1863.] Iron-Glad Ships and Heavy Ordnance. 85 IRON-CLAD SHIPS AND HEAVY ORDNANCE. THE new system of naval warfare inated armor, (several thicknesses of which characterizes the age was pro- thin plates,) harder and stronger iron posed by John Stevens of Hoboken dur- offers greater resistance to shot, and ing the War of 1812, recommended by steel crumbles less than when it is thick- Paixhans in 1821, made the subject of er. The value of hard surfaces on in- official and private experiment here and clined armor will be alluded to. in Europe during the last ten years Solid and Laminated A rmor compared. especially, subjected to practical test at Backing. European experimenters set Kinburn in 1855, recognized then by out upon the principle that the resist- France and England in the commence- ance of plates is nearly as the square ment of iron-clad fleets, first practised of their thickness, — for example, that by the United States Government in two 2-inch plates are but half as strong the capture of Fort Henry, and at last as one 4-inch plate; and the English, at established and inaugurated not only in least, have never subjected it to more fact, but in the principle and direction than one valuable test. During the of progress, by the memorable action last year, a 6-inch target, composed of the ninth of March, 1862, in the de- of J-inch boiler-plates, with a 1^-inch struction of the wooden sailing-frigates plate in front, and held together by al- Cumberland and Congress by the steam- ternate rivets and screws 8 inches apart, ram Merrimack, and the final discomfit- was completely punched; and a 10-inch ure of that powerful and heavily armed target, similarly constructed, was great- victor by the turreted, iron, two-gun ly bulged and broken at the back by Monitor. the 68-pounder (8 inch) smooth-bore The consideration of iron-clad vessels especially, and the 100-pounder rifle at involves that of armor, ordnance, pro- 200 yards, — guns that do not greatly jectiles, and naval architecture. injure the best solid 4j-inch plates at the same range. On the contrary, a 124-pounder (10 inch) round-shot, hav- ARMOR. ing about the same penetrating power, Material. In 1861, the British iron- as calculated by the ordinary rule, fired plate committee fired with 68-pound- by Mr. Stevens in 1854, but slightly in- ers at many varieties of iron, cast-steel dented, and did not break at the back, and puddled-steel plates, and combina- a 6§-inch target similarly composed. tions of hard and soft metals. The All the experiments of Mr. Stevens go steel was too brittle, and crumbled, and to show the superiority of laminated the targets were injured in proportion armor. Within a few months, official to their hardness. An obvious con- American experiments have confirmed clusion from all subsequent firing at this theory, although the practice in the thick iron plates was, that, to avoid construction of ships is divided. The cracking on the one hand, and punch- Roanoke's plates are solid; those of ing on the other, wrought-iron armor the Monitor class are laminated. Solid should resemble copper more than steel, plates, generally 4j inches thick and except that it should be elastic, although backed by 18 inches of teak, are exclu- not, necessarily of the highest tensile sively used in Europe. Now the resist- * strength. Copper, however, proved much ance of plates to punching in a machine too soft. The experiments of Mr. E. A. is directly as the sheared area, that is Stevens of Hoboken, with thick plates, to say, as the depth and the diameter confirm this conclusion. But for lam- of the hole. But, the argument is, in PRODUCED BY UNZ.ORG ELECTRONIC REPRODUCTION PROHIBITED Iron-Clad Ships and Heavy Ordnance. [January, this case, and in the case of laminated inch plates backed with wood and set armor, the hole is cylindrical, while in at 38° from the horizon was injured the case of a thick armor-plate it is about one-half as much by round 68- conical, — about the size of the shot, in pounder shot as vertical plates of the front, and very much larger in the rear, same thickness would have been. In — so that the sheared or fractured area 1861, a 3j plate at 45° was more injur- is much greater. Again, forged plates, ed by elongated 100-pounder shot than although made with innumerable welda a 4£ vertical plate, both plates having from scrap which cannot be homogene- the same backing and the weights of ous, are, as compared with rolled plates iron being equal for the same vertical made with few welds from equally good height. When set at practicable an- material, notoriously stronger, because gles, inclined armor does not glance flat- the laminse composing the latter are fronted projectiles. Its greater cost, and not thoroughly welded to each other, especially the waste of room it occasions and they are therefore a series of thin in a ship, are practically considered in plates. On the whole, the facts are not England to be fatal objections. The complete enough to warrant a conclu- result of Mr. Stevens's experiments is, sion. It is probable that the heavy Eng- substantially, that a given thickness of lish machinery produces better-worked iron, measured on the line of fire, offers thick plates than have been tested in about equal resistance to shot, whether America, and that American iron, which it is vertical or inclined. Flat-fronted is well worked in the thin plate used for or punch shot will be glanced by armor laminated armor, is better than English set at about 12° from the horizon. A iron; while the comparatively high ve- hard surface on the armor increases locities of shot used in England are more this effect; and to this end, experi- trying to thin plates, and the compara- ments with Franklinite are in progress. tively heavy shot in America prove most The inconvenience of inclined armor, destructive to solid plates. So that there especially in sea-going vessels, although is as yet no common ground of compari- its weight is better situated than that son. The cost of laminated armor is less of vertical armor, is likely to limit its than half that of solid plates. Thin use generally. plates, breaking joints, and bolted to Fastening Armor. A series of thin or through the backing, form a continu- plates not only strengthen the whole ous girder and add vastly to the strength vessel, but fasten each other. All meth- of a vessel, while solid blocks add no ods of giving continuity to thick plates, such strength, but are a source of strain such as tonguing and grooving, besides and weakness. In the experiments men- being very costly, have proved too weak tioned, there was no wooden backing be- to stand shot, and are generally aban- hind the armor. It is hardly possible, doned. The fastenings must therefore — in fact, it is nowhere urged, — that be stronger, as each plate depends solely elastic wooden backing prevents injury on its own; and the resistance of plates to the armor in any considerable degree. must be decreased, either by more or Indeed, the English experiments of 1861 larger bolt-holes. The working of the prove that a rigid backing of masonry— thick plates of the European vessels in other words, more armor—increas- Warrior and La Gloire, in a sea-way, is es the endurance of the plates struck. an acknowledged defect. There are va- Elastic backing, however, deadens the rious practicable plans of fastening bolts blow upon the structure behind it, and to the backs of plates, and of holding catches the iron splinters ; it is, there- plates between angle-irons, to avoid bor- fore, indispensable in ships. ing them through. It is believed that Vertical and Inclined A rmor. In Eng- plates will ultimately be welded. Boil- land, in 1860, a target composed of 4J- er-joints have been welded rapidly and PRODUCED BY UNZ.ORG ELECTRONIC REPRODUCTION PROHIBITED 1863.] Iron-Glad Ships and Heavy Ordnance. 87 uniformly by means of light furnaces shot which merely penetrate. This is moving along the joint, blowing a jet of not yet sufficiently tested. The late flame upon it, and closely followed by remarkable experiments in England — hammers to close it up. The surfaces do firing 130- and 150-pound Whitworth not oxidize when enveloped in flame, steel shells, holding 3 to 5 pounds of pow- and the weld is likely to be as strong der, from a 7-inch Armstrong gun, with as the solid plate. Large plates prove 23 to 27 pounds of powder, through the stronger than small plates of equally Warrior target, and bursting them in good material. English 4j-inch armor- and beyond the backing — certainly plates are generally 3J- feet wide and show that large calibres are not indis- 12 to 24 feet long. American 4|-inch pensable in fighting iron-clads. A de- plates are from 2 to 3 feet wide and structive blow requires a heavy charge rarely exceed 12 feet in length. Ar- of powder ; which brings us to mor composed of light bars, like that of The Strain and Structure of Guns, the Galena, is very defective, as each and Cartridges. The problem is, 1st, bar, deriving little strength from those to construct a gun which will stand adjacent, offers only the resistance of the heaviest charge; 2d, to reduce the its own small section.