Ship stability

“ But it is obvious that all belted or partially belted vessels, in which the belt is carried but a small height above the water for the size of the ship, must run the risk of losing both buoyancy and stability very soon if even moderately inclined in or after battle, seeing that, with a moderate inclination only, the entire armor-belt on the depressed side of the ship must disappear beneath the sea’s surface. ”

“ It will be readily understood that a curve of stability for a [109] given draught of water and position of centre of gravity ceases to be applicable if changes are made in the weight and consequent draught of water of a ship or the position of the centre of gravity, or in both. Now in mercantile steamers, from the extremely light condition in which they are launched to the uncertain loaded condition of their daily service as cargo-carriers, the variation of draught is very considerable, and imports into the subject considerations which do not obtain to any great extent in war ships. ”

“ But ships of the line, to perform their function, must keep together, both when cruising and when on the field of battle, in order to put forth their strength in combination. The innumerable detached services that must be discharged for every great organized force need for a fleet to be done by vessels of inferior strength, yet so strong that they cannot be intercepted or driven off lightly by every whipper-snapper of an armed ship that comes along. ”

“ In fact, the lifetime of an iron or steel hull is not defined to any limit, and if a perfect anti-corrosive and anti-fouling composition can be produced, the limit may be regarded as indefinite.
The foregoing remarks on our new navy apply to unarmored cruisers, a class of ships which supply a want in time of peace, but cannot fulfil the purposes of war. At such a time the armored ship is recognized as indispensable, and there is every reason why the construction of armored vessels should proceed simultaneously with that of the unarmored cruisers. ”

“ On board ship, in a small world of our own, we seem to be contained by the boundaries of the bulwarks, to be sailing beyond the influences of the land and of other ships. The sea is the same we have known for so long. Every item of our ship fitment—the trim arrangement of the decks, the set and rake of mast and funnel, even the furnishings of our cabins—has the power of impressing a stable feeling of custom, normal ship life, safety. It requires an effort of thought to recall that in their homely presence we are endangered. ”

“ While the navy should not be large, it should at all times afford a nucleus for its enlargement upon an emergency. Its power of prompt and extended expansion should be established. It should be sufficiently powerful to assure the navigator that in whatsoever sea he shall sail his ship he is protected by the stars and stripes of his country. ”

“ Longitudinal bullkheads from an inner skin through machinery spaces. Transverse bulkheads extend two decks (20 feet) above water line, the height increasing towards the ends.
Longitudinal Section and Plan of the Imperator
proportion of the passenger-carrying vessels chiefly depend for their revenue.
On the other hand, the main features of warship protection may be so applied to the large merchant ship as to render her as proof against collision with icebergs, derelicts, or with other vessels, as the warship is against the blow of the ram, the mine, or the torpedo. ”

“ The result is, that, in order to lessen these dues individually, our vessels are constructed deep in proportion to breadth, consequently are sluggish sailers, and not nearly so safe and pleasant sea-boats as they otherwise would be—many a ship, especially with light cargo, getting on her beam-ends and foundering, or not standing up under canvass to weather a lee shore. ”

“ The savage sea opens wide their straining seams; the pumps, clatter as they may, are quite unable to cope with the ingress of sea water; and the disheartened crews seek safety in a passing ship at the first opportunity. Thus it happens that many a lumber-laden sailing ship drifts deviously at the will of wind and current, a menace to safe navigation, until her hull is driven into fragments by the combined forces of Æolus and Neptune, or reaches land after a solitary drift of many weary leagues of sea. ”

“ Then came a swift order of "All ships halt!" from the distance-phone, and as we came swiftly to a halt there in the blinding, fleecy masses, motors droning still, we heard the crash of ship on ship behind us in the cloud-bank as the foremost cruisers of the European fleet drove blindly into our own, then halted fearfully themselves, milling confusedly about in fear of further collisions and with neither fleet firing now in the absolute blindness that held each ship. ”

“ A well-conditioned ship should be, in the first instance, strongly built; secondly, swift in sail; thirdly, stout sided; fourthly, her ports ought to be so laid that she may carry out her guns in all weathers; fifthly, she ought to hull well; sixthly, she should stay well when boarding or turning on a wind if required.” He then continues: “It is to be noted that all ships sharp before, not having a long floor, will fall rough into the sea from the billow, and take in water over head and ears; and the same quality of all narrow-quartered ships to sink after the tail. ”

“ This question of stability will have to be carefully watched and studied within the next few years, because there is a tendency at present towards a rapid increase in the proportion of beam to length; and as the draught of water in these large ships is limited, we must be careful that in seeking higher speeds with increased beam we do not get too much stability, and so render the vessels heavy rollers and very uncomfortable as passenger-ships. It is possible the future may see vessels of greater beam than any yet afloat in the merchant service ”

“ Ships are designed for stability when the vessel is operating normally and upright, but also to design for instability in the crisis situation where the vessel is inverted and we want it to rapidly capsize back to the upright condition again. It is also intended that this exploration of the idea will enhance the understanding of the impact of stability considerations on the design of all small craft, and enable stability to be considered at the earliest stages of the design process. ”

“ A few feet from the stem there is a collision bulkhead of extraordinary strength to protect the ship, should she run “bow-on” against any obstacle—a reef, a derelict, or a vessel attempting to cross her path; next, aft of this come three compartments for steerage passengers or cargo; then two compartments for saloon passengers; then four compartments for boilers, coal bunkers, kitchens, and machinery; two more for saloon passengers; one for second-cabin passengers, and two, those farthest aft of all, for steerage passengers or cargo. ”

“ The “seven seas” must be crossed with speed and safety, in the interest of all nations that have a mile of sea coast; but the Anglo-Saxon race, as it has contributed—from [vi] either side of the Atlantic—most largely to the mechanical and structural development of the steam-ship, now depends most vitally upon the organisation of its naval and transportation systems. Napoleon said that the strength of an army lay in its feet; no less true is it that the strength of our Empire lies in her ships. ”

“ While endeavoring to devise intricate and ingenious mechanisms to sink the submersible, we overlook the simplest safeguards for our merchant vessels. To-day, the construction of the average ship is designed to conform to the insurance requirements. This does not mean in any way that the ship is so constructed as to be truly safe. Thousands of vessels that are plying the seas to-day are equipped with bulkheads that are [xlix] absolutely useless because they do not extend high enough to prevent the water from running from one part of the ship to another when the ship is partially submerged. ”

“ The power to observe accurately the sun, moon, and planets, so as to fix a vessel's actual position when far out of sight of land, enabling long voyages to be safely made; the marvellous improvements in ship-building, which shortened passages by sailing vessels, and vastly reduced freights even before steam gave an independent force to the carrier — each and all were done by small advances, which together contributed to the general movement of mankind.... Each owes all to the others. ”

“ Now, here is a practice which should be made compulsory in the construction of all passenger-carrying steamships. Only by filling a compartment with water is it possible to determine whether that compartment is watertight. To send an important ship to sea without testing her bulkheads is an invitation to disaster. ”

“ So accustomed are we in these days to peace and plenty that we have need to remind ourselves constantly that there were no trade routes kept open, no policing of the seas, no international treaties nor diplomatic relations to prevent a peaceful merchant ship from disappearing altogether on the high seas, or staggering into port with the loss of her cargo and most of her crew. ”

“ Build his ships as he may, man them as he will, map out the ocean highways never so precisely, and mark as he may with flaring beacons each danger point, yet in some moment of wrath the winds and the waves will rise unconquerable and sweep all the barriers, and all the edifices erected by man out of their path. To-day all civilized governments join in devices and expedients for the protection and safeguard of the mariner. Steel vessels are made unsinkable with water-tight compartments, and officially marked with a Plimsoll load line beneath which they must not be submerged. ”

“ The object of stabilizing a ship is not merely to cater to the comfort of passengers who are subject to seasickness, but to save wear and tear on the vessel and also to economize time and fuel. An unstabilized ship riding a heavy sea pursues a very sinuous course; in other words, it must travel farther than it would in smooth water. The rudder must constantly be turned to keep the ship on its course, and this acts as a drag on the progress of the ship, slowing it down and wasting the power of the engine. ”

“ Add to this the fact that other men as gunners were required in great numbers—for practically every British merchant ship became defensively armed—and one can see how important to our island nation and the overseas Empire is the existence of peace-time shipping, with all that it connotes—steamships, liners, tramps, colliers, trawlers, drifters, yachts, fishing smacks, it does not matter. From all these, and from the few full-rigged ships and sailing coasters, we had to draw our supplies of personnel, and it still takes longer to train a man into a sailor than into a military unit. ”

“ To complete the representation of stability as it should be known for merchant ships, it is now recognised that curves showing the stability at every possible draught of water and for different positions of centre of gravity should be constructed. ”

“ It is easy to see that being top-heavy something must be done to give the ship support before the shores on either side can be taken away, and it is equally clear that these latter must be removed before she can slide down to the water. ”

“ Our ships are of iron; they are propelled through the calm sea by an irresistible power faster than a gale of wind would drive them; they are of proportions so colossal that many of them could sling the “tall schippes” of our forefathers over their sides, and stow them on skids as they stow their boats; and yet just the same sort of sufferings are endured now by mariners as were experienced by them in the days when a vessel of thirty tons was reckoned big enough not only to seek the North-West Passage but to hunt the unnavigated oceans after continents. ”

“ But its efficiency, such as it was, was not likely to be impaired. It had no furnace to feed, no machinery to watch, only the rude wants of rude men to supply, and rough oars to replace. A sailing ship, dependent upon the uncertain breeze, liable to be driven from her course by storms or to be detained by calms, gives no such impression of power as a steamship, mistress of her own movements, scorning the control of the elements, and keeping straight on to her destination in storm and calm alike. But in some respects the weak is strong. ”

“ Independently of the security attained by the perfect division of the ship into really water-tight compartments of a sufficient number, so that the entire filling of one or even two of them will not endanger the buoyancy of the whole, the chances of any such damage as can cause the filling of one of them are greatly diminished by the mode adopted in the construction of the ship’s bottom. ”

“ Some men, he says, endeavour to make ships perform impossibilities, as, for instance, backing their craft astern to clear a single anchor when the wind is right aft against the windward tide; or trying to back a ship with sails so set as to prevent her shooting ahead towards a danger when laid-to; or driving broadside with the wind against tide, not knowing that a ship driving on either tack will always shoot forward the way her head lies, in spite of any sail set aback. ”

“ For a while at least the startling transitions of the last decade are not to be looked for, and we can only expect greater power in greater ships on the lines already established. It is well these great transitions should not come too frequently; the ship-owner should be allowed a little breathing time, and should not be continually oppressed by a nightmare of obsolete ships. We may safely say, too, that our own country will have a greater share in shipbuilding than in past years. ”