UNDERSTANDING RO-RO CAPSIZE
Laboratorium voor
Sehespsliydromechanlca Archiof
Mekelweg 2. 2628 CD Delfl
Teü 015 - 763873 - Fax: OTS o 781838
SIDE COLLISION - CAPSIZE TESTS ON MODELS
OF TWO TYPICAL FERRIES
Ir. E. Vossnacl< Former NEDLLOYD (NSF) 17 November 1 9 9 5 Capsize-tests
Collision-Calc. + Tests
T U D e l f t
T N O - D e l f t
Ir. J . M . J . Journée, A . Goeman, C. van den Bergh, R. Onnini<, A . Versluis, P.W. de Heer Ir. A . Vredeveldt, J . U w l a n d , J . Oprei
UNDERSTANDING RO RO "RAPID CAPSIZE".
S i d e - C o l l i s i o n a n d W a t e r o n C a r d e c k
EXTRACT
Characteristic:
Both ferries are designed w i t h the cardeck over the full breadth. The casing is on the centreline.
Subdivision of Hull below Cardeck;
Ferry-62 Ferry-72
Forebody B/5 long bulkheads, afterbody, transverse bulkheads incl. 2 engine rooms
B/5 longitudinal bulkheads over total shiplength
. 6 2
C A P S I Z E
. 7 2
Englneroom extending from Port-SB Shell.
obstacles for crossfiooding In E.R rather big: main engines and auxil. Also: Semi enclosed wing compart-ments
(P.S.: Workshop)(SB separator RM)
Engine room b e t w . longit. bulkheads. Crossfiooding between void wing compartments.
Due too narrow duct in D.B. Crossfiooding is rather slow.
Vessel starts heeling
Immersion of Cardeck if stability is insufficient Capsize
I n c a s e h e e l is l a r g e r t h a n f r e e b o a r d - a n g l e Common angle = 8° - 10° no 1 '°' C a r d e c k w i l l b e f l o o d e d v e r y q u i c k l y
S O L A S 9 0
1 5° range acc to SOLAS can never be fulfilled on 8°-^0° Ferries in case cardeck space is extending over full breadth surrounded by a single shell and w i t h o u t any subdivision
Critical angle, about 1 9"^ Cardeck awash,
Toppling trailers Panic
SIDE-COLLISION
After 20 sec ~ 4 0 0 ton After 1 min ~ 1 0 0 0 ton
Crossfiooding may be slugghish and is effective only in case the ship has a positive righting m o m e n t
This sequence of events may lead to capsizing if d o w n f i o o d i n g of entered water is too sluggish
C r o s s f i o o d i n g - H e e l T e s t s T U + T N G 1 9 8 9
Schip en VVerf de Zee, No. 7, 1 9 9 0 , Vredeveldt en Journée
Simple Block Model - Midbody
- No Stabilising Effect by Afterbody - r Forebody - No Effect f r o m Flooding of Cardeck,
(Free Moving Water along Ship-Length is not incorporated) HEEL ~ 5HIP MOOeL 1 5 3 0 , M I M 1 i in* 90° _ L 5 . 'i 5 1 0 "
1
1
0 0 .1
h 1 0 2 0 - 2 0 A O S O 5 0 7 0 . s o 1 0 0 110 1 2 0 S c C Test TU Delft 1 9 8 9 in principle onlyE x t r a c t o f R e s u i t s N o v e m b e r 1 9 9 5
It is reassuring that both ships sailing in service normally w i t h a metacentric height: GM > 2 m . :
Under this condition in a calm sea both vessels will not capsize after being hit in a side collision.
F e r r y h e e i i n g a f t e r s i d e c o l l i s i o n (2 compartments near Engine-room) Time scale for fuHsize
Croosflooding inside engine-rooms is hampered by many obstacles
Oscillating mass of water in W I N G T ( C 5
Tests with reduced stability: GM = 1.6 m.
«
In case ferry-62 is sailing in service with reduced metacentric height (GM = 1 .SSm) and her initial list is 3 ° , due to excentric passengers -I- w i n d m o m e n t .
Than the ship wiil heel 13°, in about 1 2 - 1 5 seconds after collision.
The cardeck stays continuosly submerged (cardeck angle = 8°) for more than 1 minute (see diagram)
Water is flowing via hole in topside along gutter of cardeck to fore and aft end of the ship.
Vessel capsizes within 2 - 3 minutes. This is caused by the free-surface-effect of water on the cardeck and simultaneously by transient asymmetric flooding in ER due to obstacles in f l o w .
In case: Ferry-72 is sailing in service w i t h reduced metacentric height (GM = 1.60m) and her initial list is 3° due to excentric passengers -i- windmoment.
The ship is heeling 16 - 1 7° in about 1 2 - 1 5 seconds after collision. The cardeck is temporary submerged above 8° during the rolls (see diagram) Water is swallowed in gusts, 5 x, via the hole in topside and the cardeck is flooded
A f t e r coming to a rest, the ship hesitates: capsizing or not? In case the initial list is increased during the tests from 3° - 4 ° . Than the ship capsizes after 3 minutes in a calm sea.
N.B. Capsize tests in waves at a significant height of 1 Vz m and also 4 m are not yet carried out. They are of utmost importance, to investigate the margin of safety. The question:
Can the ships at GM > 2 m in service, survive 4 m waves after a side collision?
GM REDUCED FROM 2 . 0 0 M TO 1.65 M A N D 3°
INITIAL LIST
Capsize tests by TU and TNO Delft 1 9 9 4 - 9 5
Ferry .62 Ferry .72
FERRY HEELING AFTER SIDE-COLLISION (2 COMPARTMENTS OF ENGINE ROOM) Time scale for full size
With 5° freeboard angle initially, DIFFERENT BEHAVIOUR
The cardeck remains below waterline "Anti-Rolling Tank Effect" (Frahm) The ship wiil capsize! "ms SIBAJAK" ~ 1928 first trip
Large heeling angles
FERRY . 7 2
HYPOTHETIC CASE FROM FERRY .72
2 ENGINE ROOMS-EXTENDING OVER FULL BEAM VOID WINGS ARE OPEN TO E.R.
Heavy side-collision > 5 m deep
> B/5 (nonsense formula) Longitudinal bulkheads in E.R. are all penetrated
(N.B. this test is not realistic!) 2 engine compartments flooded over ships breadth Vessel is lacking stability caused by large free surface
and finally CAPSIZES
• - l i J : : U l .
Void wing-tanks are flooded GM = 1.60 M
Free surface corr - 2.5 m
Hesitating after deep side collision GM Finally CAPSIZING
DYNAMICS AND DAMPING
Interesting phenomina can be observed in the heel-time diagrams.
There is an obvious difference in behaviour between the t w o ferries after being hurt in side-collision followed by t w o compartment flooding:
In Ferry-62, the machinery spaces are arranged between Port and SB shell.
In case of a collision at the engineroom-bulkhead, the inburst of water entering via the bulb-hole in side-shell cannotEqualise over the full breadth within 1 minute,due to obstacles in the machinery spaces and workshops! The ships heel is exceeding the critical cardeck angle, allowing the inburst of free water on the cardeck, finally resulting in a capsize.
In Ferry-72, The machinery spaces are located between longitudinal bulkheads at B/5. The side collision is at the void wing-tanks^protecting 2 engine-rooms.
After the t w o void wingtanks are holed by the attacking bulb, the overflow of entered water is not sufficeintly rapid towards the opposite wingtanks. The duct in the D.B between both wingtanks is rather narrow and obstructed by many longitudinal girders.
The ferry starts heeling to 18°, and continues w i t h her rolling motion at large angles, swallowing water on deck, 4 times in gusts (see diagram). Heel-Time.
Masses of water are oscillating between port wing tanks and SB wingtanks. There is no equalisation within 1 minute, which is rquired by Dutch Shipping Inspection.
Meanwhile the freeboard, of the cardeck at the hole in the side, is dwindling because of the accumulation of water in the void wingtanks on the collision-side. The Swallowing of water is followed by continuous flooding of the cardeck via the hole in the topside.
Capsize follows
The conclusion about Ferry - 72
we should any how prevent a large inburst of water which causes a large heel.
Stop the oscillating mass of water between the opposite wingtanks.
The cross flooding duct should be closed! (crossfiooding never can be sufficiently rapid).
The result can be seen in heeling tests " w i t h foamblocks" (see diagram). Max. heel 6° - no water on deck (permeability depends on the stowage of foamblocks inside the void wingtanks below cardeck)
No capsize!
Moreover a collision deeper than B/5 bulkheads was simulated, (penetration deeper than 5 meter) heel 7° - 8 ° , no water on deck in a calm sea.
FERRY .72
/7K\
/ 7 T Y \
• a •— HAji MS. ; -• — /.-^~. - . - r - . r - iHeavy side-collision > 5 m deep closed-cross duct Penetration less than B/5 (nonsense formula) Longitudinal bulkheads: intact
2 engine compartments: intact
1 .—'
F.3An 2 L C C M _ _ ^
i f
GM = 1.60 M Hardfoamblocks in void wing-tanks inside webframes
Heeling after side-collision (2 compartments penetration) less than 5 m deep
FERRY .72
_ii a i l
-Heavy side-collision > 5 m deep
B/5 (nonsense formula) Longitudinal bulkheads penetrated on Port side 2 engine compartments flooded
GM = 1.60 M Hardfoamblocks in void wing-tanks
T A N K T O P E . R F L O O D E D J U CMcQRfl X 1.6-0.6 =\.Q M ~ POS.MVE M 0 5 T FROBKBll N O .CAP.51ZE. _ J L I -2.
Heeling after side-collision (2 compartments penetration) B/5 ' more than 5 m
FREE WATER ON CARDECK
HULL BELOW IS INTACT
= 1 3 7 . 4 0 m " E S T O N I A " " H E R A L D " "PRINCESS V I C T O R I A " = 1 4 . 2 0 m 1 9 3 4 1 3 8 7 1 3 5 3
T = 5 . 5 5 m Open b o w - d o o r Open b o w - d o o r Open s t e r n - d o o r
S = 0 . 6 2 / /
Displ. = 1 1 . 5 0 0 rn=' / / _
A CARDECK OVER FULL BREADTH IS DANGEROUS
W i d t h of W a t e r l/V = Free surface corr. 1/12 . 6 ' • 120
11500 - 0.19 SI
S c u p p e r s overboard are not reliable and too D o w n f i o o d i n g to double b o t t o m via w i d e soup ^ 1/12 . 8^ . 120 . »« — = 0.43 n 11500 10 m 12 m 14 m 1/12 . 10^ - 120 11500 1/12 - 12^ - 120 11500 1/12 • 14^ • 120 11500 = 0.87 m. U m - cm = -].^ m - CWSIZFX r r e e s u R F f t C E - < : o R R E C T i O N _ _ A B 3 o R B e D m e t a c e n t r i c - h e i o t - I I - Gl M Y 2.4 m i C U P P E Z i O \ HOW HANY r . < i « - a t >
If we Imagine an open bow-door or stern-door, and the ship sailing in rough water, large quantities of water will spread on the lee-side of the cardeck.
If we imagine a huge fire in the cardeck space, where large quantities of water are applied in order to extinguish the flames, and meanwhile d o w n - f l o o d i n g via standard scuppers is not adequately rapid, than water wil spread over a large area of the cardeck. (one or t w o feet of water is already sufficient).
As soon as t h e width of this free moving water is reaching a breadth of 1 2-14 m, the free surface correction (l/V), is fully absorbing the GiVl of the vessel, and capsize f o l l o w s immediately.
Viking Sally renamed ESTONIA
^ j ! . a . i i ; ecönan i mt. cson aca -: unco aoa o^doo aajaji_ocEa^ ang ccoa goaa r i ' / ^ ^ ^ ^ j a . J C i occaaa laac ccaa aim j csag ana
\ ' « CB a c ] aaacaa acac ' i' •• l l l l 11 I V Ï K I N O L I N E : S T t P 1 = 1 ' ' i ^ ^ -o ^ V I 5 0 R ^ O J P P Ê K i O i HOW ITANY 1 «AaiNSlBtLOW O.RDECK J LOA = 1 5 0 . 4 0 m D W = 2 S 0 0 T Pass Ul = 1 3 7 . 4 0 m GT = 1 5 5 6 7 Cabibs B = 2 4 . 2 0 m Cars M = 7 . 6 5 m Lorries T = 5 . 5 5 m ( I S m ) = 2 0 0 0 Jos M e y e r , Papenburg 19S0 = 5 0 4 4 m a n S L 4 0 / 4 5 a 4 4 0 0 K w - 6 0 0 r p m = 4 6 0 Renk Ge»r = 52 2 K A M E W A High S k e w 4 a + W Gen a 1 1 0 4 K w
DOWNFLOODING
Reduction of water on cardeck
Most of tiie ferries in service are using tiie full breadth of the vessel for stowing cars, trailers, coaches.
In case there is even 0.2 m water on this deck, equally spread, then every vessel will capsize immediately because the free surface effect is absorbing GM.
Conclusion is, that the surface of the cardeck should be subdivided wether by 3 transverse telescopic W.T. doors or alternatively by longitudinal bulkheads with W.T. doors at both ends
In this way the sum of free surface corrections is much less, w i t h a subdivided cardeck compared with a fully open cardeck space. However, at a heelangle exceeding 8° + 1 2° = 20° the water will overflow the doors (at 3 m height, (which is limit in view of ventilation).
During our test, the first observation, is that the free water is finding its w a y to the lee gutter of the cardeck where it is accumulating, in case scuppers cannot cope with the downfiooding.
In a rolling, pitching vessel, oscillating breakers may roar over the pubdoors which cannot be considered as reliable enclosures of buoyancy to our opinion.
A busy RoRo service at 1 or 2 crossings per day, might introduce indifferen-ce about reliability of moving parts, where watertightness along doorsill and hinge against shell, is of major importance in case of water on cardeck. A n y w a y , we should get rid of the free mass of water on the cardeck and increase the cross section of the scuppers. The dimensions of the scuppers acc to rules, are derived from sprinkler fire fighting.
Diameter: 0 150 - distance 10 m.
To improve the dowflooding we propose to increase the size of scuppers: 4 X diameter, 16 x cross section which might result in construction of a rectangular duct to solve the problems of access (see drawings in part B: "Water on cardeck".
We might sluice the water via outboard values, fitted w i t h non return flaps. However, we dont trust the selfclosing of the flaps by pressure of the sea-water outside.
Due to the splinters and debris accumulated after deckwash in the scupper, the flap might get immovable and might stick to half-open position.
Larger-diam-non-return valves of about 600 mm might be feasible.
These valves should be cleaned regularly via a permanently connected high pressure deckwash line (suggested by mr. Huis - Bureau Veritas, who has experience from the Dredging Industry).
Large-diameter "sluice"-outboard valves are a nuisance to super-intendants because they might stick and will increase ship owners maintenance costs. Butterfly valves as outboard valves are not accepted by class.
VIA SCUPPERS DOWNFLOODING TO THE
BOTTOM OF THE VESSEL
Down-fiooding to a lee bilge at the ship side, wether of engineroom or hold is not a realistic proposition.
It only releaves the situation in the first 10 minutes.
Later-on, the accumulated water in the lee bilge will increase heel again and reduce freeboard at lee side.
Direct down-flooding t o w a r d s the bottom of the ship in centre line is the best solution, but very difficult to realize.
Down-flooding in way of engine spaces is most complicated: where to find a bilgewater tank available at centreline?
How to clean the tank f r o m splinters?
Down-flooding to the tanktop of the lower hold in the fore body of the ship is a possibility, because water is accumulating, deep in the ship, at centre line, at small breadth of the cargo-hold (3/5 B).
Consequently the free surface correction on water on tanktop compared to B is reduced from 1 0 0 % to 21 %.
Where to lead the downfiooding is a major problem and has to be solved on each vessel individually.
S C U P P E R A C C R U L E S Dutch
Based on fire fighting by "Sprinkler"
5H£LU LOP VI £W. • 5 * Ï.M ' • C A R D E C K
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3J .j.g3»^a 0 , 2 a n -1 7 . ^ ^ ^5 E N L A R G S n l i i 'i l i
3 7 5 3 7 5 7 5 0 IJ J J J . » I.lao ^ I S O 5PA<imC 10 M ARE.A 1 AS CJCTJ.R. SPOUGE: "EUROPEAN G A T E W A Y "
RINA - march 1986 December 1 9 8 2
n
Estimation of the inburst of water at a "Medium-Collisiun" in the side.
Regarding the capsize of the "European Gateway" and studying the calculations by mr. J . Spouge to explain what happened, we resume: the inburst of water via the bulb-hole in the underwater part of the hull was e s t i m a t e d : 7 m^ x 3 m/sec about 21 m^/sec.
Installation of electr-hydr. capacity to pump at a rate of 20 m^/sec to keep pace w i t h an inburst of water is not achieveble on a normal merchant vessel ("Economically impossible"). (20 m^/sec = 1 200 ton/min = 7 2 . 0 0 0 ton/hr) Conclusion is that pumping-out "the sea" is not realistic.
1 . "exJ R O P E A C A T e W A Y
•
SPOOGE 7 T JPttDLlNK VANGUARD D Y N A n i C E F F E C T : ^ • • 5 . H E E L . E X T R A TO STATIC FLOODING W A T E R O N F R E E B . D C K -v l o " S L O P E O T ^ ^ W A S ^ U R F A C E I N E N G . R O O M 3 ^ n i N : TRANSIENT A S y n n . F L O O D I N G . O.R. S P O U & E - 7 nEUROPEAN G A T E W A Y " - HEEL VERSUS TIME
J.R. Spouge, The Naval A r c h i t e c t , March 1 9 8 6 9 0 s o '
70'
6 O ' ^ 0 ' 3 0 ' 2 0 ' 1 0 '0
3 7
MlN mi 10 50UOCESA lOWHStXO tK)a£5£N SECOHSrauCTIOM
J 1 L - I - J L I I I L J I 1 L J I 1 L J L
10
1520
M I N"EUROPEAN GATEWAY
J.R. Spouge 10 20 30 .^O .SO 60 7 0 30 30 100 1(0 110 130 WO 150 ^£C 0 1 2 M I NINGRESS OF FLOODWATER
T O N o la • 10 io AO JO 60 70 ao 30 100 110 liQ 130 wo isa Sc.C 1 2 M I NSAFETY
A new Solas r=eiJadoa has bain prtparid bv die panel maidng ic a requirimenc mac any
limjcadoQS imcased on how and where die
siuD miv be ooeracea are co be Lnduded Ln a
manuai wcucn is co reccam wim me snin ror ICS encire liie_ This is co be updaced as neces-sary.
The rapid nun-round cmes of rocos makes die [asiiin^ and seczirine of car^cjes dirncuic, and che panel proposes an amendmenc Co Solas CO ensure chac cargoes muse be orooeriv
scQwed and secured in containers or wheeled Tehicles, and ic urges IMO co consider soiu-cons in assocarion widi road O-ansporc com-
panias-Ocher recocnmendadons bv che panel on ooeradonal maccers include: a wnr'rina ian-^ija^e :o be escabiished for eacn vessel: che
The total wicfth of the MaoSfegor-talescooic door fitted lo Siljs Symphony is 9.36m.
The use of transverse bulkheads co improve passan^erroro sm .ivabilicy has found supporcia che UÏC, while r^-o sees
of prococype equipmenc have been
under test oa Baltic ferries
Despite che fact chac me IMO's panel
or experts oa tiae safety of roro
passen-ger vessels did not decide La favour of any oae mecnod of Lmpro%"ing' stixviy-abiliry standards ou these ships, the UK Department of Transport (DTp) appears. CO be advocatina' che ntdng- of transverse bulkheads Co che vehicle decks as its preferred mechocL
Research resufts
Transporc secretary Brian. iMawhinney cold the UK Parliament recently tiiac research carried out by the DTD'S
.Vtarine Safety .Agency, commissioned foUowing che loss of Estonia In
September, showed chac transverse bulkheads can imorove che surrivabiiltv of a ship with wacer on its car decks bv resincnng the spread of"water along the decks. The higher the survrvabillry stan-dard, the greater che effect of fitting transverse bulkheads.
Tn light of this research, I believe it is mcumbenf oa the Government, together with operators and che Lnter-natiotLai maritime cotoxnunity, to seek
Co agree further imorovements co
sur-vivability standards and Co introduce o-ansverse bulkheads to roll on-roU off ferries as appropriate,
''.^s always, cotisiderarioa of these
_ measures must include evaiuadoa ofthe potendal safe- • cy benents and che costs involved," said Dr .Vlawhitmey.
Fmnish ferry oper-ator Siija Line has already taken che decisioa to lest two prototypes of trans-verse bulkhead, one trom Kva^mer Ships Equipment (KSE), the other from che .VlacGrcgor Group, on two of its roro passenger ferries. Evaluation trials
The KST unit was fitted to che portside taain deck only of the 59 914gt SUja
EziTopa, which
operates berH-esn Tur.ku and Stockholm. .Is a single unit this is for evaiu-adoa only, 2S ic would not oa its own be able to provide fuH watertight ui-tegrity. At the end of the trials, KST anadoated that the ferry would be fitted
with three more doors to seal" off che main deck either side of the centre cas-ing forward and afc
Being less than Im wide when faUy opened, che flood prevenrion door results ca minimal loss of cargo apadtv, said KST. T^e hemlcvcHc door is hinged at the ship's side and can swrng through a 180 deg arc by means of direct acting cylinders. To free the lower watertight packing seal, che door must first be Ufc-ed IQOtnm before it can be swung either forward or aft, depending oa the load-ing/discharge cyde, to stow against the sfaio's side.
The outer end of the 9.4m-Ioag hinged bulkhead is fitted with a 3om sliding panel which will extend co seal against the central • casing. When retracted, the panel enables oae lane of vehldes to pass through it when the cnain door is shut. In operarion, the door will be dosed once a block of vehldes h^e been loaded ahead/astern of it and opened in front of the nett block of vehicles rar discharge.
.As hanging car decks are fitted above che main deck oa this vessel, che door is 2.1m high and not watertight between che top and the portable tweendeck, .As • o regularioas yet edst regaxtiing the design and construcdon of these trans-verse bulkheads, it is sultahcv strength-ened to resist a water head to its fuU height, sdd KST.
The .MacGregor Group has a unit on
Xysmef has this ï^ood pfevention door on test on Siija Europa.
test on the 58 377gt Siija Sympacnry.
This is a new development or the fiood control doors fitted to the 31 356gt Tastnanian fe rry -Spirit ofTa^TrLsni^m
(ex-The new 2.1m high door is of tele-scopic-type in which, the 3J2m outer blade is retracted into the main, hinged part before the door is opened, and extended out to seal against the longiru-dinnl bulkhead when the door is dosed, makiag the total width of the door 9.3óm. The faemicyde acrioa allow-s the door to swing open in both che forward and afc
FERRY . 7 2
R A P I D D O W N F L O O D I N G V I A W I D E D U C T S T O L O W E R H O L D O O W M r L O O D I N C A T C I M £ . R O O f ^ i i . \S A / P R O B L S I M --J- - ' - V ^ . » L,. -= l.=3..SO K/<J. -= . . . 7 . 3 s ~ . . ~J.l T zts - - - . - 6 . 0 8 £ , -U6<iO a 'rfy'. -= - fe^00 . 0 1 4 ? ' - ' . ~ , , a ' : . - =- . .7.17 I • -.- Ii
C A R D E C K - S P A C E . 5 U E D L V l O E D B-J". i . . _ ! / T E L E S C O P I C 5 W 1 N G I N C W T D O O R S I 03 roTAL : J 3-7é 3 1 ^ . O • ' ' : 1 1 1 1 1 >'7".. r"JCl., 33c:nJ 1 / : ' • • I : ! ' ; ; / 1 .1.0 7CÖ • '• iico i i; / : 1 1 ' liacc M P . 1; -cc i / < A r . C ' j J i p <7éO tONV.SOLAS W E i C H T O F B U L K H E A D 7 0 B E 4 M A T L E A S TP R O J . ' 9 4 B U L K H E A D S O N C A R D E C K + W . T . D O O R S PROPOSAL FRO SHIPYARD V A N DER GIESSEN DE NOORD
CAPSIZE DEPEIMDS ON:
GM - DISPL.- G Z C U R V E - D Y N A M I C - L I F T UP TO C R I T I C A L A N G L E ANGLE OF CARDECK ^.^ A N I N I T I A L L I S T O F 3 ° is O F U P T O I M M E R S I O N r7^^^5^i~y / G R E A T I M P O R T N A C H , SIZE OF HOLE ^ ^ - 4 > ^ ^ ' A = = ^ ^ , r . C A P S I Z E O R N O T S I D E C O L L I S I O N DOWNFLOODING S I Z E O F C A R D E C K D U C T S CROSSFLOODING O B S T A C L E S I N E . R . ( S E P A R A T O R R M ) CARGO SHIFT T R A I L E R S T I L T I N G W A V E S
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_ T : I I : 4 ^ 8 . S E C T O B E A V O I D E D CÜ-3J? " T W A V E . P E R I O D 11 1./I
I 1 I 0 113 It U., II .11 i p I I-3. a14
5 E C 7 t " a 3 EC i T-.3S .4.S€C W A V E R E S O N A N C ESponsons
Only buoyancy at the outside of the hull in cardeck level can effectively support the vessel against capsizing. Sponsons are creating a "lifebelt-buffer".
Note: BUOYANT WINGTANKS, INSIDE - THE CARDECK SPACE, ARE FAR LESS EFFECTIVE; and are sacrificing space for cargo
It is wise to carry out very soon Capsize Tests with ferry 0 . 7 2 fitted with sponsons as d r a w n .
Seekeeping tests of the model in waves of 1 34 m and 4 m significant height, fitted with and w i t h o u t sponsons, are of utmost importance to investigate wether the energy criteria up to the critical angle of valid.
The sponson is providing buoyancy on the right place and supports the ship like a lifebelt when heeling.
Foamblocks
Filling the sponson w i t h p.s foamblock greatly increases her function as anti-collision buffer (see penetration tests by dropping hammer on double bottom filled with drums or foamblocks, in Harlingen).
Note: Foaming in situ with polyurethane or with polyisocyanurate is the wrong w a y , because in case of fire: Toxic fumes are developed (unacceptable on a pass-ship). In case off shelirepair the removal of foam is rather difficult an dangerous.
Fire risk Inside
Considering a fire in the engineroom, or cardeck space it is a must to protect the foamblocks inside the adjoining tank by a rockwool shield of 2x 75 mm. Extensive tests with different types of foam have been carried out by TNO-Fire Research in Delft (Foamblocks stowed in steelboxes have been exposed against fire during 1 hour at final temperature at 950°C.
Closed boxes (or tanks) keep away oxygen and moisture, therefore risk of fire is rather small. Closed tanks do no suffer from corrosion because there is no condensation (however an expansion valve must be mounted). Shell repair
Considering flamecutting and welding at beltings and exposed shell-plating, the classification authorities require the local removal of combustable foamblocks. Handling via manhole of blocks at 3 - 5kg is quite easy and stowage rather rapid.
To go for minimum risk, it is wise to provide a protecting shield of incombustible foamglas blocks 2 x 150 mm (Owens corning) at the in-side of the exposed parts of the shell plating (beltings).
Foamglass blocks are used below steel storage tanks for b o t t o m support. A secondary advantage of sponsons is their suitability for rapid embarkation via slides, which are mounted on top of the sponsons. A large "Mother"-raft, connected to the bottom of the slide, is inflated and launched in combination with the slide simultaneously.
A w a l k w a y at one level on both sides of the ship is speeding up mustering and rapid "slide" into surrounding rafts wich are automatically launched from
their cradles.
"Abandon Ship" might be finished within half a hour.
Evacuation via rafts hanging on a davit crane, filled w i t h people and operated by stewards (6 rafts per hour per crane) is rediculous in case the vessel might capsize within 4 minutes.
Disadvantages of sponsons
Passing Locks of Hull is not possible anymore for ships fitted w i t h sponsons. Embarkation terminal for passengers should be removed from locks-terminal to the Humber-shore line.
Speed loss: Simple tanktests regarding speedloss by sponsons is recommended. The knuckle should be designed in line with f l o w .
Jerking Rolling behaviour might be less passenger-friendly and bad for lashings.
7 m metacentric height is far to much.
We did our utmost to solve this unsolvable problem. Anti-rollingtank on top might work well!....?
However in case, course has to be changed suddenly, and the rudder is turned to HARD SB.
The vessel starts heeling in the sharp turn.
A f e w seconds later the ship might get a violent push by the anti-rollingtank-on-top being out of phase. This is frightening for the crew, and dangerous. Slack tanks in double b o t t o m ! ?
Fortunately THE ^ R^ROFERRY has many cross over ducts available in the D.B.
which could be used as anti-rollingtanks (flume principle).
Reduction of GM from 7 m to 3m by slack tanks is possible however in case of heel at collision the mass of water will run to the lee side, of the D.B, greatly enhancing the danger of capsizing!
Final conclusion
Sponsons, having hardly any width at waterline, and where the original is the good solution.
GM is maintained and also the sea behaviour. No loss of speed
However about 500 ton loss of deadweight due to sponsons must be accepted because the sponson has no displacement anymore.
Point of discussion with the seafaring people are:
Mooring a long side w i t h a belting at 3 m above WL, and a sloped side below angle to WL 50° - 60° ?
A small tender coming along side might have difficulties w i t h superstr. On both sides of the ship there should be a suitable landing stage.
People inside the liferafts should not be endangered under the sloped side of the listing vessel.
Ro-Ro Passenger Ferries, November 1995
1 Reduction of permeability and the pros and cons of using hardfoamblocks are not mentioned in the regulations.
Hard-Foamblocks could be applied in sponsons and void wingtanks below cardeck as Has been carried out on (Ferry "SIER", Wagenborg-January '95) 2 Dynamic effects are not incorporated in the damage stability calculations. However, HP9000 computer, using "NAPA" stability programme, which does not incorporate dynamics, is accepted by authorities.
The final - damage stability - minimum requirement is very well defined, however wether the vessel will reach this final stage might be questionable. Looking at these capsize tests:
After a collision, the vessel tries to find and equilibrium, but cannot find it after swallowing water on the cardeck, with simultaneously rolling masses of water inside the damaged compartiments.
Finally the ship capsizes and will never reach the "final equilibrium" acc to SOLAS. As thought it seems more reasonable to define the surface-only, this is the positive part of the GZ curve - up to the critical angle of heel. In Holland we call this surface "Dynamic Lift"
3 The surface of the curve is a measure fore the capsize-energy required: in m.rad below the critical angle based on the famous limit of Rahola (1939) "Critical angle" applied to RoRo Passenger ferries:
Where water is entering the hull and the cardeck space is flooded (8°-14°). Where cargo starts moving, where trailers start toppling 19° - or 22° ? Where passengers get into panic 7°.
Where life saving appliances d o n ' t " w o r k " anymore Normal cargovessel, 1966 Leadline Convention:
Stability: the surface of the intact GZ curve up to the critical angle of 3 0 ° should be 0.055 m.rad. minimal
For a passenger vessel w i t h 2 0 0 0 passengers on board in damaged condi-tion, SOLAS 2 0 0 0 , should require about the same surface up to the critical angle as the cargovessel (perhaps 0.045 m.rad might satisfy). See diagram Page 4 0 .
In most ferries built before 1990 the heel angle of immersion of the cardeck is 8 - 9 ° ; beyond this angle water will enter via a hole in the side of the cardeck space.
Nowadays in the proper design, the heel angle of the cardeck immersion is about 14°
Here the subdivision of the cardeckspace might eventually provide adequate damage stabilty up to 2 0 ° - 2 2 ° , which can be realised by fitting:
- longitudinal bulkheads, fitted w i t h closing end-doors
- transverse bulkhead doors, telescopic, swinging fore and aft, subdividing the space in at least 4 compartiments.
The angle of heel is limited to about 20 - 22° (which is caused by the max. doorheight limited ati3)m, to allow for sufficient ventilation) and toppling of
trailers, NOTE : SOLAS AMEND-NOV'95 BULKHEADS AT LEAST 4 n ,N HEIGHT
Critical point on doors: watertightness of the doorsill and the hinge at shell side.
M E R C H A N T VESSEL C O N V E R S I O N S : THE F A L K L A N D S C A M P A I G N . J.R. M A N N A H , THE NAVAL ARCHITECT, FEBRUARY 1986
I N T A C T FRICATEI M D A M A G E D S7J N T A C T 1 ; L r r ; 1— o.aiS j£ï 1.0 P A 5 S V E S S E L D A M A G E D LINE ,40r ra ae susMtRCia .STANQARQ l a S O III i 1223 « S i
Fig. 6. Simpic Comoarison of Frigate and Passenger Vessel M i n i m u m G i , C u r / c s : Intact and Damaccd
RoRo vessel poses an additionai hazard in that the
suomergence of the vehicle deck would cause such a "massive loss of s u b i l i t y that catastrophic capsize could occur.
The alterations carried out on the passenger ships were not necessarily approved by the D T p , although the M O D ' s policy was to endeavour to meet at least D T p rules where this was possible. The help and assistance of the DTp in these matters • was o f crucial importance in reaching the inevitable
-ompromiscs 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 U K within her passenger vessel load line limit.
The conclusion that can be drawn on stability matters is that the use, in an emergency, of merchant vessels in support of military operations, especially for the carriace of irooos or
vital equipment, is poieniially very hazardous.
• W A L L S -i n ^ ^ / / / 13-(0 to • ;o (.z j a I N T A C T RoR© PA5S. D A M A G E D s ?ANC£>i s c-- ^ 0,10 n SURf ACS.'^ c,oi t n SA =
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0.05-SOLAS ' 7 4 - 0.05-SOLAS REGULATION IN DEVELOPMENT Base: Chris Lloyd, Svensk, SJ.Tidning 4 0 , 1 9 9 2
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0 . 0 4 5 n"o]-'j = miN-CRITESlOH UP TO 19 HEEL-UP TO ANCLE l ~ WHERE CARCO''-' |Q-5TART.S MOYlNCiO in g<;iNape: RAHOLA I
PROPOSED .FOR PA55 FERRIES
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BETrONO i s " STABlLlTY-CALCULATlONa ARE SENSELESS
DIAGRAM LEENAARS AND AALBERS
TRANSVERSE ACELERATIONS IN BEAM SEAS 11.9 S E C - 8 . 5 M (sign, height)
IM T O T A L C k U D I H C i J - l C U U J l C K A V l i r C O n P O N E M T o e P S X n A K T OM H E I S H T A S C Y E B A i E l I r t D g P Ï U C X M T F K O n D l i T A N C E o r ? : < 1-T R A J - t S v Ê 1-T U I . F O R C E » M A i J , ACCELi?e»."POrl f=0« C A R C J OM D C C K . w m o r o R c L i - J 3 J foa. E A C H i l - ï C l f l C - C O M O J - n C N VINCA GORTHON 5 ? 0 L U N C P E R l o n . . T tn P S A C T I C I - : 0 , 7 7 - 0 , 8 8 B c n ^ 0.3 n — Gtn= 2.^1 rn y--T R A X i V E R i E - A C C E L t R A y--T I O K - R A P t g H E A V y R O L U V I C R E S U L T g - r o n g E . S . OM C A R C 0 - L A S 1 M C 3 A R E C O N S I D E R A S I - Y I N C R E A S E D THIS i j i o « j \ . a a e v g L i - R E A U ^ e n iw o j j r g g » U I B E - D O A W A C E S T A ^ I U T T I S A C w i t v g o e r A v c K r L A - K C E a n fTrnoo. H t Z L AHTIC-T7;viCXJ I ^ ~ I 3 F i r ? S T W H E E U - T O - l - l F T l3"-r7 _ T Q P p U l N C : T R A U . E K 3 cuts j u c t D F T T 2 a - T 7 - ' _ 3 U D e z O R Y , 6 - u ' w E T f > t D F U t s T A x o m a i A - l S - S U P „ v w - t i x i V ^ ^ S L I P BRAUN D5 r
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SUGGESTED FOLLOW-UP RESEARCH
1 Capsize tests under different sea conditons with models .62 and .72
GM = 2 m calm sea
1 Vz m wave height 3 tests 4 m wave height
2 Capsize tests under the foregoing conditions
2 x 3 tests Models fitted with sponsons - 2 tvoes
Corresponding GZ stability calculations should be carried out by computer
3 Capsize tests under the foregoing conditions
2 x 3 tests W i t h o u t sponsons, but fitted sub-division doors and bulkheads in cardeck
50 % L - longitudinal - bulkheads at 7 m from shell Port and SB - to be closed at ends.
2 x 3 tests Transverse doors, hinged at side shell swinging 180° fore and aft - Port and SB - with telescopic extension against casing.
Doors and bulkheads to have a height of 3 m (to allow for sufficient ventilation).
