The development of a new type of Fast Crew Supplier

Date 2013

Author G e l l i n g , J.L. and J.A. Keuning Address Delft U n i v e r s i t y of T e c h n o l o g y

Ship H y d r o m e c h a n i c s and S t r u c t u r e s L a b o r a t o r y

Mekelweg 2, 2628 CD D e l f t

TUDelft

Delft University of Technology

The development of a new type of Fast Crew Supplier.

by

J . L . Gelling and J.A. Keuning

Report No. 1 8 9 5 - P 2013

Proceedings of the 12'" I n t e r n a t i o n a l C o n f e r e n c e on Fast S e a T r a n s p o r t a t i o n , F A S T 2 0 1 3 , A m s t e r d a m , The Netherlands.

FINAL SCIEIMTIFIC PROGRAM

9:30 Registration 10:15 Opening Conference

10:30 Keynote ir J.L. Gelling Damen Shipyards 11:00 Keynote R. Bogaard KNRM

11:30 Coffee break

12:00 Keynote prof Ir. J. Hopman Delft University of Technology 12:30 Keynote mr. T. Ellis - Specialised Vessel Sen/Ices 13:00 Luncfi

14:00 Session I A New Concepts Session 1B Seakeeping 1 P44 Gelling P29 Grigoropoulos POSOrvieto P13 Stojanovic P32Shahraki P I 5 Peterson 15:30 Coffee break

16:00 Session 2A Seakeeping 2 Session 28 Wash P35 Olausson P41 Pinkster P37 Allen P09 Kuroda 17:00 Opening Reception at the Maritime Museum

Tuesday 3 December

9:30 Session 3A Staictural Design 1 P05 Benson

P11 Wu P45 lyisirlis 11:00 Coffee break

11:30 Session 4A Structural Design 2 P24 Schiere

P27 den Besten P12 Tuitman 13:00 Lunch 14:00 Excursions

Session 3B Huliform design / Hydrodynamics P31 Paryshev P04 Rosenthal P20 Dlez Session 4B Seakeeping 3 P26 Walree P14 Ahmadian P18 Ommani Wednesday 4 December

9:30 Session 5A Hydrodynamic Loads P08 Fine

P34 Varyukhin P38 Serebryakov 11:00 Coffee break

11:30 Session 6A Calm Water Resistance P07 Kinaci P22 Fossati P40 Scherer 13:00 Lunch 14:00 Session 7A CFD 1 P I 6 Kobayashi P I 7 Tahara P I 9 Chen

18:30 Conference dinner at the Maritime Museum

Session 5B Seakeeping 4 P33 Davidson P48 Tascon P25 Castro Feliciano Session 6B iWotion Control 1 P28 Rijkens

P42 Deyzen P21 Yengejeh

Session 7B Dynamic Stability P01 DeJong P39 Sadat Hosseini P30 Castiglioni Thursday 5 December 9:30 Session 8A Hydrodynamics P36 Dogan P02 Gontsova P I 0 Lliopoulos 11:00 Coffee break 11:30 Session 8A Hydrodynamics P43 Cieijsen (Rijkens) P46 Zangie 12:30 Conference Closing 13:00 Lunch Session 8B Propulsion P03 Dang P23 Esiamdoost P49 Caponetto

12e International Conference on Fast Sea Transportation FAST 2013, A m s t e r d a m , The Netherlands, December 2013

The Development of a new type of Fast Crew Supplier

by

J L Gelling Director High Speed Craft, DAMEN Shipyards Gorinchem, The Netherlands J.A.Keuning Associate Professor, Shiphydromechanics Department, Delft University of Technology

Summai-y

This article describes the development of a new type of Fast Crew Supplier intended for the use in more remote and more exposed areas. The primary purpose of the ship is the fast transport of people to offshore platforms in far greater comfort than is the case with the present day designs. Great attention has been given to the prevention of motion sickness and bringing comfort for the passengers. Also emphasis is placed on the efficient transfer of the people from the ship to the platform.

Hereto a new hull has been developed, capable of attaining high speeds in an economical way. The hull is also designed for maximum comfort when under way at speed in waves. When the passengers are to be transferred to the platform, the crewboat is transformed into a ship with a high stability moment in roll and pitch. In addition a large damping for roll is achieved by this transformation.

The concept is extensively tested in the towing tank of Delft University of Technology for its resistance and motions characteristics, both at high speed and at zero speed.

The results of this study are presented in this paper.

INTRODUCTION

Operators of offshore facilities have generally two options of transferring personnel from the shore to these facilities: either by boat or by helicopter. For the more near shore facilities, predominantly boats are used. Their use is efficient, safe and economical and travelling times are relatively short. Also the comfort for the people on board can be maintained within acceptable limhs because the "exposure time" of the people to the motions etc. is relatively short. For the more remotely located offshore facilities, often the helicopter is used. This enables the people to reach these facilities in a reasonable time. Comfort onboard of these helicopters however is rather limited and every now and then safety issues are a reason for concern. In addition the use of helicopters is expensive. Therefore there

is a growing interest from operators of offshore facilities to transfer personnel from the shore to the offshore facilities using ships. Many of the ships presently used for transferring people to offshore facilities are either too small or too slow to fulfill this new role efficiently. So there is a need for a new type of ship. This new ship should be capable of attaining - and more in particular maintaining - a high forward speed in the prevailing environmental conditions with respect to wind and waves in order to keep the necessary traveling time within acceptable limits. On this new type of fast ship much emphasis should be placed on the comfort for the people on board in order to prevent typical ship mofion induced phenomena such as motion

sickness, motion induced interruptions and possibly even injuries.

In addition the new ship should offer maximum capabilities to transfer people from the ship to the, mostly fixed, offshore structures and preferably in a considerable seaway. Most operators specify significant wave heights that the system should be capable to handle, in the order of magnitude of 2.5

to 3.0 meters. Therefore the new ship is to be

equipped with an Ampelman type (or similar) of ship motion compensation system to facilitate the transfer. In this condition the ship should offer a stable platform to the Ampelman in order to optimize its performance. This implies:

• a high damping in particularly the pitch and the roll motions of the ship

• possible "tuning" of the natural period of roll to position it outside the frequency range of the sea wave spectrum at hand - or at least it's peak period

• a high stability moment, which implies preferably both a large arm of transverse stability moment (GZ) as well as a high displacement (i.e. mass)

The high mass of the ship also yields large inertia both of which prevent possible excitation of the ship in e.g. roll by the movement of the Ampelman itself.

Obviously these are conflicting requirements for the design: a high speed of a ship implies as low weight as possible to reduce the resistance. On the other hand, a high stability moment and inertia of the ship at zero speed when transferring people, asks for a large weight of displacement of the ship. As known for comfortable motions when at speed in waves, with particular attention to the resulting accelerations, a reduced value of GM with an associated long natural period in roll is asked for, while for an optimum performance when transferring people a high stability moment is asked for. High speed ships have considerable roll damping due to their forward speed but the typical hull shape of fast planing ships generates only limited roll damping when a zero speed. So a special feature might be asked for to increase roll damping at zero speed, while not increasing resistance at speed.

So the solution was sought in a very good sea keeping hull for high speeds of a proven concept.

i.e. the AXE Bow Concept. To suit the different requirements o f the crewboat for the two different conditions a transformation of the design was sought for which was executable in between the different operational shuations, a marine application of what we could call "a mutant". The design will be described here after.

T H E DESIGN

The above-mentioned boundaiy conditions were used to design a new ship. In addition it was assumed as customer requirements that the number of passenger should be 150 pax. and the calm water speed 40 knots.

For the elaboration of the various design parameters a distinction is made between the two most dominant conditions in which the ship will operate: i.e. :

• the transit condition, in which the ship sails from the harbor to the site of the offshore facility at the highest possible speed

• the transfer condition, in which the ship is at zero speed adjacent to the offshore facility on which it has to transfer its passengers

We will take the transit condition as a starting point. As a hull shape for the concept design a hard chine planing hull was adopted. This kind of hull should be capable of attaining the required high calm water speed. For this new hull a very high deadrise angle of almost 40 degrees at the midships section has been selected in order to optimize the behavior in a seaway of the ship at speed with respect to the vertical accelerations on board. This high deadrise concept has been chosen even though there is a penalty on the calm water resistance for these high deadrise angles. The added resistance in waves however will be positively influenced by this choice. To further improve on the sea keeping behavior a length to beam ratio of L/B = 5 was considered to be the minimum. In addition the high deadrise with the chine high above water in the transit condition facilitates the waterline beam increment when the ship is ballasted to its transfer condition.

Also the Length / Displacement ratio was set at

factors are known to be of great importance for good beliavior in a seaway. Assessing tlie amount of space needed for the number of passengers and crew under consideration, a hull length on the waterline of 70 meter should be sufficient. To make the passage with an expected duration of four to six hours as comfortable as possible for the passengers, considerable effort will be placed in the design for an optimal layout and selection of equipment in the passenger area. The passenger area will be situated around the longitudinal position of the Center of Gravity and as much as possible at the same height. It should be emphasized that as a starting point for the new concept design, the so called Enlarged Ship Concept (ESC) is used, which implies a considerable amount of void space on board of the ship. With the given waterline length of 70 meters, this yields a beam of 14 meters and a displacement in the transit mode of around 700 tonnes. For an improved behavior in a seaway, in particular with respect to the vertical accelerations over the length of the ship, the well proven AXE Bow Concept will be used. This bow reduces the peaks in the vertical accelerations due to slamming to an enormous extent when compared with the more conventional bow shapes. Reductions of up to 75 - 80 % are not unusual.

"bilge keels" are designed and positioned on the hull in such a way that in the transit condition (at the lower draft) they are just above the waterline at speed and in this way act as spray rails. In the transfer condition (at the higher draft) and zero speed they become fully submerged and act as large bilge keels in order to generate roll damping. To prevent high impacts on the bilge keel (spray rails) a special shape on the inside of these keels has been designed in order to make them efficient in both conditions, i.e. as spray rail and as bilge keel, without generating high wave induced exciting forces. A cross section is depicted in Figure 1

In the transfer condition a considerable amount of ballast water is taken on board. In the concept design this amount is fixed at approx.. 300 tonnes. This ballast water is taken on board to increase the displacement of the ship and thereby the stability moment in Nm and it's inertia (mass). By proper placement of the ballast tanks in length and in height, this ballast can also be used to yield a desired height of the Centre of Gravity (VCG) and thereby GM. A consideration in this process will be whether the ship in the transfer condition should be "tuned" for minimal motions or for minimizing roll accelerations. Also the radii of gyration in both roll and pitch can be influenced.

By taking in such a considerable amount of ballast the draft of the ship is increased with 0.60 meter. Through the strongly V shaped cross sections of the hull the beam on the waterline will increase with some 2.0 meters and therewith the metacenter height K M with about 1.0 meter.

A rather special feature of the hull o f the new design consists of the dual purpose bilge keels. These extend over the full length of the aft ship and have a width of approximately 0.75 meter. These

Figure 1 Detailed cross section of the spray rails / bilge keels

The main particulars of the design are presented in Table I for both conditions :

FCS 7014 Sym Transit Transfer unit

Waterline Length Lwl 70.0 70.0 m Displacement A 700 1000 tons Beam Waterline Bwl 10.40 12.25 m Draft midships T 2.9 3.5 m Draft max (bow) Tmax 3.6 4.2 m Centre of Buoyancy height KB 1.98 2.38 m Metacenter height K M 6.94 8.10 m Longitudinal position of B LCB 29.1 29.1 m Speed Vs 40 0 kn

A body plan of the design is depicted in Figure 2.

Figure 2: The body plan of the design

T H E R E S E A R C H QUESTIONS

A few questions remained to be answered when considering the application of a hull that is designed along the above-mentioned lines. These were:

• What is the effect of the high deadrise on the calm water resistance?

• What effect do the large spray rails / bilge keels have on the calm water resistance? • How big is the effect of the large spray

rails / bilge keels on the rolling motions in the transfer condition, i.e. at zero speed and possibly in beam waves?

• Will the large spray rails / bilge keels affect the sea keeping behavior in head waves in a negative sense?

• What is the best value for G M in the transfer condition considering the comfort of the people on board and the efficiency of the transfer system?

To answer these questions it was decided to carry out an extensive model experiment in the #1 towing tank of Delft University of Technology. The effects as mentioned above have been investigated by testing the model in both condition, i.e. transit and transfer, with and without the spray rails / bilge keels connected to the hull.

T H E TESTS

The experiments have been carried out in the large towing tank of the Delft Shiphydromechanics Laboratory of Delft University of Technology. The length of this towing tank is 145 meter, the width 4.25 meter and the water depth during these tests was 2.25 meters. The maximum speed of the towing carriage is 8 m/sec. The facility is equipped with a hydraulically activated wave generator of the hinged flap type.

The models have been constructed of glassfibre-reinforced plastic. The model scale chosen was 1:30. One of the models had the designed spray rails / bilge keels on and the other one not. The following tests have been carried out:

1. Calm water resistance in the transit condition with and without the spray rails, over the full speed range

2. Tests in irregular head waves with two spectra, one with a peak period Tp = 7 seconds and a significant wave height Hs = 1.5 m and one with Tp = 9.5 sec and a significant wave height Hs = 2.5 meters, both at a forward speed of 32 knots with the ship in the transit condition and with and without the spray rails / bilge keels

3. Tests in irregular beam waves at zero speed in the transfer condition, in the same two wave spectra and with a range of GM values between 1.0 and 2.75 meters.

T H E R E S U L T S

The calm water resistance of the ship in transit condition with and without the bilge keels is

Trim 0 .0.2 •0.4 \ 1(1 ft^ 20 25 30 35 40 45 .0.2 •0.4 .0.2 •0.4

•0.6 \ —t—Trim harp hull

Ï - 0 . 8 ^ -1 \ - i -T r l m bilge keels Ï - 0 . 8 ^ -1 Ï - 0 . 8 ^ -1 | . , . 2 | . , . 2 -1.4 -1.4 -1.6 -1.6 -1.8 -1.8 -2 -2 S p t t d l k n ]

Figure 3. The calm water resistance of the ship i

depicted in Figure 3. The results are extrapolated to the full-scale ship. For the tests in irregular head waves at speed only some of the results will be presented here. They are considered to be typical for all the other results. The presented figures show the results for the spectrum with the shortest peak period Tp. This is the wave spectrum with Tp = 7 sec and a significant wave height of Hs = 1.5 meters and fits closest to the typical North Sea environmental conditions..

Calm Water Resistance

SpMdIkn)

transit condition with and without bilge keels

Klld Wlïl!,lnns«, Hs=l,Sn\Cm TinJll, bin M

• tnsts V Irwighs

9 20 10 i ! Prcbibillyii(Eicii4]iKi|«]

HMd W j « i , U n s H Hs=1im, Crew Tcndtr, bije kMis

crests *r troughs T — -so 20 to 6 2 1 1/5 ProtablliljolEiceeilaiM[%I

H M J H J Ï I S , MnsH H s = U m C n « Tindir, bin hul

id*'.**

so 20 10 i 2 1 1«

PfOblbülïOtEiurilntipil

Head Waves, tan sit Hs=1 im, Crew Tender, bije keels

-CO 20 10 5 2 1 115

ProbibiilyolEicecdance[%)

Keid Wnts, tins», Ks=«m, Cmï TimiH, b i j l k ! * Hi:dWitis,nisil,Hs:1fin,CriwTiiidir,blgi kills crests troughs 77 I » to 20 (0 6 2 1 ( S Pr«b!bilyolEiMriin»|X| 1 •i insb tMjks 10 20 10 ( 2 i P n b i b B y t f E i c i i d m i p i l

Ht!dyfriEs,l[iiisil,»s=1.Cm,CrciiT(ndi<,b9gikK^ KlldWlv<s,bljl!itHs:1im,CllwTindi[,bi^ltllfc

ProblbilyolEic«djiraIlS|

H 20 11 i 2 1 P r o b i t B y o l E i c i l d m i p i

Figure 5 Distributions of heave, pitch and vertical accelerations with bilge keels To summarize the results for heave and pitch for

the transfer condition with and without bilge keels

bare hull 1.5 m Hs:

mean stdev min max

heave -3.4E-14 0.26 -0.74 1.11

pitch -2.8E-13 0.67 -2.48 1.92

bare hull 2.5 m Hs:

mean stdev min max

heave -1.7E-14 0.69 -2.27 2.89

pitch 3.16E-13 1.53 -5.74 5.03

For the tests with zero speed in irregular beam waves the distribution plots for the roll motion are shown with the model in the transfer condition both with and without bilge keels. A choice has been made for the most severe condition, i.e. the significant wave height of 2.5 meters. The GM of the model has been chosen at 1.5 meters, which is presumably the starting point for the design. The

the following data from the statistical analysis is presented in Table 3:

bilge keels 1.5 m Hs:

mean stdev min max

heave 3.53E-14 0.24 -0.70 1.02

pitch 2.41E-14 0.61 -2.30 1.67

bilge keels 2.5 m Hs:

mean stdev min max

heave lE-13 0.68 -2.29 2.43

pitch -1.5E-12 1.40 -4.28 4.43

peak period of the wave spectrum is 9 seconds and the measured natural frequency of the model in roll

Tphi is 8.3 seconds witli and 7.9 seconds witliout -bilgelceels. Tliis implies that the natural frequency in roll is close to the peak period of the wave spectrum.

Be!mWaves,operjlion!l,Hrf,5m,(3M=l.5m,CrewTen(itr,birehull

V

50 !0 10 6 2 t IS ProbabDity of Exeewiance [%]

Beam Waves, operaSonsl Hs=2.5m, GM=1.5m,Ciew Teiide;,bige keels

U 3

100 so 20 10 5 2 1 IS ProbabililyafEice«lance[%]

• low GM (1.5 meter) and high peak period Tp (9.0 seconds)

This can be seen from the results of the roll motion tests also. From the roll decay tests also the

logarithmic decrement is calculated for the ship with and without bilge keels. The following expression for the determination of 5 has been used:

x2 x3

The results are summarized in Table 4

With bilge keels GM = 2.75 m 6 = 0.49

G M = 1.50 m 5 = 0.54

G M = 1.00 m 5 = 0.55

Without bilge keels GM = 2.75 m

G M = 1.50 m 5 = 0.28 G M = 1.00 m 5 = 0.31 Table 4 logarhitmic decremant roll

Figure 6 Distribution plots for roll motion beam seas Tp = 9.0 seconds and Hs = 2.5 meter The results of the measured natural periods of the ship with the three different values for GM floating In the water is oresented in Table 2.

With bilge keels GM = 2.75 m T = 6.I sec

G M = 1.50 m T = 8.3 sec G M = 1.00 m T = l l . l sec

No bilge keels GM = 2.75 m

G M = 1.50 m T = 8.00 sec

G M = 1.00 m T = 10.70 sec

As can be seen from these data, the natural fi"equency for roll is close to the peak period of the wave spectrum in the case of:

• high GM (2.75 meter) and low peak period Tp (Tp=7sec)

DISCUSSION O F T H E R E S U L T S

The results clearly show that the effect of the bilge keels on the calm water resistance is conform what could be expected: Due to an increase in wetted area there is a modest increase in the calm water resistance. To which extent this increase can be minimized by a proper adjustment of the positions of the keels along the sections remains yet to be seen. It will certainly be considered to place them somewhat lower along the hull sections so that they increase the hydrodynamic lift in a sooner stage. This may lead to a lower resistance. This has the additional advantage that their immersed depth in the transfer condition also increases.

The results of the motions and acceleration measurements in head waves clearly demonstrate that there is no negative effect of the large bilge keels on the vertical motions. Actually the motions and accelerations of the model with the bilge keels are slightly better than of the model without. This

proved to be the case for all situations tested. Apparently in this design, the possible extra contribution of the keels to the wave exciting forces is non- existing or at least minimal.

The contribution of the bilge keels to reduce the roll motions at zero speed in beam waves is evident. In all tests the model with the bilge keels performed significantly better than the one without. A reduction of the roll motion in order of 50% is feasible. Not all possible wave spectra have been examined of course, but some rather unfavorable combinations of Tp of the spectrum and natural frequencies of the ship have been investigated. From the roll decay tests it can also be seen that the contribution of the bilge keels to the roll damping is high.

In Figure 6 the influence of the variations of GM on the roll response with and without bilge keels is once more shown. The use of 300 tonnes ballast water on a deplacement of 700 tonnes yields a good opportunity to "fine tune" the GM value for the prevailing environmental conditions.

S[f n i n c a n t ttoll A m p t l t u d * B e a m W a v i i 10

h

i :

t * ^ ' ^ . ^ ' " ^ - • -o(*rjti;*ylti.'eh3tll,STilHi

r

•

—ik—cf-efilcfji tigi i . i e b i i n Hi •

07S too IJS 150 17S JCO JJS Ï 50 i « JÜ}

GM [<n|

Figure 6 Roll response as function of GM It should be noted that in all conditions tested during the experiment the motions of the ship with the bilge keel remain well within the operational limits of the Ampelman systems.

CONCLUSIONS

From this research project it may be concluded that the new concept shows promising characteristics for the use as a Fast Crew Supply ship for the offshore industry.

Some aspects of the design, such as the propulsion and the ballast water handling and positioning

should be considered in more detail however before a final judgment can be made.

R E F E R E N C E S

[ 1 ] Keuning, J.A. and J. Pinkster

Further design and seakeeping investigations into "Enlarged Ship Concept".

Fourth International Conference on Fast Sea Transportation, FAST'97, Sydney, Australia.

[ 2 ] Keuning, J.A. and F. van Walree

The Comparison of the Hydrodynamic Behaviour of Three Fast Patrol Boats with Special Hull Geometries.

Fifth International Conference on High-Performance Marine Vehicles, HIPER2006, Launceston, Australia.

[ 3 ] Keuning, J.A.

"Grinding the Bow" or "How to improve the operability of fast monohulls".

Intemational Shipbuilding Progress, Volume 53, Number 4, 2006.

[ 4 ] Kapsenberg, Geert K., Lex Keuning and Jaap L . Gelling

Workability limits and fatigue aspects on a Fast Patrol Vessel.

Intemational Conference on Human Factors in Ship Design and Operation, Royal Institution of Naval Architects, RINA, 2009 ,London, UK,