Design development and evaluation of affordable high speed naval vessels for offshore service

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Date Author Address

September 2007

Steinberg, R., Chr. Cleary, K. Stambaugh and lA. Keuning Deift University of Technology

Ship Hydromechanics Laboratory

Mekelweg 2, 26282 CD Detft

TUDeift

Delit University of Technology

Design Development and Evaluation of Affordable

High Speed Naval Vessels for Offshore Service

by

R. Sheinberg, Chr. Cleary, K. Stambaugh and LA. Keuning

Report No. 1599-P 2007

Published In: Proceedings of the 9 International Conference on Fast Sea Transportation, Shanghai, ChIna, September 2007

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Ninth International Conference

on

Fast Sea Transportation

»

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a

Deift University of Technology

Ship Hydromechanics Laboratory

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ProceedIngs of

the Ninth International Conference

on

Fast Sea Transportation

(FAST2 007)

September 23-27, 2007

Shanghai, China

Organized by

Chinese Society of Naval Architects and Marine Engineers

China Ship Scientific Research Center

Shanghai Jiao Tong University

Edited by

Weicheng Cui

Shitang Dong

EólinKang

MingZhang

China Ship Scientific Research Center

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PREFACE

FAST2007 will be held in Shanghai, China during September 23-27, 2007. This is the 9th in a

series of world-known conferences dedicated to fast sea transportation, which is held every two

years following successful meetings previously in Norway (1991), Japan (1993), Germany (1995),

Australia (1997), USA (1999), United Kingdom (2001), Italy (2003) and Russia (2005). These

conferences proyided a forum for discussion on new concepts and designs of fast sea ships and

vehicles, matters of hydro-aerodynamics, structures, materials, maneuverability and stability,

propulsion complexes, safety and operation as well as infrastructure and economics of fast sea

transportation.

Fast2007 will bring together an international mix of academicians, researchers, designers,

builders, operators, owners, equipment suppliers, service providers, defense experts and economists

at the forefront of development in the high-speed maritime industry and will provide an invaluable

forum for information exchanges between those involved in industries. Specific vehicle types

covered include:

Passenger and cargo ships

Yachts and pleasure boats

Patrol boats

Sailing boats

Navy and coastal ships

Racing and record-breaking boats

Wing-in-ground effect crafts

The proceedings contains all technical papers presented at "The 9th International Conference on

Fast Sea Transportation (FAST2007)" held at Shanghai Everbright Convention & Exbibition Center,

China on September 23-27, 2007. The main themes of this Conference are new concepts and

designs of fast ships and marine vehicles, hull form design, propulsion, cavitation, seakeeping

behavior, control and maneuverability, hydro-aerodynamics, structure and material, safety and

operation, fast sea transportation infrastructure and economics.

Over 128 abstracts from 23

countries and regions within the themes were received by the FAST2007, and about 85 papers were

accepted for presentation at the Conference. Some of the International Standing Committee

members have also helped the Local Organizing Committee to make the selection:

-The conference was co-organized by the Chinese Society of Naval Architects & Marine Engineers,

China Ship Scientific Research Center and Shanghai Jiao Tong University. On behalf of the

International Standing Committee and the Local Organizing Committee of FAST2007, we would

like to thank ali the participants for their great contributions to the successful conference. The full

support from the sponsors, China Shipbuilding Industry Corporation, China State Shipbuilding.

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-I-Corporation, China Classification Society, Harbin Engineering University, Dalian University of

Technology, Huazhong University of Science and Technology, Wuhan University of Technology,

Jiangsu University of Science and Technology, China Ship Research and Design Institute, Marine

Design & Research Institute of China, Shanghai Society of Naval Architects & Marine Engineering,

Jiangsu Society of Naval Architects & Marine Engineering, Zhejiang Society of Naval Architects &

Marine Engineering, The Society of Naval Architects & Marine Engineers (USA), The Royal

Institution of Naval Architects (UK) are greatly acknowledged. Sincere gratitude is also extended to

all those who helped in various ways to the successful organization of the FAST2007, especially

those of the secretariat.

Weicheng Cui

Shitang Dong

Bolin Kang

Ming Zhang.

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-H--ORGANIZATION

International Standing Committee

Chairman:

Kjell HOLDEN, Vice President, Marintek, Norway

Members:

Tony ARMSTRONG, Chief Scientist, Austal Ships, Australia

Weicheng CITI, Deputy Director, China Ship Scientific Research Center, China Lawrence J. DOCTORS, Professor, The University of New South Wales, Australia Odd FALTINSEN, Professor, Norwegian University of Science and Technology, Norway Nigel GEE, Director, BMT Nigel Gee & Associates, UK

Paris GENALIS, Director, Naval Warfare, Office of the Secretary of Defense, USA Guoan LI, Vice President, China Shipbuilding Industry Corporation, China

Chris B. McKESSON, Principal Engineer, McMULLAN., USA

Torgeir MOAN, Norwegian University of Science and Technology, Norway

Kirill ROZHDESTVENSKY, Vice Rector St-Petersburg State Marine Technical University, Russia

Advisory Committee

Chairman:

Pingtao HUANG, President, Chinese Society of Naval Architects & Marine Engineers

Members:

Gang CREN, Vice President, Shanghai Jiao Tong University Guoan LI, Vice President, China Shipbuilding Industry Corp. Kejun LI, President, China Classification Society

Zhushi LI, Vice President, China State Shipbuilding Corp.

Zhiping LU, Honorary President, Shanghai Marine Design & Research Institute

Wengsun SHEN, Academician of Chinese Academy of Engineering, Dalian Shipbuilding Industry Co.,Ltd. Rongsheng WANG, Chairman, ChineseAssociation of the National Shipbuilding Industry

Yousheng WU, Academician of Chinese Academy of Engineering, China Ship Scientific Research Center Binghan XLI Academician of Chinese Academy of Engineering, China Ship Scientific Research Center Yuru XU, Academician of Chinese Academy of Engineerjng, Harbìn Engineering University

Shengkun ZHANG President, Shanghai Society of Naval Architects & Marine Engineers

Local Organizing Committee

Chairman:

Weicheng CUI, China Ship Scientific Research Center

Vice Chairman:

Shitang DONG, China Ship Scientific Research Center

Members:

Yingqiu CHIEN, China Classification Society

Ankang HU, Marine Design & Research Institute of China Bolin KANG China Ship Scientific Research Center Weiguo WU, Wuhan University of Technology

Xiaoguang WU, China Marine Design & Research Center Jianmin YANG, Shanghai Jiao Tong University

Xiongliang YAO, Harbin Engineering University

Yao ZHAO, Huazhong University of Science and Technology Renqmg ZHIJ, Jiangsu University of Science and Technology Zhi ZONG, Dalian University of Technology

Secretary:

Ming ZIIANG, China Ship Scientific Research Center

Secretariat

Balm _{KANG, China Ship Scientific Research Center}

Ming ZHANG, China Ship Scientific Research Center Ying HOU China Ship Scientific Research Center Lihua YANG, ChinaShip. Scientific-Research-Center Wenji LI, China Ship Scientific Research Center Gulhong TANG, China Ship Scientific ResearchCenter

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₍₅₉₎

Ji-ru Lin, Li-guo 5h!, Guo-hong You and Jia-yu Qian,

China Ship Scient j/ìc Research Center, China

Analysis of Bending Moments in Surface Effect Ship Structure by Russian Regulation* (595)

Ali Dehghanian, Kambiz Alempour, Hydro Aaerostatic Dept, MT University, Iran;

HamidAmjnj, Sharf Technical University, Iran

(540)

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The Whipping Vibratory Response of a Hydroelastic Segmented Catamaran Model (600)

Jason Lavroif Michael R. Davis and Damien S. Holloway, University of Tasmania, Australia; Giles Thomas, Australian Maritime College, Australia

Structure: Siamminq, Whippinq & Impact

The Effect of Air Cushion on the Slamming Pressure Peak Value of Trimaran Cross Structure (608)

Zhenglin Cao and Weiguo Wu, Wuhan University of Technology,. China

The Effect of Speed and Sea State for Probability of Ships Slamming (612)

Zhen Chen and Xi Xiao, Shanghai Jiaotong University, China

Computational Modelling of Wet Deck Slam Loads with Reference to Sea Trials (616) Michael R. Davis, University of Tasmania, Austrúlia;

James R. Whelan, INTEC Engineering PIy.Ltd. Level 2 Australia; Giles A. Thomas, Australian Maritime College, Tasmania, Australia

Strenqth & Fatique

Research on FEM Generation Techniques in Ship CAE Analysis (625)

Jian-hai Jin, Wen-hao Leng, Feng Li and Wei Zhou,

China Ship Scient /ìc ResearchCenter, China; Hai Pu, Southern Yangtze UniversityChina

Influence of Wave-induced Ship Hull Vibrations on Fatigue Damage (630)

Jong-Jin Jung, Pan-Young Kim, Hyun-Soo Shin and Jin-Soo Park, Maritime Research Institute, Hyundai Heavy Industries Co. Ltd Korea

Structural Design of Ramp in Aluminum Alloy for ACV (635)

Ping Zhang, Chengjie Wu, Yunchao Wang and Jun Wang, Marine Design & Research Institute of China (M4RIÇ), China

Strenqth I Composite Materials

Optimization of Planing Hull Structure Design (641)

Santini Julien, Philip Garret Kosarek, Regu Ramoo

Altair Engineering, Michigan, USA

Experimental Investigation of a Composite Patch Reinforced Cracked Steel Plate in Static Loading (648) Lazaros S.Mirisiotis and Nicholas G Tsouvalis,

National-Technical-UniversityofAthens, Greece - - - -

-The Right Level of Composite Technology . (657)

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Ninth International Conference on Fast Sea Transportation FAST2007, Shanghai, ChIna, September 2007

Design Development and Evaluation

Of Affordable

High Speed Naval Vessels for Offshore Service

'Rubin Sheinberg, 'Chris Cleary, 'Karl Stambaugh, 2Lex Keuning

'U.S. Coast Guard, Baltimore Ml), USA 2Delfl Technical University, Netherlands ABSTRACT

This paper presents a notional High Speed Naval

Vessel design and the important aspects of the design development and evaluation process for High Speed Naval Vessels with speed capabilities of up to 50 knots and lengths under 200 feet. New and innovative hull

forms are required to meet this unique mission

requirement. Therefore, specialized technologies,

analysis tools and systems are needed to evaluate hydrodynamic characteristics and insure the proposed

High Speed Naval Vessel will meet the mission

requirements safely, efficiently and at minimum cost. A parametric synthesis model was used to determine

the design trade space.

An extensive seakeeping analysis was performed on single chine, double chine, and round bilge hull forms. Model tests and full scale

trials were used to evaluate seakeeping criteria and performance of a parent hull form wiih a conventional bow, wave piercing bow and an axe bow. The test matrix included speed ranges between 20 and 50 knots and significant wave heights from eight to 15 feet The seakeeping analysis included a dynamic stability and broaching prediction. The notional design was also used for investigations into the trade offs between high speed hull forms, aluminum and advanced composite hull materials, propulsion systems and total ownership costs to detennine the most favorable compromise between affordability and capability given the demanding mission requirements.

KEYWORDS

High Speed Naval Ship Design, Seakeeping, Total Ownership Cost

I INTRODUCTION

Multi-mission responsibilities of homeland security,

national defense, search and rescue, maritime law

enforcement, and environmental and fisheries

protection in the 21's Centüry have increased.

dramatically in recent years. The new multi- mission responsibilities has made it necessary to consider High Speed Naval Vessels (HSNV) with speeds up to 50 knots. New and innovative hull forms are required to meet this unique mission requirement. Therefore,

specialized technologies, analysis tools and systems are needed to evaluate hydrodynamic characteristics and insure the proposed HSNVWill meet the mission requirements safely and efficiently.

The USCG involvement in this HSNV effort began with discussions within a NATO working group about the lack of seakeeping criteria for 1-ISNV operating in the semi-displacement (J)re planing) speed ranges. Subsequent to NATO discussions, a FAST consortium was established to investigate this lack of criteria. The FAST group is represented by members from the USCG, Marin, TU Delft, Damen Shipyards, Scheide Shipyard, and the Netherlands Royal Navy. The

USCG developed a baseline notional design for

seakeeping analysis and model testing. The notional

design was also used for investigations into the trade-off between aluminum and advanced composite hull

materials;

A. Total

Ownership Costing (TOC)

approach was used to identif' the most affordable pips.ayaIablc to meet mission requirements. This paper presents a notional HSNV design and the important aspects of the design development and evaluation process. The design evaluation process includes the latest developments in hull forms,

materials and seakeeping approaches needed to insure the HSNV will meet the missión requirement.

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-2 TOP LEVEL REQUIREMENTS

A notional

design has been developed for a

representative HSNV with top speed of 45 knots and a maximum navigational draft requirement of 10 feet. Brower et. al. (2003) summarizes the Top Level Requirements (TLR) for this HSNV.

3 HULL FORM ASSESSMENTS

The baseline hull form has a single chine hull with a transom shape adjusted to encompass three waterjets.

The resulting hull form, Figure 1, was used

parametrically by the synthesis computer program. Starting principal characteristics include:

LOA 189.0 fi LWL 172.7 fi Beam, WL 27.6 ft Draft, Molded 8.81ft Nay. 10.0 ft Disp. 526 Lt Cb 0.4361 Cp 0.7502

56

-Figure 1 HSNV Baseline Hull Form

3.1 Design Synthesis

The concept design was developed using the USCG Cutter Design Synthesis Computer Program.This program can determine the one combination of beam and draft that can simultaneously provide stability criteria and range.

The parametric equations, design criteria and standards

used by the computer program were modified to suit the TLR. The design space represents a range of balanced

designs for subsequent use in specific investigations and Total Ownership Cost (TOC) assessments to identify the parameters that produce a design that will meet the TLR at minimum cost. The characterization of the design space also permits rapid evaluation of the TLR and impact of specific performance requirements

on thé TOC.

3.2 Powering Estimates

Speed vs. power was determined at both the full load and minimum operating conditions. The speed and hull length places the HSNV in the semi-displacement (pre-planing) speed range. The U.S. Navy Taylor-Gertler methodology was used for Froude numbers (Fn) less than 0.416. A Swedish fast attack craft standard series was employed at Fn of 0.416 or higher. This series addresses the appropriate BIT, V/L3 and Fn

values. It is based on a block coefficient of 0.40. A

worm curve was used to adjust standard series residual resistance (Cr) coefficients. The speed and power estimate includes both estimated appendage and air drag, a correlation allowance (delta Cf) of 0.3x103, and a 8% EHP margin. The propulsive coefficients are based on KaMeWa plots of water-jet thrust versus

speed and transit engine power with the outboard

water-jets operating together, or boost engine power

using the centerline water-jet plus both outboard

water-jets operating at full power.

The HSNV employs a lightweight, efficient, triple water-jet, combined diesel and gas turbine (CODAG) propulsion plant. A centerline 160 SII boost water-jet, powered by a LM2500 gas turbine rated at 29,500

BHP, is flanked by outboard 90 SU maneuvering

water-jets, each powered by a diesel engine rated at 3,834 BHP. The diesel powered water-jets are used

for transit operations. A 500 HP, diesel powered,

3600 thruster is used for loiter operations, and as a bow thruster for maneuvering.

Deck area requirements are shown in Appendix B. The inboard profile

is provided in Figure 2. The

arrangement provides maximwn crew comfort with berthing as close to midship on and below the main

deck. Officer berthing, ward room, and messing are

on

the main deck forward of midship.

The

pilothouse is located close to midship for minimum motions as well. Notable features on the inboard profile include the enclosure for the RIB on the main deck aft and the large water jet on centerline.

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3.3 Hull Structure Considerations

The notional design has been developed assuming an

aluminum hull and superstructure designed in

accordance with the ABS High Speed Naval Craft Rules (2003). M engineering study was conducted to determine the weight savings associated with a Carbon Reinforced Plastic (CRP) hull construction

material.

The CRP study used DNV (2002) rules for HSNV and

considered a range of operating

restrictions of

unlimited, RO and Rl, with design accelerations of

3.8g's, 3.3g's

and 2.8

g's

respectively. CR?

scantlings were developed for these restriction levels.

The hull consists of sandwich construction with

Divinycell core and CR? skins. Typical structural panel weights are 7.2 lbs/sqft for the bottom and 5.5 lbs/sqft for the sides. These hull scantlings produced a lightship weight redUction of approximately half (200 Lt) that of the aluminum notional design (376

Lt). This weight reduction translates into increased

payload, reduction in power and fuel, increased range

or combination thereof.

Although use of

advanced composites provides a significant weight

savings, the CR? hull construction cost is much

greater than for aluminum; however, total ownership

cost is only slightly more. Detail design

considerations such as local structural foundations

inside the hull and local impacts outside must be

evaluated in order to move forward with the CRP option for hull structure.

3.4 Seakeeping Pertormance

Seakeeping is a major a consideration for an FISNV operating offshore. Supporting seakeeping studies included analytical predictions, model tests and full scale trials.

Analytical studies were conducted by Sheinberg et. al. (2005) to determine the limiting motions of various hull forms and the minimum size required to meet the seakeeping requirements. HSNV seakeeping criteria used for the analysis are based on NATO STANAG 4145 and NAVSEA and include:

Pitch < 3 degrees SSA,

Vertical acceleration <0.4 g's SSA, Lateral acceleration < 02 g's SSA, Roll < 8 degrees SSA, and

Slams <20/hr.

Slams per hour are minimized by Vee hull forms

considered. The limiting acceleration was increased to .55g's SSA iñ the pilothouse based on the ratio of significant amplitudes to the average of the one tenth highest peak amplitudes. Evaluation of these criteria was the subject of further analysis and full scale trials described below. The analysis indicated that a cutter of at least 150 feet LOA and preferably 180 feet LOA is needed to perform missions in demanding offshore wave environmentas shown in Figure 3.

Figure 3 Limiting Sea Conditions for Vertical Accelerations at the Pilothouse

Seakeeping model tests were conducted on the three hull forms shown in Figure 4 by the FAST group. The hull forms tested included the Parent Hull Form with a single chine and conventional bow, Axe Bow variant and Wave Piercing Bow variant. The hull forms have the same nominal length at the waterline, beam at the waterline, midship draftand displacement. The primary difference in hull forms is the bow shape. The models were tested in significant wave heights

..u.HIuIIIflhIIiIilUIuIUlU11IU"

.

U III! -III! liii III hUt

Figure 4a Parent Hull Form Used for Seakeeping Model Tests

57 -r

Single Chine HaS Lcegth Conrpoeinion - Limiting Wave Height for 035g Vertical

Acceleration at PilotHouse 17.0

A Serien Tremi Line- 4Oktrk l A

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lljÏI.flIll!OIOHiffuiniu

Figure4b AXE-Bow Hull Form Used for Seakeeping Model Tests

Figure 4e Wave Piercer Hull Form Used for Seakeeping Model Tests

of 6.56, 785, 10.3, 11.0, and 12.57 feet and speeds of

25, 35 and 50 knots.

'Selected model test results are shown in Table i for the three hull forms. The Wave Piercing Bow was not tested in a significant wave height greater the 10.3 feet due to the water run up on the bow of the model.

The parent hull form experienced

slightly more pitching motions than the Axe Bow and more vertical

5g

-acceleration at the bow.

This difference in pitch

motions is likely due to the parent hull bow flare vs.

minimal bow flare for the Axe Bowi A resonant

pitch condition was observed at speeds of 35 knots for

all three hull forms.

Pitch and heave resonant

conditions were noted in the analytical predictions (3) for the 30 to 40 knot speed range. The Axe 'Bow experienced the least deck wetness due to its increased sheer forward, while the wave piercing bow form experienced a significant amount of deck wetness from waves running up over the wave piercing bow.

The Axe bow also experienced less topside wave

impacts due to vertical bow and sides of the hull form. Figure 5 shows a comparison of the distribution of peaks and trough vertical accelerations at the bow for 35 knots in a 2.5 meter significant wave height. This comparison clearly shows the non-linear effects of

wave impacts that are critical for short term operability and limit high speed operations in head

seas.

The AXE bow concept

is optimized to minimize bottom 'and flare slamming and increased

short term high speed operability

in head seas.

Following and quartering sea model

tests were

performed.

All three models required additiòn of

fixed skegs aft for course keeping ability. The Axe

Bow model required fixed skegs twice the size of

those required for the Parent Hull Form.

Full scale trails were conducted by the FAST working

group on the MN VALIANT operated by UK

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L II4'.

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r- ---

I - -f I I i I I I i L_L J - J_. _T S-t--T' I I t I I I i. I I I I 50 20 IX 5 2 1 0.5 0.201

P,ob.biSly of EooeOd.flo. III I

00 35 3° 26 t20 45 IO AO øowWP oo i i i I I f I I J L J L LJ_I_ I I I I i I f f I I I I 1

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i I I I I I 60 20 10 0 2 I 0.6 0.2 0.1 P,obOhIIlI,OIE0000d.flO. 101 0o

Figure 5: Comparison of the distributions of peaks and troughs in the vertical accelerations at the bow at 35 knots.

Table i FAST Model Test ResUlts Values are RMS AO BOW AXE I t I I f I I L J I. J

LII J

I I I I I I I I I I I I I I I I

i

rl

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ii

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Typical levels of acceleration on the MIV Valiant were .3 g's SSA in the pilothouse and 0.8 g's SSA at

the bow in SS4.

Findings from the full scale sea trials include:

In shorter time frames (approximately 4 hours) and speeds tested, the accelerations did not limit

operations while

topside wave impacts

did

influence the creW's perception of worsening conditions from the impacts and related structural shuttering or whipping response of the hull. Crew fatigue and motion interrupts were

important issues for operations at sea for longer periods of time. This included seaway induced motion and acceleration effects on working, eating and sleeping. A sea operations lasting longer than four days were considered excessive in heavy

weather conditions.

The M/V Jaguar did not have roll stabilization and crew discomfort rand work interruption was noted as significant by the crew. The MJV Valiant had roll stabilization that was used continually. The

MN Valiant crew did not note any roll related

discomfort.

35 Dynamic Stability Evaluation

The hull forms considered for HSNV in this effort

have deep Vee sections forward to minimize Wave

induced slamming and cut away stems to

accommodate large diameter propellers or water jets. This combination of bow and stem shapeare known to cause broaching in following and quartering seas. Increased broaching contributes to loss of stability in

beam sea conditions; therefore, a broaching and

dynamic stability analysis was performed to assess these tendencies and identify corresponding solutions. In this investigation, a dynamic stability computer program (6) was used to perform the analysis. A

single analysis results in a single coherent dataset that represents the motion response and extreme motion behavior for one loading conditiOn and one wave

description over a range of operating speeds and

headings.. Multiple runsmust-bemadetocompile-a polar diagram of response across a range of speeds and

headings.

The dynamic stability and broaching analysis was conducted for a Single Chine, Round Bilge, Double

Chine and Axe Bow hull form variatiôn& Hull

60

-appendages and stem shape variations analyzed aie

shown in Table 2.

Table 2 - Hull Form Features Effecting Broaching Characteristics

No active fin stabilizers are included in the broaching analysis. The deep fore foot of the Axe Bow hull was modeled as part of the hull with a small skeg type appendage to incorporate appropriate hydrodynamic and maneuvering characteristics.

Long-crested seas are modeled using the

Bretschneider sea spectral formulation. Sea states used in the dynamic stability analysis are shown in Table 3.

Table 3 - Sea States used in the Dynamic Stability Analysis

Significant wave heights are in the midrange for each sea state. Modal periods are the most probable for the sea state. A short period SS6 based on storm data analyzed by Búckley (7) was included to investigate the broaching

tiity in iteepfwäves. - Thin data is

consistent with climatology for fast developing storms. A speed range of zero to 20 knots was used for SS 4, 5, and 6 with most probable wave period and 10, 15, and 20 knot speeds were used for the storm version of SS6.Generally, cuttersof this size and speed capability Hull Form

Type

Appendage Stern Shape

Single Chine Twin skegs/shaft bossings, rudders Shallow, flat Round Hull

One CL skeg aft,

rudders

Shallow, flat Double

Chine

Shaft struts, rudders Shallow Vee

Axe Bow One CL skeg forward.

shaft struts, rudders

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do not have good steerage below 10 knots and are capable of achieving over 1:0 knots with engines at idle. Lower speeds were included in the analysis for extrapolation of polar plot results across the speed range. Dynamic stability calculations were limited to an Fn less than 0.5 that equates to 20 knots for boats of the waterline length used in the analysis.

Broaching is determined to occur when the yaw angle exceeds 30 deg and the yaw rate exceeds 3 deg/sec. A sensitivity run indicated this practical limit did not increase the number of broaches significantly. An autopilot controls heading during the simulations. Based on the predictions, the Single Chine, Round Bilge, and Double Chine hull forms did not exceed the broach criteria in the sea conditions at speedsabove 10 knots for the sea states with the most probable wave periods. A small amount of broaching activity is evident at speeds less than 10 knots for the hull forms

considered; however, speeds below 10 knots are

seldom used in boats that have sufficient power to achieve 10 knots with engines at idle. Patrol boats of this type have relatively small rudders for high-speed operation and are noted for lack of low speed course keeping ability and maneuverability. The results confirm this generalization.

The Axe Bow hull form did experience broaching in SS6 with most probable wave period at 20 knots in

seas just off the stern quarter.

Broaching at this speed indicates surfriding preceded broaching. A

broach preceded by a surfride produces a dramatic

event. First, the bow buries itself into the back of a wave and then the stem swings beam to the prevailing

seas very rapidly.

Both wave and momentum

induced

forces combine to

prQduce

a dramatic

dynamic event.

Table 4 presents the results of broaching and capsize analysis in SS6 storm condition. The results are presented in a frequency of occurrence from 10 runs of 30 minutes each. The effects of lateral projected

under water area are evident in the results.

The Single Chine hull has skegs aft and the lowest broach

indices. The Double Chine hull has no additional lateral surface at all, and has the highest broaching

index.

The Axe Bow's forward

lateral plane increases broaching tendencies as well. Skegs aft on

the Axe Bow hull färm would likely improve

broaching characteristics; however, it is not known at

this -time how much lateral projected area would be required to counteract the effects of the deep forefoot.

Table 4 - Relative Comparison of HSNV Heavy

Weather Seakeeping

Hs=5m Tp6.32, Speeds, 10, 115, 20 knots, Headings through 360 deg. in 30 deg. Increments.

Index is the total number of events divided by nwn ber of3O minute trials forrelative comparisons.

Capsize indices are influenced by occurrence of

'broaching

events, GM and Righting Ann (RA)

characteristics and broaching events. Model tests conducted at MARIN as part of the FAST project indicated the addition of fin skegs aft reduced the broaching tendencies significantly. These skegs were between 2 and 3% of the lateral projected area of the underbody.

4 TOTAL OWNERSHIP COST

Total Ownership Cost (TOC) per operating hour is the most objective way to compare the cost of

alternative HSNV designs.

For this study, TOC

estimates included acquisition, personnel, fuel,

consumables, maintenance, admin, facilities, and disposal.

Acquisition costs were developed for

construction by weight groups and major machinery components. TOC was studied for both 18 and 35-year service lives. In the later case, each HSNV was

assumed -to -undergo a comprehensive -mid-life .SLEP

reconstruction. The TOC per operating hour for 10-ft dra10-ft will be as shown in Table 5.

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Table 5 - Total Ownership Cost for 18

Year Service Life

Table 6 - Total Ownership Cost for 35 Year

Service Life

HSNV with aluminum hulls have the lowest total operating costs per operational hour. Twin propeller HSNV have lower total operating costs than triple screw HSNV. HSNV with a 35- year service life

have a total ownership costs per operating hour which is about 3.5 to 5.5 % lower than that for HSNV with an 18-year service life. However, a service life of about 21 years, without a SLEP reconstruction, will result in about the same total ownership costs per operational hour as a service life of 35 years, which is dépendant on a relatively high risk SLEP. Given the inherent risk associated with the SLEP reconstruction of a lightly constructed HSNV it is concluded that the HSNV should be designed for a 21-year service life. -

Provisionof 168vice_84hourrange generally has

only a ± 1% impact on the total ownership cost per operational hour, depending on the -service life and-hull material. By increasing the range to 168 hours a HSNV will be able to conduct 7-day missions without

necessarily returning to base to refuel. This will

increase the actual time on station by a minimum of

7%. Therefore, increasing the range to 168 hours is

62

-obviously cost-effective. However, if speed and draft

cannot be compromised, increasing range -also

increases the required hull length. The increase in hull length could be minimized- if the navigational draft could be increased somewhat.

All four-hull materials are technically feasible and all can achieve extended service lives.

However, composite hulls currently have much higher desìgn, construction and service life risk than steel or aluminum hulls. Composite hulls also have higher acquisition and total ownership costs then steel or

aluminum hulls. GRP hulls are also heavier than

aluminum hulls. For equal range, speed and draft aluminum results in lower acquisition cost, and lower total ownership costs per operating hour than all other

materials. The galvanic corrosion of aluminum hulls

can be prevented with appropriate grounding,

prevention of the- contact of dissimilär materials and control of stray current. This will require rigorous quality control,

training and management, but

is

considered achievable at low risk.

It is therefore

concluded that the HSNV hull should be constructed

of aluminum.

This study demonstrates that a HSNV of 180-ft. LOA

(170-

ft LBP), fitted with triple

propellers and

constructed from aluminum will achieve a sustained

speed of 30 kflots, a range of 168 hours, and a

navigational draft of 10.35 feet, which includes a 0.50 ft. trinilsquat margin, i.e. 9.85 feet at even keel with no

trim at the end- of service life. A -twin propeller,

aluminum hull HSNV would be less costly than a triple screw HSNV. However, for twin propeller designs, the length required to generate a range of 168 hours is assessed to be excessive, whereas an LOA of about 189 feet would be- required to achieve a 30.0 knot sustained speed at the minimum threshold speed of 84 hours. This option would have a navigational

draft of 9.45 feet.

These two aluminum HSNV options with 30 knot sustained speed are summarized

as follows:

Table 7 - Total Ownership Cost for Changes in

(24)

The twin propelleroption will be about 7% less costly,

but, because it will require at least one refueling

during each deployment, it will be on station at least 7% fewer hours. Thus, the total ownership cost per hour on station of both options will be nearly identical.

The shorter-range design obviously has less

operational flexibility. Consequently the shorter,

deeper draft, longer range, triple propeller aluminum HSNV is assessed to bethe most effectiveoption.

5 CONCLUSIONS AND RECOMMENDATIONS

This paper describes the design of a notional High

Speed Naval Vessel (HSNV) and related

naval

architecture required to evaluate the performance associated with a high speed requirement. Findings

related to the design evaluation include:

The combination of synthesis model, TOC

analysis and supporting studies

provided a

methodology for design of the most mission

capable HSNV at minimum cost. Aluminum

hull construction provides the most affordable TOC to meet the TLR for this HSNV.

Advanced composites offer significant hull

structure weight reductions of approximately half

at

an order of magnitude of cost increase

compared to aluminum hull structure. This

translates into substantially more payload or

range for a given HSNV size at a higher

construction cost. Detall design considerations such as local structure foundations inside and local impacts outside must be evaluated in order to move forward with the CRP option for hull structure.

The seakeeping analysis indicated thata cutter of at least 150 feet and preferably 180 feet LOA is needed to perform missions .in demanding

offshore wave environments.

For semi-displacement hull forms, wave impacts dominate short term crew comfort and long term crew fatigue are limited by vertical accelerations. HSNV with vertical bow sections experience less bottom and flare wave impacts, but must be

desined with more lateral plane aft for adequate directional stability in heavy weather.

6 ACKNOWLEDGEMENTS

The authors would like to acknowledge the significant

contributións of Mr. Ken Brower from the USCG,

Jorgen Jorde from LMG Marin, Norway and all

participants in the FAST project including Frans van Wairee and Gert Kapsenberg, MARIN, Peter van Terwisga, Royal Netherlands Navy, Jaap Gelling, Damen Shipyards and Rob vd Graaf Royal Scheide. The opinions expressed herein are those of the aUthors and do not represent official policy of the U.S. Coast

Guard.

7 REFERENCES

Brower, K., Cleary, C., (2003) "Top Level

Requirements for a High Speed Cutter for Offshore Service" USCG ELC Project Report.

American Bureau of Shipping (ABS) (2003) "Guide

for Building and Classing High Speed Naval

Craft".

Det Norske Ventas DNV), (2002) "High Speed, Light

Craft and Naval Surface Craft

(HSLC&NC) Rules".

Sheinberg, R., Cleary, C., Stambaugh, K., Ashley, A., (2005) "Seakeeping Performance of High Speed Cutters", ASNE.

NATO "Common Procedures for Seakeeping in the

Ship Design Process", STANAG 4154,

Edition 3.

MARIN, (2002) "FREDYN User's Manual Version 9.0".

W. Buckley, (1988) "Extreme and Climatic Wave Spectra for use in Structural Design of Ships", Naval Engineers Journal.