r
FEB. 1984
Lab. y. Scheepsbouwkunde
ARCHIEF
Technische Hogeschoo
Deift
Sonderdruck au
Jahrbuch der Schiffbauiechnjschen Gesetischafi
l6Rand L982
Spnngcr-Ver!ag Berho Hc.!dberg Ne York Tokyo
V
Development of Large Cellular Containervessels By E Vonack, C. T. Buys, S G Vrlead, Newbuilthng Department, Nediloyd RecSeñjdiensten, Rotterdam, and
A. logik, J. y. 4. Seek, N.S.M.H., Wageningen
(1) Propuhon - Fuel Coniumption
IfltTOdUCtiOfl
Modern trends in cargo liner ship operation call for changes in ship design in various aspects, almost all aiming towards improving their economy. Differently from ten years ago, changes are aim-ing mainly towards savaim-ings in propulsion fuel expenses. l'bis is because fuel costs in the late sixties being just 'part of total' costs, nowadays they are rather dominant.
Therefore the emphasis in changes at present is laid vety much on Reducing the Fuel Consumption-Versus-Speed
Consequently, whilst adding improvement in other fields as well, we arrive at a number of changes in
design, as follows:
- Slow-turning large-diameter propeller(s);
- Slow-turning long-stroke diesel engine (long. scav.) with a minimum number of cylinders; - Continuous optimalisation of hull form, especially at stern and at the bow;
- Excellent surface preparation and painting;
- "Self-eroding" underwater antifouling paint giving minimum frictional resistance; - Shaft generator;
- Thrusters at bow and stern - for ease, safety, and rapidity of manoeuvríng around of
(rela-tively) long ships in confined port spaces;
- Qrginol bulbous bow.
8ubous bow otte'
C S Q
win
y wi
20 Bose line
-.1
Fig. 1. Conversion of bulbous bow Nediloyd Dejima with onginal bulb, (right). Nediloyd Deift with shortened bulb, (left)
246 Development of Large CelluLax Containervessels 2x - --
=
=.- .
r_..
E I-==.==I
.graI[?O p
Fig. 2. Thirdienertion cellular container vessels for Europe-Fszeast service in "Scandutch" consortium
N
s
Fig. 3. Main particulars of ships shown in Fig. 2
Development of Luge CeiJular Containervesseis 247
381 P3 I T LIS CLFT SS.ip ClIMA ¶972 1972 1972 1973 158Z
puns ¡ois
L4tA e... 775,27 I 274,32 R 275,09 I 2r, I 1.ib 6.P. 257,60 - 257,60 - 259,00 -273,00 32,28 32,31 - 32,31 -32,3'-sth,
.1d.d 32.21' 32,23 32,20 - 32,24 54ptA, .I4sd, to Ipp.r4. 23,90 23,90 26,00 - 29.00' 0.014 tO d a. 20,96 - 14,39 iDi. 17,70 20,46'0..i.
z. 11,61 I 11,60 I 11,41 I 12,72 8 C A PA Cull IS 35.000 t 34.730 5 34. t 49So ' 22 000 24 623 23 827 t'o. !!!_ ocseDtap2.t
58.446 t 56.730 t 58.828 t 71 77 ... 71.977 t Ct..a.,-' 1.. a. (?R) 1,2 1. L608 20'-x.. 964 950 840 1.252 364 356 374 434 LXV. Look (3-b)(?Z) 850 838 20-Xx.. 850 874 810 932 416 430 386 466 Or t.t.2 (?) Of aA ..fsr. 110 110 100 110 (At..s/8.lee) ()'60) (54/60) (52'50) (44/70)Pi0 PULS ICR
L L.A DI-.' Dt.s.1
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PS .A 33 Lo0.
- u_575. O.v._a850/1700s I è W- %84 U ..t7p. 8U P..t.r Wb.. S..zto
10 071. 9 1. 9 1. Sts.l Zsv,.1/St. t.o..o -c_t.,. 0.4t0 23.400/1,5 22.500/117 22.500/117 40.550/136 2S40/ll2 - IOk./t75. 0.V.-850/17003 S à W- 184D -t7p. '84U
-12 2. 12 l. 12 1. - 26.204/115 30./119 30.J119 -TotAl b.A.p. 75.000 75.000 75.000 81.100 50680L....il.b et &.800. 34,20 I 34,17 U (oet .5.rsbl.)
30,60 U
PRO PILL Li S
1 z Vor. PItok, 5.-I1.A.. I z V.r.Pitok, 4-12. 1 z Vor.Pltok, 4-bl.
(Re et.,. 1...) c_t
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6,25 1, 39,7 t 1.90 I, 40 t ...38,6 t
-Std.. 2 z fIxok p1t, 6 12M.. 2 z ttzM p., 6.'.b 2 i ft.p., 6-bl. 2 z ft p., 5 JQ 03? Li 5,85 I, 19,6 iI z i.2 Ip, V.z.patM Pt.. 6,7 .2 s.M Pr.... 136-140 5,85 U, 19,6 t I z l. Ip, V.P P2... 6,7 .2 ooM Pp 136-140 ... 19,3 I z 3.000 15. V.P. Pia. 6,7 ol -150.155 1 DZi 6,30 U 4& 2 z 1. Ip, V.P. Pt.. 7 .2 ..M Pr0... 165-168 650-1 516 RI . IC ro s i u_p s ¡ i -?7p. 3l-.pM. 54x. door'
- 340f...
..
Abt. 48 .2 abt. 48 .2 abt. 46 .2Abt. 98 .2 - 602*1 AL1I.II.L2T PlV5 45 t 4 z 1.300 [8(1742 Ip) 48t 96t 5 z 1. [8(1350 Ip) 5 z 960 fl(1313 Ip) 3 z 1500 [I120, 3t 2 +2z 900L1 7e 500 40 Pr.s / S of L.b.p. 85-128 / 13,3 5 83-.127 / 13,3 5 88-128 / 11,2 S
248 Development of Large CelluLar Containervessels
lx
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(i972)-!LI3UIO u8 (i972)
E E P 17 R S ¶9 )Fig. 4. Thirdgeneration cellular container vessels for Europe-Fareastservi in "Trio" consortium
SB CAPACITI ¡S
D.pl.ot
Lpp z kid z D .14 .o t.a.r. BsS.. d..0 (?I.7) 2O'-z 4O-z.. AX.. ds (?L)(4.-) j.1j 20-X... 717 d: 40'-Xzs. 150 Ord tojal (?R7) Of .tci r..f.r. 40 TOIlAS B Oros. l.ttPRO POL! ICI IMS/t7D. p.ri o,.i.r. tOr ...5 ..h.p./ pDop.r.v. 3.!.?. tots.l II kO Cs.r4.o My ky
DveIopment of Large Ceflulax Containervessds 249
1972 1972 1.2.5. L.l 1.2.5.
I.i
289,50 I 288,75 I 274,32 274,22 Psc.zP...x.
3.2,26 32,26 -24,60 24,60 -13,03 13,03 -JOP.R 2041 288,75 I 274,32 psa-ml. 32,26 24,60 13,03 48.542 t 49.600 t 49.74.2 t 42.470 t 51.5.40 2, 'lo2 21 23400 24 2'O 73.642 t 73.64.2 t 73.642 t 65.870 t 4l0 217.800 .3 217.800 .3 217.800 .3 219.800 .3 209.500 .3 1.9 1. .708 1.284 1.708 1.126 1.104 418 332 418 432 418 1.020 556 4 856 or 7.020 150 428 2.967 2.804 2.800 3,010 2 z 40.560/136 81.120 2 z 2.500 r. 2 z 1.25015 S%. turb3.z./2 St. t.J62.z./2Pb.i.r-..i.r/L III P-5 / R III
121, 145 T/b.r .t 718/13.8 ?/hx 65,6 ste, 5.13 C 63,4 bar, 516 C 2 z Stal..La...2./LP 40
2s Q2/i.L.
2 z 46.000/140 88.000 3 z 1. n 440V 60!.2.
90C '973 1972 79871.2.5. Kiel 30.8 Ve.., Ia.61. R.LW., Kj.l
66 .JA. 66./d.66
2 z 6.750 2 z 6.750 2 z 6.150 2z 1.000 bp, Par.?. 2 z 7.000 HP/TP 2z1. HP/TP
(2 z 71 ? (2 z 177) (2 z 'It7)
Pisa, Dzy-R.,/b Pia., D-)/& Pia., D-A
PLO PPLAJIftJT?
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38.425
Stess tu.rbt.n./2 SI... tarRioe/2 Di...1/2
P-. / III .a.i./ ¡952 90/1601 115/138 ?/br 64,5 t5, 515 C 2z St.0_L.ajal/AP40 2 z 40.560/736 2 z 27.200 /122 81.120 54.400 3z 1.& r. 440V 6CR. 2z 15 2 1.9%¡JIS 440V 401e I z 1.650 n
5. Main partcuIars of ships shownin Fig. 4 287,70 I Z73.00 -32,26 32,19 25,00 -12,03 -287,73 u 271,00 32,20 24,00 -13,06 58.385 8.?. 37.93.4 2 z 2.800 15 450V 608. 7 1900 15 450V 601. 2 z ,.ioo n 2 z 6.l5 2 z 6.100 , 6 bi. 2z 1. IP/VP 2 z 1. 15(3.300 V)/ (2z Il T) Pi P11.5. Pt.., h.P-misi... Pi.., 12 3 - 9,1 58.889 R.?. 57.887 RI'. 57.249 R.?. 35.191 - 34.014 33.967 P-S / III /732 7/br 64,7 bar, 516 C O, kgi.1.i. 2 z 44./14O 88. PROPII.I.ZB S BO STR 605 ?5 3 ?4 B ILS Z 1k! P7.41'? trS-.nsr.%or. Bol t.s/Pr.qucy Dj.. 36aZt (r.t.F
r
250 Development of Large Cellular Containervessels
MOO RN TAaLE BAY BS S V EN DR KA E SI
!.--..'-
. .
J U X L?, 7&r
Development of Large Cellular Contamervessels 251
¶979 ¶979 1974 ¶979
4.0.1., 1$ 1.2, 0p ¡.1.1. ¿3.ot (oft) V.0.3.1. Ist.
Fig. 7. Main particulars of ships shown in Fig. 6
CAPAÇ ¡?5 ¡:5 (.t z. ¿zf t) 47.197 5 49.149 t 31.771 5 48.637 i 24 3 2: j.&q 2706 71.542 5 71 27 t 71.343 1 LPp z l(.) z 4ptl(.) 193.367 .3 '50.4)5 .3 Cozt&iz.x, 1.780 1.780 1o. 6.08 (rL) 20-x. l.036 1.004 388 1.0)2 372 388 298 378 £v. 6.08 (rL) 20' -box.. 656 672 548 660 326 3)0 274 330 0r t.t.2 (TL)(..rvta.) 2.436 2.452 1.532 2.448 - ()(ox)2.696 2.770 2.000 2.708 st 08.108 1.st.rs 941 308 YL 151 43 (IC 154 box4O') (Abows/IsO.. 4k) 55/886 132/176 / 35/886 PIOPOLS ¡Ql
[ii41qUt Di...1, 2 z Dt..., 2 i 01.s.1, 2 z Di.1, 2 z
aoo /IJ., 1 8 52.-90/160 Is..1_ 3.2sz, 9 0-9Q I 1 / *2 0.-90 D. 308.14e! 3s11.r, e DO-90 I p11115 I 013 (f08) 1.0.3.1., 5.16 LtA ... 258,501 267,00* 241,201 258.501 Lt b.,. tA, .Xtr. 248,20 - 250,00 24.2, 247,00 -32,26 I 32,24 I 32,20 I 32,26 I 24,15 24,15 - ¶9,50 24,15 13,03 ¶3,03 - ¶1,70 13,03 s.. LI.P./I.P.1. 25.660 / 122 30.150 / 122 34.800 / 122 26. / 122 V.5.2 LIP. 51.360 60.300 69.600 53.600 710 PILL 113 2 z Pt 11508 2z LP. 21 PP., 6,50. 2zP.P.,6,35I 6-bl08s. 5-6108.. 4-6108.. )0W?I,D5?II3 2 z l. IP I z 1.500 IP 1 z 1.400 IP (V.P.) 2 z 1.000 IP 75..
LLU
I P D P ¡ I 1, Ops. io4 1, I.M2s.o. 6 z 1.500 D pt 1, I.erly C1c.081, $I-3...
2 z 1.360 D , 1, Op..I-2..o.
2 z 1.360 D 1, 6 z 1,100n
2 z 1,000 D V.1te./Pr.qscy 440Y / 60 Ii oc 440 V / 60 Ii oc 450 T / 60 Ii icI5A PLL1 ITPLL IA.
252 Development of Large CeUular Containervessels
Four to five mooring winches fore and aft: Utmost simplicity in lay-out and in construction:
Minimum number ol rewmembers:
Sophisticated and reliable equipment for control and for communication:
Reefer containers to be of integral type if their number is relatively low - about 250 units per vessel.
Vessel Types Under Consideration
Already soon after the outset of I.S.O-container trades rather big vessels have been introduced on the trunkline routes. (For the purpose of this paper we have the Europe - Far East and vv. trade in mind) (Figs. 2-7).
As for propulsion and steering arrangements. various kinds and configurations were chosen or
accepted by the equally various owners.
\iain movers were either steam turbines or diesel engines. There were twin-screw and triple-screw u n its.
Nearly all had single-rudder steering, but skegs varied from wide-open to completely-closed types
and semihalance rudders as well as skeg-rudders were applied.
Fuel Consumption in Service
For marine engineers and naval architects it is an exceptional and rare opportunity if results from real practice are available for comparision (Figs. 8li).
Of some eleven ships in the same service recently such an opportunity arose where a number could be compared, viz.
Ship designation Propellers Main mover types
Korrigan" 2-screw steam turbines
Nedllo i Dejirna/Deift 2-screw steam turbines
Nedllo d Houtman/Hoorn 2-screw diesel
BP!BS 2-screw diesel
--N". "T'. 'S 3-scre diesel
Results of compilations from a number of voyages showed that at 20.5 knots service speed.
average consumptions per day were as follows:
Conclusion (A) - Steam v.à.v. Diesel
The difference between steam and diesel was about 90 tons per day in fuel consumption at the speed of 20.5 knots.
This fact made it clear to a number of shipowners that it was necessary to convert their main
movers from steam to diesel.
Note: Other owners may maintain their steam turbine plant, mainly with a view to possible future downward trend in fuel oil quality. By example - we assume - Hapag Lloyd thus converted their steam turbine ships from twin-screw into single screw with a propeller of slow-turning and large diameter type in their endeavour to save on fuel oil expenditure and retain the reliability of the steam plant.
Conclusion (B) - Triple-screwv.à.v.Twin-screw
Twin-screw diesel is better than triple-screw diesel propulsion as to fuel consumption.
Note: The centerline propeller of triple-screw ships, working in the zone between the race of the two side-propellers does not take advantage of the wake belt which normally on
single-screw vessels increases the propulsion efficiency ("Hull Efficiency").
Main mover type Propellers Ships Average consumption
Steam turbine 2-scre Nedllovd D 196 202 tons, day
Die'el 2-screw Nedlloyd H 112 tons/day
Diesel 3-screw "S", 'SL". "T" 124-130 tons/da.
3CvCf 250 200 150 100 50 O
Development of Large Cellular Containervessels 253
15 15 17 18 19 20 21 22 23 24 25 kn 27
a Speed lServfte)
Ftg. 8 a and b. a) Fuel consumption of Diesel-vessels, b) Daily fuel consumption in t/d
Recent tests in Lyngby-Hydro showed the optimum twin-screw to be about 4-6 % better than the optimum triple-screw vessel (SSPA already mentioned this phenomenon earlier.) (Fig. 17). S-. . - N. Hoorti in service -.5
:.
- . -'
- Pilot-PilotIEI
¿
N.Rouen o S«p Ship s Hoorn N (3-screw) T 13-screw) (2-screw) N. Bahrain 5peeJ 5$ J 3 S SL I5E. T N flY' S! VPSS% DL 25-5TAM OP K W005S SSu' H2SSL
EF ESaS5L
(Cv.rt Íroa Stsaa) $tLYI ' ,, I'Sa*W 23 173 15,) 165 202 251 261 303 160 165 185 149 22,5 161 169 172 18_ 239 247 286 149 174 175 141 22 151 159 160 176 227 235 273 137 164 165 132 21,5 149 147 149 165 216 223 263 129 154 156 125 21 14 139 138 155 205 212 248 120 145 147 118 2).5Y 124 130 128 146 196 202 237 112 134 139 '12 20 117 121 118 137 187 192 226 105 128 131,.. re_ ç.,. fl n*sA WOh/ ev
Conat. - 5._ I W1
10 St... a. AAL
Afl
13 Sei:cono. Ta Te 2.5 To
/thty DO ir, .crt: Di) DO
80 Ta FOL8D prt ir, port:
7
1T
To DO
300 t /24 h
254 Development of Large Cellular Containervrsaels
Conclusion (C) - Sea Margin
From the practice figures we also learned that for the mmss Nediloyd Houtman/Hoorn class vessels
- having a chlorinated rubber underwater painting system at the time, the sea-margin on the Far East-Europe andv.v. route amounts to about 13 à 14% forS years lifetime (Fig. 8a).'
Moreover, improvement would still be possible by the application of modern anti-fouling paint of
self-eroding kind on the ship's (sun-lit) sides for the prevention of fouling by algae.
We expect that this will result in a sea-margin of some 10-12% only, in future.
Nediloyd Dejima/Deift, after conversion to Diesel have exact the same fuel consumption in com-parison to Nediloyd Hoorrt, Houtman at 20,5 knots.
Conclusion (D) in Fuel Consumption Difference on Similar Vessels
From separate information (figures not compilated by us) we learned that of very comparable ships in size, main movers, propellers and rudder, but of different owners/operators, the fuel
con-sumption levels differed appreciably. (Ships Nediloyd H v.à.v. ships "BS" and BP".)
350 t /24 h 300 250 200 150 50 Ship DM Turbine a 5 202224 kn - 202 Difference to t/24h DM Motor ---t---- fl2 16G 140 120 40 zo O
I N. B.: Sea margin upon thais is 1.13 1 1.14. Margin upon Tank-S.H.P. is 1,18.
Fig. 9a and b. a) Actual fuel consumption figures Steam and Díieset. Vessels of mç.rabIe hull shapes but slightly different lengths. b) Fuel oil consumption-to-speed ratio. H (t x 1.18) Nediloyd HoutrnanfHoorn, at 10.6 M draft,
1.18 P,j Tank; H (t) Nediloyd Houtman/Hoorn (d Tank); D (sp) NL Dejima/Detft, Savice Pilot-Pilot ( P
Tank 1.13); D (sn) NL DejunalDelft, normal at sea ( P4 Tank 1.065); D (ta) NL Dejim.a/Delft, PdT3flk inclusive appendages
H11118 Service, from Pilot to Pilot.
Normal at sea: 1.02.Triats.
Tank. inCL. appendages.
N11
-OIP
Ad4
0,--..,, OIP us K, K, b b 14 16 18 20 22 24 Speed Ika) Ship N MUftí 100 o Q-E 80 C o w 60Development of Lage ceuuiar Conzainerveuels 255
Possible causes may be found in the following differences:
- Quality of hull forni (i.e. slender pipe with brackets on Nediloyd H's propeller shaft may give
less resistance than the fat bossing of the vessels BS and BP);
- propeller design; - hull roughness.
Other causes may be the possible driving of the turbo-generator by the auxiliary boiler (instead of by the exhaust gas boiler) during legs at reduced speed. In such cases the exhaust gas temperature often is too low for steam production by the exhaust gas boilers.
Propulsion Features on Poible Future Tonnage
In case any future units of appreciable size - say 3000 TEU or over - would be required, our basic assumptions for the design would be: an MCR of 85-90%, sea-maigin 12-14%, draft 12,5 M.
Propellers
- Twin-screw? In case 20.5 knots mean service speed is wanted, with peaks of 23 knots max. for keeping up to schedule, then Nediloyd would proposea twin screw vessel.
- Single screw? In case 19.5 knots mean service speed is required only, with peaks of 22 knots max., then Nediloyd has the courage to go for single-screw. (Courage, because of greater risk of
pro-peller-induced vibrations and noise hindrance on a high-powered sLngle-screw vessel than on a twin-screw vessel.)
Service Speed
A reduction of service speed from 20.5 down to 19.7 knots will bring the fuel consumption down to an extent of some 12 tons/day.
vaar-t.d h,. ) si.. DO. e. f3. or .j. ;'ort
- kPlOUTM* . ' . '75 N. 2.kw. '7 338ES 33573 56L 1616 3E)) .26 633,.593,. 123, 23,,4
2t
286,7M.MOO$ 3 '7
!2 L!
663..'si
336,4 94677 466. KNOT5 21633 1761, 486,3 83, 223 11. 20,3 T/E3..
rego p 1. 2S..s'rrAjl '7: 324Y 1585 1)371 C 1376 19 2.k'w. '7 294) 14)2 13343 0 1363 23 3. k. '7247 163
17362 !2
. 94317 4..3 43152 2 4725 63 FNOI3 ',2G T 20,3 ' -J e oc T 25-STeAM -NI..Df4JT '.k. ''.. 26.?). 1,3. 13735 16)- 15 2.4w,'). 3z114 147 1)999 13 1657 253.. '7. J4
9370<. 4..7j..9
1,) 4333 51. KMOrS 2 5 3 :/:::. 4 20 T0,Ç000,,uzs 45. 2 700T VR256 Development of Large Cellular Contamervessels 300 250 200 150 100 50 o 350 300 250
200_202
1507
100 Ship DM Ship J f./
Shp NI
146 Ship K237
-./ r. b Ship Dl J-:.y.. 15 20 22 25 15 20 22 25 15 20 2225 ka
a
21 23 21 23 21 23 1520 22
25 15 20 22 25 15 20 22 25 15 20 2225 kn
b 21 23 21 23 21 23 21 23Fig. IO a and b. Fuel consumption/24 hours.
a) a twin screw steam turbine ships; b) triple screw motor ships
Shaft Horsepower Maximum
At 19.7 knots service speed the mean level of shaft horsepower lies at about 30,000 1-IP on one screw. At this or lower level there normally would be only minor trouble
as to vibration, noise, cavitation-erosion to the propeller and as to fracturing of ship'sstructure above the propeller.
However, we strongly object against utilizing more horsepower continuously. This objection is based on experience with the first generation containershs,
especially those having their
accomrno-dation right aft.
¡ I I Ship SL
200 1/24 h 150 100 50 200 t/2.h 150 9g 150 1.13' 200 t/ 2 4hi loo 50 o
u.u...-
...
uuuiuua
lUUV4
UluUlPNA
...u.au
UU!U
....zu...
u.r '
....
u.,
uu..
u, '
l.l.
P Rcu.u...
uu....
...u...0
uu...
uuuuuuu
Fig. 11 a and b. Fuel nsumpton/24 hours twin sew motor ships
20212223 2 25kn 15 250 20212223 2425kn 250 15 2021 2223 2425kn Shp H 5h
llI
/
200 150 135 t zoo 150All
ll2t 100 5G/
I'll
100 50 o OI'll
Ud
L) Od 118 50 o -95 A4Yç
/. .._
U
..._
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...I
Development of Large Cellula: Containervessels 257
Nedfloyd H Nediloyd Deift Nediloyd Deimo
1 year service 1/2 year service Z months service
Chtorin. rubber SPC antitouling SPC anti outing
b 15 20212223 25kn 15 20212223 2Skn 15 20212223 ZSkn a 15 250 200 150 loo 50 O
258 Development of Large Cellular Containervessela 55000 SMP 50000 45000 40000 35000 30000 75000 20000 15000 10000 5000 50000 SMP 45000 40000 35000 ¡ 30300 25000 20000 15000 10000 5000 o 17 18 ¶9 20 21 22 23 24 25 26 277 8 Speed )kn)
-9 10 11 12 13 ¶4 ¶5 Draft rn)Fig. 12. Nedlloyd Houtman+Hoorn, SHP-V-Draft(NSMB). Built as diese! vessels, 1977
125m 12.0 ¶1.5 11.0 10.5 10.0 9.5 m o 17 18 19 20 21 22 23 24 25 25 277 8 Speed )kri)
-9 10 11 12 13 14 15 Draft (mf-Fig. 13. Nediioyd Dejima + DeIft. SHP-V-Draft,NSMB tests Steam to Diesel. June 81
IIliAIU
23 22/i 21 '/ r,l9kn
__I!1
'II/WAl
iMl
llffi':
lR/IP
F,
(4Ull
24kn 23'/i... 23i
22 '/2 /2 kn35000 BHP 30000 100 -'i. 25000 75 - 20000 50 15000 10000 25-5000 O
Development of Large Cei1u1a Contamervessels 259
P 104S y.iau. anoraK PA I.045..YtI4I. C0ND,TIOK
(ItnoIAn A'.)n'\ P0. I-18 ,*.fIAI C.0 5RVl(°N .1.13 f ¶NIAL ca.DrT.0n al
IO,an) P 113 ,- - SrqvuCt
Fig. 14. Specific fuel consumption in pr*cti Diese' and Stearnturbine
Hull Lines Aft Ship
The hull lines of single and twin-screw models are (to be), according to the latest developments and much attention has been (and has to be) paid in keeping the "12-o'clock" wake peak of the
single-screw ship, as small as feasible (Figs. 16, 18, 19).
32450 hp 224 5 Fuel consumpiion\ in service 1.09 higher Caloric vQlue 3/. Margin
j5/
138 148 155 162 Separation 122RPM5°°°1 "F red I IL RIA 70-87 84 R 94-102 egOh\
RND9O 112 Specified Service Oelft. Hoorn Oejirno HoutmanWCDLOY P4OUIMAN* NtDL.L.OVD Dt IMA +
2ca.cL V TANK A T A i.l8 V TA.AN A A 2.4 III l.13 . 10.6" .. IQ.fl - 14Ar ¿41V I 5 400 A 70 2.4 .3 I.3 -I?i T9OO
i8
'7 7' .2 8100 67 l 600 l S 77 8/; IS SIDO 20 400 A 67 24 31 i.u8 St 87 I5 ISj 21000 23300 162, 162 82 93 33 20 2500 23 300 .65 89 35 04, ilS 20 no 24000 23700 161 160 33 IO SSi Il5 II 35800 64 ucD 120 Dl 17400 '38 104 II/ !I 2,000 64 ¡lO 130 ZI 29300 37 I0 I 25 23 30400 63 113 40 ¿3 .31300 I2 II7 32 22, 23 32800 35300 l3 60 29 38 131 63 21, 23 33500 300 15$, 33 Itsl'I
134 ISt' 23f 38300 IZ 42 176 Sii 1*800 15$ 144 6324 LI000 n 62 24 16ø l.I8 99 .24 .45100 n 15$ 24 157 IlS_77
mmss"NEDLLOYD HOUTMAN+HOORN"
SLAGEN LJJSTJE PROPULSION PERFORMANCE fP TANK a 1.045 TRIAL C0NDITJCS Dii
- gPUD - Powis-NDLLOYD: D° 2o.Jti*D 10 t't' 3ULZ&R l NOII II to 15440 9HP/ lit SPIt 1o0J102i440 9112/ ptOPLi19 III SPn 0. sao _LIP2 w1l6.r, t4.6 7I P. 9140 (0 411.1015 CINSAL TyA14KwI.Q6 - rrna.b.CØNDITIONS,. i.øaFig. IS. Propulsion performance mmss Nedlloyil
Houiman/l-(oorn (built as Diesels) and Nedlloyd "D".Iype
(after conversion Steam lo Diesel)
o'. Q I. P.1 , S P L I D , I. IslOt., SOP. toi.i , OIÄfl 011*1. 5&UPI'lc* .0/C
-'
look .. . . ri.00 olI, dr.i.5i;, la o.f TOn. J ¿4 hoU,. 4r.er P. 1911 s I ;.;t 0.'i IONtl
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'56'7 *04 8sic2 114 16,3 J,0o I Go,J i.e 114 Ils il' 6,4 I ¡ç;Io IS' i1iÇÏ ta' PIS i ¡6Propulsive Power Needed, Single-screw v.a.v. Twin-screw types
The difference in propulsive power needed for single-screw and twin-screw for obtaining the same
speed is marginal according to the latest prognosis (Fig. 17).
Intensive model testing shows only very little favour for the single-screw design, to the extent of i % (within accuracy range). The modern extrapolation method using form factors concludes that the
twin-screw ship exceeds her single-screw counterpart slightly.
(Scale effect in wake, hull efficiency, scale effect in appendage resistance.)
Thickness of boundary layer is proportionally 3 times larger in the model. Resistance of appendages is about twice on model scale.
Propeller Diameter
Model testing for a big-sized vessel ought to be done with large slow-turning (97 RPM) type
propel-lers for both designs, diameters of around 7300 MM for the twin screw design and around 8600 MM
for the single screw version. Even 75-90 rpm are becoming available.
Single screw Perils
In case of break-even or near break-even between the single-srew and twin-screw versions as to propulsive power, the single-screw ship might - notwithstanding lower investment costs - still loose
her advantage if her propeller is designed with a relatively large blade surface area.
Such large(r) surface, however, may be necessary in view of reduction of cavitation, hullpressure fluctuations, vibrations, resulting noise et cetera.
The propeUer thus is to have a moderate skew'. mainly for reducing the higher harmonic(s) blade excitation. "Extreme skew" makes the fixed pitch propeller too vulnerable for going "astern" (Fig. 20). A few highly skewed propellers got ,,tulip"-shaped after a "crash-stop". Only c. p.
propel-1ers can have extreme skew because of their uni-directiorial rotation.
Development of Large Celluiar Containervessels 261
5915 A Single screw For Erst contr.
5974 A 7.in screw Fo Erst conf r.
Fig. 16. Single screw versus twin screw
o 3 4
Fig. I?. kelat ive companson belween
hull-resislance and propulsive efficiency
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.° 117_.. n...
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a Model No. 5915 A
b9
6 7 aDevelopment of Large Cellular Containervessels 263
A Model No. 59156 Crape off-s o 50 II. loo c lop
Fig. 18ac. Reduction of wake peakby softening curvature ord. 4-3. This is most important for all single-screw ships
Twm-screw Ship Experience Regarding Living Conditions and Reliabity of Service
Nedlloyd's experience with twin-screw ships is very favourable for this type as to fuel consump-tion level and especially the low vibraconsump-tion level. From that point of view. Nediloyd's Newbuilding Department would go 'the safe way' for twin-screw, especially in case of ready chances of higher speed 'bursts'.
Also, the reliability in service with a twin-screw plant is higher than the single-screw propulsion. The twin-screw ship could sail with only one engine working whilst the other one is not working. its propeller having been uncoupled and just 'windmihing'. The working propeller (fixed pitch) should not overstrain the engine to which she is coupled, however.
The rudder will need about I to 2 degrees angle in order that the ship sails a straight course. This way, the inactivated engine could have maintenance or be repaired at sea without the ship being delayed too much or being tossed around by waves. Each engine to havea built-on "shaft generator".
Sailing on only one of two Engines
When not for maintenance or repair purposes, the twin-screw ship could sail - for economy reasons - on one engine.
Such could happen when late(r) arrival is wanted. By this method a too low load on both the main engines is prevented and so troubles from bad combustion (liner wear, piston-ring breakage) will be
264 Development of Large Cellular Containervessels 5 6 7 a g a I 3S70 t600
ir'T'
t.;
Ql
Dl
o, Qotshptti
Tr& lin g i vi 300 5. Bese edge riwcrd o. 2 3 TrQilingb Bossing pipes of nediloyd H edge upword
Fig. 19a and b. a) Twin-screw Fareast container vessel. Wide transom, sohigh stability, High speed, yet
vibration-free. Wake peak about 25 . b)Twin-screw container vessel with similar propeller and rudder arrangement to Fig. a.
Bossing pipes enclose shafting, thus prevent corrosion. NSMB model nr. 4751 "Otto". Engines 2 x 8RND9OM Sulzer-type
less. However, speed then will be limited to some 15 knots only. Means for easily mechanically declutching should be incorporated into the design should such use be the intention of the owner!
operator.
Both engines to have a shaft generator. Auxiliary diesels to be I + I + 1)2, providing the ship with
a capability for rnanoeuvring and also meeting the reefer load.
Twin-screw Versus Single-screw from Out-of-pocket Costs Viewpoint
The twin-screw ship will ask up to 4% more investment costs and does require more maintenance in the engine room.
But she will offer the feasibility of reaching about 23 knots - against only 22 knots of the single-screw version - should schedule backlog be met.
The single-screw version would be a cheaper proposition as to investment and maintenance costs. So, when service speed is definitely downgraded from 20.5 to 19.5 knots, the choice for the twin-screw can hardly be upheld. Although the feasibility for keeping schedule may be important. we cannot but emphasize the considerable reduction in fuel costs (and consequently slot costs) when
3O
Development of Large Cellular Containervessels 265
_tejo
Fig. 20. Increase of ske' reduces "higher-harmonics"-excitation. Geometry of 4-bladed pTopeller model no. 5520. Nedlloyd Rochester: propeller diameter: D = 6500; pitch ratio at 0.7 R: P07/D = 0.907;expanded blade area ration AE/Ao = 0.726; chord length0 7/diameter c07/D = 0.420. thickness/chord length07 t/c07 0.0305. Dimensions
are given in mm for ship
(2) Hull Form - Single/Twin/Triple Screw Introduction
The hull form of the fast sailing ship anno 1850, having a "cod's head" and a "mackerel-tail" has developed since into the present "seagoing motorlaunch" with a V-shaped forebody and a pram-type transom stern - the container carrier. This form will provide sufficient seaworthyness and stability (Figs. 21-24).
Prismatic Coefficient
The optimum prismatic coefficient as function of speed-length ratio normally lies between 0.61 and 0.68 (diagram of Benford). Higher fuel prices will tend to make ships of finer lines and in each
separate case a remunerativeness calculation should be made.
Shortly after the oil crises, fuel costs rose to about one-third of the total exploitation costs and the pnsmatic coefficient reduced from .66 to .64. In case vessel has to bear a certain cargo-weight at a treshold draft, it pays to keep the fuller prismatic coefficient, however (limited draft in port).
Afterbody
From 1850 onwards, the transom stern developed intoan elliptic stern. After 1920 the elliptic stern became a cruiser stern. As from 1968, the cruiser stern was cut off to a transom stern and in the year 1970 the transom was widened to the full ship's breadth (Fig. 25). So
we are back to
the 1850 "privateer".
The new afterbody is in fact a well approved old one as on fishing vessels. Buttocks' steepness to be 9 to 11 degrees (maximum 12 1/2 degrees) and this should not be exceeded so as to prevent flow
separation.
One of the main advantages of the wide - pram-type - stern is the large stability provision within
a given over-all length. Also hold space and notably deck space have thus been improved.
Also rolling angles are smaller in comparison to those of finelined cruiser-stern vessels under same
266 Development of Large Cellular Containervessels 0.90 0.85 0.80 'O.75 Q) - 070 0.500 06 OB 10 12 iL 1.6 18 V (Vinkn) 'V[ )Lin ft.)
Fig. 21. Optimum prismatic coefficient on speei/tength ratio (Optimum on V/Jt) by Benford, U.S.A.
The drawbacks of the pram-type stern are there too, e.g.:
- The larger frictionai surface - in comparison to a cruiser stern hull - when the stern is in the
water.
- The slamming which sometimes may occur during heavy weather or when the vessel is laying in
a swell-bound roadstead.
- A flat stern over the propeller also is more prone to transmit the propeller-excited pressure fluctuations into the hull and superstructure, causing vibrations and noise hindrance to the
crew.
Midship Body
- A large bilge radius is favourable for obtaining low resistance. Nedlloyd prefers a soft bilge
rather than inclined ship-sides with a hard bilge. (Difficulties with pilot ladder.)
- Rolling should in first place be kept within limits by loading the vessel to the right metacentric height - preferably GM = 0.4 to 1.0 M. (This is the modern terminal shipplanners' duty') Anti-rolling fins have their drawbacks because of the high fuel prices as they require some three
percent of the fuel consumption and the lower service speed would ask for larger fins
nowa-days in comparison to 10 years ago (then 25 knots, now 19 knots).
- Anti-rolling tanks should be very large to have sufficient effect. Adequate corrosion protection of the tank walls against the heavy water-wash is not solved yet for a :5-years' lifetime of the vessel, Also, it is very difficult to design a sufficiently wide duct below the cargo hold for an
unhampered cross-over flow.
Forebody
Originally, the ttss "Bremen/Hongkong Express" and "Nediloyd Delft/Dejima" (Fig. 26) had been designed in 1969 for 27 knots sea speed and many tanktests were carried out to the order of the
owners in co-operation with the builder, Bremer Vulkan, for the purpose of obtaining a softly-increas-ing speedl power curve.
A cylindrical bulb, combined with a shoulderless forebody (iwo. section lito 13 - an idea by Prof. lnui of Tokyo University) was adopted and indeed the vessels' hulls showed an almost complete
0.65
aso
a .jCTOtO.sp
Development of Large Cellular Containervessels
267
Fig. 22 ac. Curves of sectional areas. a) Europe-Fareast L020= 273 m; b) Safcon L0.20 = 247 m, draft = 12.00 rn;
c) Safcon model (mmss Nedlloyd Hoorn/Houtman)
lack of bow wave at the 25-28 knots speed
range in a calm sea. Lowest s.h.p. values at top speed were attained with this hull (Fig. 1).
However, after the fuel crisis of 1974, the service speed had to be reduced to a 20-21 knots level (max. peaks 23 kn) which new condition did require
a considerably less massive bulb. Tanktesting in
1980 learned that about 3
% fuel saving could be attained when replacing the original bulb by a
smaller one and we decided to do so.
We expect that speed loss due to bulb action
- when the vessel is pitching in heavy headseas - wili also be less.
(Note: Many a model basin designs a bulb for full draft, calm sea and top speed only. In most instances this is because the shipyard has to fullfìlla minimum horsepower at a deep contract-draft' Such bulb type soon may act as a "brake" instead for the vessel in real service.)
268 Developmentof Laige Cellular Containervessels
The U-type fo r e body frame
s hap e which is favourable at the high speed/length ratio (25 kn - 27 kn) should nowadays be redesigned into a more V-shape because the V-forebodygives
more lot-rn stability (KM value is considerably increased).
V-shape should not require more horsepower at the lower speed/length ratio's in comparision to
the U-bodied vessel (at high speed the U-shape is better).
Extra contaïners can be accommodated whilst keeping the original metacentric height. which
means that the earning capacity of the V-bodied foreship is larger.
A fine e n t r a n ce a ng1 e a t t h e load li n e is strongly advisable in order that the ship in
rough weather may slice through waves easily.
Sufficient fr e e board a n d reserve bu o ya nc y should be designed into the forebody for keeping the foredeck free from green water. Smaller vessels should have a long fo'cs'le. Builders
should noi save steel-weight on this item!
Large amounts of w a t e r ba Il a s t in the ship's ends are to be omitted so as to reduce the moment of inertia.
Fuel oil
t a n k s to have the centre of gravity rather far forward (0.4 L from F.P.P.) in order tokeep the ship at the proper trim without the necessity of large amounts of waterballast in the
fore-body. This fact raises the problem of fuel-oil heating far away from the engine room. Nediloyd has established that a flared forebody is advantageous in head
seas.
A k nu c k 1 e she e rl i n e in the higher part of the forebody will act as a wave breaker and meanwhile create a box-type hull girder of sufficient compressive strength. on both sides of hatches numbers i and 2 - which is important when divinginto a wave. Such knuckle - to our opinion - is preferable to a wave-break on the deck mounted on a slun forebody.
By the way -- last but not least - the knuckle sheerline perhaps is the last rudiment of ship's beauty - a sheerless container vessel, blocked up with boxes is an awful sight.
Twin-screw Hull Form
The attractive feature in the lines of the twin-screw ships (block coefficient 0.60-0.68) is the straightforward character of the desi-i (Figs. 22. 23. 29.31).
A fishtail' deadwood, together with a skeg-rudder. a design that warrants good
coursekeeping (even when sailing in following seas) also gives proper shallow-water and slow-speed direc-tional stability.
A wide 'pram'-shaped afte rbody
- as said before - is ofgreat benefit to largecontainer-ships and roro-vessels from stability and cargo carrying points of view. The immersion of the transom. however, should not exceed 0.6 M so as to limit extra fuel consumption by turbulence.
Free-flow propel I e rs. mounted on slender shafting. having a high entrance velocity will provide a high propeller efficiency and - because of the low wake - there will be much less vibration
in comparison to single-screw ships.
Contrary to the vibration troubles experienced on the single-screw Autralia-run vessels of the first generation containerships. it is noteworthy that the twin-screw Far East-run containervessels - even when utilizing up to 2x40,000 shp for attaining a 27-knot sea speed - are quite free from vibration.
This fact is greatly attributable to the slender pipe or bossing around the wingshafts resulting in an axial wake of not more than 25 % to 30 .
Shafts should be enclosed in pipes inorder to prevent corrosion. We intend to utilize Mannes-mann pipe, with oval section, unstiffened. Experience is excellent with a 1900 pipe on many ships!
Airwing-design b rack e t s, supporting the slender pipes, seem to have no harmful effects to the
wake field and do not give cause to propeller-excited vibrations.
B o ss i n g s designed for creating contra-rotating water flow - for the purpose of increasing the
propulsive efficiency - should - as we see it - not be applied. The wake peak will
be larger and will excite cavitation and vibrations. As was experienced on a number of ships.
Sufficiently large t i p cl e a rance between the propeller and the ship's hull is also a 'must' for a good design in order to keep hullpressure fluctuations at a lowermost level.
The larger tip clearance will tend to have the
position of the propellers far
out and wellC
a
b
Fig. 23 a-c. Twin-screw hull. a) Europe-Fareast containership model 3956 for Nediloyd Dejima/Nedlloyd De],ft; h) Twin-cres Safcon ship lines (development stage) L0.20 = 247 M; c) Twin-screw Safcon ship lines (as built) L0.20 = 247 M. moddl 4751 "Otto", Nediloyd Hoorn Eur-Southern Africa, Nedlloyd Houtman Eur.-New Zealand
---.
P4
Fig. 24 a-c. Single screw hull. a) Single screw safcon project in development stage L020= 247 M; propeller on pipe; b) Single-screw Southern Africa - Fareast ntainer project 1975 L020 = 207 M; C) Pram with
gondola,
single-screw "Universal" containership project 1981 L020= 202 M
270 Development of Large Cellular Containervessels
Unfortunately this will cause the waterfiow (race) further out and so away from the single rudder, thus resulting in a poor steering capability.
On Nediloyds "Dejima/Deift" this deficiency is remedied by the ru dde r having been givena great length (6 M on 290 M ship's length, i. e. 2.2% of Lpp) and a hard-over rudder angle capability of 45 degrees (instead of the commonly applied 35 degrees). Now, the rudder blade still can reach into the propeller race if required for accurate steering in confined and shallow waters, especially at
slow speeds.
From a manoeuvring point of view, the position of the propellers should preferably be
close to the skeg and well forward. This arrangement, of course, will result in strong hullpressure fluctuations, i.e. vibrations and noise hindrance, fracturing etc..
On these points - i.e. tip clearance versus manoeuvring feature - a compromise has to be found for the position of the propellers. Experience, up to now, obtained by Nedlloyd's "Dejirna/Deift" and also by Hou tman/Hoorn has shown their stern arrangement to be a good compromise: proper
steer-ing. no vibration. (Shafts should be kept parallel by all means in order to guarantee good manoeuvring capabilities.)
&f t
bettsr tci
pru. witb prp.1iir oe pl
- øt optt]. Sn
- .ln. far forv.rd
- WSld ts.riggood
Fig. 25. Development afterbody 1968-1973 *i T
Development of Large Cellular Contarnervessels 271
Fig. 26. Nedlloyd DrIft
Single-screw Hull Form
On the conventional type fast cargo liners the propeller aperture developed already (1950-1965) from a narrow to a wider one (Figs. 25-28). After that period, the shaft-horsepower was nearly
doubled. The preference of Nediloyd is for the propeller-on-pipe arrangement so not for the Stern Bulb design. In this context we must mention that three vessels ("Abel Tasrnan", "Hollandia",
1970:
25-
Z7kn 136 112 rpm 1981 115 rpm 97 90 rpm - 22 kn272 Development of Large Cellular Containervessels a C ta.gerrtial b
uuI
Fig. 28 a- r. Wake single-screw. a) Wake containervessel s.s. Abel Tasman/Sydney Express 32450 s.h,p.. i 10 RP\l.
b) Results of 3-dimensional s'ake measurements on the Abel Tasman model. c) Variations of resultant spt'ed, strong
variations of angle of attack
"Zeelandia") having around 27,000 to 30,000 shp on their single propeller (block coefficient about 0.60-0.64, some 1600 teu capacity) are all three suffering from aft-end vibration to a greater or lesser extent. This is directly related to the location of the engine "far aft". The design of such
high-powered (single-screw) container-vessels -- as to keeping vibrations within bounds - is very difflult
-Even more so this counts in case of roro-ships. Their aft hull is even more flat of shape over the propeller. The trim balance of such vessels will require the Centre Of Buoyancy to be as far aft as
feasible, which means a full afterbody, whilst at the same lime the free flow into the propeller dise requires an afterbody as slender as feasible. As always in naval architecture, a compromise has 111 be reached: Engine foundation to be stiff, meanwhile the a ft e r h od y should he slender, fuel
C
Development of Large Cellular Containervessels 273
N1
- .-..,..
Fig. 29 ac. Wake twin-screw, a) Wake Nediloyd Dejima. ' 1900. pipe + struts 86-ModeÇ c'i Far-East container slur
is Nedlloyd Dejima; results of 3-dimensionalwake measurements b S-hole Puoi tube
Approaches to Propeller
Some vessels, having a blunt afterbody inimediately ahead of the propeller and those having a rather sharp turn-of-the-bilge in way of the engineroom, do suffer from separation of the water-flow towards the propeller (Figs. 32, 33).
Even slight afterbody variations have already strong influence on flowlines towards the propeller. The fullness - or rather slenderness - of the foot of sections 3 and 4. i.e. in way of the stern-end
of the main engine, can be decisive in respect of separation of flow.
-T
T-'1'
'Tî-:
-:7T
4suu
,.
at.
tangential
b274 De'welopment of Large Cellular Containervessels
Fig. 30. Left: Nice triple-screw arrangement of "Selandia"-Fareast containership. Right: fat bossings of tin-scre
passenger-liner
Aperture Clearance
Other vessels have been designed with (too) smal] clearance in the upper part of the stern frame just ahead-and-above the propeller. This causes a wake peak in the "I 2-o'clock' position of the propeller to a possible extent of 65% to 75% - with an inherent vibrations hindrance!
b
F low
Fig. 31 a and b. a) Slender pipe with struts, pipe without internai stiffening (!). internal access up lo the sterntuhc seal, b) Development from o (circular) to O (oval) section in order to reduce resistanceand wake
RoPo Model 5141D Probably sepzotion RoPo Mcdel 5190 o RoRc Mode' 5247 2 2 3350 3 3
Engine should be positioned more forward Fig. 32. Flow lines towards propeller lip in top-position (l2o'cJock') showing
the enormous influence of the
shape of cross sections in
way of ordinates 2-3-4 (where the main engine is posit onedi
Development of Large Cellular Containervessels 275
RoRo Model 52O
wonderful flow
276 Development of Large Cellular Containervessels
3
o
,oG
Fig. 33. Single-scre with engine "far-aft" often
causes vibrations. Above is the outcome of 3-dimensional stake
measurements by meansof Pilot-tube on a toro ship model for three
configurationsoftheship's bottom(Gondola)
in way of the main engine seating
Angle of Entrance to Propeller
In short, in case of flowlines towards the propeller having to makea sharp bend. separation of floss occurs and a stagnated flow above the propeller can then activate bursts of hull vortex cavitation (mrnss "Straat Nagoya"-class. "Antilla Bay").
On certain vessels, suffering from Propeller-excited vibrations, a 'tunnel plate' has been mounted above and ahead of the propeller which directs the inflow ofwater more accurately, shielding oft' the separation.
Results often were very good (e.g. on "Sea-Land Economy". "Melbourne
Express") enabling the use of more horsepower at reduced vibration levels.
However, there also is a case where a mal-designed leading edge of
some kind of tunnel in the shell at an angle to the flowlines is acting as a water-stumbling barrage ("EncounterBay"-class).
U 5 A ARAB 'w. RO-RO 'So.
0
'G303t MODE FAT GONDOLA 5141 MO SIIÑDfP '-wa 51410r
.a NEOLLOYD OCS1E - AFT EPC ' ENGINE
the rudder ja 3% of 1_pp end the rudoer area is 28 er c.n of 1_pp a 10 n,.
MEDLLOV' 7TERDA'T
Development of Large Cellular Containervessels 277
-Jo
r_'.2,_.
--. T
Fig. 34. Location and foundation of engine; 1) too hard curve: floss -retarding 2 rnprovement for new designs
From experience, it has been found that ships with a propefler blade frequency of 5 x 130 13ô revs/mm. and 6 x 106-110 revs/mm (Fig. 25). often suffer from full resonance of bulkhead panel vibrations in the afterbody The vessels suffering worst from such vibrations have been established to
be those with the accommodation right-aft and with propeller-tip speeds over 40 m'sec.
The higher harmonics, i.e. those of 3 and 4 times blade frequency. are the main culprits of these
vibrations. In these high frequencies exaci resonance predictions are almost impossible.
The results are vibration and connected noise hindrance to the crew and even damage to the struc-ture in the afterpeak area, damage to piping, bearings and instruments.
These troubles have frequently led to the practice of sailing at reduced power (and consequently
less speed).
Vibrations in the first-generation class of containerships were at an acceptable level only if sail-ing below 27,000 shp. which habit resulted in a reduced service speed of 21 knots on the Europe-Australia and v.v. run,a reduction of one fufl knot of the normal capability.
278 Development of Large Cellular Containervessels
For the naval architect it is a relieve now to have the possibility to apply lowerpropeller revolu-tions, i.e. 90-100 rpm, instead of the former 122 rpm. This allows for lower tip speeds.
The flow of water should be kept "undisturbed"as far as feasible for (both twin- and) single-screw vessels. Ifa wake peak of 55% is to be accepted or is unavoidable, thus causing cavitation and hull pressure fluctuations, a shock absorber over the propeller, mounted on the flat afterbody might be
tned (Tests at TPD-Delft and N.S.M.B.-Ede on this subject are done.) (Fig. 18).
Achievements 1971-1981 in Countering Vibrations
In 1971 we experienced the vibration-free propulsion with the twin-screw vessels. These vessels had been fitted with propellers on shaftings enclosed in slender pipes and supported by
stream-a 05 b go' Flow sep5rtion low speed Zone
High velocity
-Motor
0°
50 w 0
Fig. 35 ac. Flow around engine foundation, a) Flow lines Afihody with Gondola: h) Curves of constant velocits.
model 5190, c) Results of 3-dimensional Pitot-tube measurements
1.0 o > o C 0° 100 go, 1BC, 270'
Development of Large Cellular Container-vessels 279
-Fig. 36. Ceflular containership "Unen" design 1981. (For 'EMEC" service and 'EUROSAL" service
lined brackets. Following this good experience, we designed a similar arrangement for a subsequent
project (SAFCON), viz:
- One model fitted with twin-screws on pipe (Fig. 17). - One model fitted with one screw on a pipe (Figs. 24, 25).
The wake belt on both models was very weak (about 25-30 only) and trouble from vibra-tions not expected.
The single-screw vessels, however, needed more horsepower for the same speed. This was caused by the propeller being of a smaller diameter and larger blade area and thus of lower efficiency.
The single-screw vessel lacked wake and therefore also the hull efficiency was low. ("No wake no vibrations/no hull efficiency".) For good order's sake, we have to mention that al] conclusions had been drawn without taking into account the Scale Effect (from model to ship)on wake and thrust deduction. 'Full Scale' will give a benefit to the free flow arrangements and a drawback to
280 Development of Large Cellular Containervessels
o.t
0.3 0.4 Q.)j5
E LDE
LINES LW EhJL.. Ax:. V5.)! Y CO ENS SI
AXIAL *lPEPT5 I 3O4 9C i 35 i83 lOP 725 270 3 5 35 TANGEPT1AL CO0OtE%iS I 0/. .1
Fig. 37. Wake field measurements 'Universa
containervesse! ('Unco". at 10.60 m draft. Ship model no. 5901
. i't
no. 39912. speed 19.0 kn., draft 10.6 m., model condition screw aperture I, bulbous bo IThe disappointing result on propulsion performance for the vibration-free single-scres pranl. type with propeller on pipe leadus to further developments in single-screw hut] form:
We try to accommodate the diesel engine
- which for reason of economy should be positioned as far aft as feasible - in a streamlined bossing (we name it "Gondola") underneath the pram-hull.
Tl-ijs bossing should be as slender as possible in order to reduce the wake peak (Figs. 34-37).
Therefore the web frames on the tanktop should enclose the aft-end of the diesel engine, includ-ing the thrust block. The engine is 'hanginclud-ing in a slinclud-ing of shell platinclud-ing andwebs.
Marine engineers should help the naval architects out of the quandary
by making this engine
seating a stiff one, yet allowing space for the fitting of filling pieces after lining up.
Nedlloyd's "Universal" containership design(single-screw) is from 1981.
The speed/power performance looks very good from predictions by tests at N.S.M.B.Wageningen.
The "1 2-o'clock" wake peak is less than 50%.
Contra-rotating vortexes appear to be relatively small and we expect that there will be only little excitation of vibrations.
0%
p
Development of Large CeUula.r Containervessels
281
The Source of the Evil and a Guide to Avoidance
lt is the very firstmoment, when signing the building
contract where length and deadweight are guaranteed, that the baby may be doomed to vibrate all hergrown-up life:
Engine far aft, a fat afterbodyand a narrow propeller
aperture are causing the evil:
The building yard tries to offer the maximum carrying capacity - to the future owner/oper-ator - against the lowest feasible price and consequently shortestpossible vessel.
This ship then turns out to have a blunt afterbody,small aperture, high wake.
Improvements of the hull form at a later stage after negotiations are often hardly
feasible.
Remoulding efforts by model basin and utilisation of
wake-adapted (skew-back) propellers can hardly
do sufficient to soften the vibrations evil or the poor efficiency,
as main dimensions remain in the
wrong combination.
So: Wrong dimensions
are to be prevented
at the contract stage!
(Whichusually is far before tanktesting could be started!)
In otherwords:
tanktesting actually
should be done before contract!
RefereaesNSMB Reports:
Contr. model 4248 October '78. Austr. contr. "AbelTasman", ANZECS: model 3865 March '70. Far East contr. Deft/Dejíma.ScanDutch:
model 3956 January '72; model 5902 Juni '81; Far East conti. DelftJDejima.
Scandutch, model 4751 December '74,South Air. Europe Safcori
conti. "Hoorn/Houtman"
SEACSÍANZECS;
model 5163 March '77, Container project, not built, ZAVO; model 5268-5308 March '77,Container Hongk.-Austr.,
AAE "Asian Jade"; model 5655 Sept. '80:Contr.
South Afr.-Far East, not built; model 5736 Sept. '80, Conti. South Afr.-Far East,MHI design; model 5901 Auf. '81, Conti.Universal typ - EMEC-Eurosal: model 5783 Oct. '81, Conti.Panmax:
model 5914 15. Sept. '81,Contr. Far East singletwinscress,
model 5943 June '82. Conti."Keco"-design. Ro-Ro model 5100-5104 Sept. '76, RoRo contr.
Austr.-Malaya, ANRO; "Anro Asia";
model 5120-22 June '77; Shoribody version, for MiddleEast seice;
model 5141-5131: model 5150; model 5190: model 5247 Febr. '79, Gooeseneck; model 5274 Nov. '77,Long-body version, NLL
Rouen/Rosario:
Calculation boundary layer flow around 3 RoRoafterbodìes. March 1979 Raven, Interim report simplified Hull forms August '78:
model 5650 Nov. '80, Pass/Carferry twin skeg-twin screw; model 5896 June '82. singleskeg-single screw;
model 6061 Sept. '82, heavy lift conti. RoRo carrier model 5896 July '82,Trailer-passenger ferry. model 6901 Sept. '82,Trailer-passenger ferry.
Treatises by the same author on the subject of shìp's development: Verre Oosten
Conrainerschepen. Nautisch Techniscti Tijdschrift.Aug./Sept. 1973.
Developments of ship's afterbodies. Propellet-excitedvibtattons, May 1973. Lips.
Triliingshinder bij schepen.T.H. DeIft. mt. Periodical
Press, 1977.
Developments of afterbodyor contr./roro vessels. 1978
translation by BSRA of ¡PP'77.
Cost aspects in linershipping. May '72 + Oct. '73.
Ti-i Detft Symposium paper. Efficiency in liner shipping- Anno 1979. Nedlloyd/Europori.
Nediloyd Lines' RoRo-concept
for the Middle East. Holland Shipbuilding. Apr.'79. Ontwikkelingen in delijnvrachtvaari. Juni 1980, De
Ingenieur. DeIft-Dejima-Houtman-Hoorn. Aug. '75, Unieschakel.
Containerschiff Bremen Express. Hansa, ¡972, iii concertwith Br. Vulkan/Hapag Lloyd.
Haven en Terminal Planning.T. H. AfdelingCiviek
Tech,iek "Havertsl", 1980.
Good Steering Properties
for Conafrserships: TheMotorship, 1979. Liner fleet re-tonnaging f Vessel development.ECT-conference, 1982.
282 Development of Large Cellular Containervessels
Development of large cellular containerships
Summary
Under the influence of changing circumstances of living at the one hand and economic pressures on the other hand il is of utmost importance to have proper tools of trade.
In shipping this means efficient yet liveable ships for the - necessarily capable - workforce needed to handle
them.
In this treatise we touch at a number of subjects encompassing both the efficiency and liveabil,tv.
Efficiency items are eg. comparison of fuel consumption quantities of ship by type of main propulsive englne (steam versus diesel), comparison by number of propeflers. Also by comparison of aft-ship configurations for their influence on water-flow efficiency and avoidance of propeller-excited vibrations. Vibrations, besides giving habit-ability hindrance, may endanger structure and instruments.
However, vibrations cannot always be avoided because of certain demands put to ships form and lay-out on account of the cargo (viz, a wide afibody for stacking area and stability purposes). In order to arrive at next-best, the emphasis is laid on proper and repeated tanktesting. Outcome of many such tests are given, often by way of
