A lifebelt around the ship - No rapid capsize

1.940 1945 CONVOYS

F(LtjNc1 TIlE TwEENDCKS O MERCHANT LINERS

AROUND Ti(E WATERLINE, AT THE SHIPS SIDES

wiî4 ErIPTY

OIL DRUMS

AFTER 8EIN

HIT) 5INKIN

TOOK 3EYERAL HOURS

AND 5pIIPS SANK UPRIGHT

(D.K.SROWN UK)

TECHNISCHE UNIVER$rrEIT

Laboratorium voor

Scheepshydromechan;ca

Archief

Mekolweg 2, 2628 CD De!ft

Tel.: 015-786873- Fax:

015 78iC3

A LIFEBELT AROUND THE 5HIP

NO RAPIt CAí5IZE

£UMMAY

E'IER

)NCREASINC' ROAD-t-tWLAE (..LEARLY INDICATES THPJ

THE RO-RO-SE.A-TRANSPORT OVER THE 5HORT DISTANCE

IS AN ESSENTIAL LIMK OF THE FAST DOOR TO DOOR

CONCEPT.

-

SEA-TRANSPORT 0F

PASSENGE.RS,HIGHVAWE cARGO AND

CHEMICALS MUST BE AS SAFE AS POSSIBLE TO PREVENT

LOSS OF LiFE AND AVOID POLWTIOM-HAZAROS.

TRANSVERSE BULKHEAD 'COIIPARTIMEMTATIOH IS NOT

COIIPATIBLE WITH THE

RO-RO CONCEPT.

IT IS THEREFORE ESSENTIAL THAT WE FIND OTHER

r1EANS

TO AVOID RAPID CAPSIZINC

IN CASE OF A

COLLISO1'4 AT THE SHIPS

SIDE

OR

ROONDING.

THIS PAPER DEALS WITH PERNANEtIT BUOYANCY

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FAST CAPSIZING

PROPOSALS OR PERMAME,lr BUOYANCy

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TWN i'OIP WINGTANK5 AR COr1PULORY

Recent accidents with Ro-Ro passenger ships show rapid capsizing;

Current methods to assess damage stability

are inadequate;

In this paper possible improvements on

existing ferries and new designs are described to obtain a higher standard of safety. QUESTIONABLE DAMAGE STABILITY:

EUROPEAN GATE'J AY;

TRANSIENT ASSYMETRIC FLOODING

(Spouge).

TYPE OF SUBDIVISION

PE R M E AB IL IT Y

INCREASING BUOYANCY IN SHIPS WINGS,

SIDE

' ALLS (D.K. Brown, Aston and Rydill).

HOW TO MEET FUTURE STANDARDS

PROPOSED BY IMC' SL'B-COM. SEPT. '87

LONDON. (JR HAMNAK)

IMPROVING EXISTING FERRIES - NEW'

DESIGN

HULL INTEGRITY, WATER ON CARDECK,

FINS

RAPID DISEMBARKATION: 'MES'

STABILITY CHECK, CARGO PROBLEMS,

PROCEDURES

STEERING - MANOEUVR!NG AT PORT

ARRIVAL IN STRONG 'INDS.

HEELING IN SHARP TURN AT FULL SPEED

BY

A SUDDEN

'HARD OVER' RUDDER

Questionable Damage Stability Range

Ro-Ro passenger damage stability requirements for

psenger ships according to the SOLAS 19Th

Convention, including the amendments, should be

revised.

The British Department of Transport (1980) and The

Netherlands Shipping Inspection (1983) improved

SOLAS by implying extra requirements: Final Stability Arm > 0.05 m-Range 70 minimum. Furthermore, during any stage of flooding the margin line should not 5e immersed.

This

stability

standard is applicable to passenger

vessels and Ro-Ro passenger ships without making

any difference.

In

R0 Ro PA5SENE FEIRIE5

However, it should be realised that both types are

behaving quite differently when struck by a flared

forebody with an extending bulb underneath. On the conventional passenger ship, when listing, the bulkhead deck often comes quite near to the

waterline and when rolling in waves, flooding over

the bulkhead deck can easily occur.

However, the

flow of water entering is limited by fire bulkheads

and partitions between cabins.

On the Ro-Ro vessel there is no compartmentation in

the Ro-Ro space above the bulkhead deck, (which

normally extends over the full breadth), and in a few

minutes a large mass of water can move freely and

wildly over

a

large surface of

this

vehicle deck.

The moment of inertia

of

the vessel's waterline is

enormously reduced and rapid capsizing is likely

within a few minutes. For this reason Ro-Ro vessels

should comply to a higher damage

stability

requirement.

In view of the increasing traffic density, and the

quite realistic probability of being hit at a partition

bulkhead, a 2 compartment standard for all Ro-Ro

vessels should apply.

Moreover an alarming phenomenon is

indicated b)

Mr. Spouge in his 'Investigation of the Sinking of the

Ro-Ro Ferry EUROPEAN GATE' AY'

(The RINA Apr. '85, The Naval

Architect,

March, '86), the so-called 'Transient Asymmetric Flooding.' After being hit at her side by the bulb of SEASPEED VANGUARD, a mass of water entered via the

bulb-hole which represented a wave front

moving into the engine room. Equalising of the surface went

on quite slowly.

The dynamic character

of this

calamitous insult on the

ship's

stability

has been underestimated.

The sloped surface (10-13°) caused a larger angle of

heel than would follow from the assumed standard

'static'

flooding calculation. This complication caused the side

of the bulkhead deck to dip

well below the waterline diminishing the moment of

inertia.

The flared bow of the SEASPEED VANGUARD had

holed the

topside of

the EUROPEAN GTEV, AY

allowing water to enter freely.

Personally I greatly appreciate this thorough

investigation; for the first time attention has been

paid to the 'Dynamics of Transient Asymmetric Flooding' which caused the unexpected immersion of the bulkhead deck, followed by flooding of the Ro-Ro

Further research on this subject

is urgently needed

and should be carried out on a large scale.

Scale

errors on model testing are to be avoided. Consequences on Type of Sddivision

Transverse Subdivision

Should flooding calculations be carried out

in the

future by application of 100 sloped masses of water

entering during the first minutes? (PiNI LOÛD CALC.) Longitudinal Subdivision

In a vessel which is subdivided by continuous

longitudinal bulkheads (at B/5 from the ship

sides)

the rate of overflow of the mass of water from the

port wing tank to the SB wing tank, via the

cross-over duct, plays a very important role in the

heelirg of the vessel; ducts should be made as large

as possible (2-3 frame spacings at least).

The Netherland Shipping Inspection requires a

maximum overflow time lapse of

1

minute in which

case this

asymmetric effect may be

disregarded.

Research on the rate of overflow should be carried

out on a large scale imitating all discontinuities and

sharp edges of the vessels cross-over duct, assuming several sizes of the hole in the damaged shell.

Perm eab il t

Current permeability figures appear to be unrealistic: SS 90 for engine rooms is

applied, however a more

likely figure for engine compartments is 90-95 9 In order

to minimise immersion and heeling of

a

vessel by masses of water entering,

it

is logical to

reduce the

permeability of the flooded

compart-rints, especially in the waterline.

Per rnanent buoyancy could be applied

in the

void

wing spaces by stowage of empty drums; this idea.

according to Mr. D.K. Brown, was carried out on

merchant vessels sailing in convoys during World War

II, by stowing empty oil drums in the sides of the

tween deck spaces ai waterline level.

One of these

ships HECTOR was hit by 6 torpedoes and still took

several hours to sink.

Moreover the ship sank

in

upright condition.

Permanent buoyancy should be developed and might improve Ro-Ro Passenger

vessels which are

built

under the 1965 Rules and presently do not comply

with the later 1980 Standards of the British Department of Transport.

Polythene drums or balls seem to be suitable in the

void wing spaces because they cannot corrode and

can be easily removed. (Many alternatives are

mentioned in the table of

At any time the ship structure and appendages should

lu

be accessible for inspection.

Considering the fire-hazard, the polythene drums _are

to be kept at a safe distance from shell plating and

bulkheads, where outside repair welding is

likely to

occur.

Drums could be lashed either

vertically or hori-zontalh, depending on location.

Polythene balls bundled in nets might also be applied in narrow compartments, (collapse-safety because of natural form).

Steel drums are heavy, might rust and will collapse

at 6 metre water pressure.

However they might be suitable in the wings of engine compartments because of fire-hazard.

By proper stowage a permeability of 50-60% could be

achieved, and it

_{is a challenge to all of us to find a}

practical method of

tilling the

void spaces during

fitting

out

and local

removal in case of repair. Loss of deadweight and costs of permanent buoanc seem to be reasonable.

A much greater increase of damage stability

range

can be achieved by surrounding the Ro-Ro space by a double hull: so-called 'Side Walls. (Aston and Rydill,

The Naval

Architect,

April, '87).

In case of a wall width of 0.13 B. the moment of

inertia of

the waterline is doubled and the vessel

could survive a completely flooded cardeck.

In case of application of side walls,

having about

8

ft. 'container-width' and filling these

_subdiided

spaces by polythene drums, the vessel most probably

will surive a collision at her side.

The depth of impact will be reduced by the more

resistant steel structure in the ships side.

(On top of the side walls a marine 'escape slide and raft can

be accommodated to allow for a rapid

disembarkation).

The Ro-Ro design of maximum hull safet is

characterised by continuous:

Longitudinal bulkheads at

B/S below

the

bulkhead deck (without

watertight doors). Void Wing tanks

filled

up with drums.

Side walls around the Ro-Ro space.

Engjrieers could sail with

watertight

doors in

transerse

E.R. bulkheads 'open in order to be

capable of immediate action in case of fire,

short circuit or leakage.

Closing these watertight doors is no longer a must

'within one minute' because engine compartments are

THE LIFPELT

Ivir. D.K.Brown of the British Linistery of Defense

save me a stron

support to the oriina1

football-proposal on buoyancy durin

RINA, Juxìe 198E, on The

Sfeship Froject: Ship Stability and Safety. He told

about lessons from the past learned in World

ar II,

when empty oil drums it ships sides in the t.eendeck

saved the ships from rapid capsizing.

Since l96

a few RoRovessels capsized rapidly

with loss of life.

- A fast capsize should be IWP0S$IFLE when considerin

passen;ervessels and shis - carrying danerous cargo.

- A practical LIFEBELT around the vessel, whether

in-side or outin-side (sponsons) of the shell should leave

time to get 20CC lives off the vessel.

- It is right to distinguish between: preservation of

waterplane inertia and preservation of buoyancy in the

hull.

- However, we must consider the inuial heavy list in

the first minutes after the collision, if extra

per-manant buoyancy is only installed in the

aterline area.

- I)rnnis deeper down, than

half of the draft will

support the ve:sel already at a smaller list.

- Square- or shaped blockbuildinrs of polystyrene foam,

well lashed, appear to he the cheapest solution for

buoyency insice void wing spaces. Low specific aeiht

makes it attractive: 15 K/m3. Howver, it should be

of fire retarding quality, and coverea by fireproof

material to prevent a fire which might be caused by

flame-cutting and welding during repairs on caroeck

and shell.

FOL

the moment, steel- or aluminium drums seem to be

a practical solution for permanent buoyancy in the

wina of bransvrrse engine spaces but these spaces

will

ive many problems because they are normally

- We

hosld envisage the sidebox or

double-hull-principle

hich is applied to cellular containerahips,

containe_bulkcarriers,

nd cherical tankers.

- The floating drydock has to float on her sideboxes

and in case the width of these boxes is 0,13 b, the

waterplane inertia of the boxes 'is identical to the

wa Lerplane inertia at breadth b be tween the

boxes.

-

e should desin a RoPovessel to be

c.able to float

on her sideboxes with centre

hold(s) flooded.

- To obtain Ibis

ho.'ever, the sideboxes are to be

filled with permanent buoyancy and damage is suppooed

to b

no loner than 0,03 L

+ 3

m

ein

the 1enth of

aaiiage, defined by Ih0.

-

'rrboord of the sicleboxes to he oluate in order

to ooapen3ate the lost buoyancy.

- The Catamaran cannot

be applied

ith crossf1oodin

ducts ano permanent buoy-3ncy is strongly recommenced

into the side hulls to preveflt a capsize after

buLl-Oam a ge

- Asmmetic

buoyancy in a vessel to be avoided as

stated by J!r Brown as a warning to deai:ners.

- Many so called nonwatertight compartments hold back

water for a long while, particularly refrigerateu

spaces and strong rooms; quite lnre asymine cric

moments could develop.

Pules to apply real actual premeabilities in view to

be able to calculate with permanent buoyancy are

J1j_

(4

PLATRF:D SPONSONS

- In principle I aree on slihtly flared sides ir

crãer to provide reserve buoyancy needed for situations

of vehicledeck floocing, while minimizing the morcase

of beam of the ship in the waterline and the associated

increases in rolling stiffness and ship resistance.

- In first instance I tried to improve the safety of

existing PoRo-ships without the application of sponsons.

- Sponsono are very effective indeed, howevcr very

expensive for the owner, because of the fact that

conversion does not apply to the ship only but terrr.inls,

rampconnectio'ns most probably are to be adapted and in

sorne cases any increase of beam is even imposaible

(locks-Hull).

- Sponsons are adaing about 6(0 ton to the lightweight

of a common ferry and without extra displacenent the

draft might increase 0,2 ni

- Adding draft to a ferry is strictly prohibited;

and many ferries already are suffering from toc much

draft-aft, due to a stern being too slim.

- Therefore I scetched the sponsons with vertical sicea

ana gave Lhern a very soft bilge racius in cIder to

minimize extra resistance.

- My sponsons might be too bulky but give an

extra

buoyancy to compensate for the extra weight.

- 1oreoever, flared sides are a nuisance to the ships

staff when msnoeuvring alongside quas or into a lock

at high-tide and low-tide.

- Many beltings are necessary at several levels to

avoid damage to the shell plating and the seafarers

are asking us to provide vetical ships sides as far

as possible and fit the vessel with vrtical cylindric

- As a note I

like to mention the application of

flared sides to con LainersLips orLälulnbercarriers,

in order to obtain a more balanced stat ilit

in

badea- and in ballast condition.

- A practical problem turned out to be the pilot-ladder

bein. unstable, free han.in

without support by

the shell.

- After bein

into service a vertical box 'ith

sloped sides baa to be v.eloed to the flared shell

locally.

- This however does riot

apply to ferries, because

these vesaels aon't need a pilot.

PRORCSSIVE FLDODING

IS PREVENTED

BY FIRE- Bu LKHEAS AND CA5INPARTITION5

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Sinking of the ro-ro ferry "European GatewaV'

Dec '82

13'

.R.

POUCE.

Tn

NPyAL ARC.IIITE.CT

MARCH 8'

EXTRACT:

Maximum penetration of the bulbous

bow was 2.Om from the side shell (2.2m

from the line of moulded beam), al-Though the O.5m deep homes caused damage up tot 2.5 m inside the shell.

Maximum penetration of the upper

deck was 3.5m from the side shell

(4.Om from the line of moulded beam j.

The technical investigation

of the flooding

The object of the investigation of the flooding was to determine firstlywhat had caused the unusually rapid heeling and sinking, and secondly what,¡f

any-thing, could have been done to prevent

It.

Traditional damaged stability

calcu-lations

The EUROPEAN GATEWAY complied with the current UK statutory require-ments for subdivision of passenger vessels,

which implement SOLAS

1960. These effectively require a one-compartment standard, where the ship will survive with any one compartment below the bulkhead deck flooded.The

bulkhead deck for the EUROPEAN GA-TEWAY was the main vehicle deck,and the spaces above this deck are neglec-ted in the calculations since they are not required to be watertight, although

they would have

provided some

buoyancy, especially in a rapid ssnkng.

Traditional damaged stability calcula-tionS, which were used at the design stage to check that the ship complied

with the rules, Indicate that sinking

would initiolly have been on an even keel (i.e. no 11511, since the compart-ments which flooded were symmetri-cal about the centreline. The free-surfa-ce loss due to water spreading over the four compartments below the bulk-head deck would eventually have been sufficient to give the ship a negaive metacentric height (GM). which would have caused a sudden capsize, or at least a lurch to an angle of loll. This does not agree with the available evi-dence (figuur 131, which strongly

indi-cates that the ship began to heel

imme-diately after the collision, and that this heel steadily increased, at least until the Ship grounded. A more detailed consideration of the flooding is impos-sible using this approach of its omis-sion of time dependency. The traditio-nal approach is therefore unsuited to explain this rapid sinking.

Probabilistic damaged stability cal-culations

Aithough the probabilistic approach is only a sophisticated application of a, large number of traditional damaged stability calculations, and therefore contains the same faults, it does indica-te the general level of safety of the ves-sel in terms of survival following floo-ding.

The EUROPEAN GATEWAY would flot comply with the new probabilistic

da-maged stability regulations adopted in 1MO Resolution k265 (viii) as an alter-native to SOLAS 1960 for passenger ships. This requires a subdivision index (based on the ships length, passenger! crew numbers and lifeboat capacity) of 0.583, while the ship'i achieved index (based on simplified point probabilities of compartment damage and ship sur-vival) was only 0.437. Limited experien-ce with these subdivision indices

indi-cates that the EUROPEAN GATEWAY was safer than most Ro-Ro vessels, due

to its substantial subdivision below the main vehicle deck; but was

considera-bly less safe than required under the probabilistic regulations, largely due to its lack of freeboard to the mein vehicle

deck.

Causes of the heeling

Various possible causes of the obser-ved heeling were considered at the

In-vestigation, concentrating on those

which may have started the process oil, since once a list to starboard was achieved, water collecting on that side of the ship would help to continue the heeling. lt would certainly have requi-red a considerable moment to achieve this initial list, since the EUROPEAN GATEWAY'S roetacentric height before the collision was 2.87 m, with free-sur-face losses of 0.74 m. This would requi-res moment of 12.OMNm,to cause a list, and 24.2MNm to immerse the main vehicle deck (i.e. the lip of the hole abo-ve the waterline).

l'ransient asymmetric flooding

The generator room, which flooded

first, is a shallow "U" shape, containing the generator and numerous pumps, pipes, floorplales and pillars. The da-mage hole was on the starboard side,

extending for half the height of the

compartment, while the only

signifi-cant

exits were the comparatively

small doors to the engine room (on the

centreline aft) and to the stabiliser

room (on the forward port bidet. It is li-kely that the many obstructions to the

flow of water across thi& compartment prevented the water surface becoming level, which is the implicit assumption in ;raditional damaged stability calcu-lations.

In the initial stages, the wave was ob-served to move across the comport-ment like a wall. Subsequently, as Wa-1er poured in at about 20 tonnes/sec on the starboard side, a considerable gre-dient would probably have remained 'on the water surface, albeit badly

dis-'totted by the turbulent flow and the

sioshing response to the ship's motion.' This effect could have caused heeling to starboard, decaying from the initial large heeling moment to a negligible moment as the compartment filled up. A mean slope of 10, for Instance, oit

the water surface ¡n the generator

room would cause a heeling moment of12.4 MNm.

Such asymmetric flooding of symme-trical compartments has not been pro-posed before, to the author's knowed-ge, but both NM) Ltd and the German consultants Schiflko

(on behalf of

Townsend Thoresen) were Indepen-dently driven to conclude that this ef-fect must have been present, since the otherpossiblecauses described above seem inadequate to explain the obser-ved heeling. Subsequently, the Court reached the same conclusion.

Some lessons from the

accident

Improvementa to damage contiol procedures

The nkirig of the EUROPEAN GATE-WAY following the collision occurred mainly because it was impossible to close the watertight Coors sufficiently quickly. Until this accident, it was com-mon for UK ferries to operate with we-lertight doors in the machinery spaces open, except in fog. The relevant sec-tion of the Merchant Shipping Reg ula-' tions, 1980, states that every watertight door "shall be kept closed at sea except when it is required to be opened for the working of the ship". The practice is therefore justified to some extent by the need for the small complement of engineers to have immediate access to all the machinery compartments in ca-se of breakdowns or fires. The Court considered that it was reasonable for the EUROPEAN GATEWAY to have open the two doors furthest aft, but that it was not necessary for the working of the ship to leave the door between the generator room arid the stabiliser room

open.

The NMIFLOOD simulations suggested that even with this door closed, the EU-ROPEAN GATEWAY would probably have sunk ¡n the weather conditions at the time of the accident. llttiough she

might have survived in calm water.

(Data from Ref. 3 was used to evaluate the 1ielihood of capsizingdue to wa-ves.) With all doors initially open, the

* simulations demonstrated that only

power-operated doors, closed within 50 seconds of the collision, could have saved the ship. The Court accordingly recommended that all ferries be fined with power-operated doors (Indeed, this had largely become UK practice following the accident).

Improvements to the subdivision of Ro-Ro ships

Afthough the EUROPEAN GATEWAY satisfied the current UK requirements for passenger vessels, it proved to be vulnerable to this type of accident in the particular circumstances where the hull was breached below the waterline and also just above the bulkhead deck. This deck (the main vehicle deck) beco-me imbeco-mersed at only 1O heel, allowing water to flood the entire length and

width of the ship. The NMIFLOOD si-mulations showed that once 12 heel had been reached, water entered this space at such a rate.that even with all, watertight doors closed the ship would eventually have capsized or grounded. Probabilistic methods of calculating damage survivability may well provide a more reliable basis than the current damaged stability and load line rules,' both for assessing possible improve-ments and for regulating the subdivi-sion of these ships.

implications of transient asymmetric flooding

Only the lack of a better explanation for the sinking of the EUROPEAN GATE-WAY points towards the existence of asymmetric flooding in symmetrical compartments.

Furthermore, ¡lis likely that such a phe-norrienon would only occur in certain crowded compartments or with certain sizes of damage holes. Nevertheless, the concept has considerable impor-tance for the assessment of the dama-ged stability of ships. In particular. it suggests that rapid local flooding may be accompanied by rapid heeling, and that in such cases the statutory free-board requirements may be inadequa-te to prevent exinadequa-tensive further floo-ding. More research into this pheno-menon is underway at NMI Ltd. Finally. a model reproduction of the sinking, in-cluding consideration of scale effects,

would confirm or modify the

NMI-FLOOD simulation, and could be exten-ded to show the probability of this type of sinking recurring in the future.

Conci us ¡on s

The sinking of the Ro-Ro ferry, EURO-PEAN GATEWAY, following a collision, occured surprisingly rapidly. The tech-nical Investigation, although relying on somewhat uncertain evidence, was 'able to interpret the collision accepta-bly, but was driven to postulate a new phenomenon - transient asymmetric flooding - to account for the rapid

heel-ing of the EUROPEAN GATEWAY.

The sinking occured because the ship had its three watertight doors ih the machinery spaces open at the time of the collision, and could not close them sufficiently quickly. A simulation of the flooding revealed that the doors would have had to have been closed within 50 seconds of the collision to have saved the ship. Furthermore, the extensive' vehicle deck, exposed by the damage, end the low freeboard of this type of ship, made the EUROPEAN GATEWAY certain to sink once st had reached 32° heel in its damaged condition.

The investigation demonstrated that power-operated watertight doors are essential for Ro-Ro ferries, but that even with these, such ships are extre-mely vulnerable to rapid flooding. As the Report of the Formal lnvestige-tion warns, "it cannot be satisfactory to proceed upon the basìs that no passen-ger vessel will ever again suffer a fate

similar to that of the EUROPEAN

GATE-WAY". lt isto be hoped that the lessons' from the sinking of this ship will be hee-ded in time to prevent the Catastrophic loss of life, which must surely occur, Ifa fully-loaded Ro-Ro ferry is ever the vic-tim of such a collision.

-.5 LOPE OF WATER5URFACE MER.

flooding Simulation Result.s-Flowrate through

Holes (tonrles/.sec)

FloodingSimulation ResultsTransient

Effects

Time Below Abovc Time CG Offset Moment Slope

(sec) Waterline Watci-Ithe (Sec) (m) (kNm) (de5)

0-00 0-00 0-00 0-00 0-CO 0-00 0-00 10.00 22.04 0.00 10-00 4-51 8421 07 8-62o 1976 0-00 20-00 3-90 14596-42 1201 30-00 15-65 0-22 30-00 3.33 16780-48 1312' 40-00 13-32 0-88 40-00 2-81 15718-68 I3600 50-00 1231 156 50-00 2-33 13686-77 1291° 60-00 1165 2-15 60-00 1-90 11428-45 12-28° 70-00 II-45 281 70-00 I-51 917670 11-42° 80-00 Il-41 3-69 80-00 1-17 711081 10-78' 90-00 Il-40 4-95 90-00 O-87 528210 ¡0-82° 100-00 I l-31 643 100-00 0-61 37 16-79 11-92° 11000 10-81 9-07 110-00 O-40 2407-00 14-76° 120-00 10-37 12-82 120-00 0-23 1376' ¡9 19-30° 9.57 17-92 130-00 0-II 641-86 13-02' 140-00 910 23-62 140-00 0-03 192-67 5-13 15000 0-00 1721 150-00 0-00 7.49 0-27

II

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EUROPEAN GATEWAY

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DYNAMIC EFFECT:

,ETRA

TO STATIC FLOOIN

-

-SLOPE OF WATR5LJRFACE IN EN.ROOM

'TRANSIENT ASYMM. FLOODING.'4

90°

80

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DEPT OFTRANSPORI/ RECONSTRUCTION A L C

THE NAVAL AnCHrrECT LIAR.

TOWNSEND THORESEN RECONSTRUCTION

2

o o TOWNSEND THORESEN RECONST RUC TI ON NMIFL000 -SIMULATION

I

//

MASTERS STATEMENT

-1

_,1 GROUNDING

I

/ A A

/

TOWNSEND TIÇORESEN RECONSTRUCTION

-3MIN

EUROPEAN GATEWAY

HEEL VER5LJ3 TIME

a.R. SPOUGE

KE TO SOURCES

O SURVIVORS STATEMENTS

£ TOWNSEND THORESEN RECONSTRUCTION

C DEPT OF TRANSPORT RECONSTRUCTION

II

I I I I i I I

In reply to Mr Hannah, the estimated vertical centre of gravity (KG) in the casualty condition was based on an inclining

experiment which was carried out on this ship in November 1980. The centres of gravity of the trailers on board were assumed tobe 2 m above the relevant deck, as advised in the stability booklet. The KG estimate was therefore as good as is usual with such estimates, but Mr Hannah's concern about its accuracy is

-certainly justified, since the implicit suggestion, a variation of which is made by Mr Heather, is that a higher KG and hence a lower metacenu-ic height (GM) could have allowed the rapid heeling to be interpreted in a traditional way as a simple lossof static stability, without having recourse to transieut asymmetric flooding.

The author would agree that the GM could have been slightly lower than estimated, and consequently that thiriagnitude of the transient asymmetric flooding could have been somewhatless but is convuìced that this does not allow the transient effects to be dispensed with altogether. It should be noted that, although the GM is commonly over-estimated, there is no actual evidence that

¡t was so in this case.

Fig. 14 gives the simulation results requested by Dr Morrall for the maximum damage case defincd in the current damaged stability regulations, which for this ship consists of damage 69 m wide, extending from the baseline upwards without limit and 4 m inboard from the ship's side. With the watertight doors closed, and using the same transient effects as in the simulation of the actual damage condition, the vessel heels over rapidly,but

fails to Immerse the main deck sufficiently, before the ecacrator room fills and the ship rights itself with a final freeboard of 093m. Water shich reached the main deck during thc transient heeling causes a residua! heel of 34°, With the watctlicht doors

the ship heels over and capsizes thin 40 sec of the collision. lt must be noted, however, that the transient eflects for this condition are even less certain than for the actual damage

case.

OPEN WATE1TICd-tT DOORS

TO BE CLOSED WITHIN

30-50

SEC!

20

10

o

o

30

40.SEC

O

bOORS TO BE CLOSED

Mr Heather's forthright comments on watertight doors are appreciated. Mr Meek and Mr Adams, Mr Brown, Mr Hobson,

Mr Cleary and Lt Fiebrandt, and Professor Kundu all raise the saine issue. Mr Brown makes an apt reference to the sinking of HMS VICTORIA, which was holed by the ram bow of another warship. lt was calculated that the vessel would have survived if all watertight doors and gun ports had been closed; and although an order to this effect was given one minute before the collision, it would have taken three minutes to carry out, and by then the flooding was out ofcontrol. lt is not difficult to conclude that watertight doors which are slow to close are extremely dangerous, and it is tragic that merchant ship designers had

Iorgottcn this by the time the EUROPEAN GATEWAY was built. Mr Brown and Mr Heather further judge that watertight doors

should not be fitted below the waterline at all. However, this deceptively simple conclusion ignores the good reasonswhy the doors were put there in the first place.

Doors between machinery spaces are used for many

watchkeeping and maintenance tasks, as well as tor escape routes in some vessels, and their elimination would make these tasks much more difficult. This may be acceptable on well-manned warships, but the small increase in complement, which Mr Brown allows would be necessary, may be economically unrealistic on merchant ships. The use of remote machinery monitoring and fire detection systems (which the EUROPEAN GATEWAY did not have) make doors less vital, but any restriction in access tothe

source of an accident such as a fire may allow it to get out of control. Watertight doors therefore, whilei,lccreasinthe vessel's safety in the event ola collision, which isa renioc risk but has

extremejy serious consequences, also increase its safety in the event oímachinery fires and other similar accidents, which are rather more likely though less serious. The question of whether or not to fït watertight doors and, if fitted, whether to leave them open or closed, depends on balancing these two risks. The Inquiry into the loss of the EUROPEAN GATEWAY decidedthat with the data at present available any conclusion could onlybe subjective. (Their interpretation o the legal position isgiven in

reply to Mr Cleary and Lt Fiebrandt). The author's subjective conclusion is that power-operated watertight doors are necessary, and that they should be left open only where the frequencyof

engineers passing through them is high and the risk of collision is

low. Collision data certainly support their closure in fog, arid may also give support, as Mr Heather recommends, for their closure when coming into and out of harbour.

JR. SPOUGE

y-/

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kAFT5

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FER EUROPEAN GATEWAY +SPONSONS

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PERMANNT

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PRO P0SAL:

FUTURE STABILITY 5TAt4DARD5

How to meet future standards EroEosed by 1MO, Londen

1979?

TDamage stability of passengerships.

Draft amendments to regulation 11-1/8 of SOLAS 1974

issued by the 1MO Subcomi ttee on stabi li ty 32e

session.

Required Stab.Arm Curve in final damaged condition:

CZ min = 0,10, range min = 15°, area min 0,015 m rad.

In intermediate stages: CZ min = 0,05 m range min = 70

Maximum angle of heel

15° before equalization

7° after flooding of

1

comp.

12° after flooding of more comp

In final damaged condition, heel inq moment by pass..or

boats.or wind, H moment

(CZ-0,05) x displacement

should be met.

- CZ min = 0,10 m,

is logical to our opinion.

- area min = 0,015 m, up to the critical angle,

is

eTf'Thing the amount of enérgy whTch could be absorbed

by the damaged vessel and is

in line with the famous

stability-criteria of Rahola.

- range min =

tôb

of no sense, because of

the fact that the critical angle has been passed

a I ready.

on a

ro ro vessel the critical angle is at

inrnersion

of the cardeck(-8°)

P

P20

on a pass.vessel the critical angle is at

ininersion

of the corridor (-14°) which is running along the

wing cabins, on top of the bulkheaddeck.

PI

Th.s

proposed area 0,015 mrad and 15° range are

difficult to implement on a current type of ro ro

passengervessel, which is characterized by a low-level

bulkhead deck, with the ro ro space extending over the

ful I

breadth above this deck.

- With two engine compartments

being flooded, the free

surface reduction is large and presents generally the

most critical damaged condition.

- Because of the

low freeboard, the character of the

CZ-curve is

in stead of normally L-1

and to meet

the requirement of CZ min = 0,10-range min = 15°, the

onliest way is to design a very beamy 'stiff' vessel.

Reason for this

is the small heeling angle (7°-8°) at

which the bulkhead deck is reaching the waterline and

where the GZ stability arm is at

its maximum.

P20

-

Recent calculations are indicating a value of min.

intact GM required of about 5 m! which will result in

wildly rocking motions of the ship when sailing in

-

Increase of freeboard is offering no good solution,

because of the centre of gravity is raised

simultaneously. Moreover, the extra space gained below

the bulkhead deck cannot be used for ro ro cargo.

Meanwhile the danger of capsizing is still there if

the full breadth of the cardeck is covered by water

which might happen in case of firefighting.

- My conclusion is, that the current ro ro eass

desin

should be abandoned:

buoyant sidewalls around the ro ro seace should be

erectea whTch wTTFalfowTor the 0,015 mrad

PTOC ALCL

requirement in damaged condition.

-

In this design the definition of a margin line is

complicated and,

to my opinion, the requirement of

keeping this line above water has lost its

signi f icance.

-

In the case of a pure passengervessel, the 0,015 mrad

requirement in damaged condition could be met by using

'buoyancy' above the bulkhead deck which is created by

the presence of fire bulkheads and cabin partitions,

retarding progressive flooding.

- For the distant future, where large Catamaran type

passengervessel might appear, permanent buoyant wing

hulls are a necessity, because this type cannot

regenera te s tab I I

i ty. mi res

FrACTC. buOyANCy e

IMPROVING EXISTING RO RO PASS SHIPS TO A POSSRILE HIGHER

F TA

To my opinion, existing ro ro pass vessels should not be

reduced in their carrying capacity.

- Transverse gull lot me bulkheads

will hamper the ro ro

principle.

- Lonqitudinal separation bulkheàds in the ro ro space

are unpractical.

- Permanent buoyancy in the winqs of

the ro ro space

will reduce earninq capacity and does not reduce the

increased heelinq in the first minutes.

- Sponsons are preferable and extra displacement - aft

will solve the general problem of 'STERN-TRIM', a

shortcoming of many ro ro vessels.

However, the ro ro terminals should be adapted to the

Improving the safety of ro-ro ships : BUOYANCY IN

W1NC5

A study by J. G. L. Aston and L. J. Rydill (University

College London)

THE. t'4PVAL ARCHITECT APR.87

Q0

TRN5VER5E 5L.JEDiVI5ION

LOlTUDlNL SUEDIVIS ION

A S E

+ EtDE WALLS ,FLARED

IN Tfr CT DAMACE

The mprovementi to stability shown in the IWO cases above come partly from the in-crease in waterline beamofthe flared hulls

but mainly from the reserve ofbuoyancy provided in the added side companmenis. Further ests have shown the sensitivity of the stability improvements to the

distribu-lionof this buoyancy rcscrvc. Cases havc been examined ¡n which the flared idc

corn-partmenls were taken from the existing

water line, thereby preserving the original

GM value. The

results show

that submergence of the vehicle deck takes place

before sufficient buoyancy from the side

compartments can corne into effect, so that although equilibrium and positive stability

can be achieved, the equilibrium angle is

ex-CCSSiVC.

t

--EL ItISUI.

'

Equilibrium modifica tion dema9e ib).

condition

for hull

with extreme

The second modification

L

shows

the obvious advantage of incorporaung reserve of buoyancy high upon the vessels sidcs.

. ße

I

/

+ SlDLWALL

FLAR t

H U P

700 LATE.'

OT EJflCIE4T

/

VOLO wLNTkN'<:

SITUATION IODA)'

ßID

eor.s -i .yosD-W1N.VM(5+

_CS-FLOiNC

_LJC15

FUTURE FOR EX3TING VE5ELS

lo. V I ?LR 4M1 B

fIV1

IN FiRST MlNIT TO R O J LE EL wATEfl QN R. R. LCt. TO ßC

;-s--!'.

_1°

IJC.TS XjERFLQví .1

8AD

CTO OF CAC PIsC 5.fE SUQYAMCy

roO LATE.

¡N REUCINC4 KEEL

Pf.RIiANNr 3uANCY _{y ORWIS/PSPE5/eALLS}

The ENLAr?ED SEAM WILL INCREA5E

INTACT

\ >2M

RDUCT(ON OF PaM1'LIT7

POSI5LIT7 OF ROLLING IM BEAN

5EA5

TAE;LlRFIN5 WILL E

L.E'5 EFFEC.TIV

A rLARE

HULL

WILL PRODUCE LARC4ER ROLL

ArIPINC

Û, S

0,

MERCh'ANT VESSEL CONVERSIONS: ThE FALKLANDS CAMPAIGN

R. 1-tANNAM

ThE NAVAL ARC'T.CT

INTAC T 0,05 -u,: 0, IN TAC T o 7.3 RA 7 Cz',, OC r

MARCIN LINE NOT TO BE SUBMERGED

5TANDARD tEO DTE (BNSI

DAMAGED DAMAGED

Fig. 6.

Simple Comparison of Frigate and Passenger Vessel

Minimum GZ Curves: Intact and Damaged

T PIE.

RoRo vcsscl noses an additional hazard in that the

submergence of the vehicle deck would cause such a

massive

loss of stability that catastrophic capsize could occur.

The alterations carried out on the passenger ships were not

necessarily approved by the DTp, although the MOD's policy

was to endeavour to meet at least DTp rules where this was

possible. The help and assistance of the DTp in these matters

was of crucial importance in reaching the inevitable

ompromises which were necessary under the emergency

circumstances. However, of the five vessels primarily engaged

to carry large numbers of troops. only one sailed from the UK

within her passenger vcssl load line limit.

The conclusion that can he drawn on stability matters is that

the use, in an emergency, of merchant vessels in support of

military operations, especially for the carriage of troops or

vital equipment, is

potentially very hazardous.

CZ

4-ANc.>

Ei ,>o,o

SiJRFfrcE) O0I

I1RA

.ER0POS.D 'f

r)

u.cor-i.

/

-

/

o,S

/

/

0,3

/

o, Z

- Q'

-A--o - t to LO

.t

,o

:o

6o

7°,iU,t.

---

---i RAÑC CANftOT e. ULF IL LED

61 It-ItS TiPE

'11/

LARC.E

5ID WALLS

F 1. t G AT E

PASS VES5E.L

(

'r- £I

WALL

/

I

/

it

¡ o to Q Q

SQ óo 70

PASS

NW P:.'_

14J

:

STABILITY OF PAS5.VESSEL IN

DAMAG1E.D CONDITION

EXPLE

¡

IN CASE OF 11-tIS VE5SEL

E(qUILI8RILJrI

ce9 - r849/O.4

f

SHOULD N0TEAEEO7

ON PA5SENER VESSEL

co

o

IO

3A.Ç ARE INT&rIEDIATC IACE5

RM1OLPS PRINCIPLE:

AREA>,,O.015 M.RA.

UP TO CRITICAL hEEL

IZr°

= 0.020 INDRAWINC)

"RAHGERE(4'UIRENENT 7\

HAS NO SENCE"

u

, ARIiOPtSTARLUIV

Aduli

111101111 Ii!IiL'iI

lllilIIPiu1liHP!

IuhuhiiIII,!i'Îi

III ÌIIi!!1iIIIO

1i!!IiIIUIl

:;ííìiiiiiiIiiiIiiII

2

y4

6

r

iQ 12 14 16 8 HEEL

EqtJILI.

CR TICAL CIR. V. HOON - v.UC. N.

fOCS SLUT

INTERPRETATION 01

¿MO 51F 32 wPb

_cZ

LONDON SEPT 040

MINIMUM Z,OiÓM

o io IM DRAWING 0.22 M C 410

,cj

'

-'i

/

/

/

PASSEMGER SHIP

CMC?IICL 7ANKER

3

Mi

?AI41C> 7-ID'

'r

-i

I

PASS TERRY

ir---r1.,

t

3 TYPES o 5H1P5

DIFEJEWT 51h3.CURVES

7

IN DAMAGED CQNDITON

ALL SHIPS.HOWEVER. ARE

ShOWING TIlE SAME

YNArSIC

STABtLIT-VALUE: 0,015 fl.

up-ro

TPE% OWN SPECIFCC.RI1ICM. ANGLE.

0.20

0.10

o

0.10 - AREAQ015 M-RAD ¡

ÌiI

10°

I5

200

I

/

5°

0

I5

-4-o

250

RAMC.E 20°

CHEMICAL

ÍANKER

0,015 MR*

CARDECK OVER rULL EAr1

OO15 MR

AREA,

UP TO CRITICAL ANGLE (RAiOLL)

3 5H1P5 4AVIH

5Al1E

YNM11CI.IFT

iw tAMAE. CONDITION

URTI-(ER RE5EARCPI r1%CHT INDICATC,WThER IT IS TOO LARGE OR TOO

rtALL..

0.3OM

Z

I/I

5TPBlLITYARI1 GZ

0.40....

030_

I

0.20 -

_I

I

'

I '

/

I

t

/

I

¡t

0,10

I &'

/

,I

'Ii

O.ZtO

O.30_

0.20

ojo

o

RA.MGE 120

RANC6°

PA5SENC,ER SHIP

F C R R V

ELIMINAR'Y FOPO5 TION

RARDIÑC IA11A-STABILITy. (çuteriENrS

5rA3ILJT

ARh

2. TO A LEAST

0,10 M

AcA 3

Z cuRve T0 6E Ar LEAST

O,oIs MRAO

- UP To TI1- CRITICAL

Th

SO CJ.L

YAr1.AL LIFT

'. ATT

CIitICiAL ANLE

15

IM LtN. wITh

RAHOLA'S PRINCIPLE..

CRITICAL ANCLE

WHERE PRORE55iVE FL.ODIN

START'S

WttERE CAR0

1ARî5 r1ovIt4

wNR. PANIC STARTS AtoN PAsS

i

/

/

/

/_

I

/

. I J I -. O.OI5M4

o

Ii

_I T i

111,11

5 10

20°

PA55ENER SHIP

M

5TP6ILITY ARtI

PROPOSED

A RANCE.. BEYoND ThE CRIT. ANGLE To 8

U5 AS INDICATION ONL..'Y

/

INCREASE OF YEIT DISTANC

-i

DY'.IAMIC LiFT :AREA.t,R

W1RE. UFE SAVING APPL.1ANCE

ARE FMLI.

-Cori PARIS ON

98O

TANDA

W/

T5H ALTHCL1 LE

tS 5iAN.P

B'y tUT

AL)TtOtTI(

'1f

OOIS MRA AREA UP TO C..R%TICAL ANGLE (RAPIOLA)

PS PRLIMNAR)' PROPOITtOr'a FOR DYNArtICAL'LEYR'(LFT) ßtI4C AVAABLL

JURHRRESEARCP1 M I Q. I-fT I N D '(AT ,WETI-f Cf IT IS TOO LARc.OÇ TOO SMALL.

t

7

rARir4 LUCE rO

çEPT Ar_ wAtE(?..

LJ(INC1

PLL E.1AC.$ OI-

LJr4C.

CZ oo_

0.30_

WANTED 8)' THE DE5(NE.R

FURTME(? RE$EARCH

ECARDINC TI-E DYNAMICAL EFECT

DUE TO THE (NCESS OF VJATEÍ

IN THE DAMAGED VtSSEL

TAN ser

y

TRIC

_FL(.OINC

DF TIANVE.R5.

PRrriNTS.

CROSS FI.00DINC VIA DUCTS 3E1WEE

WINC- COrIPAR1t1NT.5

F)ENCE SIZC Ot

Ar1A., 5Z

AN SAP OF oL?cr.

It'IFLUEN(E

p tAF4Et1T

L)OyANCy INSIDE Wit

CorPi.RTrlEN1S

PROçREStVE FL.00DIM

Of

TOP OF BUL.KHEAP PECK

INFLU.NCE OF

I(E. BULKHEADS /CA3IN PARTITIOt'S

ESEA1Ci1 REARDIN

PErMEA8II.Iry, Wh(CM SEE!15 TO

REALISTIC.

PR1. EN

coris

o,S - o,9o-o1'g ?

P ER ti PROVISION R. o,6o

-

o,SS

DYEtoPrtENT

OF PRrt'ENT

BUoyANcy

MD

P lO 11

P 26 28

P 27 28

P 23 30

P 79 3t

This

VCyA$Cy TO BC.

?RC1CAL IN tIAN) ASPECTS

COST

RSSrANCE To cOrPRE.sio

WEIt1

,,

cORROSION

It'S1ALLATlON (LASHIt'IC)

FIRE HAZARO

RErIOVA L.

IN CPSE NARRE(UIRES1ENi5 WILL BECOME MAPJDATORy

WHAT TODO '?

(ARA,D.0I5 tIRAD

DYNAMtCAL UFT)

to ro ro passenger ferries not complying with

980 STArDAD.

How io CRAT

A LIFEBLT AROUND THE 5HIP

For instance 'EuroEean CatewatEe: to have sponsons

filled with drums

'Modern ferri' complying with 1980 standard and

consequently not suffering from inTnersion of the

bulkhead deck, might be improved by filling the void

wings with polythene drums and engine room wings with

steel drums.

Adding sponsons only in case of absolute necessity,

which could be concluded after research on transient

asyninetric flooding.

Norsun/Norsea

ferry: filling void wings with

polythene drums or alternative buoyancy if necessary.

'New Desjn': continuous longitudinal bulkheads and wide

waiTs around ro ro space.

HULL INTEGRITY

Hull inteqrit, some critical technical asEects

- All doors ¡n access oEeninas to the car deck to be

Ti r drfFErFaTcator TTht.

- closed television circuit on cardecks at door control

stat ions

- water on cardeck to be drained quickly via large ducts

or pipes towards tanks or bilges in the lower parts of

the vessel (free surface effect of these slack tanks

to be kept small).

Scuppers with non return valves to overboard should be

avoided because of possibility of clogging

(maintenance is difficult).

- stabi lizer fins to 'fold in'

in aft direction.

Surrounding structure should be such, that main

compartments to be secured even after the fin has been

hit by an obstacle.

- WT-doors closing system self contained and remotely

control led.

RaEid disembarkation in case of emerenc

- no sleeEino accorrrnodation below the bulkhead deck

r- Treeboard deckt on new ro ro pass. ferries!

- wide escaee routes - dimensions according to

international agreement by 1MO.

- self contained emerencyIi2hti

- wide musterstations preferably on low-deck-level

connected to 'MES'

- suitable means of escae throuh ships side

- Disembarkation by means

oT low

level marine escape

slides ('MESJ and rafts.

- quick releasedieseldriven man overboard boats

(type

rigid inflatable) to serve the flotilla of rafts.

(s FA

OAViTCAMS)

Stab i

li ty check

- rTTT dTFrecordina civacies

ç

- weihin

ol Treiht vehicles

v EI

Nc.3c'L

T TRr.L

-

electronic loadmaster suitablefor use on ro ro

ve s seTs

- exElicit

stability instructions (including influence

oT trim by head and by sterT presented in accessible

form.

- alle existing ferres to be subjected to Eeriodic

stabil it

check in 4 years intervals: lightweight

cFeck and inclining test (if necessary)

Carao related Eroblems

-

lasing of veFicTes

- seaworthy stowage of cargo in containers

- dangerous cargo

- responsibility

Procedu re s

- mandatory formal systems aEaroach

- checkHst beTore aeparture/arTval

- unilormi t

in termino

1o91

Steerin

and manoeuvring:

-

Ability to manoeuvre into port entrance and alongside

berth in strong wind (uProBF 7)

sea swell and current.

"hrCI1 -LlT FLAP

uDDE.rc

POwRFL)..

QW .JS[E.R5

-

Course keeping ability when slowing down with C.P.

props at zero pitch in which case rudders are

blanketed.

- Good 'crabbing performance' by

rudders, propel 1ers and

thrusters, to allow for moving in transverse direction

only.

- Ability to turn on the spot.

Course keepina at sea; possibility of broaching in

oblique following seas.

- Considering the danger of large

heeling angles in case

of a sudden 'hard-over' ruddermanoeuvre at ful I

power.

.This isa special problemon fast,

'short-length',

'built-up' vesseishavinga small turningcircleat

full speed.

"Herald of Free Enterprise" would have heeled by

centrifugal moment at 19,5 knots, in a turn of 21Z m

diam. (1,7L) with intact GM = 1,6 m to a static angle

of about 25°.

Taking into account the dynamic behaviour, the max. heel

would have been larger.

SEecial case: "Herald of Free EnterErise", leavin

Zeebru9e, March 6th,

1987

- During Tspeeding up', the cardeck got burdened by a

free moving mass of water, which entered via the bow

door opening.

- Her stability went down rapidly and

the tender vessel

became very sensitive to small rudder manoeuvRes and

flow disturbances (squat).

00T5%DE OFTE.PIER A SW!NC TO5B 5rARTED

-

Beyond a certain angle of heel, the flared

belting-forward touched the sea and after irrvnersing started to

excite a

large side force in combination with the

forward skeg.

- The yawing moment of this side force overruled by far

the steering moment of the vessels rudder to?ctwhen

trying to steady the ship

IN HER SWIML

10

58.

- The 'counter rudder'

might even have increased the

centrifugal capsizing moment f9361Ran'

Il disaster,

whale catcher,capsized in turn).

- Additional to this effect came

the capsizing moment by

the sternwave, overrunning the vessel.

- The heeling moment of

the mass of water on the cardeck

moving to the

' lee side' must have been the main

e

p''

.

w'op

NO 5LEEPIN ACCOMMODATION BELOW ThE BULKHEAD DECK

FIN5 SHOULD FOLD-IN

IN AFT-DIRECTION

A'

ryP

FODt AFT.

\ ,/

NOT RISKY

ALA

NORLN

Ñsy; 4ß,'

FOLDIsA FWP. PQD (CIi$ '7' 1At

1.

45

NOT