Albrecht Von Hesse
10-27-06, 10:00 PM
There's been a bit of discussion over anti-sub nets: how they worked, how effective they were and why they seem to so easily sink our boats when we hit them. I did a bit of research and this is the best description of anti-submarine nets I could find.
Submarines operating in the vicinity of enemy ports or bases may expect that enemy harbors will be protected with anti-submarine nets and mine fields in conjunction with surface patrols. These areas should only be penetrated when the mission demands. Locations of swept channels and openings through barriers may be determined by observing, at periscope depth, the ingress and egress of enemy surface craft. Areas that are well lighted at night most probably indicate the presence of mine fields. The regular anti-submarine net can be expected to extend to the bottom, where the depth is 200 feet or less. It is probable that the net will be made of 5/8 to 3/4 inch steel wire with about 12 feet mesh. Some anti-submarine nets are made up of heavy steel bars designed to block passage. Another consists of chain and dangling wires primarily to foul submarine's propellers. Others are mine nets, in which a submarine struggling to free itself makes its presence known ashore, where shore controlled mines are exploded at proper places along the barrier. Either shore controlled or contact mine fields may be expected in the vicinity of nets. Nets may be expected to be patrolled by craft equipped with depth charges. If it is necessary to attempt penetration of a net or mine area, it should be done with the tide is running the strongest in the direction of advance. Net cutters, mine cable cutters and clearing lines should be in use, if available. The submarine should submerge until near the bottom, or to a depth below 200 feet; if there is a greater depth of water, then proceed at slow speed in an effort to penetrate without contact. It is best to strike nets as near their moorings as practicable, because there is less wire whose elasticity must be overcome, and because less surface disturbance will result. If it is found that penetration can not be effected, back clear before becoming broadside to the net, thereby fouling the propellers. If it is possible to do so, attempt penetration at night to provide for the contingencies that it may be necessary to surface in order to clear, after fouling a net. After passing the net, any unusual noise of cable or chain on the hull may be assumed to be from a mine anchor. Attempt to clear by maneuvering at slow speed, in order to avoid pulling the mine down to contact detonation. Ingenious uses of various types of nets may be expected. For example, the mine net is non-rigid and folds around the submarine, as it moves forward. A mine in the net detonates, when contact is made. Avoid ordinary fishing nets and stake lines of the drifting type. If any portions of them are carried along by the submarine, they reveal the presence of the submarine. Rough weather and heavy storms usually cause considerable damage to anti-submarine nets and mine fields. It is therefore advisable to attempt to penetrate an area suspected of being so protected, immediately after a storm. In penetrating mine fields, great advantage accrues if it is known what type of firing mechanism is employed, i.e., whether contact or antenna type, how old the field is and hence how effective, the state of tide and tidal currents, and whether planted as an anti-submarine or general field. If it is known that the field is for general defense, safer penetration will be accomplished (most likely) by running under, at full speed and good depth. If an anti-submarine field exists and it is known that contact mines are used, better success will be obtained by attempting passage on the surface during high tide with strong tidal currents.
(credit: http://www.history.navy.mil/library/online/ss-doc-5.htm )
Submarines operating in the vicinity of enemy ports or bases may expect that enemy harbors will be protected with anti-submarine nets and mine fields in conjunction with surface patrols. These areas should only be penetrated when the mission demands. Locations of swept channels and openings through barriers may be determined by observing, at periscope depth, the ingress and egress of enemy surface craft. Areas that are well lighted at night most probably indicate the presence of mine fields. The regular anti-submarine net can be expected to extend to the bottom, where the depth is 200 feet or less. It is probable that the net will be made of 5/8 to 3/4 inch steel wire with about 12 feet mesh. Some anti-submarine nets are made up of heavy steel bars designed to block passage. Another consists of chain and dangling wires primarily to foul submarine's propellers. Others are mine nets, in which a submarine struggling to free itself makes its presence known ashore, where shore controlled mines are exploded at proper places along the barrier. Either shore controlled or contact mine fields may be expected in the vicinity of nets. Nets may be expected to be patrolled by craft equipped with depth charges. If it is necessary to attempt penetration of a net or mine area, it should be done with the tide is running the strongest in the direction of advance. Net cutters, mine cable cutters and clearing lines should be in use, if available. The submarine should submerge until near the bottom, or to a depth below 200 feet; if there is a greater depth of water, then proceed at slow speed in an effort to penetrate without contact. It is best to strike nets as near their moorings as practicable, because there is less wire whose elasticity must be overcome, and because less surface disturbance will result. If it is found that penetration can not be effected, back clear before becoming broadside to the net, thereby fouling the propellers. If it is possible to do so, attempt penetration at night to provide for the contingencies that it may be necessary to surface in order to clear, after fouling a net. After passing the net, any unusual noise of cable or chain on the hull may be assumed to be from a mine anchor. Attempt to clear by maneuvering at slow speed, in order to avoid pulling the mine down to contact detonation. Ingenious uses of various types of nets may be expected. For example, the mine net is non-rigid and folds around the submarine, as it moves forward. A mine in the net detonates, when contact is made. Avoid ordinary fishing nets and stake lines of the drifting type. If any portions of them are carried along by the submarine, they reveal the presence of the submarine. Rough weather and heavy storms usually cause considerable damage to anti-submarine nets and mine fields. It is therefore advisable to attempt to penetrate an area suspected of being so protected, immediately after a storm. In penetrating mine fields, great advantage accrues if it is known what type of firing mechanism is employed, i.e., whether contact or antenna type, how old the field is and hence how effective, the state of tide and tidal currents, and whether planted as an anti-submarine or general field. If it is known that the field is for general defense, safer penetration will be accomplished (most likely) by running under, at full speed and good depth. If an anti-submarine field exists and it is known that contact mines are used, better success will be obtained by attempting passage on the surface during high tide with strong tidal currents.
(credit: http://www.history.navy.mil/library/online/ss-doc-5.htm )