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CHAPTER XVI

HULL STRENGTH
 

16-1. Foreword. Cruisers, destroyers and auxiliaries have been lost by breaking in two as a result of impaired structural strength. After serious underwater explosion, considerable buckling and tearing of structure takes place (see Chapt. XV). When the main structural members are ruptured or wrinkled the vessel may break up in a seaway. The importance of these facts is obvious. Accordingly, the ensuing discussion is concerned with strength features built into a ship and how they are affected when the ship is damaged.

16-2. Beam theory. An elementary knowledge of structural theory is necessary to our proposed study.

If a simple beam is supported at its two ends and various vertical loads are applied over the center of the span, the beam will bend (see fig. 16-1). As the beam bends the upper section of the beam will compress and the lower part will stretch. Somewhere between the top and bottom of the beam there will be a section which will neither be in compression nor tension; that part we term the neutral axis. The greatest stresses in tension and compression occur about half way between the supports, or near the middle of the beam's length. In the case of an I-beam, the greater mass of structural material is placed in the upper and lower flanges to resist the compression and tension. Very little material is placed in the web which is near the neutral axis because the web takes little of the tension or compression stresses; however, it does take care of shearing stresses. The latter are sizeable near the supports.

  16-3. Ship in seaway. A ship in a seaway can be considered similar to a beam with supports and distributed loads. The supports are buoyant forces of the water and the loads are the weight of the ship's structure and material within, such as fuel, water, ammunition, etc. The worst condition of loading and support for a ship occurs when it heads into or away from the sea, with waves approximately as long as the length of the ship. A quartering sea can also produce this condition if the ship's bow and stern either are in troughs or crests at the same time (see fig. 16-2 and fig. 16-3).

16-4. Sagging stresses. The ship shown in fig. 16-2 is supported by waves, with the bow and stern riding crests and the midship region in the trough. This ship will bend with compression at the top and tension at the bottom. The ship is said to be sagging, and in this condition the weather deck tends to buckle due to compressive stress, while the bottom plating tends to stretch due to tensile stress.

16-5. Hogging stresses. When the ship shown in figure 16-2 advances half a wave length, so that the crest is at midship and the bow and stern are over troughs, as in figure 16-3, the stresses are reversed. The weather deck is in tension and the bottom plating is in compression, and the ship is said to be hogging.

16-6. Ship girder. In its resistance to hogging and sagging stresses, the main body of the ship can be likened to a long beam, resembling a box girder. Therefore, it is often referred to as the hull girder or

Figure 16-1. Diagram to show the effect of load placed over the center of a beam, and cross section of an I-beam.
Figure 16-1. Diagram to show the effect of load placed over the center of a beam, and cross section of an I-beam.
 

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ship girder. Its principal strength members are at the top and bottom, where the greatest stresses occur, and these top and bottom flanges are joined together by side webs. The top flange consists of the main deck plating, especially the deck stringers, the sheer

Figure 16-2. Diagram to show tension and compression when a ship is in a sagging condition.
Figure 16-2. Diagram to show tension and compression when a ship is in a sagging condition.

Figure 16-3. Diagram to show tension and compression when a ship is in a hogging condition.
Figure 16-3. Diagram to show tension and compression when a ship is in a hogging condition.

strakes of the side plating, and any continuous deck girders. The bottom flange consists of the bottom plating, including the flat keel, garboard strakes, "B" strakes, bilge strakes, etc., plus the vertical keel and any continuous longitudinal girders in way of the bottom. If an inner bottom is fitted, it also contributes to the lower flange. The side webs of the ship girder are composed of the side plating, supported to some extent by any long continuous fore-and-aft bulkheads. These side webs take up the shearing stresses which usually are greatest at the quarter-length points of the ship.

The major strength members of a destroyer hull girder are indicated in figure 16-4.

16-7. Transverse framing. Transverse frames and continuous transverse bulkheads contribute greatly to the strength of the hull girder by tying its various members together, stiffening them, and preventing

  buckling when under compression. The stanchions throughout the ship also serve to brace and stiffen the hull girder and tend to hold deck plating in position. On auxiliaries the transverses are major strength members. The longitudinal strength of a merchant-type vessel is taken up by the plating of the shell and decks, which need stiffeners of considerable size to prevent buckling.

16-8. Plating in compression. Both the top and bottom flanges of the ship girder must take compressive stresses as the ship alternately sags and hogs. Unstiffened plating can take very little compression. A plate will buckle in compression at a small fraction of the load that it can withstand in tension. Therefore, the plating making up both the top and bottom flanges of the ship girder is stiffened by having shapes welded or riveted to it. The stiffening members include shapes such as I-beams, tees, channels, angles, and the like. They may run either longitudinally or transversely. The best system is to have the stiffeners run both ways to form a cellular web structure.

16-9. The strength deck. The term strength deck is generally applied to the deck which acts as the top flange of the hull girder. It is the highest continuous deck, usually the main or weather deck. On a merchant-type or destroyer-type ship, where the main deck is the only continuous high deck, it is the only strength deck.

16-10. Lower strength decks. If the second (or third) deck is continuously and integrally built into the vessel's structure, it will take some of the stress, although not as great a share as the main deck. These stresses are considered in the design of lower continuous decks, and the function of such decks should not be overlooked after severe structural damage. If the main deck is destroyed, the second deck becomes the strength deck, and will actually be subjected to higher unit stresses than the main deck was for a given hogging or sagging condition. (A similar situation arises if the bottom is destroyed. Intensified stresses are placed upon the next higher structure that takes the load.)

16-11. Upper decks and superstructure. The decks above the main deck usually are not strength decks, and do not contribute to the strength of the hull girder. These upper decks must be interrupted at intervals down the length of the ship by expansion joints. Otherwise they will tend to take up some of the load of the strength deck and probably will fail. Cracking and buckling of deck houses and superstructure results

 

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Figure 16-4. Diagram to show major strength members of a destroyer's hull girder.
Figure 16-4. Diagram to show major strength members of a destroyer's hull girder.
 
if this principle is neglected. The flight decks of most carriers are not strength decks. They are, therefore, interrupted with expansion joints. These upper decks and houses carry the gravity loads above them and on them down to the hull of the ship.

16-12. Local strength. The structure of a ship is called upon to resist three types of local stresses, in addition to those of the ship girder. They are as follows:

1. Hydrostatic pressures.
2. Solid weight loads.
3. Dynamic loading.

16-13. Hydrostatic pressures. The pressure on a submerged body is proportional to its depth in the liquid, and acts at right angles to the surface of the object. Each square foot of shell surface is subject to a pressure of 1/35 of a ton for every foot of depth of liquid (or 64 pounds per foot of depth). The water pressure is applied to the shell and transmitted through the frames, decks and bulkheads. Although the horizontal pressures of water exerted on each side of the ship cancel each other, the force still acts upon the hull. The decks, transverse framing, and bulkheads prevent lateral crushing of the hull by the horizontal pressure of the water.

16-14. Pressures due to flooding. If the shell of the ship is ruptured and flooding follows, the hydrostatic pressures formerly exerted on the shell plating

  are now placed upon the bulkheads of the flooded compartments. This is why bulkheads require stiffeners to prevent them from bulging, and why bulkheads that are farther below the waterline are thicker, require more stiffening, and are given higher test pressures. Flooding water will exert a considerable upward pressure against the overhead deck of a flooded compartment if the deck in question is some distance below the waterline. This pressure will be undiminished if there is an air bubble trapped above the flooding water. Therefore, some thought must be given to the problem of shoring weakened decks downward as well as upward, and to the consequences of opening a hatch, scuttle, or manhole over a flooded compartment. Hydrostatic pressures also are imposed upon bulkheads and decks by the contents of intact fuel and water tanks.

16-15. Solid weight loads. The weight of every object on the ship, solid or liquid, rests at some point on a deck (or bulkhead). Included are fixed weights such as guns, barbettes, boilers, turbines, and steel of the structure itself. The crew and the consumables aboard ship also must be provided for. The load from these various items must be supported and transmitted to the shell of the ship, where it is resisted by the hydrostatic pressure.

To prevent a concentration and possible excessive stress, large loads such as guns, turrets, barbettes, and handling equipment are distributed over a wide area by means of structural bulkheads and girders.

 

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16-16. Bottom framing. The bottom framing, in which floors and keel are integrated, forms a rigid cellular construction. It is to this bottom framing that loads of great magnitude are brought, by stanchions, or in the case of temporary loads, by shoring. It is sometimes necessary to shore all the way down from the main deck in cases of unusual topside cargo. Other heavy loads, like the ship's main propulsion machinery, are bolted to foundations which are built directly on top of the bottom framing.

16-17. Dynamic loading. In addition to local stresses due to the above loads which are static in nature, the various members of a ship's structure may be subjected to dynamic loads of unpredictable intensity and duration. Pitching and pounding, wind pressures, collisions, the recoil of gunfire, turning forces, inertia due to changes of motion, and blast effect from the bursting of enemy shells, bombs, or torpedoes, all impose dynamic stresses of varying magnitude and time on the inner and outer portions of the ship. If plates are turned out from a torpedo hit, the resulting scoop action may build up a greater pressure in the flooded compartment than would be caused by the hydrostatic head alone. It is difficult to estimate the size of structure necessary to withstand some of these impulses, and they are allowed for on the basis of experience, plus liberal safety actors in designing for static loads plus some dynamic toad. For this reason there is a considerable excess of strength built into Naval ships.

16-18. Panning. Panting is the term applied to the action of a section of plating when it pulsates in and out under the influence of waves or dynamic impulses. To overcome this tendency additional members are provided in the region of dynamic loads. The panting frames or breast plates in the fore peak are an example. A tendency of plating to pant can be overcome temporarily by shoring.

16-19. Underwater explosion damage-large ships. Underwater explosion damage impairs the strength of a ship in two ways. Structural strength members are damaged by being ruptured or buckled. Flooding of compartments also takes place, thus increasing the loading on the previously damaged ship girder (see Chapt. XV).

A given underwater explosion frequently opens a bigger hole in the shell of a large vessel. The large ship, on the other hand, is better able than a small one to withstand the destruction and loss of structure, inasmuch as only a small proportion of the main structural members will be damaged. These main structural

  shapes and plates are also considerably heavier and are more numerous than in the case of a small ship. The chances of serious structural failure on a large ship due to a given underwater explosion or bomb hit are small.

16-20. Underwater explosion damage-small ships. In the case of auxiliaries, cruisers, destroyers and other small ships, underwater explosions in the midship region have ruptured a large proportion of the principal strength members. Following extensive damage to the major strength members ships of this type may break up, unless the strength of fractured members can be replaced before the vessel is subjected to the action of heavy seas.

If the structural damage is severe, partial restoration of the main strength members may be necessary before proceeding far (and then only at reduced speeds) even with a calm sea and when destination is not too far away. Such repairs if not practicable underway can frequently be accomplished at advanced bases.

16-21. Explosions at bow or stern of small ships. Underwater explosions at either the bow or stern of a slender, small ship, such as a destroyer or destroyer escort, usually cause local destruction which is intense, but neither widespread nor particularly serious. However, the effect of such an explosion is to shake this type of vessel like a whip. Waves of flexural vibration pass down the length of the hull, producing stresses like those in hogging and sagging but of shorter duration and of greater intensity. The result, although not usually obvious, can be serious. It consists of compression failures in the midship region, evident in wrinkled deck plating, wrinkled shell plating, buckled longitudinal girders, and either buckling, laying over of flanges, wrinkling, or other failure of any of the members in the waist of the ship that contribute to her longitudinal strength. Such failures may be hidden from sight below the waterline, under boilers, behind stores and equipment, or beneath the surface of subsequent leakage water. It is a feature of compression members that once buckled they can never again develop even a fraction of their original strength. Attempted straightening is of no avail; the only effective measures are replacement or duplication.

16-22. Flooding and the ship girder. The load on the ship girder is increased by the entrance of damage water. The increase in stresses due to this augmented load depends both on the amount and on the location of the flooding.

 

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Damage and consequent flooding in the middle length increases sagging stresses. This means increased tension at the bottom and compression at the top. Measures to correct trim caused by damage in the middle length should be of a nature to reduce sagging stresses. This may be accomplished by any or all of three methods, as follows:

1. Pump liquid in the midship region overboard (either damage water or liquid in intact tanks; consider stability before pumping intact tanks overboard).

2. Move liquids from midship region to ends of the ship.

3. Counterflood the high end of the ship.

Flooding at the ends after damage produces trim and increases hogging stresses. This will increase the tension at the top and compression at the bottom. In this condition the correction of trim (which at the same time would reduce hogging stresses) is as follows:

1. Shift liquids toward midships.

2. Pump liquid near damage overboard (damage water or liquid in intact tanks; check stability before pumping intact tanks).

When a ship is severely damaged so that bow or stern is likely to break off, the correction of trim by other than methods prescribed above may cause loss of the bow or the stern.

16-23. Repairs. Repairs to main strength members (top or bottom) must take into account both tension and compression stresses. For tension it is necessary to provide sufficient cross-sectional area of material, whether this be plating or shapes. Compressive stresses require more cross-sectional area and in the form of either shapes, or plates with stiffeners. Stiffeners on plating should run parallel to the other intact

  stiffeners in the vicinity. As many as possible should be tied into intact stiffeners. In placing stiffeners on plating they should be spaced not more than 100 times the plating thickness, or stiffener thickness, whichever is smaller. If possible, this distance should be reduced to about 60 times the smaller thickness. Compression failures (buckling or wrinkling) in the midship region are just as dangerous as complete rupture of structure. A member which has failed in compression by buckling retains only a very small part of its former strength. Wrinkled shell and deck plating must be replaced, not straightened, for the restoration of strength. Buckled or ruptured longitudinal beams must be replaced with shapes of greater cross-sectional area. The new shapes should be welded to the intact sections of the original longitudinals. Lengths of these new members should be from 20 to 30 feet; they may have to be provided by welding short pieces together. The material for these repairs can, if necessary, come from the structure of the upper decks and superstructure which do not add to the structural strength of the ship girder. In any case, emergency repairs must afford a considerable lap at each end where new material is anchored.

Wrinkled bulkheads and stanchions divert their share of load to some other part of the ship. To prevent further failures by the overstressing of these other parts of the ship, the overhead which the damaged supports carried should be shored. Ruptured side plating near the quarter length points should be repaired, to carry the heavy shearing stresses.

16-24. Summary. After damage, both time and material will be limited. An understanding of what members carry the major part of the stress will permit application of available energy and efforts toward restoration of the principal strength members, and the reduction of stresses in the most effective manner.

 

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CHAPTER XVII

ESTIMATE OF THE DAMAGED SHIP'S SITUATION
 

17-1. An intelligent estimate as a basis for action after damage.

"ASIDE FROM CASES INVOLVING LOSS FROM FIRES OR STRUCTURAL FAILURES, WAR EXPERIENCE HAS DEMONSTRATED THAT NO MATTER WHAT THE LIST OR TRIM, IF THE SHIP DOES NOT SINK WITHIN A VERY FEW MINUTES AFTER DAMAGE, THERE IS A GOOD CHANCE OF SAVING HER BY PROPER DAMAGE-CONTROL MEASURES. THE CASES OF LOSS BY BODILY SINKAGE, PLUNGING, OR CAPSIZING SEVERAL HOURS AFTER DAMAGE HAVE BEEN ENTIRELY ATTRIBUTABLE TO PROGRESSIVE FLOODING."

In order to make the most of these chances properand prompt measures are necessary. The need foran intelligent estimate as a basis for action is obvious.Such an estimate will involve a consideration of fourmajor factors, as follows:

1. Ability to keep the ship afloat.
2. Ability to control and extinguish fires.
3. Ability to stay in action or repel attack.
4. Ability to reach a safe haven.

17-2. Ability to keep the ship afloat. The following factors have an important bearing upon the ship's ability to stay afloat:

1. Whether or not flooding is progressing.
2. Effectiveness of immediate corrective measures.
3. Transverse stability.
4. Reserve buoyancy.
5. Longitudinal stability.
6. Structural strength.

17-3. Determination of whether flooding is progressing. The first step to be taken is to determine whether or not flooding is progressing. This can only be. done by a careful survey, including observations to determine the rate of increase of list, trim, and bodily sinkage. Repair parties should be trained in the rapid collection of information on the extent of flooding, and in the making of prompt, accurate reports back to damage-control station.

17-4. Effectiveness of immediate corrective

  measures. Other steps including the plugging and patching of holes, and the removal of damage water with the available capacity of undamaged pumping and drainage equipment. The presence of fires may, of course, hinder parties to such an extent that it becomes impossible to establish flooding boundaries, or rid the ship of the water. In other cases immediate corrective measures may be largely or wholly effective.

17-5. Transverse stability after damage. Except in the case of ships with torpedo-protection systems, a substantial underwater explosion usually results in the entrance of a great mass of water with extensive free surface, the combined result of which is a reduction of stability. The seriousness of stability loss can be gauged by the extent of the free surface, and by the behavior of the ship with respect to list and tenderness. List, or capsizing in the ultimate case, is due to negative GM, or unsymmetrical flooding, or a combination of both. Whatever the cause, list is undesirable. List acts to reduce stability, as well as to make it more difficult to fight the ship.

In the case of battleships and large aircraft carriers high original GM practically assures positive GM after damage. List may result from flooding of voids in the torpedo-defense system. One torpedo hit may cause a list as large as 10°.

Other ships may develop very small, or even negative GM. Negative GM is rare if liquid ballasting instructions are followed, but the possibility must not be overlooked after damage. The following facts should be given particular attention:

1. GM usually is positive if flooding is limited to one main compartment.

2. In the case of cruisers, destroyers, and similar types negative GM may result if more than two main engineering compartments are partially flooded, or if there is extensive partial flooding in wide compartments on decks near the waterline. In these ships loginess or extreme tenderness is a danger sign, whether accompanied by list or not. (A logy ship has an extremely long or indeterminate period of roll.)

 

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Figure 17-A. In this case wooden plugs, mattresses and pillows were shored in place to keep the sea out.
Figure 17-A. In this case wooden plugs, mattresses and pillows were shored in place to keep the sea out.

 

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3. Escort carriers, large auxiliaries, and similar types may develop negative GM if two or more main compartments are partially flooded, or if there is extensive partial flooding high in the ship. Loginess or extreme tenderness is a danger sign when in combination with considerable list. If there is little or no list and the ship is logy, stability characteristics probably will be satisfactory if remaining freeboard is large.

4. Calculation of GM by timing the period of roll after damage is not reliable. In a seaway or after damage there is no definite relationship between GM and the period of roll.

5. An enlarged copy of the flooding effect diagram in damage-control headquarters will facilitate taking proper action. If the flooded areas are marked on the diagram, the damage control officer will have a visual picture of the extent of flooding. In addition, as explained in Chapter IX, he can read off the list that would result from filling various off-center spaces with the ship intact (the values of list on the diagram are calculated for a certain displacement and intact GM).

6. If the flooding is unsymmetrical, it is safe to assume that GM is positive when the list is not out of all proportion with the flooding effect diagram.

7. If the flooding is known to be symmetrical and there is an appreciable list, the situation will be definitely identified as one of negative GM. If the list is small, the ship will loll (roll with a slow, "undecided" motion) from side to side under the influence of a small disturbing force such as waves, weight movements, or rudder forces. If the list is large, the lolling tendency may be obscured by lack of sufficient disturbing force; and the ship will not even feel logy.

8. If the flooding is unsymmetrical and if there is extensive free surface, negative GM should be suspected when the list is out of all proportion to that indicated by the flooding effect diagram. The ship may not be logy or extremely tender if the list is large.

9. In order to visualize the dynamic stability still remaining after off-center flooding has caused the ship to list, refer to figure 17-1. In this figure we have a static stability curve for the intact ship, the angle of maximum righting arm being 44°. Superimposed on this is the inclining-moment curve due to moving a weight off-center.

  In this example the angle of permanent list, 22°, is equal to one-half the angle at which the maximum righting arm occurs on the intact stability curve. The shaded area represents the residual dynamic stability. It should be noted that this residual dynamic stability is much less than half the original total dynamic stability. In addition, if the list had been due to off-center flooding, the combined effects of added weight, free surface, and free communication would normally have resulted in a smaller stability curve than the original intact one. The residual dynamic stability due to flooding, therefore, would be even less than that resulting from moving a weight off center to produce an equal permanent list.

17-6. Reserve buoyancy after damage. Battleships and large aircraft carriers have great resistance to above-water damage due to their construction. Armored sides and decks, in conjunction with minute subdivision, restrict the extent of damage to reserve buoyancy resulting from any single hit. Although large carriers have relatively light armor, subdivision between hangar deck and waterline is minute, with accompanying beneficial effect on damage resistance. Subdivision will limit the extent and severity of any progressive flooding.

Underwater damage to these larger ships is likely to be extensive as a result of the heavy explosive charges used. Flooding will be restricted by good subdivision and watertight integrity. Vital areas should not be flooded, but may be. In the case of older battleships, loss of reserve buoyancy may be a deciding factor after several underwater hits.

Ships other than battleships and carriers are likely to have reserve buoyancy seriously impaired as a result of direct hits by bombs and shell fire, or due to near miss bombs. Within the ship, decks and bulkheads will be pierced by fragment holes, and closures such as doors and hatches may be blown open by blast. If the ship's side above the waterline is holed, some flooding may take place as the ship rolls. Reserve buoyancy as well as other stability characteristics will suffer. A heavy underwater explosion will result in the entrance of a great mass of water. Flooding will be limited by subdivision, dependent upon the type and complexity of the ship.

In any case the relative amount of freeboard remaining after damage will be a good indication of the residual reserve buoyancy. This assumes, of course, that repair parties are successfully patching and

 

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Figure 17-1.
Figure 17-1.
 
plugging holes, that opened closures are being forced back into place, and that weakened flooding boundaries can be successfully shored.

17-7. Longitudinal stability after damage. The freeboard remaining at the ends of the ship may be used as a measure of the residual longitudinal stability. Trim is not apt to be fatal unless the sea is washing over the weather deck. In fact, ships have steamed long distances with their sterns submerged.

17-8. Structural strength. Large size and presence of heavy plating, bulkheads, decks, and framing permits battleships and large carriers to take a considerable number of hits without danger of structural failure. On other ships underwater explosions in the midship region have ruptured principal strength members, causing some losses due to breaking in two. Destroyers have been prone to this casualty after midship torpedo hits. Explosions at the ends have broken off the bow or stern, in addition to causing compression failures in the midship region due to flexural vibration. Flooding in the middle length increases sagging stresses, while flooding at the ends increases hogging stresses. If the ship does not break in two immediately, a prompt, careful examination should be made of the principal strength members (main deck, stringer plate, sheer strake, bilge strake, and keel). Shoring of decks and bulkheads may be beneficial if stanchions have been disrupted.

17-9. The ability to control and extinguish fires. Explosions, often are followed by fires which hinder

  corrective measures employed to keep the ship afloat. Also, such fires may lead to gasoline or magazine explosions. Damaged fire-fighting equipment or ruptured fire mains may make fire fighting exceedingly difficult. Ships were lost early in this war because of such reasons. Subsequent development of firefighting methods, material, and training has resulted in far better potential control.

17-10. The ability to stay in action or repel attack. The ability to stay in action or repel attack depends on a number of factors, including the following:

1. The ability to stay afloat.

2. The ability to control and extinguish fires.

3. List and trim. These may be so affected that successful gunnery and aircraft operations are not possible.

4. Restoration of vital systems and services, Loss of power arid damage to vital equipment may make accurate gunfire impossible.

5. Mobility and maneuverability. This includes speed available, fuel remaining in intact tanks, possible use of propellers to steer if steering gear is damaged, and the state of communications for ship control.

6. Present weather and weather forecast. In her damaged condition the ship may have to avoid heavy weather in order to keep afloat.

7. Tactical situation. Further action may be forced on the ship by the enemy, the ship may be needed to bolster depleted forces, or it may be

 

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permitted to leave for an advanced repair base, depending on the tactical situation.

17-11. The ability to seek a safe haven. If the ship is unable to remain in action or if the tactical situation permits it to leave, the next problem to be faced is whether or not it can reach a safe haven. This will depend upon:

1. The ability to stay afloat.

2. The ability to control and extinguish fires.

3. The course and distance to the nearest haven.

4. Possibility of beaching. This should always be considered when the ship would otherwise be lost by progressive flooding, structural failure, or uncontrollable fires. There have been numerous cases wherein ships that were deliberately beached to save them were eventually repaired and put back in service.

5. Present weather and weather forecast.

6. Towing vessel. If the ship has lost mobility and maneuverability, it may still be possible to save her by towing. This assumes that a towing vessel is available.

7. Tactical situation. The tactical situation may be such that efforts to save the ship would endanger not only the men aboard her but also endanger rescue vessels standing by. This may well be true in submarine waters, or when enemy aircraft are near, based either on carriers or ashore.

  The decision with respect to such matters rests with the OTC.

8. Seamanship to safeguard impaired structural strength. If the ship is in danger of breaking up, maneuverability must be such as to permit avoiding head seas. Likewise, towing operations will have to be conducted on the same basis.

17-12. Function of a salvage party. If, after all efforts, it appears that a damaged ship will not remain afloat, the personnel not required in the salvage party should abandon first. The salvage party should remain on board to continue their efforts to keep the ship afloat as long as a vestige of hope remains. The salvage detail will be under the supervision of the damage control officer and the engineer officer, and can be composed of all personnel in repair parties (including engineering). A certain number of men in the gunnery department should be retained to man available antiaircraft and secondary battery guns.

17-13. Making a decision. The advice that the damage control officer gives to the Commanding Officer should be based on a careful consideration of all of the factors discussed in the preceding pages. It should be understood that conditions with respect to most items will not remain static. Revised estimates are required as the situation improves or becomes worse.

 

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CHAPTER XVIII

CORRECTIVE MEASURES AVAILABLE
 

18-1. The basis for analysis. Certain corrective measures are undertaken immediately in all cases of damage. These include emergency measures to halt progressive flooding, to control and extinguish fires, and to restore vital functions. The choice of others will be based upon the estimate of the situation, and depend upon both the type of ship and the type of damage. Unless corrective steps are selected to suit the individual case, matters may be made worse rather than better. Proper action taken promptly may mean the difference between saving the ship and her crew and losing them. Therefore, the damage control officer must have a thorough understanding of the effects of the various available corrective measures on transverse stability, reserve buoyancy, longitudinal stability, and hull strength.

18-2. Types of corrective measures available for restoring seaworthiness. Corrective measures available for restoring seaworthiness include the following:

1. Determination and establishment of flooding boundaries.

2. Suppression of free surface (including removal of damage water).

3. Weight removals (including removal of damage water).

4. Weight transfers (usually transfers of liquids).

5. Weight additions.

6. Restoration of vital functions (including power, mobility and maneuverability).

18-3. Determination and establishment of flooding boundaries. Immediately after being hit, steps should be taken to determine and establish flooding boundaries. This is the process of selecting and making tight the boundaries at which the stand to arrest and confine the flooding will be made. Adjacent to the spaces which flood almost immediately after damage there are apt to be a number of spaces which will flood more or less slowly. Considering the pumping facilities, the ability to plug leaks, and the importance and size of the compartments concerned, it may be deemed inadvisable to deal with all of them

  immediately. Minor leakage will be unimportant if it can be held under control. The boundaries chosen should be as near the damage as possible, but the first consideration is to locate them so that a successful effort to limit the flooding can be made.

Compartments near the damage must not be opened up for inspection until it is certain that there is no water against the opposite side of the closure. Investigate the presence of flooding by use of sounding tubes, by trying air-test fittings, or even by drilling small holes, - not by opening doors, manholes, or other large closures. When using sounding tubes, etc., it must be kept in mind that the escape of air is an indication of partial flooding. Release of the air bubble may result in complete flooding of a partially flooded compartment.

In addition to the foregoing, a number of other factors should be considered. If the ship is listing, inspections made along the high side are less hazardous than those made along the low side, but are not so apt to reveal danger spots. Activity carried on in the vicinity of the damage should not be allowed to result in doors and hatches being left open unnecessarily. Plugging and patching fragment holes must follow closely behind the inspections. It must be remembered that serious leaks may exist through channels that are not readily detected; among these possibilities are the following:

1. Piping systems having openings in spaces remote from the damage. Drains of all types should be under suspicion.

2. Piping systems under pressure, such as the fire main, may be ruptured.

3. Ventilation ducts. Closures should be inspected.

4. Electric cables, through which water may pass to points distant from the damage.

5. Cable stuffing boxes.

6. Leaks near the bottom of spaces such as open drains, and leaks at bounding angles which may soon be covered by the flooding, making their detection difficult.

 

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Bulkheads subjected to water pressure on one side must be closely watched and shored if necessary. Experience in the present war has shown that welded bulkheads, unless actually damaged by the explosion, will take appreciable deflections, such as may be expected with the greatest amount of flooding on one side, without danger of rupture or serious leakage. In the case of riveted bulkheads it may be necessary to resort to shoring if the bulkhead deflection appears excessive and riveted joints begin to leak seriously. Shoring may also be necessary to support riveted decks, doors, and hatches. The load on the bulkheads may be increased when the ship has way on, due to the dynamic pressure of the water. This is more apt to be serious when the ship has lost her bow, or when a side tank is open with the side flared out, acting as a scoop.

A second line of defense behind the selected flooding boundaries should be designated, and prepared for establishment in case the original boundaries fail.

18-4. Suppression of free surface. The most effective step is to rid the ship of as much of the flooding water as possible. The means by which this may be accomplished are discussed in Chapter XXIX, and include:

1. Use of ship's drainage systems.

2. Use of portable submersible pumps or gasoline handy billies.

3. Draining into engineering spaces below.

4. Jury-rig suctions to ship's drainage systems.

5. Bucket brigades.

The effects of such removal on seaworthiness are as follows:

1. Improves GM and stability characteristics by removal of free surface.

2. Improves reserve buoyancy.

3. If flooding is high, improves GM and stability characteristics by removal of high added weight.

4. Improves stability characteristics by removal of list and trim.

5. Improves GM and stability characteristics by increasing freeboard.

6. The improvement is greater for spaces wide in athwartship direction, or when the space is high in the ship.

7. Reduces sagging stresses if flooding was in the middle length.

8. Reduces hogging stresses if flooding was at the ends.

Another way of suppressing free surface is to press full wide slack double-bottom tanks (intact) from higher wing tanks. This should be done symmetrically

  with respect to the ship's fore-and-aft centerline to prevent adding more weight on one side than the other. Such action:

1. Improves GM and stability characteristics due to suppression of free surface.

2. Improves GM and stability characteristics due to lowering of weight within the ship. The tanks from which liquid is to be taken should be selected with care, in view of the danger of additional free surface during the transfer. In cases wherein the stability after damage is critical, and when flooding in large compartments has been retarded a few feet below the overhead, it may be advantageous to permit solid flooding to the overhead. This, of course, requires that there be adequate reserve buoyancy.

18-5. Weight removals. The restoration of seaworthiness through removal of weight from the ship may be accomplished either by throwing solid material overboard or by pumping liquids overside from intact tanks and damaged compartments. The primary objective of such efforts usually is either to improve GM or to correct off-center weight. Important secondary effects usually are evident in the case of trim, reserve buoyancy, and stresses in the ship girder. If the primary objective is the improvement of a critically reduced GM, the methods resorted to are (1) suppression of free surface (which has already been discussed in Article 8-4), and (2) jettisoning of topside weights.

Jettisoning topside weights involves casting loose and dropping overside such items as boats, anchors, loading machines, ready lockers, fire-control gear, depth charge and torpedo equipment, superstructure, guns, and gun mounts. Such weights usually are jettisoned from the centerline and/or from the port and starboard side symmetrically, to avoid creating off-center weight. The symmetrical removal of high weights lowers the center of gravity, thus improving GM and stability characteristics. If damage has rendered GM negative, jettisoning topside weight is especially beneficial in removing the attendant list, and will bring the vessel upright if G is lowered enough to restore positive GM. If damage has introduced off-center weight, the improvement in GM will diminish the size of the list due to this given amount of off-center weight.

Jettisoning from the centerline to improve GM cannot completely remove a list which is due in part to off-center weight. Hence, it may be desirable to remove a certain amount of high weight from the

 

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Figure 18-A. Portable electric submersible pump about to be lowered through the scuttle
Figure 18-A. Portable electric submersible pump about to be lowered through the scuttle
 
 

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listed side only, in order to bring the ship's center of gravity back into the centerline plane. Jettisoning topside weight from the "down" side improves GM and corrects off-center weight simultaneously. Extreme caution is necessary not to over-correct the listing moment; there must be no guessing as to the magnitude of such moments.

Like any weight removal, jettisoning improves reserve buoyancy and freeboard. This in turn has a beneficial effect on stability characteristics. Although it is probable that little can be done to improve trim or hull strength through jettisoning, care should be exercised to avoid aggravating these factors further.

The primary objective of the weight removal may be correction of off-center weight, rather than to improve GM. In this case the most effective measure -obviously-is to remove the off-center weight itself. If the latter happens to be damage water, pumping it over the side is dependent on the ability to first plug the holes through which it entered the ship. If the off-center flooding water is loose, stability is improved both by the list correction and by removal of the free surface. If the off-center flooding is solid (no free surface) stability is improved by correction of the list, but inevitably there is a temporary creation of free surface effect during the process. This is unimportant if the compartment is less than one-half the beam of the ship.

Care should be exercised in pumping out solid flooding to avoid further reduction of a critically small GM by removal of low weight. In unwatering the ship, priority should be given to the removal of loose water and high flooding ahead of solid filled compartments, leaving to the last any compartments that are low in the ship.

If flooding boundaries cannot be restored sufficiently to permit removal of off-center flooding, list correction can be effected by pumping liquid (oil or water) overside from undamaged wing tanks. The general result of this is to improve stability characteristics by removal of off-center weight, while causing a loss of GM due to removal of low weight. The reduction of GM becomes marked in the case of bottom side-tanks. Avoid pumping out double-bottom tanks after damage. This combines the harmful effects of broad free surface and removal of low weight.

Removal of liquid from normally filled wing tanks diminishes torpedo protection. In battleships and large aircraft carriers it is advisable to retain at least one liquid-filled layer in the torpedo-defense system.

Pumping liquids over the side improves reserve buoyancy and freeboard, and this in turn improves

  stability characteristics. Removal of as much of the flooding water as possible is the first consideration, with priority of removal based upon precautions cited above. Pumping oil or fresh water over the side may involve the loss of badly needed fuel, feed water, or potable water. Fuel oil, Diesel oil, or gasoline should never be pumped over the side where they will contribute to burning oil slicks around a ship which is dead in the water.

Trim can be effectively improved by pumping out flooding from the ends of the ship, or by emptying the contents of undamaged peak tanks. This may reduce stability characteristics slightly due to removal of low weight, but the gain which results from correction of a severe trim mitigates this loss. Other benefits of trim correction are better propulsion, better maneuverability, a drier weather-deck, and hence a more seaworthy vessel.

The additional stresses imposed on a damage-weakened hull girder by flooding water are ameliorated by removal of the damage water. The pumping out of intact tanks in the neighborhood of the flooding also helps, but low weight removals for this purpose may reduce stability. Flooding amidship heightens sagging stresses; in such case avoid trim correction by means of removing weight from the ends of the ship as this tends to further aggravate the sagging stresses.

If a ship has a considerable list but the flooding is known to be symmetrical, special care must be taken to prevent creation of a transverse moment, which can produce larger list on the opposite side, or result in capsizing.

18-6. Weight transfers. Shifting solid objects aboard a large ship to correct list and trim is not practicable; not only would it be too slow, but watertight integrity also would be endangered. Either sluicing or pumping fuel oil or ballast water from one tank to another are the only feasible methods of rapidly shifting large weights.

Sluicing involves opening valves and letting liquid run by hydrostatic head from one tank to another. It may be used to correct list where power for pumping is not available, or to move liquids to tanks with pumping connections if the liquid levels are such that the flow will be toward the high side. Sluicing, in itself, is detrimental to seaworthiness if the flow is toward the low side or after the levels are equalized. It has small effect on trim, but can cause a serious reduction in GM and stability due to creation of increased free surface. Accordingly, sluice valves should

 

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be closed at all times except under the one special condition described above. An open sluice valve connecting two adjacent tanks divided by a centerline bulkhead creates the same free surface effect that would exist if the two tanks were one large compartment.

On a listed ship, sluicing athwartship usually aggravates the list (the liquid runs down hill). Before sluicing, a careful check should be made to insure that the liquid will flow away from the down side. Sluicing may be effective, however, in draining liquid from a higher level to a lower level. Thus, a high wing tank on the listed side might be sluiced into a bottom centerline tank to remove list and improve GM. Sluicing should be controlled carefully, with valves locked shut as soon as the transfer is completed. Normally, it should only be done when it is necessary to move liquids to where they can be pumped.

Liquids available for pumping include fuel oil, ballast water, and to a much smaller extent reserve feed water and potable water. Pumps used include fuel-oil transfer, fire and bilge (ballast system) and emergency feed. Systems employed are fuel-oil filling and transfer, fuel-oil tank drain and ballast, reserve feed transfer, fuel-oil service (rarely), and freshwater service (ineffective). In ships having torpedo-protection systems, one liquid layer should always be retained for protective purposes if this is at all possible. The effects of liquid transfers may be tabulated as follows:

1. Wing tank to diagonally opposite wing tank on the same level.

a. No effect on GM or reserve buoyancy.

b. Improves stability characteristics by removing list (if GM is not negative).

c. Creates small additional free surface during transfer; thereafter, free surface is the same.

d. Improves stability, propulsion, seaworthiness, and maneuverability by removal of list and trim.

2. High wing tank on listed side to low bottom tank on centerline or opposite side.

a. Improves GM and stability characteristics by lowering weight.

b. Does not affect reserve buoyancy.

c. Improves stability characteristics by removing list.

d. May be some additional free surface during transfer.

e. May be used to correct trim.

  3. Peak tank to peak tank at other end.

a. Does not affect GM or reserve buoyancy.

b. Improves propulsion, seaworthiness, and maneuverability by removal of trim.

c. May be some additional free surface during transfer.

d. Possible effect on longitudinal strength must be considered.

18-7. Weight additions (or counterflooding). The term counterflooding refers to the practice of deliberately taking sea water aboard in tanks or compartments opposite to the damaged tanks or compartments to reduce both list and trim simultaneously. For example, after damage on the starboard quarter, counterflooding may be undertaken forward and to port. The disadvantage of further loss in reserve buoyancy should be overcome, as soon as possible, by transferring liquids to correct list and trim, and pumping overboard the water taken in for counter-flooding.

All ships can counterflood peak tanks for correction of trim. In the case of vessels possessing torpedo-protection systems, counterflooding is the most rapid means of correcting list. Other ships are not designed for counterflooding through sea valves. On occasions when counterflooding may be necessary, use may be made of hose connections to the fire main. This, however, normally is a slow process.

When counterflooding, certain precautions should be observed, as follows:

1. Keep air escapes open to permit the spaces to be filled solidly.

2. Close counterflooding valves after use to prevent free communication with the sea.

The effects of counterflooding may be analyzed as follows:

1. On ships having torpedo-protection systems, the counterflooding of voids (in protective layer) which are opposite the flooded area results in:

a. Rapid removal of list (makes possible maintenance of maximum speed, maneuverability, and resistance to damage, and provides a level deck for gunnery and aircraft operations).

b. Improvement of stability characteristics due to removal of list.

c. Loss of reserve buoyancy due to reduction of freeboard.

2. Counterflooding off-center tanks diagonally opposite flooded compartments on smaller vessels (this usually is neither possible nor useful).

 

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a. Improved stability characteristics due to removal of list.

b. Loss of freeboard and reserve buoyancy.

c. Some correction of trim.

d. Introduction of added free surface during counterflooding (important if tanks are wide).

3. Counterflooding low centerline spaces to improve GM (ballasting).

a. Possible use in cases of lolling (DD, DE, CVE, etc.).

b. Loss of reserve buoyancy and freeboard.

c. Transient free surface.

4. Counterflooding peak tanks to correct trim.

a. Slight loss of reserve buoyancy.

b. Slight transient free surface.

c. Improved propulsion, seaworthiness, and maneuverability.

d. Reduction of hogging stresses if ship is damaged in the middle length.

Large shifts or changes in weight cause relatively small changes in trim. It is axiomatic that full correction of large trim after damage is impossible except by pumping out the flooded spaces. Freeboard at the damaged end of the ship cannot be materially increased by counterflooding. Moreover, counterflooding is accompanied by increased mean draft and loss of reserve buoyancy. Except when steps to correct list can be selected to correct trim also, it will usually be advisable to delay complete correction of trim until flooding boundaries have been established, which will permit pumping out flooded spaces.

Therefore, some large ships have adopted the "waist" principle of counterflooding in two steps: first for most of the list,-the major menace, then for

  trim and the remainder of the list. This requires establishment, prior to action, of a counterflooding doctrine, to meet an anticipated list of 7 - 8°. When the damage control officer issues the order "counter-flood port" (or starboard, as the case may be), the appropriate repair party promptly opens counterflood valves to a pre-designated group of voids in the waist of the ship, thus taking action to remove a 7 - 8° list. As more exact information on the location of the hit is received and analyzed, secondary orders are issued to counterflood additional wing voids near the undamaged end of the ship, to compensate for damaged trim and the remainder of the list. The net result is compensation for both list and trim, with minimum confusion in communications (generated by lengthy orders involving the numbers of all voids to be flooded), and initiation of list removal without loss of time in damage-control headquarters. Upon receipt of exact information, original orders can be modified, and the extent of counterflooding adjusted. But the major objective-prompt removal of list and trim, is attained with minimum possibility of confusion and minimum loss of time.

A well-understood counterflooding policy as part of damage-control doctrine is absolutely necessary. Responsible personnel of every ship should be well aware of all possible applications and their associated effects.

18-8. Restoration of vital functions. Damaged pumps and ruptured piping will have to be repaired. If the ship is to continue in action or repel attack, it is essential that power, mobility, and maneuverability be restored as soon as possible. These functions will likewise be required if the ship has to seek a safe haven and towing is not practicable.

 

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CHAPTER XIX

RESTORING SEAWORTHINESS
 

GENERAL MEASURES

19-1. Fundamental approach to the problem. When a ship incurs damage the first step is for repair parties to take action automatically to arrest flooding, put out fires and initiate generally those emergency measures which are dictated by the exigencies of the situation. Organized measures fall naturally into four consecutive steps:

1. Determination of the extent of damage.
2. Estimate of the situation.
3. Restoration of seaworthiness.
4. Restoration of fire power and offensive functions.

With respect to the first two measures it may be stated that haphazard and unsound decisions based on incomplete, inaccurate information have done more harm than good. Misapplication of energy and loss of valuable time inevitably result unless a well-organized plan of action is conceived and followed. In selecting proper corrective measures there is no substitute for sound judgment, based on accurate information.

19-2. Determination of the extent of damage. It is necessary that the damage control officer receive prompt, complete, and accurate information as to the extent of damage. This information will flow in to the damage-control station not only from repair parties, but also from other activities in or near the affected areas, as well as from observers topside. The latter frequently are in a better position to tell where the bomb, torpedo, or shell exploded, since below-deck personnel on the spot often are wiped out or injured by the casualty, and since communications from the affected area are likely to be disrupted.

However, the primary source of information will be the repair parties, which have sent out investigating teams, sounding groups, and so on. The facts to be determined include the following:

1. Flooding-its extent and progress.
2. Fire-areas affected, and types of fire.
3. Structural damage.
4. Impairment of vital systems and equipment.

  Information received in the damage-control station, including reports of immediate corrective measures instituted by repair party groups, are collated and evaluated there in arriving at the estimate of the situation.

19-3. Restoring seaworthiness. Since the estimate of the situation has been discussed in Chapter XVII, no further mention of this topic will be made here. A few general items with respect to the restoration of seaworthiness may, however, be noted. In every case of flooding, regardless of the type or size of the ship, two of the corrective measures discussed in the preceding chapter can and should be instituted without delay. Flooding boundaries must be determined and established, and steps must be started to remove damage water. Quoting from FTP-170B, with regard to damage-control measures after flooding:

"THE MOST EFFECTIVE STEP IS TO RID THE SHIP OF AS MUCH OF THE FLOODING WATER AS POSSIBLE."

Until the ingress of water has been halted or slowed, efforts to effect its removal are apt to be unavailing. Hence, on-the-spot efforts of investigating parties and ship's personnel in the affected area immediately after damage, including the temporary plugging of holes, are of vital importance in establishing flooding boundaries. Attention should also be given to the fact that doors and hatches left open by escaping personnel at the time of the explosion must be closed and dogged.

Methods of ridding the ship of damage water, by use of built-in drainage and piping systems, portable pumps, sluicing to low spaces, and the like, are discussed in Chapter XXIX and elsewhere.

19-4. Fire fighting. Inasmuch as most explosions are accompanied by incendiary effects, ship's personnel frequently must fight fires while investigating damage and establishing flooding boundaries, or must carry on fire fighting simultaneously with these and other measures. Actual cases are on record wherein crews have conducted long and successful battles against fires, meanwhile being forced to control flooding. The

 

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danger of internal flooding from water used to fight fires, with accompanying free surface effect, must be kept in mind in all such incidents.

19-5. Restoration of vital functions. Seaworthiness requires that the ship be capable of moving under her own power, and of being steered. Hence, steering control and main propulsion must be restored as soon as possible after damage. In addition, further action may impend, so it is always important to restore fire-control circuits, ammunition supply, and other impaired facilities associated with the maintenance of fire power.

SHIPS WITH TORPEDO-PROTECTION SYSTEMS

19-6. Probable situation after damage. Assume that a large combatant ship with a torpedo-protection system receives damage. The corrective measures discussed in the first section of this Chapter will be initiated. But in addition, certain other measures probably will be appropriate.

Above-water damage in these ships will not affect stability seriously, and reserve buoyancy should not suffer greatly. Some vital functions may be impaired. For example, fire-control circuits from directors may be destroyed. Generally speaking, however, underwater damage will be more troublesome. A typical estimate of the situation after a torpedo hit on a battleship would show the following:

1. Extent of flooding. In all probability good watertight subdivision will act to limit the flooding. Depending upon the exact location of the torpedo hit, there may be some flooding of vital areas inboard the holding bulkhead, but distribution and segregation will operate to minimize loss of fighting efficiency from this cause. Flooding will be progressing slowly through the fringes of the damaged area. There will be a hole in the third deck, through which some flooding will take place, aggravated by the list which follows the hit. The damage water will be mixed with fuel oil from breached tanks.

2. Stability and list. As a result of off-center flooding, the ship will list immediately to the damaged side, to an angle of from 5° to 10°, depending upon the location and extent of damage. Inasmuch as broad free surface is not extensive, flooding is low in the ship, and GM was originally large, the loss in GM will not be of consequence. The same may be said of decrease in stability due to the list. The list, in conjunction with damaged, projecting shell plating,

  will adversely affect speed and maneuverability. In addition, list imposes difficulties in ammunition transfer and loading, and in operation of main and antiaircraft batteries.

3. Reserve buoyancy. The loss of reserve buoyancy should not be of serious consequence.

4. Trim. Increased trim by the stern will be unimportant. Trim by the head may slow the ship slightly, and increase steering difficulties.

5. Structural strength. As discussed in Chapter XVII, this will probably be a minor consideration in the case of battleships.

19-7. Corrective measures after underwater damage. It is apparent, then, that the only additional corrective measures necessary are those employed to combat list. Three methods are available: counter-flooding, internal transfer of liquids across the ship, and pumping liquid overboard from the damaged side.

If the tactical situation requires immediate use of maximum speed and maneuverability, and optimum fire power, counterflooding should be begun without delay. The loss in reserve buoyancy is recognized and accepted under these conditions, on the basis that it will be restored by further corrective measures. Time and situation permitting, list can be removed by transfer of fuel or ballast water from intact tanks on the damaged side to voids on the other side. In any case, this measure should be instituted along with counterflooding, and the counterflooding water pumped out as transfer continues to compensate for the list. Thus reserve buoyancy is improved.

A similar corrective moment is obtained by pumping ballast water or fuel overboard from intact tanks on the damaged side. If some of the damaged area can be patched, removal of damage water will accomplish the same end; obviously, however, there will be a considerable area where destruction of structure and dimensions of damage will make this impossible.

When counterflooding, the 'waist" principle mentioned in Article 18-7 can be used to good advantage, since time is of the essence. The other measures described should be so planned as to leave one liquid layer everywhere ,on the damaged side, for torpedo defense. Bottom tanks should not be pumped out, since reserve buoyancy has not been critically diminished. If fuel is pumped overside from wing tanks, the loss in cruising radius must be recognized.

SHIPS WITHOUT MAJOR TORPEDO PROTECTION

19-8. Probable situation after damage. After

 

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attack by bombs, shell fire, or shallow torpedo, cruisers, auxiliaries, and smaller ships suffer serious loss of reserve buoyancy as a result of fragment holes and destruction of watertight structure above the waterline. If the ship is holed, water will enter during the roll, and the flooding effects will be akin to those resulting from underwater damage. They will, in fact, reduce stability even more, since the added weight of flooding water is high in the ship, and the opportunities for broad areas of free surface are more extensive. Furthermore, impairment of vital circuits may be of severe consequence due to lack of splinter protection and little duplication of structures. In most instances, underwater damage, be it from a torpedo or bomb, will be accompanied by above-water damage, and the effects will be additive.

Flooding due to a torpedo hit is apt to be of more grave consequence as the size of the ship decreases, since the lack of major torpedo protection places the task of restricting flooding on the major transverse watertight bulkheads. In any event, a part or all of vital spaces will be flooded. Flooding will progress more or less rapidly around the damaged area. The decks over the site of the explosion will be destroyed, and bulkheads in the vicinity will be disrupted. Fuel oil may be mixed with the flooding water. In the case of aircraft carriers or tenders, and ships carrying aircraft, free gasoline may be present.

The impairment of reserve buoyancy usually will be of considerable consequence, so much so that deliberate admission of additional water to the ship (counterflooding) to compensate for list or trim usually is fraught with danger. Freeboard may be dangerously small, particularly if the ship is listing. In fact, the ship's survival, if heavy weather is impending, may depend upon whether reserve buoyancy and freeboard can be regained in part.

Explosions which destroy portions of the ship girder, such as the main deck, stringer plate, sheer strake, garboard strake, or keel, will reduce longitudinal strength. Incorrect measures or improper ship handling may increase stresses sufficiently to cause the ship to break up.

The GM of most ships will be positive if the flooding is limited to one main compartment. However, extensive underwater damage will result in a greater degree of flooding in most cases. In the case of cruisers and destroyers negative GM may be developed if more than two main engineering spaces are partially flooded, or if there is extensive partial flooding in wide compartments on decks near the waterline (as may result from riddling of the ship's side), or

  from a combination of these circumstances. Loginess, or extreme tenderness is a danger signal, whether accompanied by list or not. The same holds true for escort carriers, large auxiliaries, and similar types, except that loginess or extreme tenderness is a danger signal only when in combination with a list. If there is little or no list and the ship is logy, stability probably will prove to be satisfactory if remaining freeboard is considerable. In the case of destroyer escort vessels and the new flush-deck and 2,100 ton destroyers negative GM after damage is less likely to occur because intact GM is large and main compartments are relatively small. High original freeboard also increases the stability of these ships.

Heavy trim will develop if the ship is hit near one end. Trim by the stern will not be so troublesome as trim by the bow, which decreases stability (usually), speed, and maneuverability. In addition, boarding seas forward may destroy or interfere with the use of the forward battery.

The lack of longitudinal subdivision and maintenance of liquid in wing or side tanks decreases the chances of developing heavy list after damage; however, some list usually results due to off-center flooding, or in some cases, dislocation of heavy weights such as machinery. The ill effects of list on mobility, maneuverability and fire power have been discussed. In addition, list seriously decreases stability, ship's seaworthiness, and resistance to further damage.

The possible combinations of list and stability have been described in Chapter XIV. They are:

1. Unsymmetrical flooding with positive GM. If list checks reasonably well with that indicated in the flooding-effect diagrams, this is probably the situation that exists.

2. Unsymmetrical flooding with negative GM. If the ship is logy, and list is badly disproportionate to that indicated by the flooding-effect diagram, this combination should be assumed to represent the situation.

3. Symmetrical flooding, with negative GM. If flooding is known to be symmetrical and list is appreciable this condition prevails.

19-9. Corrective measures for unsymmetrical flooding with assured positive GM. In addition to the measures described (Articles 19-1 through 19-5 above) pump liquid overboard from intact, narrow, deep side tanks (not bottom tanks) on the low side. This entails decreased protection in the areas inboard of such tanks, and, if fuel is pumped overboard, a loss of cruising radius. Jettisoning topside weights from

 

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the damaged side of destroyers and other small ships will serve to reduce list. This latter expedient usually is not of value in the case of large ships.

Liquid in intact wing or side tanks on the low side should be transferred to partially full tanks on the other side, and the latter pressed full. If there are any empty tanks on the high side, they may be filled similarly. However, existing ballasting instructions call for keeping wing tanks ballasted to the waterline, hence they will not normally be empty. If heavy trim exists, the peak tank at the high end may be filled with liquid from the low end of the ship; with due consideration to longitudinal strength (see Chapt. XVI).

Counterflooding for list is not often practicable, since there normally are no empty wing tanks. Off-center compartments could be flooded by use of the fire main; however, the corrective moment usually will not be large, since the lever arm of the added weight is not great. The additional free surface involved during the counterflooding operation is undesirable, the time required is lengthy, and the sacrifice in reserve buoyancy may be of major importance.

19-10. Corrective measures for unsymmetrical flooding with suspected negative GM. Since the list should be reduced as rapidly as possible, corrective moments can be and should be applied somewhat less than the known inclining moment. The latter can be estimated as follows: Estimate the weight of water in each flooded off-center compartment, and the distance of its center of gravity from the ship's centerline. In each case w times the distance from the centerline gives the inclining moment. The total of the inclining moment for all flooded off-center tanks is obtained by adding the individual inclining moments.

All the corrective measures described in Articles 19-1, 19-2, 19-3, 19-4, 19-5 and 19-9 are applicable. When using those described in Article 19-9 care must be taken, as stated above, that the total restoring moment resulting from jettisoning, pumping liquids overboard, or transferring liquids is somewhat less than the known total inclining moment.

In addition, measures to improve GM should go forward concurrently. These include pressing full any slack bottom tanks, sluicing liquid from wing tanks on both sides to empty centerline low spaces, and jettisoning topside weights symmetrically on smaller ships, such as destroyers. If reserve buoyancy remaining permits, GM can be improved by flooding low centerline spaces from the sea, one at a time, taking care that they are filled completely. Improvement of GM will also act to reduce list, since righting arms increase

  as GM increases. Never pump out low cr bottom tanks.

19-11. Corrective measures for symmetrical flooding with suspected negative GM. When broad areas of free surface exist and flooding is extensive, the measures noted in Articles 19-1 to 19-5 must be augmented to improve GM. Measures for improvement of GM listed in Article 19-10 (last paragraph) are applicable. In addition, when reserve buoyancy is adequate, it may be desirable to allow partially flooded large compartments, such as engineering spaces, to flood solid, under control, by venting the air bubble. Jettisoning will be of positive value on smaller ships, but care must be taken to jettison equal weights from both sides, or centerline weights.

19-12. Shoring for seaworthiness. Shoring methods are discussed comprehensively in Chapter XXXVI. The applicability of shoring can, however, be considered in connection with restoring seaworthiness. In the case of welded ship construction, bulkheads are not apt to fail under the hydrostatic pressure of flooding water unless they have been badly distorted by explosion, or unless exposed to heavy dynamic loading by entering seas, as is the case when the bow of a ship has been lost. In such event the foremost bulkhead and the next aft should be shored. Similarly, if the side of a ship is damaged by explosion and flared out, the scoop effect when the ship is underway increases the load on the first intact watertight bulkhead aft, which may require shoring.

Decks will not always withstand hydrostatic head. Therefore, decks over flooded low compartments should be carefully watched, and shored if they show signs of excessive deflection, or incipient leakage due to local failures. Hatches require the same careful inspection.

19-13. Judicious ship handling. The chances of survival and return to port can be materially enhanced by careful ship handling and good seamanship. For example, if stability is poor, or if the ship has a heavy permanent list, courses selected should not parallel the trough of the sea. If the bow structure is damaged, speed should be lessened. With heavy bow trim, head seas should be avoided.

19-14. Longitudinal strength considerations. In the selection of corrective measures possible increase of longitudinal stresses and suspected or known impairment of the ship's longitudinal strength must be taken into account. The strength of smaller ships may be impaired by the whip or flexural vibration following an underwater explosion at one end. In any of the

 

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ships under consideration here, strength is impaired by destruction of a portion of any strength member, as stated in Article 19-8.

Flooding usually accompanies such damage, and the weight of the flooding water increases the stresses in hogging or sagging, depending upon whether it is near one end or the waist of the ship. Fortunately, stresses are relieved somewhat by the removal of damage water, or liquid from intact tanks in the area, both of which are measures indicated for restoration of stability and removal of list. If trim is heavy after damage, stresses will not be so dangerously increased if trim correction is undertaken by transfer of liquids along the ship, rather than by counterflooding peak tanks.

  When impairment of strength is known or suspected to exist, the ship can be handled to reduce hogging or sagging stresses in the seaway. Speed should be slow, the ship should not meet long swells or large waves head on, and should not be exposed in a quartering sea to waves with trough-to-trough distance approximately the ship's length.

It is rarely possible to restore lost strength while the ship is at sea, but upon reaching haven, repairs must be undertaken to achieve this purpose before beginning voyages of considerable. length. Heavy welded plate with lengthy laps beyond the damaged area must be installed over gaps or ruptures in strength members. Buckled material has little compressive strength, and must be reinforced similarly.

 

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CHAPTER XX

STRANDING
 

20-1. Foreword. There are three important points to keep in mind in case of stranding. These are:

1. The necessity of keeping the ship from going farther aground or broaching to the sea, which make it more difficult to salvage.

2. The possible loss of stability due to grounding, especially in connection with large changes of tide.

3. The structural strength of the ship, and the possibility that it may break up.

20-2. Procedure when stranded. When a ship goes aground, it is the natural desire of the Commanding Officer to attempt getting her off under her own power. In an effort to accomplish this, he usually desires to lighten ship, thus reducing mean draft. There is, however, danger that the ship will only work farther toward the beach if this is done, thus complicating future salvage operations. There is also possibility of the ship broaching to the sea and being subjected to pounding of the waves.

The following procedure is recommended in most stranding cases to minimize the dangers indicated above:

1. No attempt should be made to refloat the vessel under her own power if wind and sea conditions indicate the possibility of the vessel working harder aground, pounding, or broaching to the sea.

2. Kedge anchors to seaward should be laid as quickly as possible to prevent the vessel from working farther ashore, and/or broaching to.

3. The vessel should be weighed down-not lightened-in an effort to keep from working harder and higher on the beach, and to prevent damage caused by working and pounding of the vessel on the bottom.

  Thus, instead of following the natural desire to lighten ship, "weigh it down" by flooding holds, low tanks, etc. Then, when salvage operations are attempted, it is a relatively easy matter to lighten the ship and pull the vessel off with the aid of beach gear.

20-3. The effect on stability. Only rarely have vessels capsized after going aground. However, there are a number of factors having an influence on stability characteristics which should be considered in any case of grounding. These include the form and texture of the beach or object upon which the vessel has grounded, the location of the force exerted upward against the ship, the shape of the hull, the range of the tide, and the state of the wind and sea.

Relatively soft beach material will tend to assume the shape of the ship's bottom and thereby act to prevent capsizing. This is particularly true where the portion of the ship resting on the bottom is wide. If the ship is on a pinnacle or narrow ledge along the centerline, a large fall of tide may result in capsizing. If the pinnacle or narrow ledge is off-center, an upsetting moment may accompany a drop in tide. Unfavorable winds and seas may increase the transverse upsetting force.

In order to make the ship as stable as possible, any free surface should be eliminated. If available, some barges may be brought alongside to act as sponsons, or outriggers. Soundings should be taken around the ship. The information obtained may be plotted relative to a transverse sectional view of the ship's bottom to show whether the bottom will exert pressure against the ground to resist capsizing. In the past, vessels have developed lists varying from 1° or 2° up to 20°. Often this has been due as much to the contour of the ground as to reduction in stability.

 

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CHAPTER XXI

PREPARATIONS TO RESIST DAMAGE
 

21-1. Importance of adequate preparatory measures. Adequate preparatory measures are of great importance for a number of reasons, including the following:

1. They tend to keep the ship effective as a fighting unit by maintaining the ship's qualities of resistance to damage.

2. They protect the lives of the crew.

3. They tend to insure the future tactical usefulness of the ship.

4. They provide a sound background for proper decisions as to which corrective measures will save the ship after damage.

21-2. Factors to be safeguarded and measures employed. The factors which preparatory measures are designed to safeguard, insofar as the ship is concerned, are as follows:

1. Transverse stability characteristics in general.

2. Reserve buoyancy.

3. Resistance to damage by fragments, flash, and fire.

4. Armored freeboard.

5. Absence of trim.

6. Absence of list.

7. Structural strength.

In safeguarding the foregoing factors, the damage control officer should employ the following measures:

1. Maintain strict adherence to specified liquid loading procedure.

2. Weight control.

3. Maintain watertight integrity and watertight integrity discipline.

4. Have adequate equipment in proper operating condition.

5. Assure thorough organization and training of personnel.

21-3. Strict adherence to correct liquid loading procedure.

Minimum liquids. For all combatant ships, and most auxiliary types, specific instructions have been issued as to the minimum liquid loading for war service. The considerations governing the

  determination of minimum liquids to be carried may be summarized briefly, as follows:

1. In practically all types of ships, side tanks (including wing tanks) should be kept filled to the waterline, or filled to the top (95% full in case of oil) if the top is below the waterline, in accordance with instructions furnished to the ship, in order to minimize the angle of heel after underwater damage.

2. In some types of ships, tanks low in the ship are required to be kept full, or ballasted, to insure adequate stability by keeping the center of gravity down.

3. In ships possessing torpedo-protection systems, the liquid loading prescribed is based on requirements for minimizing structural damage and consequent flooding, and to minimize angle of heel after damage.

4. In ships having wing tanks, liquids in wing tanks abreast vitals serve another important function. They reduce the velocity of fragments resulting from torpedo hits, which otherwise might cause serious damage.

Liquid loading prescribed for battle. "The optimum battle condition loading prescribed for ships incorporating torpedo-protection systems includes the liquid required in the torpedo-protection system. Additional liquid is of no advantage from the standpoint of protection. Additional liquid increases displacement and the corresponding loss of freeboard is disadvantageous. In these ships the optimum liquid loading specified for each ship should be reached as soon as possible after leaving port."

"Cruisers and light carriers (CVL's) present a different problem. In addition to the liquid required in side tanks for fragment protection and wing tanks for avoidance of large heeling moments, some liquid is required in bottom tanks purely for stability. The liquid in the minimum service condition is based on all three factors and is the least amount satisfactory. Stability is improved rapidly by carrying more than this minimum amount. There is, however, an upper

 

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limit where the gain is not worth the adverse effects of loss of freeboard, as discussed later. In these ships there is an advantage in carrying somewhat more than the minimum service condition liquids."

"For certain cruisers, destroyers, and destroyer escort vessels, light service displacement is the term which has been adopted for the condition in which minimum liquids are carried. The term covers a condition corresponding to the minimum service condition described above. Minimum service condition and light service displacement have the same meaning." -FTP-170B.

In order to assist in maintaining the most satisfactory distribution of liquids from the standpoint of torpedo protection, use is made of a fuel-oil sequence table. This table gives the order in which oil in the fuel tanks should be burned. The usual tank sequence calls for using the fuel-oil void tanks first, before starting on the fuel-oil ballast group. Thus, tanks not absolutely necessary for adequate stability and torpedo protection can be emptied first in the interest of reserve buoyancy and adequate freeboard. A fuel-oil sequence table is frequently given in the Damage Control Book, usually on the flooding effect diagram. Sometimes a Type Commander will issue special directives concerning this sequence, and occasionally ships must make up their own tables.

The Booklet of Inclining Experiment Data for all recent combatant ships gives loading and stability information for the conditions discussed above, as follows:

BB's, CVB's, and CV's - optimum battle condition.
CB's, CA's, CL's, CVL's,
DD's, and DE's-either minimum service condition or light service condition.

The loading for these conditions is, or will be, set forth also in the Damage Control Book for each ship. It should be emphasized here that the primary purpose in setting up these conditions is to establish minimum liquid loading for the purposes of underwater protection, stability, and general ability to survive damage. In battleships and large cruisers this minimum is also the optimum liquid loading: it should be reached as soon as possible, and wherever possible should not be exceeded. In smaller ships the minimum liquids may be exceeded somewhat, if desired, by keeping certain bottom tanks filled for improving stability.

Damage Control Books for certain classes of auxiliaries likewise include liquid loading instructions for the best protection against damage. From time to

  time, the Bureau of Ships or Type Commanders may issue special directives modifying liquid loading instructions. A damage control officer reporting to a newly constructed ship should check on this item. In all cases ship's personnel should adhere closely to the liquid loading instructions.

21-4. Limiting displacements. Problems involved in weight control are (1) limiting displacements, (2) maximum stability, (3) optimum trim, and (4) minimum list.

The Bureau of Ships has, on many occasions, issued warnings and instructions against overloading - in general and specific terms. Operating at excessively heavy displacement has several very important disadvantages which may be briefly summarized, as follows:

1. Adverse effects on intact ship:

a. Speed reduction. The effect of increased displacement is most pronounced in light, highspeed ships like destroyers, but is also very noticeable in cruisers, and to a lesser degree in battleships and large aircraft carriers. (Increased propulsion resistance due to the deeper draft cuts down maximum speed, besides increasing the power required at a given speed.)

b. Cruising radius reduction. Increased displacement, of itself, by increasing the power required for a given speed, reduces cruising radius. Of course, if the overload consists largely of oil, increased radius will be achieved, but at the expense of reduced economy. If the overload consists of items other than oil, a definite reduction in radius will result.

c. Seaworthiness. Overloading will reduce freeboard to the weather deck and thus give a wetter and less efficient ship in rough weather, even when the ship is intact.

d. Reduction of reserve buoyancy.

e. Range of stability. A ship may have excellent initial stability (high GM), but so little freeboard due to overloading that its range of stability is reduced.

f. Reduction of armored freeboard.

g. Strength. Overloading increases the longitudinal stresses imposed on the ship. Extreme overloading, coupled with heavy weather, may lead to structural distress or even failure.

2. Study of the foregoing items makes it obvious

 

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that further adverse effects due to damage are likely to result in loss of the ship.

"The adverse effects of overloading, as discussed above, have long been recognized with respect to merchant ships as well as warships. In the case of merchant ships, definite limitations are placed on displacement, with some variations for the zone of operations and the time of year. The limiting displacements are indicated by Plimsoll marks on the sides of the ships, showing the limiting drafts or "load lines" under the various conditions specified. Many merchant ships converted for Naval use are required to keep within the limiting loads represented by their original Plimsoll marks. Limiting loads have also been prescribed for a certain few Navy-built ships where special considerations made this advisable. In extension of this principle, the Commander-in-Chief, U. S. Fleet, has approved a recommendation of the Bureau of Ships that limiting displacements be established for all combatant ships, and be promulgated for the guidance of the forces afloat, with the full understanding that these displacements may be exceeded on the authority of responsible commanders where circumstances warrant the acceptance of the additional risks involved. The Bureau of Ships has already issued this information to the forces afloat for some classes of destroyers. Limiting displacements are being determined for other combatant types and will be promulgated for guidance as soon as practicable. Eventually, the limiting displacements and corresponding drafts will be stated in the Damage Control Book for the guidance of each ship."

"Increments of displacement resulting from many items of load in excess of requirements remain with the ship throughout an expedition and thus exact a penalty on power of survival. Reference is made to the practice of loading ships to the limit of their capacity as regards space in order to provide provisions, stores, ammunition, etc., for possible contingencies of service. Logistic planning should place less emphasis on the endurance of combatant ships now that the system of advanced bases and additional supply ships allows more frequent opportunity for replenishing supplies. Supplies in excess of probable requirements for specific missions should be carried in auxiliaries rather than in combatant ships. Alterations involving the addition of heavy weights to the ship should he compensated for, when possible, by the removal of ^equal amounts of weight at the same height above the keel."

"The situation with regard to loading instructions

  may be summarized briefly, as follows: For each combatant ship, the minimum liquid loading is specified. This, together with the other consumable loads necessary for any particular expedition, will establish the minimum displacement the ship should have on leaving port. There will also be specified an upper limiting displacement for guidance. Those responsible for loading should, therefore, endeavor to keep their ships at operating displacements somewhere between these two figures, insofar as compatible with the requirements of the mission in hand. Adherence to this policy will pay dividends in improved ability to withstand damage, in simplifying the damage-control problems after damage, and, in extreme cases, will result in saving some ships which might otherwise be lost.''-FTP-170B.

21-5. Maximum transverse stability. In order to maintain maximum transverse stability, it is necessary to carry out proper liquid loading, as discussed in Article 21-3, cruise with a maximum freeboard (see Article 21-4), and prevent the accumulation of large unusual weights high in the ship. When the loading is increased by bringing expendables aboard, it is not only in the weight of such material but also its height above the base line which establishes the final stability. Stability will be enhanced by stowing and removing in a sequence of locations that tends toward the addition of low weights and the removal of high weights. It is also wise to enlist the assistance of the entire ship's company in keeping weights stowed in their proper places. Types of unusual weights high in the ship may be:

1. Large quantities of stores and provisions.
2. Emergency cargo.
3. Extensive icing.
4. Large numbers of survivors.

In addition to the foregoing requirements it is necessary to conduct a routine removal of accumulated bilge water in machinery spaces. The free surface effect is the same as though the spaces were flooded to an equal level.

21-6. Optimum trim. Most ships are designed to operate with no trim. Others, such as LST's and certain cargo ships, are designed with a drag. In all cases, cruising at the designed trim results in increased speed, increased economy of fuel-oil consumption, and less danger of loss by plunging if damaged. Control of trim is obtained by proper ballasting, and by proper distribution of weights taken aboard.

21-7. Minimum list. Every ship is designed to

 

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Figure 21-A. Adequate materials must be provided for damage control operations. In this picture shores are being passed down a scuttle.
Figure 21-A. Adequate materials must be provided for damage control operations. In this picture shores are being passed down a scuttle.

 

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operate without a list. This is necessary in order to permit the most effective gunnery and aircraft operations, increased speed, proper operation of machinery, and maximum fuel economy. In addition, list on a ship always has a detrimental effect on the morale of the crew.

Excessive listing can normally be avoided by cooperating with the gunnery, supply, and engineering departments in the preparation of a definite sequence in which to stow and remove the contents of magazines, storerooms, and fuel tanks. The engineer department will always be ready to shift liquids in those tanks not required to be ballasted for torpedo protection and adequate stability. In fact, the "oil king" probably will do this of his own volition, since the power plant operates better when there is no list. The flooding effect diagram gives figures for the undamaged ship which will be useful in estimating the heel involved in shifting oil from one side of the ship to the other.

21-8. Maintenance of watertight integrity. Each undamaged tank or compartment must be kept watertight if flooding is not to be progressive. Watertightness may be lost by:

1. Corrosion.

2. Loosening of boundaries or joints. This may result in leakage in void' compartments, cofferdams, non-frequented storerooms, etc.

3. Defective closures or fittings.

4. Lack of care in making alterations.

5. Failure to secure access closures.

A detailed discussion of upkeep will be found in Chapter XXX.

21-9. Adequate equipment. It is absolutely necessary that sufficient equipment, in good operating condition, be kept available at all times to handle flooding and other damage. Equipment on hand will include that required to

1. Pump out damage water.

2. Plug and patch holes.

3. Shore and repair structure.

4. Restore vital functions.

Equipment is dealt with in a number of Chapters in this book, and the equipment of repair parties receives special treatment in Chapter XXXV.

21-10. Organization and training. Personnel attached to repair parties should be trained to report the numbers of those compartments that are flooded, the depth (or estimated depth) of water in each, and the condition of boundaries (decks and bulkheads) which surround each of the compartments in

  question. If the ship has taken on a list, they should also indicate where their sounding (or estimated depth) was taken. Information on list, trim, and draft during and after damage will be necessary. Personnel on the topside should report the freeboard on the listed side. More complete discussion of organization and training will be found in Chapters XXIII, XXIV, XXV, XXVI, and XXVII. Needless to say, it is a very important subject, and should receive special attention.

21-11. Officer-in-charge of damage-control station. On some ships damage-control organization places an assistant in charge of damage-control station. In such event it is recommended that this assistant be assigned definite duties in liquid loading, weight, and stability control. This assistant at the damage-control station in battle acts as an aide to the damage control officer in matters regarding:

1. Coordinating the engineering activities of the "oil king" with regard to distribution of liquid loading.

2. Insuring the readiness of damage-control diagrams, charts, publications, bills, data, etc., for use during and after damage. In the preparation of the jettison ship bill the effect on GM of each item jettisoned may well be pre-calculated and entered on the bill.

3. During and after damage coordinating and charting reports of damage sustained, as sent in from the repair stations.

This officer is thus made responsible to the damage control officer for most of the detail work involved. He also be, the coordinator of the work of the damage-control station, inasmuch as the senior assisting damage control officer should be stationed elsewhere in the interest of "spreading the risk." If it becomes necessary for the damage control officer to leave the damage-control station, the assistant is well fitted to supervise its activities during the absence of his senior.

If the ship is large enough to provide a commissioned officer of the watch in damage-control station during cruising conditions, the officer-in-charge may advantageously be placed on this watch bill as the senior watch-stander in damage control. His presence on watch in the damage-control station will improve its functioning with regard to matters of organization, stability, and watertight integrity, besides expediting his own work. On smaller ships this usually will not be possible, since the assistant probably will be

 

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Figure 21-B. Fragment damage occurs topside also.
Figure 21-B. Fragment damage occurs topside also.
 
required to stand topside watches; however, he can well be given the supervision of the ship's watertight integrity watches.

Because of the large amount of executive and administrative work which must be done by the damage control officer and his senior assistant in matters of organization, ,education, training, and coordination of damage control with other departments, it is recommended that the officer-in-charge of

  damage-control station be made responsible to the damage control officer for all detail work which concerns the following subjects:

1. Organizing and training of personnel assigned to damage-control station.

2. Preparation of damage-control bills, damage-control diagrams, etc.

3. Custody of the damage-control publications, in-chiding the work of keeping them up to date.

 

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CHAPTER XXII

DAMAGE-CONTROL ORGANIZATION
 

22-1. Purpose of damage control. The objective of damage control is the maintenance of the maximum offensive power of the ship. To achieve this purpose, effective damage control:

1. Preserves watertight integrity.
2. Preserves buoyancy and stability.
3. Preserves maneuverability, mobility and seaworthiness.
4. Controls list and trim.
5. Effects rapid repairs.
6. Provides adequate protection from fire.
7. Provides protection from chemical attack.
8. Facilitates care of wounded personnel.

Accomplishment of these aims will result in keeping the ship afloat in its best possible condition, minimizing, or even nullifying, the enemy's most destructive efforts, and thus maintaining the ship's maximum offensive power. Thus damage control is an offensive function, as well as a defensive provision.

22-2. Fundamental elements. Four fundamental elements of a successful damage-control program on board any ship are:

1. Organization.
2. Education.
3. Training.
4. Maintenance.

These elements are not listed in the order of their importance. Each is necessary to complete the program, and all of them are essential on even the smallest of ships. A conscientious consideration and observance of the principles embodied in these four elements will enable any ship to put forth its maximum offensive effort. A very brief description of what each of the four fundamental elements entails follows.

22-3. Organization. Organization of the ship for the purpose of controlling damage involves establishing:

1. A battle damage-control organization.

2. A war cruising damage-control organization.

3. Departmental and divisional organizations for. maintaining conditions of closure.

  4. Departmental organizations for the proper maintenance of equipment vital to damage-control procedure.

5. Training and educational programs (for officers, men, and all battle-station groups).

22-4. Education. The educational plan should provide regularly scheduled programs for instructing the entire ship's personnel in:

1. Necessity for thorough application of damage-control principles.

2. Ability of ship to resist damage and remain afloat.

3. Methods for attaining damage-control efficiency.

4. Methods used by other ships in successfully overcoming war damage.

5. Mistakes made by other ships in combating war damage which should not be repeated by own ship.

6. Responsibility for maintenance of material conditions of closure, watertight integrity, and damage-control material and equipment.

7. Their individual damage-control duties and responsibilities.

8. Their ship's organization for attaining the objectives of damage control.

9. Knowing their ship and its systems as thoroughly as possible.

22-5. Training. The program of training should provide regularly scheduled instruction for the entire ship's personnel, in accordance with their individual damage-control duties in:

1. Proper setting of material conditions of closure. '2. Maintenance of the highest possible degree of watertight integrity.

3. Proper use of interior battle communications.

4. Proper operation, use and maintenance (for damage-control purposes) of hull and engineering systems.

5. Proper operation, use and maintenance of damage-control material and equipment.

6. Making emergency repairs.

 

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7. Making their way about ship under adverse conditions.

8. Locating damage, leaks, etc., under adverse conditions.

9. Fighting fire.

10. Working out type damage-control problems.

11. Overcoming attack by chemical agents.

12. First aid.

In providing this training separate programs are necessary for officers, men, departments, division war cruising groups, battle-station personnel, repair-party organizations and any other groups which stem from the general organization of the ship. These programs must be further adapted to "in port" and "at sea" (war cruising) operating periods.

22-6. Maintenance. Regular schedules of inspection, maintenance, repair and replacement should be maintained in addition to the training drills. The purpose of these inspection, maintenance and replacement schedules is to assure (1) watertight integrity, (2) proper operation of hull and engineering systems for damage-control purposes, and (3) satisfactory condition of all material sand equipment necessary to the attainment of damage-control objectives.

22-7. Sources of information. There is a large amount of information and data available which is essential to the development and operation of an effective damage-control program on board ship. A list of publications available for use (most combatant ships) is appended to this Chapter. Most important among these are the following items:

1Damage Control Book.
1General Information Book.
Booklet of General Plans.
1Booklet of Inclining Experiment Data.
FTP-170B, (Damage Control Instructions-1944).
FTP-222, (Defensive Chemical Warfare Manual).
Fire Fighting Manual-1944 (NavShips 250- 688).
Uses and Applications of Portable Emergency Pumping Equipment (NavShips 250-689).
BuShips Hull Allowance List.
Engineering Casualty Control Book.

22-8. Conditions of readiness for action. The existence of conditions of readiness for action is referred to here because of their influence on material conditions of closure.

Conditions of readiness are numbered. Readiness

  condition one is general quarters-the readiness condition in which battle stations are fully manned. Readiness conditions two and three call for less complete manning of stations. There are many modifications of these readiness conditions on different types of ships, or in different task forces, usually indicated by adding a letter to the readiness condition number.

It should be noted that many ships (DDs, DEs, etc.) have only two conditions of readiness: condition one (general quarters) and condition two (war cruising).

22-9. Material conditions of closure. For damage-control purposes, ships are classified according to the number of progressive steps through which they may go in effecting complete closure for battle. Thus there are two material condition ships using material conditions baker and able, and three material condition ships using material conditions x-ray, yoke and zebra. Three material condition ships usually are the larger types.

Material conditions able and zebra are the final material conditions of closure for battle, attaining maximum material resistance to damage consistent with operating the ship offensively. Inasmuch as material condition baker and material conditions x-ray and yoke are considered minimum standards only, Commanding Officers may establish modified material conditions of closure to suit varying readiness conditions for war cruising. This practice is more common in the case of large ships.

FTP-170B states that material conditions baker or yoke shall normally be maintained in port or at sea, except when manning general quarters stations (Chapter 11).

It should be understood clearly that conditions of readiness for action pertain to personnel manning their stations, and that material conditions refer to states of closure of doors, hatches, valves, and other fittings and systems. These two distinct types of conditions should not be confused with each other.

22-10. Classification of fittings. To permit quick and accurate setting of the proper material condition of closure, fittings are classified and marked X, Y, Z and W. This system of classification is fully described in Chapters 7 and 8 of FTP-170B and includes designations for doors, hatches, valves, and other fittings and systems whose proper operation is important in obtaining the designated material condition of closure.

The classification of fittings with the letter X, Y or


1These publications are not prepared for, or issued to some auxiliaries, etc.
 

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Figure 22-A. The gas mask is not a substitute for the rescue breathing apparatus shown here. The latter permits working in toxic gases against which the gas mask is valueless. The airline hose mask also provides air from an outside source.
Figure 22-A. The gas mask is not a substitute for the rescue breathing apparatus shown here. The latter permits working in toxic gases against which the gas mask is valueless. The airline hose mask also provides air from an outside source.
 
Z conforms with the three steps taken in closing up a three material condition ship. Thus:

Three Material Condition Ship
Condition Fittings Closed
X-ray X
Yoke X and Y
Zebra X, Y and Z
W (opened or operating)
Two Material Condition Ship
Condition Fittings Closed
Baker X and Y
Able X, Y and Z
W (opened or operating)

A modified material condition zebra or able is one in which certain doors, hatches, and ventilation and flushing fittings are opened or operated to provide some relief or food for a crew required to be at battle stations for an abnormal length of time.

  22-11. Examples of circled X, Y and Z. There are certain X and Y fittings which must be operated or opened when proceeding to battle stations without the usual delay in obtaining permission to do so. In this category are: (1) doors to magazines and handling rooms, (2) accesses to other battle stations which may have been so classified in order to afford increased watertight integrity in material conditions baker or yoke. There are other X and Y fittings which must be opened or operated during action in order to fight the ship. In this category are ammunition-passing scuttles and many valves. These fittings may be designated by enclosing the classification letter in a black circle. They shall be also "circled" wherever they appear in compartment check-off lists and damage-control bills.

There are certain Z fittings which may be closed or operated in special circumstances and in exception to rigid adherence to the material condition in

 

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existence. In this category are (1) access fittings opening to the weather which normally are open in material condition baker or yoke but which must be closed at darken ship, (2) ventilation fittings which are normally closed in material condition able or zebra but which are opened or operated upon authority of the damage control officer to conduct periodic ventilation of battle stations in interior spaces, (3) cutout valves for salt-water cooling of ice machines which are normally closed in material condition able or zebra but which may be opened upon authority of the damage control officer during protracted periods at general quarters to maintain normal conditions in refrigerated spaces. These fittings may be designated by enclosing the classification letter in a black circle. They shall also be "circled" wherever they appear in compartment check-off lists and damage-control bills.

It shall be distinctly understood that the enclosure of a classification letter in a black circle as authorized above does not alter the meaning of the classification letter. Circle X and circle Y fittings giving access to battle stations may be opened without special authority only while proceeding to battle stations after general quarters has been sounded and when proceeding from battle stations after secure has been ordered. Ammunition-passing scuttles shall only be open during the actual period of ammunition transfer. Circle Z fittings shall never be opened during general quarters without special authority from damage control. The Z is enclosed in a circle merely for the purpose of ready identification. Circle X and circle Z classification should not be used on destroyers and smaller vessels.

No other variations from standard designations or markings are authorized. The practice of using various colors and symbols on classification labels to signify special variations on standard doctrine and procedures, which seems to have been adopted by a few ships, shall be immediately discontinued. These variations serve no useful purpose and tend to break down proper damage-control doctrine. Confusion is the inevitable result when personnel are transferred from one ship to another." - FTP-170B.

22-12. Damage-control bills. Damage-control bills should outline the procedure for operating the various systems, in conformity with the designated material conditions of closure, so that the objectives of damage control can best be attained.

The descriptive matter, tables and diagrams contained in the ship's Damage Control Book, are essential to making out damage-control bills. These bills

  sometimes are inserted in the Damage Control Book, but there is a growing tendency toward making them up into a separate book.

In addition to the standard damage-control bills listed and described in FTP-170B, Chapter 8, (doors and hatches, ventilation, drainage, fire main, etc.), a general damage-control organization bill, introductory to the others, and a damage-control communication bill, have been found useful in the case of many ships.

Other additional bills for systems or special procedures not listed in FTP-170B, Chapter 8, frequently are made out by individual ships. When believed to be of value to other ships, they should be reported to the Type Commander and the Bureau of Ships.

22-13. Compartment check-off lists. The purpose of the compartment check-off list is to provide, in each compartment, an itemized list of all classified fittings and other facilities employed in damage control by personnel responsible for setting material conditions.

These lists are developed from the tables, diagrams and fitting classifications listed in the ship's Damage Control Book and damage-control bills, and are checked by careful inspections of the individual compartments conducted by responsible personnel. These lists must be subjected to frequent checking and rechecking by divisions having cognizance and by the damage-control organization.

Each list should be permanently posted in its particular compartment, and should include all classified fittings and certain other facilities necessary to effective damage-control procedure. In addition to the name and number of the compartment, a list should show the name, number, location, purpose, classification (if any), and division responsible for the proper operation of each fitting. Instructions contained in FTP-170B, Chapter 8, should be carefully followed in the preparation of compartment check-off lists. It is important that a master copy of each list be kept on file in the damage-control office, and that it be kept corrected as changes are made.

22-14. Watertight integrity. The term watertight integrity may be defined as the effectiveness of the subdivision (watertight boundaries) of a vessel as measured by its ability to limit flooding resulting from damage. This effectiveness must be maintained as nearly perfect as possible.

Many hull piping systems of ships are essential to the attainment of damage-control objectives. Yet the very characteristics which make them useful create great hazards to the maintenance of ship's essential

 

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watertight integrity. Unless this is thoroughly understood, and the necessary steps taken to counteract the potential danger, an otherwise sound damage-control program may not serve to save the ship when severe damage is experienced.

22-15. Damage-control material and equipment. The Bureau of Ship's hull allowance list for each ship tabulates the material and equipment allowed that ship for damage-control purposes. The list is in a continual process of revision effected by frequent

  letters, general amendments, etc., from the Bureau of Ships to the ship concerned. The ship's supply officer can be of great service in expediting the requisitioning and procurement of all new material and equipment authorized for damage-control purposes. Continuous maintenance and replenishment of material and equipment already on hand is necessary. Frequent checks of the amounts on hand is most desirable. Fixing of responsibility for this in one reliable individual and requiring frequent reports are essential.
SHIP'S DAMAGE-CONTROL LIBRARY

Title Procurement Source
1. FTP-170B Reg. Pub. Iss. Office
2. FTP-222 Reg. Pub. Iss. Office
3. FTP-186 (FTP-209 for auxiliaries) Reg. Pub. Iss. Office
4. U.S. Navy Regulations BuPers
5. Fire Fighting Manual BuShips
6. Uses and Applications of Portable Emergency Pumping Equipment (NavShips 250-689) BuShips
7. General Specifications for Building Vessels of the U.S. Navy BuShips
8. Appendices to the General Specifications
No. 4-Specification for Riveting
No. 5-Specification for Welding
No. 6-Instruction for Painting and Cementing No. 9-Gaskets and Packing
No. 10-Nomenclature of Decks, Numbering of Watertight Compartments, Labeling
BuShips
9. BuShips Manual (including those Chapters from the C and R Manual and M.E.I. which are still in effect) BuShips
10. Nomenclature of Naval Vessels U.S. Superintendent of Documents
11. Gas! Know Your Chemical Warfare BuPers.
12. BuShips circular letters and bulletins in force BuShips
13. Diving Manual-1943 BuShips
14. Catalog of U.S.N. Training Films BuAer
15. Various Fleet and type directives on damage control Fleet and Type Commanders
16. List of authorized alterations Type Commanders and BuShips
17. Special liquid loading instructions (including ballasting) Type Commanders and BuShips
18. Sequence table for burning fuel oil (Flooding effect diagram modified by special directives) Type Commanders and BuShips
19. Damage Control Book BuShips or Building Yard
20. Booklet of Inclining Experiment Data BuShips or Inclining Yard
21. Booklet of General Plans BuShips or Building Yard
22. General Information Book BuShips or Building Yard
23. Schedule of watertight integrity tests and inspections BuShips or Building Yard
24. Damage-control allowance lists (Parts I, II, III) BuShips
25. BuShips hull allowance list BuShips
26. BuShips machinery allowance list BuShips
27. Hull Machinery Performance Data Book BuShips
28. Engineering Casualty Control Book Ship or Type Commander
29. Damage-control bills Ship or precommissioning detail
 

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Title Procurement Source
30. Compartment check-off lists Ship or precommissioning detail
31. Copies of hull plans Building Yard
32. Ship's Organization Book Ship, Type Commander or precommissioning detail
33. Book of Detail Specifications BuShips
34. War damage reports BuShips
35. Gas defense bulletins BuShips
36. First-aid bulletins BuMed
37. Enlarged copies of damage-control plates and diagrams Building Yard or BuShips
38. Shipper's Manual (Crivelli) BuPers
39. Handbook of Damage Control BuPers
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