Navies of the world

by Edward W. Very

Stern-posts are now invariably made in single solid forgings, and are plain scarfed to the keel as with the stem. Compartment bulkheads form an element of great transverse strength. There is no fixed rule for their application in war-vessels, but the usual number is seven. Of these, one is placed well forward, called the collision bulkhead, another is far enough aft to just enclose the screw-shaft stuffing-box, two others are respectively forward of the boilers and abaft the engines, and the others divide the remaining space as is best suited. Above the water-line, doors of a sufficient size to render free passage are worked in the bulkheads and are on hinges having clamps by which they may be screwed up water-tight. Below the water-line the doors slide either horizontally or vertically, being worked by gearing on the main-deck. The wing-passages are provided with small sliding doors generally kept closed. The compartments of the double bottom are connected by sluice-valves worked from the main-deck.

These points constitute the main peculiarities of iron ship-building as it is at present carried on. There are constant modifications made in details, many of which are of the greatest importance, but a description of them would be out of place except in a work on iron ship-construction.

Iron Sheathed with Wood.

It has been stated that in no navy (except that of the United States) are there to be found iron ships of the pure construction. When iron ship-building was first introduced in England, two iron sloops were laid down and experiments were carried on with targets representing their sides, to find out the effect of shot upon them. The frames of these vessels were spaced only one foot apart, and it was found that a very serious amount of splintering took place when a shot penetrated. It was also found that for thicknesses beyond half an inch the projectile was broken to pieces on contact. This advantage for iron was, however, soon counterbalanced by the rapid increase of calibre, change to rifled guns and high velocities, and the introduction of steel and chilled projectiles. The great advantages offered by iron construction, however, rendered its introduction an absolute necessity when it became a question of speed. The rapid fouling of bottoms, with its consequent loss of speed, could only be overcome by coppering, and this necessity introduced another and far more serious difficulty, that of galvanic action. The introduction of the system of sheathing iron with wood is due directly to Mr. Grantham, an English builder. The main principles laid down by him were to have widely spaced transverse frames, and on the exterior of the iron skin to work a system of angle-irons which should in themselves bring up the strength of the hull to the standard, making up for the loss by wide spacing. The iron skin having been covered with pitch, a wooden filling was introduced between the angle-irons, wedged solid so as to form a complete wooden casing. Over this was placed a layer of tarred paper, and then the sheathing proper of the ship was fastened by brass screw-bolts to the wooden filling, completely insulating the iron hull. This sheathing could then be coppered. These exterior angle-iron frames, being worked as a support to the inner ones, take, as a rule, an opposite direction. Thus if the main inner frames are transverse, the exterior ones are longitudinal, and vice versa. Grantham’s method is in reality the one shown in the description of the Russian composite system.

The English Admiralty method is somewhat different. Here the sheathing is in two thicknesses, the inner course being tap-bolted to the iron skin, the bolt-heads being sunk well into the planks and covered with pitch. The outer course shifts seams and butts with the inner one and is secured with brass screw-bolts. Over this course comes the copper. The Admiralty system is the one followed in France in the construction of the first and second rate fast cruisers. The difficulties of insulation are not yet solved by any means. Could the sheathing be absolutely excluded from moisture the system would be perfect, but as yet no means have been devised by which the wood can be prevented from becoming wet and thus serving the part of the porous jar in a voltaic cell.

In examining and discussing different systems of construction it is necessary to always keep in mind the great distinctions between composite, iron, and iron sheathed with wood. Those who cry down the wooden construction, in view of the rapid deterioration of the American unarmored fleet, must bear in mind that this fleet was constructed of the worst possible material. In discussing the advantages of the composite system, those of the diagonal system must not be lost sight of. Above all, it must be remembered that the disadvantages of the pure iron construction, as evidenced by English and French target experiments, have never been overcome. The iron and steel sheathed with wood is an amelioration, but as yet it is by no means a satisfactory one. Although England has totally discarded the wood construction, it must be remembered that France holds her own with but a partial introduction of iron and composite in her highest and lowest rates. The subject of constructional development is still in its experimental stage, and to those nations who, unlike Great Britain, cannot depend upon legislative support and sympathy, nothing is more dangerous to the healthy development of an efficient unarmored fleet than a hasty adoption of a new constructional type.

Armored Vessels.

ARCHITECTURAL DEVELOPMENT.

It would be useless to attempt to assemble in chronological order the many propositions that have been submitted to or even entertained by different maritime governments looking towards the building of armored vessels. The first serious attempt made and effectually carried out was by France in 1855, when there were built five floating batteries carrying an armor of five inches, which, although almost totally unmanageable from their bad lines and realizing a speed of but four knots, went into action on the 17th of October in that year and silenced the batteries of Kinburn.

These vessels taught nothing with regard to architectural development, but at the instance of France the English Government built nearly at the same time some vessels quite similar, and the attention which this movement caused led to a consideration of the suggestions of Captain Coles, who, in the same year, sent into action the little cupola vessel Lady Nancy.