettison their mines and fight, run for it with or without the mines or hope the escort force could keep them safe and continue with the field?
How vulnerable would a destroyer with a deck load of mines be to a catastrophic hit?
From the maps and timetables in Schenck the two furthest west sets of minefields look like they would be very risky to lay and unprotected once they are down. The British had lots of very active minesweepers and they were sweeping constantly. The A and B barrages would be hard pressed to not be breached. In addition the groups laying this fields might well run into Royal Navy surface forces, night flying Coastal Command or Fleet Air Arm patrol craft or even coastal batteries. Even if they trade 1 for 1 in ships sunk and damaged those are losses the Royal navy and afford and the KM cannot. The minelaying forces consist of almost half of the available Destroyers and Torpedo Boats available.
Does anyone have a map of the British minefields in these areas at this time?