TRANSACTIONS OF SECTION G. 273 



2. The Paravane. By'RoBT. F. McKay, M.Sc, A.M.Inst. C.E., 



A.M.I.Mech.E.' 



The Paravane has been developed as a weapon to fulfil two purposes : — 



(1) To attack a submarine. 



(2) To protect vessels from moored mines. 



In order to differentiate between the two, the one used for attacking sub- 

 marines is termed the 'Explosive Paravane,' and the other for protecting vessels 

 against mines is called the 'Protector Paravane.' A further differentiation 

 in Protector Paravanes has been to call all those used for protecting warships 

 ' Protector Paravanes,' and those used for protectinij merchant vessels ' Otters.' 



The basic principle of all three is the same. They are in effect a form of 

 water-kite which can be towed by a vessel and will run outwards and downwards 

 from the towing vessel. 



The Explosive Paravanes carry a large charge, amounting in some cases to 

 over 300 lb. of T.N.T. The Protector Paravanes, or Otters, carry a form of 

 cutter, but no explosive charge whatever, the cutter being used for severing the 

 moorings of the mines. 



In general, a vessel fitted with either form of apparatus tows two Paravanes, 

 one on either side, by speciallv manufactured wires. A depth-keeping mechanism 

 is fitted in the tail of the Paravane or Otter whereby the depth at which it 

 is being towed may be previously fixed. Variations in the speed or course of 

 the vessel thus have no effect upon the depth of the Paravane. 



Ex^plosive Paravanes are necessarily more complex than the protector type, 

 and, in addition to their charge of T.N.T. . carrv the necessary firing gear 

 and denth-recording device, etc. The explosive charge can be detonated by 

 an electric current which passes through a core in the towing wire. Various 

 methods of detonation, automatic or deliberate, are arranged. Safety devices 

 are inserted in the firing circuit so that the Paravane cannot be accidentally 

 fired whilst it is on deck or in the water near the ship. 



The method of attack by the Explosive Paravane against a hostile submarine 

 is for the attacking vessel to proceed to the spot wherp the submarine was last 

 seen, and there to rake the water with the two Paravanes, which will be 

 towed at a depth of perhaps 200 feet. 



The success of the Explosive Paravane has been very remarkable, when it 

 is realised that this form of attack is only used when other methods, such as 

 the torpedo, the gun, or the ram, have failed. The only form of attack of a 

 like nature is the depth charge. In comparing the results obtained by the 

 Paravane with those obtained by the depth charce. statistics show that the 

 depth charge destroyed four times as many submarines as the Paravane. Due 

 consideration must be given, however, to the fact that depth charges were 

 fitted in twenty-five times as many vessels, and accordingly, proportionately to 

 the number of vessels fitted, the Paravane is many times more efficient. 



The action of a Protective Paravane or Otter can best be likened to a broad 

 wedsre being formed in the front of the towing vessel. Each Paravane is 

 towed from a point as far forward and as low down as possible by a specially 

 constructed steel wire, and the hydroplane on the Paravane exerts a heavy pull 

 upon these wires. These wires, therefore, form a wedge, kept in place by the 

 tension produced by the dynamic reaction of the water upon the Paravane. 

 Mine-mooring wires which strike this wedfre are deflected away from the ship, 

 and passing along the towing wire are guided into the cutter lawvs on the head 

 of the Paravane and instantaneously severed. The mine-sinker drops to the 

 bottom of the sea. whilst the mine floats to the surface, where it can be seen 

 and destroyed by gunfire. 



The success of the Protector Paravane or Otter has been even more striking 

 than that of the exnlosive type. Out of just under 200 British war vessels fitted 

 with this device, fifty-three have cut mines involving a total tonnage of over 

 half a million t-ons, and representing a money value of about sixty millions 

 sterling. 



^ See Engineering, Sept. 19, 1919, p. 389. 



