PROTECTION OP WARSHIPS.

New Zealand Herald, Volume LII, Issue 15906, 1 May 1915, Page 1 (Supplement)

PROTECTION OP WARSHIPS.

Bt 0. B. BABHAM. Until a very few years ago the submarine was not regarded as having any possibilities as a weapon of offence, and consequently the question of protecting -the bottoms of warships against torpedo attack by underwater craft' had received next to no consideration. As a matter of fact, it was not until 1908, when the British "C" class of submarines with a displacement of 314 ,321 tons,' two tubes, and an underwater speed of 10 and a surface speed of 14 knots, were being completed and the bigger " D " submersibles, of 540-595 tons, three cubes, and surface and submerged speeds of 16 and 10 knots respectively, were beirig-'aid down, that submarines were considered as vessels likely to prove of any value for other than coast defence work. With the introduction of the improved. "E " class, '28 to 810 tons, four tubes, and a surface speed of 16 and a submerged speed of 10 knots, the British Navy received a valuable addition to its striking power, and the idea of designing underwater craft for defensive purposes was definitely abandoned by all the Great Powers. Following the new policy, the "F," "V,"and "W" classes of ocean-going submersibles were added to the British Navy, hut for obvious reasons particulars cannot be given of any of the more recent vessels. Up to the time when the late " D's" and early " E's,' were laid down it was considered that no exceptional protection -was necessary for a warship save on those parts of her hull which could be struck by either projectiles or torpedoes fired from surface craft. Steel wire nets are the only form of protection against torpedo attacks that have as. yet proved at all successful, and ■the drawback to nets is .that they can only be.used when a'vessel is at anchor. The nets, which are rolled up and [ rest on a ledge round the hull when the vessel is,- steaming, can be slung out on booms and form a protective apron, descending into the water to a depth of 20 to 2oft, at a distance of some 30ft from the hull* But it has been pointed out recently by an eminent naval authority that torpedo nets are by no means to be depended upon, and he gives. it '.as his opinion that the best means of protecting a .vessel, against torpedo ,attacks is to provide an ample secondary battery, so that the attacking ship or ships may be sunk before . they can discharge their tubes at effective range., ' ' ; .: . A torpedo, fired from a surface craft, is perfectly visible and it is : possible, .by effective machine-gun fire, to ,hit and explode its war-head before- it' can reach the hull of the vessel at which it is aimed. It has been said that this has been done in the present war,, but it would seem that there should' exist some more positive form of protection than gunfire from torpedoes fired in the usual way. /

: Bat with attack from submarines or Bubmersibles, the case i^. different, as neither > the torpedo nor the attacking vessel can be Been. There is a- '-. popular idea that a; submarine must have her periscope ebove water the'whole of the time she is in commission, but this is an utterly fallacious impression. .-■ -A submarine can see through her periscope the exact position of a vessel when some miles distant. 'She can then creep along, steering by dead reckoning until she has arrived in the vicinity: of '.her target. Plate glass portlights in her' conningtower serve to • enable her; to pick ; her way up and down, backwards and : forwards, until : the loom' of I the /warship's hull strikes dark through the green water. The submarine can then rise and choose her position ;without.; once : using the periscope, ?au fire ,«; her torpedo at her leisure. Then a quick 'dash away, and in-a quarter of an.Wr three miles distant and ho; one in i the world eon!d, pose, out: the direction i" which she Sad !

_ _.. . gone.. ; , '• ': '/'H'-H",".' Bv 80Jn! '<• designers, the idea of ? JongK iiduial subdivision as a means of miniriisin^the' effects of ? torpedo attack has >^en'adopts, and it is claimed for.'-this liethod of construction 5 that '.it- is also a jrbtection { in case': of internal explosion >r collision. It is necessary, however, ;b' : supplement ' this . wits an efficient ;vstem of transverse : bulkheads, and \ theso atter,are often a source of weakheis in. practice Many Have favoured the- provision of a flexible - diaphragm between.an inner and. outer armouring, the'- theory" being that this would either bring to'rest altogether any projectile •which' pierced . the outer armouring, or at any rati 'so reduce : its velocity -that! it would ' be i unable ' to '*!,make/, ik way through the inner plating. ; * •'* The -great nival architect, 'Sir Phillip Watts," has. expressed the view that, all that was nenessary was to provide deep inner .bottom' spaces .backed;?with tough plating. He- frankly admitted J'that up to f the i present sufficient importance \ had ■ riot been; paid to. the'menace of the submarine, and said that: recently the : question as tto whether the bottoms *of warsnipslshould,' or should riot, bo armoured had-, been discussed' on more than one occasion. ', - S' A> \ ■;'; r • 'A' point to which . attention has recently been "directed is- that up to the present no modern warship has been sunk by torpedoes," fired from under-sea craft. Several vsemi-obsolete ships ':' have-; been' destroyed," but no modern battle unit-has foundered, . It is .-'said \ that some months ago a 1 very powerful ■ vessel went .down after remaining ' aftoab for some ten or fiftesn hoars, but it- is jextremely improbable- that she was submarined,. the : general opinion being that she struck a mine. A- French: battleship of , the Courbet type was ■: torpedoed •■ by oue of the J German "U" class; ■ the Austrian Dreadnought, Viribus >. tJnitis, ■■■■' was torpedoed -' by a French ' submarine: ? and 1 , "the -' Goeben, battle-cruiser, was . torpedoed shortly after coming into the , hands "< of "'her" present owners. Not- one of these , ships sank. Nevertheless' they we're, pat : -out of action, a fact which > goes 'to nhow that modern ' methods of: protection arc only partially effective. A ship out of action is as ' useless as one sunk,' and there.'is■ a further point that apparently it is impossible to properly repair a modern warship when damaged -by a torpedo. The only way the Goeben could bo repaired was by' running concrete into the gash which was torn in -Her side. She had, to' have several hundred tons of cement plastered over her plating, and 13 now practically a useless ship so far as speed and'steering goes. The Viribus was repaired as aarefufiy as the dockyards at Fiume could carry out the work, but her speed has been reduced by from four to five knots, and she steers particularly badly since the work was completed. Bottom armouring, . the method of protection alweys advocated by those who know Isast about the subject, could not be adopted, at any rate for battlecruisers, as it would seriously impair i their efficiency. for example, if the Tiger [were plated "over, her bottomshe "is a 28.000-ton boat-with 4in plating, the thinnest skin that eciild resist the blow of a modern torpedo explosion, her body armouring would have to 'oe reduced to -a thickness not more thaa . 7Jin or else her speed would be cut .down. The real protection against torpedo attack from submarine craft is to provide vessels with underwater sight and hearing. A submarine is of metal: she carries within her a powerful closed electrical circuit whe'.i she is submerged, and she is exceedingly noisy. Is it beyond the wit of the engineer to devise some form of apparatus, with a largo closed circuit in which the approach of a submarine would set up induced currents? Can no wireless system -be devised in which the ' waves "sent ' out would be affected by the approach nf an electri-cally-driven vessel? Some form of submarine .telephony might be perhaps devised. But it appears certain that study and experiment could find a means whereby the poworfui current flowing from the storage batteries of a submarine.to her driving motors, a circuit ! in ? which current is flowing during the whole of v the ■time tho' vessel is -travelling under : water, could 'be made • a betrayer ;of -'its' own whereabouts. , ••; , ■-.%. •-,.. " '■;: ;