Stability TheoryContentsList stability and stress data required to be supplied to ship under the current Load line Regulations, stating for each how such information might be used...................................................................................................3Explain why the information provided by a curve of statical stability, derived from K values should be treated with caution............................................................................................................................................!"iscuss the use, limitation and relative accuracy of E#$% of the following means of stability assessment. . .!&ith regard to the modern shipboard stability and stress finding instrument....................................................'(tate the hydrostatic and stability data already pre)programmed into the instrument...................................'"escribe the information to be entered into the instrument by the ship*s officer..........................................'"escribe the output information.....................................................................................................................'List the surveys required by the current Load Line regulations for a vessel to maintain a valid Load line $ertificate...........................................................................................................................................................+List the items surveyed at a periodic Load line survey, describing the nature of the survey for E#$% item.. .+(tate with the aid of a labeled s,etch, the minimum stability criteria required by the current Load line Rules.............................................................................................................................................................................-&ith regard to Load Line rules distinguish a .ype # vessel from a .ype / vessel and explain why they have different .#/0L#R freeboards.........................................................................................................................-.he current Load line rules permit a reduction of the permissible minimum initial 12 for some vessels with timber dec, cargo and the inclusion of the volume of this cargo in the derivation of the cross curves.3utlinethe circumstances under which this reduction is allowed and explain why this reduction is permitted............4"escribe .ype 5#* vessel under the current Load line Regulations, including the flooding, (tability and assumed damage requirements for a newly built vessel....................................................................................6"escribe the provisions of the current Load Line regulations governing the ability of some .ype / vessels towithstand flooding due to damage and the stability in the final conditions.......................................................6(tate the general requirement for a .78E / vessel to be given the same .#/0L#R freeboard as .78E # vessel of the same length..................................................................................................................................9:&hen converting .#/0L#R ;REE/3#R" to /#(5 "3 value must be interpolated between two sets of displacement to arrive at a desired displacement5 "! values dependent upon displacement and the displacement is dependent upon accuracy of weights onboard including the lightship displacement and "! The lightship "! and displacement may have changed !2 values are based upon assumed trim condition which may not be the same as actual Complicated by ,ree trim where the vessel changes trim with heel This condition is very much obvious in case of smaller vessels li'e offshore supply vessels trimming by the stern reducing the water plane area .eduction in water plane area reduces stability and therefore the "3 values Thus the !2 curve obtained using "3 values of fi-ed trim cannot be used with free trim ynamic factors ) synchronous, parametric rolling* cannot be appreciated by inspection of a!2 curve"iscuss the use, limitation and relative accuracy of AC# of the following means of stability assessment%implified %tability tables e.g. -a+ 'G.se #n the ships stability boo'let as a diagram or a table5 To assess compliance with statutory minimum stability re0uirements ?liminates the need to use cross curves or !2 curves for different loading conditions&nitial -etacentric #eight /G-0.se etermine initial stability of the vessel Can assess the vessels stability at small angles of heel #(@ Load Line .egulations states minimum !( values for different types of vessel Aowever in order to comply fully with the regulations other aspects are re0uired1ith regard to the modern shipboard stability and stress finding instrument%tate the hydrostatic and stability data already pre*programmed into the instrument. imensions and general particulars Capacity of all internal spaces BC!1LC!1,S( of all internal spaces )cargo, ballast, fuel, ,:* Aydrostatic particulars C isplacement, draught, TPC, (CTC, LC+, LC,, "( Light ship data C Light ship displacement and "! "3 data Stability limits )Loadline, !rain, Timber* Simplified Stability ata )e5g5, (a- "!* Stress Limits !rain Loading data )!rain loading boo'let* :ind Aeeling ata #ce Allowance ata"escribe the information to be entered into the instrument by the ship2s officer Location1weight of deadweight items )cargo, fuel, ballast, stores, fresh water, passengers* Load Line ;one .55 of seawater1doc' water .55 of li0uids )fuel, ballast, li0uid cargo* S5,5 of bul' cargoes )e5g5 grain*"escribe the output information eadweight summary Trim and draught )forward, aft, midships, freeboard* Aeel Stability Assessment C !(, !2 curve, dynamical stability etc5 Simplified Stability diagram and assessment5 Stress Assessment C Shear force, +ending moment, Torsion5 !rain loading assessment5 Local load assessment C e5g5, container stac' weightList the surveys required by the current Load Line regulations for a vessel to maintain a valid Load line Certificate. &nitial %urvey C Conditions of assignment of freeboard Annual %urvey Cwithin 8 months either way of the anniversary date of the load line certificate5 The surveyor will endorse the load line certificate on completion of annual survey Renewal %urvey C at intervals not e-ceeding % yearsThe period of validity may be e-tended for a period not e-ceeding 8 months for the purpose of allowing the ship to complete its voyage to the port of survey5List the items surveyed at a periodic Load line survey, describing the nature of the survey for AC# item.The following are chec'ed for condition and 1 or weather tightness )hose test as necessary*6 Superstructure 1 dec' house weather tight doors C effective means of closure and of securing weather tightness )dogs, clamps, hinges, weather tight seal* Aatch covers C effective means of closure and securing weather tight )cleats, clamps, wedges, rubber sealing* Side scuttles )portholes* C effective means of closure and of securing weather tight )clamps, sealing, hinges, deadlight operation* Side cargo doors C effective means of closure and of securing water tight )clamps, sealing arrangements* @ther dec' openings such as sounding pipe covers ullage pipe covers, tan' lids, sighting ports, manholes )dec' scuttles* C effective means of closure and of securing water tight )hinges, clamps, sealing arrangements* Air pipes C permanently attached means of closure5 !au;e to fuel tan's Bentilators C effective means of closure and securing weather tight )unless over a specified height* ,reeing ports in bulwar' C free movement of flaps Scuppers, inlets and discharges C effectiveness of non=return 1 storm valves Access C wal'ways, ladders, safety rails, bulwar's in good condition ec' fittings and appliances for timber load lines Load line and draught mar's Ccorrectly positioned and visible Any changes to hull or super structure which may affect stability )significant increase in Lightweight of ship* Any departure from recorded DCondition of Assignment )as detailed in D.ecord of Particulars* Presence of stability information +oo'let and 1 or Loading programme%tate with the aid of a labeled s!etch, the minimum stability criteria required by the current Load line Rules. #nitial !( not less than 45$% m5r5 (a-imum !2 at least 4574 m5r5 Angle of (a-imum !2 not less than 84E Area between 4E to 84E = not less than 454%% m5r5 Area between 4E to 94E )or >f* = not less than 454F4 m5r5 Area between 84E to 94E )or >f* = not less than 45484 m5r51ith regard to Load Line rules distinguish a 3ype A vessel from a 3ype 4 vessel and e+plain why they have different 3A4.LAR freeboards35P A 35P 4esigned to carry only li0uid cargo in bul' 3ot a Type A vesselAllows a small freeboard i5e5, less reserve buoyancy!reater freeboard than Type A The longitudinal hull framing in Type A vessels results in a high degree of sub=divisionsLess degree of sub=division?-posed weather dec' has high degree of integrity?-posed weather dec' has low degree of integrity Access to under dec' compartment is through small dec' openings which have watertight steel coversAccess to under dec' compartment is through large hatch openings which have only weather tight coversAigh degree of safety against flooding because of low permeability of loaded cargospacesBulnerable in heavy weather due to floodingAigh degree of sub=division Less degree of sub=divisionType A and + vessels have different tabular freeboards because6 The structural layout of both vessels are different ifferent types of cargo carried Permeability of the cargo tan's in Type A ships are low compared to Type + ships #n the event of a compartment flooding, oil from cargo tan' of Type A vessel will e-it the vessel causing a decrease in displacement and draught and increase in freeboard5 #n type + ships, the sea water will enter the space resulting in increase in displacement and draught and reduction in freeboard3he current Load line rules permit a reduction of the permissible minimum initial G- for some vessels with timber dec! cargo and the inclusion of the volume of this cargo in the derivation of the cross curves.6utline the circumstances under which this reduction is allowed and e+plain why this reduction is permitted (ust have timber certificate (ust have Assigned Timber ,reeboard (ust have solid stow of dec' cargo full length of dec' The vessel must have positive stability at all times and should be calculated with regard to6$5 #ncrease of weight due to absorption of water75 #ce accretion if applicable85 Bariations in consumables95 ,ree surface effects of the li0uids in tan's%5 :eight of water trapped in the bro'en spaces within the timber dec' cargo The stability calculations should include $%& increase in weight due to water absorption during the voyage5 "3 values may be increased for additional freeboard but only G%& of the dec' cargo volume may be used for additional reserve buoyancyThe reduction in the minimum permissible !( is due to6 ec' cargo stowed on full length of freeboard dec' acts as additional reserve buoyancy The additional reserve buoyancy is applicable only when the dec' cargo is well secured over entire length of the ships cargo dec' up to at least the standard superstructure height Timber dec' cargo provides a greater protection for the hatches against the sea The "3 values may be increased for additional freeboard however only G%& of the timber volume may be considered as reserve buoyancyZ GBZ GBFig. A Fig. B The principle of inclusion of the timber as reserve buoyancy in the derivation of the alternative "3 data is illustrated in the following figure #n figure A when the vessel is heeled beyond the angle of dec' edge immersion, !2 values are small when reserve buoyancy of the timber is not included i5e5, the !2 values are derived from ships ordinary "3 values #n figure + by using "3 values which include G%& of the volume of the immersed timber as reserve buoyancy causes an outward movement of + which increases the !2 values This increase in !2 value increases the range of stability and dynamical stability"escribe 3ype 7A2 vessel under the current Load line Regulations, including the flooding, %tability and assumed damage requirements for a newly built vessel3ype 7A2 ship @nly li0uid cargo in bul' A high integrity of the e-posed dec' and low permeability of loaded compartments Small access openings closed by watertight gas'eted covers of steel or e0uivalent material$looding requirements )@ver $%4m in length in summer load condition on even 'eel* Capable of remaining afloat in a satisfactory condition of e0uilibrium after flooding of any compartment with an assumed permeability of 45F% (achinery space shall be treated as a floodable compartment with an assumed permeability of 45H%%tability requirements )Condition of ?0uilibrium* ,inal waterline after flooding is below the lower edge of any openings through which progressive flooding may ta'e place ,inal angle of heel not e-ceed $%E )$GE if dec' edge not immersed* The metacentric height )!(* in the flooded condition must be positive The residual stability after flooding$5 .ange of stability of 74E75 (a- !2 not less than 45$m85 Area under !2 curve at least 454$G% m5r5Assumed damage requirements Bertical from the base line upwards without limit Transverse e-tent of damage e0ual to 74& of beam or $$5%m whichever is less Longitudinally between transverse bul'head "escribe the provisions of the current Load Line regulations governing the ability of some 3ype 4 vessels to withstand flooding due to damage and the stability in the final conditions.4*89 $looding requirement At the summer draught Capable of remaining afloat in the prescribed condition of e0uilibrium After flooding of any single compartment with an assumed permeability 45F% @ver $%4m, machinery space is regarded as floodable with assumed permeability 45H%4*:99 $looding requirement Capable of remaining afloat in the prescribed condition of e0uilibrium After flooding of any 7 fore and aft ad/acent compartments with assumed permeability 45F% @ver $%4m, machinery space alone regarded as floodable with assumed permeability 45H%%tability requirements )Condition of ?0uilibrium* ,inal waterline after flooding is below the lower edge of any openings through which progressive flooding may ta'e place ,inal angle of heel not e-ceed $%E )$GE if dec' edge not immersed* The metacentric height )!(* in the flooded condition must be positive The residual stability after flooding95 .ange of stability of 74E%5 (a- !2 not less than 45$mI5 Area under !2 curve at least 454$G% m5r5%tate the general requirement for a 35P 4 vessel to be given the same 3A4.LAR freeboard as 35P A vessel of the same lengthType + vessels can be given the same tabular freeboard as Type A of same length if the following criteria are satisfied6 Type +=$44 vessel satisfying the following conditions at summer draught6$* Steel watertight hatch covers 7* Access to the engine room protected by dec'house8* Provided with open rails for %4& of the vessels length9* Crew access between poop and detached bridge by open rail gangway or under dec' passage%* Shall remain afloat after flooding of any two fore and aft ad/acent compartment with an assumed permeability of F%& at summer draught1hen converting 3A4.LAR $R46AR" to 4A%&C $R46AR" as specified in the Load line Rules a number of corrections have to be applied/a0 List the geometric features of the ship which give rise to these corrections These corrections are for Type + vessels Aas a greater freeboard than type A vessel Aas lesser degree of sub=division Aas only weathertight large dec' openings Access to under dec' compartments is through large hatches in Type + vessels There are two classifications6 Type +=I4 and +=$44 3ype 4*89$* Any type + ship which is over $44m 7* Steel weathertight hatch covers8* Jualifies for a I4& reduction in the tabular freeboard of the difference between type A and type + freeboards 3ype 4*:99$* Any +=I4 ship over $44m 7* Steel watertight hatch covers 8* Access to the engine room protected by dec'house9* Provided with open rails for %4& of the vessels length%* Crew access between poop and detached bridge by open rail gangway or under dec' passageI* Jualifies for a $44& reduction in the tabular freeboard of the difference between type A and + freeboards/b0 +plain the reason for each of these corrections and indicate how each correction should be applied to 3abular $reeboard /actual values not required03ype 4*89 ) 4*:99 correction 4*89 :ith steel weathertight hatch covers 0ualifies for a I4& reduction in the tabular freeboard of the difference between type A and type + freeboards 4*:99 Jualifies for a $44& reduction in the tabular freeboard of the difference between type A and+ freeboards1ooden #atch correction Tabular freeboard increased if hatches other than those of the steel pontoon type on the e-posed freeboard dec'1raised 0uarter dec' or the forward 7%& of the super structure dec')i5e5 Position $*$lush dec! correction Bessel no more than $44m ?ffective length of the superstructure is no more than 8%& of ships length Tabular freeboard increased4loc! co*efficient correction +loc' co=efficient is measured at H%& of vessels depth Tabular freeboard is increased if bloc' co=efficient e-ceeds 45IH&dentify the additional corrections required when converting 4A%&C $R46AR" to A%%&G(" $R46AR", e+plaining the reason for each correction"epth correction The standard freeboard depth of a ship under the .ules is L1$% #f the freeboard depth e-ceeds L1$%, freeboard is increased #f the freeboard depth is less than L1$%, the freeboard may be decreased$5 Provided superstructure is at least 45IL amidships or trun' over entire vessel lengthCorrection for position of dec! line ,reeboard must be capable of vertical measurement A vessel with a rounded gunwale, freeboard must be corrected by the vertical difference between the actual position of the dec' line and the correct position%uperstructure correction ,reeboard reduced if superstructure of sufficient standard height or trun' of minimumheight and width This reduction will vary according to the length of the superstructure1trun' as a percentage of the vessels length .eduction proportional to length of superstructure1trun' if not standard height1breadth #f the superstructure or trun' is of less than the standard height1breadth then the correction will be reduced proportionally%heer correction Load Line rules assume a standard sheer for the vessel #f greater sheer than standard, basic freeboard decreased #f less than standard, basic freeboard increased #f the vessels amidships superstructure is less than 45$L, freeboard is not reduced4ow height correction The Load Line rules contain a formula for calculating minimum bow height based on the vessels length and bloc' co=efficient +ow height less than the calculated height, freeboard increased%ummer $reeboard Assigned only on @wners re0uest C only freeboard increasedCorrections are then applied to the Assigned Summer ,reeboard in order to determine the Tropical, :inter, ,resh :ater and Tropical ,resh water freeboardsA ship is loading in a port in a tropical ;one for one in the 1inter (orth Atlantic ;one duringwinter months."escribe the various precautions and considerations which must be borne in mind at the loading port in order that the voyage is accomplished safely and in accord with the statutory requirements, for e+ample the Load Line rules (inimum statutory stability re0uirements$5 #nitial !( not less than 45$% m5r575 (a-imum !2 at least 4574 m585 Angle of (a-imum !2 not less than 84E95 Area between 4E to 84E = not less than 454%% m5r5%5 Area between 4E to 94E )or >f* = not less than 454F4 m5r5I5 Area between 84E to 94E )or >f* = not less than 45484 m5r5 The vessel must comply with the load line regulations throughout the voyage, particularlyto ensure intact reserve buoyancy )Cargo hatches, ventilators, sounding pipes, air pipes, freeing ports* The vessel is going to another load line ;one and should be loaded so she does not breach the load line re0uirements Sufficient bun'er reserve for contingency plans Loading in a tropical ;one the mar's cannot be immersed more than the :inter load line with due allowance for fresh water, stores and bun'ers #f less than $44m in length in the :inter 2one she cannot immerse more than :inter 3orth Atlantic mar' Calculate consumption of fresh water and bun'ers up to entering the :inter 3orth Atlantic ;one Bessels stability condition throughout the voyage must ta'e into account ice accretion Stow heavy cargo as low as possible to lower ! Ade0uate lashing arrangements for dec' cargoes particularly for heavy lifts Shearing force, bending moments and torsional stresses must be well within limits (inimise free surface effects by completely emptying1filling tan's +allast tan's are not to be completely full to allow for free;ing li0uids ?-ternal fire lines must be drained ec' e0uipment stowed correctly )cranes, derric's etc*A vessel assigned timber load lines is to fully load with timber on dec! and in holds in a port in a 3ropical f* = not less than 454F4 m5r5 Area between 84E to 94E )or >f* = not less than 45484 m5r5Calculation to assess a vessels compliance should include a $%& weight increase in the timber dec' cargo due to water absorption5Alternative "3 tables ta'ing into account the increased freeboard due to a timber dec' cargo of a specified height may be used with an assumed reserve buoyancy of only G%& of the timber dec' cargo due to an assumed permeability 7%&5/b0 "escribe the various causes of any deterioration in the ship2s stability during the voyage The vessel is loading timber in tropical ;one and in most cases the cargo will be in a dry condition5 As the vessel progresses towards the destination in the loaded passage, she proceeds to the :3A area5 #t is possible that the timber cargo may absorb more moisture which may increase the weight more than $%&5 This reduces the !( and therefore !2 curve5 ,ree surface effect when fuel and water is consumed from the full tan's which reduced !( and therefore !2 curve5 Consumption of fuel, stores, ,: during the passage will cause ! to rise reducing the !( and therefore !2 uring winter seasons, as the vessel moves towards higher latitude, will encounter series ofdepression resulting in bad weather5 Seas on dec' will cause raise in ! due to added weight and also cause ,S? which reduces!( and !2 curve :hilst e-periencing heavy seas, if any of the lashing gives way and cargo brea' loose, it can result in catastrophic result due to deterioration of the stability of the vessel5 #f the vessel is e-periencing severe wind and spray on one side, it can result in unsymmetrical icing on dec' and superstructure As a result of this the vessel may list or loll over to due to increase in weight on one side5 This list or loss will reduce the vessels stability by way $5 reduction in !(75 produces heeling arm85 reduction in Area under the curve or the ynamical stability95 .educes the range of positive stability of the righting lever curve5%5 .educes the ma-imum righting lever5 #f the vessel is lolled over, then the situation is further worsened5 This is because, if the vessel is e-periencing severe weather and is lolled over then wind and wave motion will further heel the vessel5A vessel with a high dec! cargo will e+perience adverse effects due to strong beam winds on the lateral windage areas. +plain how the effects of steady and gusting winds can be determined and state the minimum stability requirements with respect to wind heeling under the current regulations A vessel with high dec' cargo will have considerably reduced stability when sub/ected to strong beam windsStrong beam winds acting upon large lateral areas of the ship will create an angle of heel The lateral area may be a combination of freeboard and height of cargo:ind heeling moments are produced by the force ),* over a lever )s* inclining the vesselTotal wind heeling moment )tm* < Force x Distance= F x A x s1000 Aeel continues until an e0ual opposite righting moment is produced!2 at angle of heel < Heeling MomentW= F x A x s1000x W :ind heeling moment is represented on a !2 curve by wind heeling )hori;ontal* arm Aori;ontal as the wind heeling moment is presumed to not change as the vessel heels:indage Area )A*Lever )s*C:ind ,orce ),*:ater resistance+.ighting (oment > heel:ind Aeeling (omentAeel!2 (inimum stability re0uirements$5 Applies to container ships with75 Lateral windage area greater than 84& of the beam85 Shipbuilder must supply !2 curve for worst possible service condition with95 Total windage area and position of centroid and lever to half the draught Steady wind heeling moment )K* )tm* < F x A x s1000 ),* 9H5% 'g1m7 )A* Lateral windage area )s* istance of centroid from L raught !usting wind heeling moment < steady wind heeling moment - $5% Steady :ind Aeel >$ is not more than I%& of )>de* Angle of ynamic Aeel )>dy* not more than )>f* S7 is e0ual to or more than Area S$"escribe the effect of a heavy list on a vessel2s stability :hen a vessel is listed ! moves off the centre line directly toward the off centre weight 3egative !2 is actually a capsi;ing lever 3egative !2 up to the angle of list 2ero !2 at the angle of list Positive !2 after the angle of list (a-imum residual !2 is reduced5 )Loss of !2 < !!A - Cos >* (a-imum loss of !2 when the vessel is upright )Cos > < $* ynamical stability is decreased )lost area under the heeling arm* Angle of ma-imum !2 slightly increased .ange of stability is reduced5 Angle of dec' edge immersion easily reached on the listed side :ith the ship already listed, the angle of list can be easily increased dangerously by e-ternal )wind and wave* forces An unstable vessel lying at an angle of loll to starboard has an empty double bottom tan! subdivided into four watertight compartment of equal width. 3he tan! must be ballasted to return the vessel to a safe condition"escribe the sequence of action to be ta!en and the possible effects throughout each stageAn angle of loll is created by a negative !( from a rise in ! when in the upright condition causing an unstable condition and the vessel to heel to port or starboard5 The empty double bottom tan' should be ballasted as follows6 Completely fill the inner low side a* @n commencing filling the free surface will initially increase the angle of lollb* As the tan' is filled the additional weight reduces the negative effect of free surface until the tan' is completely full and free surface is eliminated5c* :ith the additional weight of the full tan' ! has begun to lower Completely fill the inner high side $5 @n commencing filling the free surface will initially cancel out benefits of the additional weight on lowering !75 @nce completely filled the free surface will be removed85 :ith both inner tan's completely full any listing moment created by one will be removed by the other595 ! will continue to lower subse0uently increasing !( Completely fill the outer low side$5 ,illing the outer low side before the outer high side will prevent the vessel suddenly heeling over with enough momentum to cause a capsi;ing moment575 ,illing the outer low side can increase the angle of heel by introducing a listing moment85 ,ree surface will be present until the tan' is completely full95 @n completely filling the tan' ! will have been lowered considerably and the angle of lollto have also decreased Completely fill the outer high side $5 ,illing the outer high side last allows the danger of a sudden dangerous roll through the vertical to an angle of loll on the other side to be prevented75 ,ree surface will be present until the tan' is completely full85 @n completely filling the listing moment created by the full outer low side tan' has been removed95 :ith the tan's full # would e-pect ! to be lowered substantially restoring a positive !( and returning the vessel to the upright condition5#f not another tan' would need to be filled!?93"escribe how a vessel lying at an angle of loll may be returned to a safe conditionAn angle of loll is caused by a rise in ! creating a negative !( when in the upright condition causing an unstable condition and the vessel to heel to port or starboard5 ?nsure heel is due to a negative !( rather than an off centre weight creating a listing moment Alter course to put the ships head into the waves eliminating e-ternal heeling moment fromwave action which could create a moment large enough to capsi;e the already vulnerable vessel :ith consideration to wave and wind heeling moments 'eep the angle of loll on the same side to prevent a sudden and violent roll Lower ! by6$5 Shifting weights lower75 e=ballasting or transferring from high ballast tan's )high wing tan's*85 +allasting segregated low tan's )double bottom tan's* minimi;ing free surface during filling95 .educing free surface by pressing up lower tan's and completely emptying high tan's%5 ,illing one tan' at a time to reduce the free surface at any stageI5 ,ill the lower tan' before the higher tan' to prevent the vessel rolling through the verticalto an angle of loll on the other side with enough momentum to create a capsi;ing moment+plain the effects on the virtual loss of transverse G- due to the free surface effects whenthe slac! tan! is subdivided /a0 3ransverselyLossGM=L x B3x RDof Liquid12x xn2 ?ffective length and breadth of the tan' remains Dn refers to the longitudinal sub=division5 Area available for the free surface remains ,ree surface effect remains/b0 LongitudinallyLossGM=L x B3x RDof Liquid12x xn2 Area available for the free surface is reduced by the longitudinal sub=division ,ree surface effect is reduced and virtual loss of !( is then reduced Birtual loss in !( is proportional to the s0uare of the number of subdivision )n7* A tan' longitudinally sub=divided will therefore suffer less free surface and an increase in number of sub=division decreases free surface and decreases virtual loss of !(%tate the formula to determine the virtual loss of G- due to a free surface liquid within a rectangular tan!, e+plaining each of the terms used,ree surface correction ),SC* < Loss in !( < L - + 8- . of li0uid in tan' $7 - M - n7 )L* Length of tan' )+* +readth of tan' . of li0uid in tan' is the relative density of the li0uid in the tan' )M* Bessels displacement )n* 3umber of longitudinal subdivision of the tan'%tate the purpose of the inclining e+perimentTo determine Lightship "! Lightship LC! Lightship displacementList the circumstances when the inclining e+periment is required to ta!e place on passenger vessel :hen built After ma/or modification ?very % years #f any significant change is found with$5 Light displacement changed by 7& 75 Lightship LC! changed by $& of ships length+plain why a vessel2s Lightship 'G may change over a period of timeAccumulation of ebris in enclosed spaces Sediments and mud in ballast tan's Coagulated residues in bun'er tan's and bilges Paint coatings on internal and e-ternal surfaces .edundant spares Lost property on passenger shipsChanges to Ships structure #nternal furnishing particularly on passenger ships Bessels e0uipment e5g5, cargo handling gear.emoval of corrosion from ships structure"escribe the precautions to be ta!en by the ship2s officer before and during the inclining e+periment Ship initially upright +arges cast off (ooring lines slac'en down !angway removed 3o wind or little by the head or stern #n tidal conditions at slac' water !ood U"C for increase in draught due to heel Loose weights removed or secured All fittings1e0uipment such as derric's1cranes stowed in normal sea going position ,ree surface should be minimi;ed$5 All tan's empty1full75 +ilges dry85 ec's free of water All personnel not re0uired sent ashore Communication between person in charge and control station, the weight handlers and each pendulum station+plain why the values of trim and metacentric height in the freely afloat conditions are important when considering the suitability of a vessel for dry doc!ing3rim The vessel should enter the dry doc' with a small stern trim Upthrust )P ,orce* generated when the stern touches the bloc's increases as buoyancy decreasesPForce(t )=Trimx MCTCLCF Therefore a greater stern trim creates a greater P force-etacentric #eight /G-0 Birtual loss of !( commences as the ship touches the bloc's )Critical Period* and continues to worsen as P force increases (a-imum virtual loss of !( occurs at the Critical #nstant immediately before ta'ing the bloc's forward and aft as P force is at its greatest (ust have positive !( at the Critical #nstant5 .ighting moment created by the upward acting buoyancy force must be greater than the capsi;ing moment created by P force until ta'ing the bloc's forward and aft A larger capsi;ing moment will overcome the smaller righting moment and heel the ship Loss of GM=P x GWP ,rom the formula, loss of !( is directly proportional to P force and "!The values of trim and metacentric height of the vessel in the freely afloat conditions are importantfor the purpose of dry doc'ing the vessel when calculating the loss of !( due to P force and the resultant positive or negative value of !( and the value of the righting moment compared to the capsi;ing moment at the critical instant5"escribe the methods of improving the initial stability if the G- at the critical instant is found to be inadequate The loss in !( is directly proportional to the "! of the vessel5 Lower ! by :. Transferring high weights lower =. ischarging high weights >. e=ballasting high wing tan's and ballasting double bottom tan's .educe trim:. +allasting forward tan's=. e=ballasting aft tan's>. Transferring ballast forward from aft tan's erric's, cranes and riggings in stowed position (inimise free surface by completely filling1emptying tan's "eep minimal stern trim as proposed by the dry doc' plan+plain why it is beneficial to have small stern trim when entering dry doc!PForce(t )=Trimx MCTCLCF Therefore a smaller stern trim creates a smaller P force Stern frame is stronger than the bow and therefore better able to bear the P force A trimmed vessel can be aligned with the bloc's easier than a vessel on even 'eel"escribe the two methods of determining the upthrust /P force0 during the critical period$5P force )t* < .eduction in T( )cm* - TPC Throughout the dry=doc'ing procedures the true mean draught of the vessel reduces5 The DP force may be considered to have the same effect on True mean draught as if weight had been actually discharged5 Change in draught < : 1 TPC75PForce(t )=Trimx MCTCLCF #n the critical period after touching the bloc's aft the ship undergoes a change of trim The change of trim is the same as if a weighte0ual to the P force had been discharged from a position at the aft perpendicular "iscuss how a vessel2s still water rolling period is affected by changes in the distribution ofweight aboard the vessel :eights loaded at a large "! will reduce the vessels !( due to the increase in the vessels "! Loading a cargo with a high .5 at a low "! will increase the !( more than loading a cargo of a lower .5 at the same height above the 'eel :eight distributed toward the rolling a-is will reduce the radius of gyration :eight distributed away from the rolling a-is will increase the radius of gyration The natural rolling period for the vessel is given by T < 7 N " ?!( - g The above formula shows a change in !( or radius of gyration will change the roll period"escribe the different rolling characteristics of a vessel in a stiff condition and a vessel in tender conditionThe natural rolling period for the vessel is given by T < 7 N " ?!( - g T < period of roll in secondsg < acceleration due to gravity )F5H$m1sec7*" < .adius of gyration%tiff condition rolling characteristics ,rom the formula the rolling period is proportional to the !( Large !( cause a short rolling period !reater resistance to being rolled and will roll to lesser angles of heel ?-cessively stable, large righting moments cause the ship to return to the upright very 0uic'ly when heeled !enerally a ships natural rolling period is greater than the wave period5 Stiff ships have shorter rolling period and therefore more vulnerable in abeam sea3ender condition rolling characteristics Large !( cause a long rolling period The ship will have less stability, smaller righting moments causing a slow return to the upright Small righting moments offer limited resistance to rolling, causing the ship to be rolled to larger angles of heel The ship will be slow to return to the upright and will tend to remain at the e-tent of the roll for a comparatively long time+plain why a vessel laden to the same draught on different voyages may have different natural rolling period The radius of gyration may vary for every voyage )with same draught* as the distribution of weight with respect to the rolling a-is may vary #f the weights are moved away from the rolling a-is, the radius of gyration is increased resulting in a longer roll period with the ship will rolling slower (oving weights inwards towards the rolling a-is will cause the ship to roll faster Large !( creates a shorter roll period )stiff ship* Small !( creates a longer roll period )tender ships* So a change in !( for the same draught will result in change in rolling period as discussed above+plain the term %ynchronous rolling and describe the dangers, if any associated with it Synchronous rolling is the name given to the condition when the ships natural roll period is the same as the apparent wave period5 @ccurs when the waves push each time the vessel rolls causing a progressively heavier roll Theoretically this could cause the vessel to eventually capsi;e Aowever Synchronism is less li'ely to happen because6$5 .olling period increases at large angles of heel75 The wave period tends to vary over time85 The ships natural rolling period will be greater than the wave period Tender ships )long roll period* are less vulnerable in abeam swell than a stiff ship )short roll period* #f the sea is forward of the beam the apparent wave period is reduced whilst the sea abaft the beam increases the apparent wave period Therefore the sea on the 0uarter will increase the li'elihood of synchronism angers associated with Synchronous rolling6$5 Capsi;ing 75 Cargo shift, especially dec' cargo85 Structural damage to the vessel )rac'ing, surge of li0uids*95 Personal in/ury%5 own flooding%tate the action to be ta!en by the ship2s officer when it becomes apparent that the vessel is e+periencing %ynchronous rolling Alter course changing the apparent wave period Alter speed e-cept when the wave is not on the beam Alter vertical distribution of the weigh )+allast* changing !( Transfer weight vertically to change the !( Change the ships radius of gyration by winging out weightsA vessel2s side compartment is flooded as a result of a collision. "escribe the counter measures that may be ta!en in the event of flooding Close all water tight doors Use of ships pumps to remove water from the flooded compartment .estrict ingress of water Cross flooding C ballasting the other side of the vessel to bring the ship upright )movement of weights may also be considered* +allasting, when combined with cross flooding may result in the damaged area being raisedabove the water line .emoval of weight, particularly from the upper parts of the vessel )eg empty swimming pool* Shore up internally to prevent loss of ad/acent compartment Consider beaching .eference should be made to the stability data onboard providing guidance for sustainmentof damage #n addition the S(S should be brought into operation5 This usually involves informing ship owners of the situation and gaining access to advice from e-perts associated with Classification society and 1 or salvage companies"escribe the general provisions of the current Passenger %hip Construction Rules governing the ability of a Class & Passenger vessel to withstand flooding due to damage, and the stability in the final condition +ul'head ec' is the uppermost dec' to which watertight bul'heads are built (argin line is at least GImm below the upper surface of the bul'head dec' ,loodable length is the ma-imum length of a compartment that can be flooded so the ship floats at a waterline tangential to margin line depending on the permeability of the compartment$5 Permeability for cargo and store spaces )I4&*75 (achinery spaces )H%&*85 Passenger spaces )F%&* The vessel should remain afloat in the event of damage to any compartment ,actor of sub=division* is determined by ships length, passenger number and the proportionof underwater space used for passenger1crew and machinery spaces Permitted length between bul'head < ,loodable length - ,actor of sub=division+plain the e+tent of hull flooding assumed when calculating the ship2s ability to survive hull damageAssumed damage Bertical e-tent is from the 'eel upward without limit Transverse e-tent is 74& of the beam Longitudinal e-tent of damage is the least of$5 $$m between bul'head 75 8m O 8& of the length of the vessel #f the damage of a lesser e-tent than indicated above would result in a more severe condition regarding heel and !( loss, such damage shall be assumed for the purpose of the calculation5Assumed floodingThe number of compartments involved in the assumed flooded condition are based upon the factor of sub=division5 Lesser the factor of sub=division, lesser the Permissible length of the compartment and hence more the number of compartments ta'en into consideration for assumed flooding5 Aowever at any instant not more than 8 compartments are assumed to be in flooded condition5The vessel must be able to withstand the flooding of the following number of compartments$5 ,actor of sub=division more than 45% Any $ compartment75 ,actor of sub=division between 45% and 4588 Any 7 ad/acent compartments85 ,actor of sub=division 4588 or lessAny 8 ad/acent compartmentsProvided that where the re0uired factor of sub=division is 4588 or less the assumed longitudinal e-tent of damage shall be increased as necessary so as to include any 7 consecutive main transverse watertight bul'heads5Required %tability after $looding#n the final stage, after any e0ualisation )cross flooding* measures, the vessel must comply with the following condition (argin line not submerged .esidual !( at least %4mm ,inal heel not to e-ceed6$5 GE )one compartment flooding*75 $7E if )two or more compartment flooding* Positive residual !2 curve with a range of at least $%E Area under residual !2 curve at least 454$% m5r5 up to6$5 77E )one compartment flooding*75 7GE )two compartment flooding*85 >fwhichever is least (a-imum residual righting lever to be the greater of6$5 45$4m 75 Aeeling moment O 4549 m isplacement

Aeeling moment to be the greater of6$5 Crowding of all passengers towards one side75 Launching of fully loaded davit launch survival craft85 :ind pressure 6utline the additional factors ta!en into account to determine the permissible length of compartments in ships built after :@@9 Permissible length < ,loodable length - ,actor of Sub=division The features of the ship that are considered in determining the length for the purpose of subdivision calculation includes6$5 +loc' co=efficient 75 ,reeboard ratio85 Sheer ratio95 Compartment permeability%5 Bessel lengthI5 Passenger numberG5 The proportion of the underwater space used for passengers1crew and machineryspace The permissible length between the compartments is reduced )due to decrease in the ,actor of sub=division* when$5 The length of the ship is more75 (ore number of passengers are carried85 (uch of the space below the waterline is used for passenger1crew accommodation and or machinery space"iscuss the stability problems associated with the 3owing vessels and precautionary measures to improve the stability of such vessels %tability problems All harbour tugs can e-perience very large athwart ship forces when towing Such forces result in large heeling moments causing the vessel to heel over to a large angle reducing the vessels dynamical stability ?specially when the towline is short and has low elasticity ynamical forces during the towing operations induced )e5g5 a sudden surge in the propulsion unit* and changes in trim caused by the pull on the tow line !irting is a sideways pull on the tow line when the ship is pulling away from the tug lying abeam to the direction of the pull5 The heeling moment is a capsi;ing momentPrecautionary measures A large beam1length ratio increasing the freeboard and reducing the height of the towing point Using long tow lines with high elasticity reducing sudden heeling moments caused by high pea' forces .is' of girting can be reduced by using !og1+ridle rope !og1+ridle rope used to hold the towline down at or near the stern of the tug which ensures that the tug is brought into line with the direction of the pull avoiding a capsi;ing moment .educing speed of towed vessel reducing the ris' of girting .educing speed of towed vessel also reduces the vessels bow wave and the produced heeling moment on a tug as ta'ing a forward line+plain the meaning of $ree 3rim and its particular reference to offshore supply vessels ,or supply vessels "3 values are based upon free trim5 "3 values are reduced to ta'e into account the effect of the vessel trimming by the stern when healed at large angles :here reserve buoyancy of the forward superstructure ta'e effect, causing reduction in !2 ,ree trim is e-plained as follows6 ,ree trim effect in offshore supply vessels with high forecastle )normally forward superstructure* and a low wor'ing after dec' :hen ship is heeled to immerse the after dec' line, the forecastle remains well over the water line The water plane area aft has been lost causing , to move forward5 The ship trims by the stern As the ship heels further the reserve buoyancy of the forward superstructure ta'es effect causing LC+ to move forward This accompanied by the continuing forward movement of LC, causes the ship to trim significantly further by the stern as it continues to heel This situation leads to the danger of the aft dec' flooding Stability is greatly reduced due to the reduction in water plane area and hence reduction in the "3 value #f the "3 value has been calculated for fi-ed trim this will result in an incorrect !2 curve and will show that the vessel has better stability than it actually has at large angles of heel beyond the angle of dec' edge immersion Therefore "3 values of the ship should be derived on a free trim basis "3 tables should have the statement DCorrected for ,ree trim"iscuss the stability problem associated with the design and operation of a conventional 6il Rig supply vesselLoading)"ischarging cargo at sea Affects the vertical, transverse and longitudinal position of ! :ith cargo operations ta'ing place with the vessel rolling and pitching in a seaway Li0uid cargo with ,S? loaded resulting in virtual loss of stability+cessive %tern 3rim Created by longitudinal distribution of loaded weight @ccurring during cargo ops or cable1anchor handling Causing immersion of after dec' reducing water plane area and critically reducing stability1ater entrapment The wor'ing dec' is often used to carry drill supplies, machinery, pipes etc5, some retaining large amounts of water after shipping seas (ust be allowed for in stability calculations$ree 3rim ,ree trim negatively affects !2 Loss of stability after the dec' edge immersion due to vessel trimming by stern after heeling%tabiliser 3an!s (any vessels are fitted with flume stabili;er tan's Counter=productive during cargo ops or cable1anchor handling A heeling arm results in water in the stabili;er tan' moving to the low side increasing list Loss of stability due to significant generated free surface effect1hat are the recommended measures to improve stability of the offshore supply vesselsA ischarge high cargo first Use ballast to counteract negative effects on stability from loading1discharging (inimise and calculate for initial ,S? when ballasting at sea Calculate for ,S? of li0uid cargo being discharged on vessels stability Load1discharge cargo to maintain ade0uate trim and1or freeboard at all times Ade0uate drainage should be made between stowage rac's and freeing ports Use of pipe plugs to prevent water retention Allow in stability calculations for the entrapment of water Use "3 tables DCorrected for ,ree Trim for calculating !2 curve Calculate vessels stability considering ,S? from stabiliser tan's Test emergency means of discharging stabiliser tan's At sea close transverse connections between port and starboard cargo1service tan's"escribe the stability problems associated with a conventional Ro*Ro ferry Unrestricted vehicle dec' e-tending the length and breadth of the vessel, vulnerable to ,S? Substantial loss of stability and capsi;e after vehicle dec' flooding Causes of flooding6:. amage to bow1 stern door at sea=. +ow1stern door left open at sea>. +ow1stern door open and unattended during loading 1 discharging operationsB. Loss of watertight integrity due to collisionC. Loss of water tight integrity due to a vehicle shift in heavy seas8. Use of water curtains and inade0uate drainage Lac' of time in port for calculation Lac' of detailed information about cargo units and disposition Aigh "! of cargo units on vehicle dec' Bulnerability of .o=.o units to shifting in heavy weather Aigh windage area of .o=.o vessels1hat precautionary measures must be adopted to improve stability of Ro*Ro ferries Automatic draught gauges at stem and stern with remote reading ensuring the flooding of the vehicle dec' in port is avoided A loading computer must be available to the ships officer in port for rapid calculation of stability before the departure #ndicator lights on the bridge to show when shell1loading doors are open1closed Aeavy .o=.o cargo units weighed ashore and the information provided to ships officers Such units must be secured by chains to the dec' #ncreased drainage for vehicle dec's Stoc'holm agreement provides enhanced stability re0uirement for .o=.o passenger ferries with %4cm flood on vehicle dec' Sub=division on the vehicle dec'"escribe %toc!holm agreement with reference to the stability requirement of Passenger Ro*Ro vessels Purpose $5 Lays down the stability re0uirement for Passenger .o=.o vessel75 These upgrades S@LAS F4 standards85 Ta'es into account the effect of water accumulation on the vehicle dec' after damage, ma'ing the ship safer in heavy seas95 Applies to all Passenger .o=.o vessels operating on scheduled international voyages between or from designated ports in northern ?urope irrespective of ,lag Requirements $5 emands that a vessel satisfies with the re0uirement of S@LAS F4 with a constant height of water on dec'75 The height of water on vehicle dec' is based on a 954m significant wave85 The height of water should be 45%m if residual freeboard at the damage opening is 458m or less95 The height of water should be 454m if residual freeboard at the damage opening is 7m or more%5 #ntermediate values can be determined by linear interpolation