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Cincpac File No.
Serial 03662

December 14, 1942



From: Commander-in-Chief, United States, Pacific Fleet
Subject: Paravanes, use of against moored mines.
Reference: (a)  Opnav Conf. Itr. Op-30Ml-BP (SC) S81-2 Ser. 0257130 of 10/9/42.

1.Reference (a) is quoted for information:

"1.   The following information and recommendations relative to the use of paravanes are promulgated herewith for such distribution and use as is desired by the addressees. Commandants of all Naval Districts are included as addressees in order that this information may reach merchant ships fitted with paravanes.

"2.   Various types of anti-sweep devices which may be encountered in a moored minefield fall into two general classes as follows:
      (a) Devices causing explosion of the mine proper when swept.
      (b) Obstructors designed to part or foul the sweep wire.
      The first group includes mines equipped with a device to detonate the mine either when the mooring cable is severed or when the antenna mine is actuated by contact with the steel sweep wire or paravane body. The obstructors may be merely a mine mooring too large or heavy to be severed by the paravane cutter, a moored float with static cutters in the mooring, or a moored float designed to part the sweep wire by setting off an explosive charge in contact with it.

"3.   Mines fitted with anti-sweep devices, when encountered by the paravane tow rope, are likely to damage either or both the ship and paravane. The use of a rubber covered tow rope reduces the likelihood of damage to the ship by explosion of a cut mine by delaying the severing of the mine mooring until the mine is deflected a greater distance from the ship, perhaps to the paravane cutter. This type of tow rope prevents detonation of the antenna type mine by the galvanic action of the tow rope though it may also, deflect the antenna to the paravane where it will be fired. The insulated tow rope thus affords increased protection to the ship against mines arranged to fire when swept but results in decreased spread of the paravane through increased drag. The endurance of this type tow rope as compared with the standard three strand tow rope has not been determined.

"4.   No effective countermeasure has as yet been developed for use with paravanes against obstructors.

"5.   The following arguments for and against the streaming of paravanes are listed.

For (a)  They give effective protection against ordinary moored mines.
(b) They may be the means of discovering a mine field.
(a) They reduce the endurance and maximum speed available to ship.
(b) The risk of submarine attack may be increased during the short period when speed is reduced for streaming and recovering paravanes.
(c) Antenna mines and mines that fire on being cut may destroy the paravane and damage the ship. In these cases the use of paravanes with standard tow rope increases the effective beam of the ship and mines that might have been missed may be exploded.


"6.   In weighing the advantages and disadvantages of paravanes, it appears the arguments for are greater than those against; therefore it is recommended that as a general rule paravanes should be used in waters likely to be mined. It is pointed out, however, that the general protection afforded by paravanes has been materially reduced by the new dangers to which paravanes and towing wires are exposed.

"7.   Unless rubber covered towing wires are used, it is not considered desirable that paravanes be run in the known vicinity of antenna mine fields except in areas where there is a strong probability of encountering other types of moored mines as well.

"8.   If paravanes are used, it is possible that a mine mooring may become caught in a paravane. At low speeds of ship the paravane loses much of its outward thrust and may bring the mine dangerously close to the ship. In such instances to prevent the mine being brought closer to the ship, effort should be made to slip or cut the paravane adrift without slowing.

"9.   In regard to moored mines, the following facts should be kept in mind:

      (a)  Offensive minelaying is normally confined to waters (100 fathoms or less) through which shipping must pass. Haphazard minelaying in an ocean area is of little value and is seldom undertaken.
(b) Moored mines are secured to the bottom by a fixed length of cable and are therefore submerged deepest at high water. A tidal stream causes the mine to dip still further below the surface. Thus the best opportunity to pass over a mine field is that time at or near high water when the tidal stream is the strongest.
(c) In rough weather mines may be effective against a ship which could pass safely over them in calm weather. Pitching and falling into troughs of waves make this possible."

  Chief of Staff.

   List IV
   P, NTS, NTSA, XI, 2, 3, 4, 8,
   Y8, 11, Z, SP,
   ENS, 6, 28, NA11, 12, 27,
   37, 54, NB18, 49, ND11-15,

P. V. Mercer,
Flag Secretary.




National Archives & Records Administration, Seattle Branch
Record Group 181, 13th Naval District Port Director's Office - General Correspondence 1924-44

Transcribed by RESEARCHER @ LARGE. Formatting & Comments Copyright R@L.

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