comparative analysis of naval hydrofoil and dispacement ship design_john larsen grostick

8/12/2019 Comparative Analysis of Naval Hydrofoil and Dispacement Ship Design_John Larsen Grostick

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A COMPARATIVE ANALYSIS OF NAVAL HYDROFOILAND DISPLACEMENT SHIP DESIGN

John Larsen Grostick


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DUDLEY KNOX LIBRA**NAVAL POSTGRADUATE SCHOOLSoAEREY.CAUFORN.A 93940

A COMPARATIVE ANALYSIS OF NAVALHYDROFOIL AND DISPLACEMENT SHIP DESIGN

byJOHN LARSEN GROSTICK

Submitted to the Department of Ocean Engineering on 9 May 1975in partial fulfillment of the requirements for the degree ofNaval Architect and the degree of Master of Science in NavalArchitecture and Marine Engineering.

ABSTRACTThe current generation of naval hydrofoils have higher

speeds, superior seakeeping performance and the same payloadcarrying capability as naval displacement ships of the samesize. This performance is the result of significant differencesin areas other than the foil system. By comparing a hydrofoiland a displacement ship, differences in design criteria,standards and practices can be identified. Having identifiedthe major differences, the displacement ship can be redesignedto hydrofoil standards. With both a hydrofoil and a dis-placement ship designed to the same standards, the impact ofthe hydrofoil's design standards on a displacement ship canbe assessed, and the costs and benefits of a hydrofoil whencompared to a displacement ship designed to the same standardscan be evaluated.

Thesis Supervisor: Clark GrahamTitle: Associate Professor of Marine Systems


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ACKNOWLEDGEMENTS

I wish to express my thanks to Professor Clark Grahamwho provided the impetus to pursue this topic and acted as asounding board for the work as it proceeded to completion. Anote of thanks also goes to the many kind individuals at theNaval Ship Engineering Center, and Naval Ship Research andDevelopment Center who made time in their schedules to provideme with the insight they have gained through the design of thecurrent generation of hydrofoils. To my unflinching typist,Mrs. Sandy Margeson, goes my special thanks for her patiencein translating this into a legible manuscript.

To my wife and sons goes the greatest measure of thanksfor the understanding and patience they have had during thesethree years when they have had to compete with my studies fortime and attention.


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TABLE OF CONTENTS

ABSTRACTACKNOWLEDGEMENTSTABLE OF CONTENTSLIST OF FIGURESLIST OF TABLES

CHAPTER 1 INTRODUCTIONCHAPTER 2 CHARACTERISTICS OF HIGH PERFORMANCE

SHIPSSection 2.1 Hydrodyanmic Aspects of HighSpeed ShipsSection 2.2 The Impact of Weight and VolumeSection 2.3 Hydrofoil Design Criteria andStandards

CHAPTER 3 A COMPARATIVE ANALYSIS OF NAVALHYDROFOILS AND DISPLACEMENT SHIPS . .Section 3.1 Selection of ShipsSection 3.2 Method of AnalysisSection 3.3 Computer Model

3.3.1 Objective of the ComputerModel3.3.2 Description of the ComputerModel .3.3.2.1 Weight Algorithm .3.3.2.2 Volume Algorithm .

3.3.3 Limitations of the ModelSection 3.4 A Comparative Analysis of a SmallHydrofoil and A Planning Craft

3.4.1 Analysis of PHM and PG-84 .3.4.2 Comparison of PHM andPG-843.4.3 Redesign of PG-84 to PHMStandards3.4.4 Sensitivity Analysis of theRedesigned PG-843.4.5 Summary of the Analysis ofPG-84 and PHM

2

34

6

8

9

13

131525

28

283139

4141424749

505055596668


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Section 3.5 A Comparative Analysis of A LargeHydrofoil and A Displacement Ship . 713.5.1 Analysis of DEH and FFG-7 . . 713.5.2 Comparison of DEH andFFG-7 713.5.3 Redesign of a High SpeedDisplacement Hull Form toDEH Standards ....... 803.5.4 Sensitivity Analysis of theHigh Speed DisplacementHull Form 883.5.5 Summary of the Analysis ofDEH and FFG-7 89

CHAPTER 4 CONCLUSIONS 92CHAPTER 5 RECOMMENDATIONS 94

REFERENCES 95APPENDICES

APPENDIX A SHIP DATA 97APPENDIX B POWERING ESTIMATES 104APPENDIX C COMPUTER PROGRAM LISTING Ill


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LIST OF FIGURESFIGURE TITLE PAGE1 The Sustention Triangle 112 Speed Capabilities in Head Seas for VariousTypes of Ships 163 Weight Trend For Hydrofoil Lift Systems 184 Ship Structural Weight Relationships 205 Machinery Weight Fraction Relationship toPropulsion Plant Specific Weight 246 Brequet Range Correction Based on Fuel Fraction . 4 67 Computer Model Flow Chart 4 88 PG-84 - PHM Comparative Weight Fraction Analysis. 519 PG-84 - PHM Comparative Volume Fraction Analysis. 5210-11 PG-84 - PHM Specific Parameters 5312 Comparative Weight Fractions for Upgraded PG-84 . 6313 Comparative Volume Fractions for Upgraded PG-84 . 6414 Sensitivity Analysis of Upgraded PG-84 toSingle Parameter Changes 6715 Sensitivity Analysis of Upgraded PG-84 toMultiple Parameter Changes 6916 DEH - FFG-7 Comparative Weight Fraction Analysis. 7217 DEH - FFG-7 Comparative Volume Fraction Analysis. 7318-19 DEH - FFG-7 Specific Parameters 7420 Upgraded FFG-7 Comparisons 8221 Comparative Weight Fractions for Series 64and DEH 8622 Comparative Volume Fractions for Series 64and DEH 87


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23 Sensitivity Analysis of Series 64 Hull Form ... 90B-l FFG-7 Shaft Horsepower Estimate at High Speeds . no


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LIST OF TABLES

TABLE TITLE PAGE1 Ship's Characteristics ..... 322 Weight Classification 353 Volume Classification 384 Specific Parameters 405 Performance Requirements and Parameters forUpgraded PG-84 606 Upgraded PG-84 Weight and Volume Estimate .... 627 Performance Requirements and Parameters forUpgraded FFG-7 818 Performance Requirements and Parameters forSeries 64 Hull Form 849 Series 64 Weight and Volume Estimate 85A-l PG-84 Weight and Volume Data 98A- PHM Weight and Volume Data 100A- DEH Weight and Volume Data 101A-4 FFG-7 Weight and Volume Data 102


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CHAPTER 1INTRODUCTION

The technological advances of the past two decades havebrought the hydrofoil from its infancy to full developmentas a naval combatant. The hydrofoil is the first of theclass of high performance ships to reach this stage ofdevelopment. The trend toward larger and slower navalcombatants, which has been observed in the area of displace-ment ships, has been reversed by the hydrofoil. The speedcapabilities of the hydrofoil place it in the class of highperformance ships while its small size reverses the sizetrend offering with it the economies inherent with reducedsize.

The objective of this analysis is to determine thedesign criteria and standards which have made the hydrofoila feasible ship and to make an estimate of the characteristicsof a displacement hull form of similar size with the hydro-foil's design criteria and standards. With the hydrofoiland displacement ship having the same design criteria andstandards, imposing the same performance requirements inareas such as speed and endurance allows the evaluation ofthe positive and negative aspects of the hydrofoil and thedisplacement ship on an equal basis.

Classifying hydrofoils as a high performance shiprequires identifying the relationships between differenttypes of ships or vehicles. Jewel in reference 1 presented


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a method of categorizing vehicles by the identification ofthe supporting force or sustention. This method is conven-ient for it characterizes all vehicles operating at the air-water interface by some combination of three forms ofsustension.

Unpowered Static LiftPowered Dynamic LiftPowered Static Lift

This can be presented in the form of an equilateral trianglewith the three forms of sustention at the vertices as shownin Figure 1. This figure provides an insight into the natureof the current generation of high performance vehicles, forthey rely upon powered lift for their primary means ofsustention. Hydrofoils are an example of the powered dynamiclift type vehicle and hovercraft are an example of thepowered static lift type vehicle. Unpowered static lift ischaracteristic of large displacement type ships. However,small displacement ships such as planning craft generatedynamic lift forces at high speeds and are not solely staticlift vehicles at these speeds.

For this analysis two basic types of vehicles will beexamined. In the high performance ship category, the hydro-foil will be used. High performance in this context willmean a vehicle with its primary support at its operatingspeed provided by powered lift. Hydrofoils fall in thiscategory as shown in Figure 1. To provide a conventionalship for comparison implies that it be a displacement hull

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UNPOWERED LIFT STATICDESTROYER

PLANNINGCRAFT

STATIC LIFTHYDROFOIL

POWERED LIFT DYNAMIC LIFT

FIGURE 1 The Sustention Triangle [1]

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form. However, as the size decreases and speed increases,ships with displacement hull forms have increasing sustensionby powered dynamic lift as they enter the planning regime.Various types of planning craft are examples of this effectas shown in Figure 1. To ease the confusion over therelative fraction of sustention and if the vehicle shouldbe termed high performance or not, hydrofoils will becategorized as high performance ships and other vehiclesoperating with a lesser fraction of powered lift will beclassed as displacement ships.

The selection of the destroyer hull form for use asthe displacement ship model is both traditional and basedon the evaluation of the destroyer hull form by Mandel inhis investigation of novelship types [2]. In Mandel 'investigation, he postulated that a 2,000 ton destroyer witha machinery plant specific weight of 5 lb/SHP could attaina speed of about 65 knots. This shows the impact of asingle area of improvement to hydrofoil standards demonstra-ting that a destroyer can compete with a hydrofoil on thebasis of speed. Based on Mandel' s assessment of thedestroyer as the best of the displacement hull forms, itwas chosen as the vehicle to use in the comparison. However,at high speeds and at relatively small sizes, the destroyeris surpassed in performance by the planning craft. Thus fora small ship for use in the comparison a planning craft waschosen.

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CHAPTER 2CHARACTERISTICS OF HIGH PERFORMANCE SHIPS

High performance ships have characteristics which aresignificantly different from a displacement ship operatingat a lower speed. These characteristics are both inherentin the ship type and a result of design effort. They aremajor factors in the suitability of a high performance shipto fill a mission requirement, and conversely the possiblerange of the performance variables; speed, range, and pay-load carrying capacity.

The purpose of this section is to identify the areas inwhich there are significant differences between high perfor-mance ships and their displacement counterparts. Thesedifferences are due to the hydrodynamic aspects of the highperformance vehicle, the mission requirements which it mustmeet, and the differences in design criteria, practices andstandards which are employed to make the high performanceship feasible.

2.1 Hydrodynamic Aspects of High Speed ShipsThe hydrodynamic forces which result from moving at high

speed at the air-water interface have a significant effect onthe viability of the ship as a useful platform. The linkbetween hydrodynamic performance and ship impact is therequired shaft horsepower for a fixed speed and displacement.A relative measure of the hydrodynamic forces and the hydro-dynamic performance is the lift-drag ratio ( ) . In

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estimating propulsive power requirements the lift-drag ratioprovides the influence of hydrodynamic performance.

SHP . 6.87 x Va n x

whereV = speed in knotsn = overall propulsive coefficientL = lift or displacementD = drag or resistanceA = displacementSHP = shaft horsepower

For the same size ship at 45 knots, comparative lift-dragratios are shown below:

Comparative Lift-Drag Ratios [20]Destroyer Hydrofoil PlanningCraft

Displacement(tons) L/D L/D L/D200 15.0 8.82000 12.3 12.2

The relative hydrodynamic efficiency of the hydrofoil at thesmall displacements is apparent; however, this advantage isreversed by the time the displacement reaches 2000 tons. The

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impact of the lift-drag ratio will be apparent in other areaswhen the effects of hydrodynamic performance on ship designrequirements are examined.

The other major area of hydrodynamic performance, whichis the strong point of the hydrofoil, is the seakeepingperformance. From a qualitative point of view, the abilityto maintain speed in a sea state reflects a good measure ofthis performance. The general superiority of a hydrofoil inincreasing sea states is shown in Figure 2. This is thesignificant advantage which the hydrofoil has gained byisolating itself from environmental excitations. The costof this isolation in terms of foil weight and volume will beexamined in further detail in Chapter 3.

2.2 The Impact of Weight and VolumeFor a large displacement ship operating at relatively

low speeds, the impact of weight addition is either a slightreduction in speed or a slight increase in size to accommo-date the extra propulsion machinery and fuel to maintainthe desired speed. Whichever choice is made the effect doesnot jeopardize the feasibility of the platform. The effectof a weight addition on a hydrofoil can have a more signifi-cant effect. Due to the nature of the dynamic forces whichprovide lift, both speed and displacement are constrained toa band of operating profiles. If the increase in displace-ment exceeds the hydrofoil's maximum take-off weight, theship is no longer feasible and either some payload item or

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copoHuto>5-1OCOra

CO

(00)

H p_)W 5CUH4-> COh ah x:X COfOa


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fuel must be sacrificed. The alternative is an overallincrease in size. Unlike the displacement ship where onlythe containment portion must increase to provide thenecessary volume and bouyancy to support the weight additionand its effects, the hydrofoil must also increase foil sizeand weight to provide the support for an increase in totalweight in excess of the maximum take-off weight.

Both ship types have the spiraling effect of the weightaddition, resistance increase, propulsive power increase,fuel increase, and ship volume increase. The hydrofoil hasthe additional impact of the growing foil system and an upperlimit on foil size.

The foil system represents an overhead which the shipmust absorb in other areas if it is to be a useful platform.The weight of the foil system is significant and its impactincreases with size as predicted by Hoerner [4] and reflectedin recent hydrofoil designs as shown in Figure 3. 1 Theoverhead increases with increasing displacement and foil sizegrows until the feasibility limits for foil size arereached. As a result hydrofoils are highly integrateddesigns where weight and space are at a premium. The design,1 Hoerner 's prediction of foil weight as a fraction of fullload displacement is

Wf -2 1/3j=6.5 +1.3x10 W 'Where Wf is foil weightand W is full load displacement.

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UJ

UJQ_

225OnXUJ

UJf->to

20

15

b

/ ,GEh l-l

PH MJjOE? jjei ,

P jH-I

100 I0(FULL LOAD CLONG TONS)

FIGURE 3 Weight Trend for Hydrofoil Lift Systems [5]

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as a result of this high degree of integration, does notevolve but rather bursts into existance when the platformbecomes feasible and integrated in all aspects of the design.To be able to absorb the overhead which the foils haveimposed, hydrofoils have relied heavily upon the applicationof technology somewhat foreign to displacement ship design.The technology and the weight consciousness is more akin tothe aircraft industry than the marine industry.

The impact of weight consciousness is significant if onelooks at the relationship between foil weight and payloadweight. For a wide range of displacement ships the averagepayload weight fraction is about 12 percent. 2 By contrastthe average foil system weight is in that range also. Ahydrofoil designed by conventional displacement ship standardswould have little if any payload carrying capability. Theresult of weight consciousness is that the hydrofoil alsohas a payload weight fraction of about 12 percent.

The advances in lightweight structures are one majorarea of improvement. The impact of aluminum structures isshown in Figure 4. Structural weight fraction and structuraldensity both show the impact of lightweight hull structures.

2 Payload is defined as weight groups 4 and 7, Amunition,Aircraft and Aircraft related fuel and stores. The payloadweight fraction is the ratio of payload weight to full loaddisplacement.

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CDrot9fO


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Structural StructuralWeight DensityFractionHydrofoil Ships -20% 2-3 lb/ft

3

(Aluminum Hull Structures)Naval Displacement Type -30% 5-7 lb/ft 3Ships(Steel Hull Structures)

The differences are not restricted only to small ships.Structural estimates for a variety of ships indicate that analuminum hull structure is on the average 55 percent of theweight of a steel hull structure [6]. 3 The use of aluminumas a hull structural material is not without its complicationsIt has a definite fatigue life and also requires specificmeasures to protect it from the effects of fire. The advan-tages are significant and the payload carrying capacity ofhydrofoils would be severely limited if aluminum structureswere not feasible.

Speed, hydrodyanmic efficiency (lift-drag ratio) andpower plant size and weight are all closely related. Therelationship between power requirements and speed reflectsthe hydrodynamic influences,

SHP VLn D

3 An aluminum hull structure for DDG-2 (Figure 4) would resultin a structural density of 3.5 lb/ft 3 and a structural weightfraction of 15.6 percent.

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and the relationship between propulsion plant specific weightand machinery weight fraction reflect the influence of thepower plant type.

Wm ,SHP. , . (-g-) (oan)where

SHP = required shaft horsepowerA = displacementV = speedL = liftD = drag or resistancen = propulsive efficiencyWm = machinery plant weightcom = propulsion plant specific weight =

propulsion plant weightinstalled shaft horsepowerrefore

Wm , V comA

nLD

As Mandel observed the gains in speed have been due tothe reduction in specific machinery weight rather thanimprovements in the lift to drag ratio [2]. The inferenceis that to keep the ratio of machinery weight to displacementwithin bounds the specific machinery weight must decreasewith increasing speed and rapidly decreasing lift-drag ratio.

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An indication of this effect is shown in Figure 5 for arange of effective lift-drag ratios and speeds of 45 and 30knots. Restricting the available weight fraction formachinery establishes the limits for the specific machineryweight. Conversely the range of available machinery plantssets the limits on the machinery weight fraction. Examiningthe specific machinery weight of conventional prime moversfor both displacement ships and hydrofoils shows the impactof the high horsepower density of the current generationhydrofoils.

Power Plant Type SpecificMachineryWeightMachineryWeightHL/D=10

Fraction forV = 45 kts.nL/D = 5

Steam (Destroyer)[7]Gas Turbine(Destroyer) [7]Gas Turbine(Hydrofoil)

2 6 lb/SHP

15 lb/SHP

5 lb/SHP

0.355

0.21

0.07

0.71

0.42

0.14

The impact of the power plant specific weight in the smallship range (n-pr=5) shows the necessity for lightweight powerplants. Along with the increase in the power to weightratio is an accompanying reduction in volume.

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0.1 0.2 0.3 0.4MACHINERY WEIGHT FRACTION 0.5

FIGURE 5 Machinery Weight Fraction Relationship toPropulsion Plant Specific Weight

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ft 3/SHPSteam (Destroyer) [7] 2.5Gas Turbine (Destroyer) [7] 1.5Gas Turbine (Hydrofoil) 0.75

Since volume represents containment weight, hull structure,auxiliary systems, and outfit and furnishings, the reductionin volume is in fact also a reduction in weight.

The impact of volume is apparent not only in themachinery area but throughout the ship for hydrofoils. Theweight to support a cubic foot of volume based on currenthydrofoil standards is about 4.3 pounds. 1* This is thepenalty for enclosing in structure and providing outfittingand services to a cubic foot of unused volume. Thus theemphasis is on volume as well as weight.

2.3 Hydrofoil Design Criteria and StandardsThe hydrofoil designer's motivation for weight consci-

ousness was discussed in the previous section and the impactof weight in some major areas was investigated. However,there are some areas where an effort to save weight or volumemay be quite subtle or have an unanticipated impact. Severalof these areas are intact and damage stability; systemredundancy; reliability, maintainability and availability;habitability; operating profile and margins.**Based on current hydrofoil standards of 2.5 lb/ft 3 forhull structure, 0.94 lb/ft 3 for auxiliary systems and,0.86 lb/ft 3 for outfit and furnishings.

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Damage and intact stability are an area in which thedesigner may be tempted to encroach in an effort to saveweight. In the current designs this has not occurred for thesame stability standards apply equally to hydrofoils anddisplacement ships. In the same manner the customaryredundancy in areas such as power generation; propulsionsystems and other systems affecting mobility have not beencompromised to save weight.

The requirements for reliability, maintainability,and availability are much harder to assess. The operatingprofile and the ship's maintenance concept all impact theseareas. The complexity of the foil system must be acknowledgedas a factor in the overall availability of the ship. Thetrend to make the ship compact as a whole indicates thataccess and thus, in some degree, maintainability has to becompromised.

The area of habitability offers one of the best inroadsto the reduction of volume and weight. Hydrofoils are bycurrent standards austere but reflect habitability standardswhich are by no means unacceptable. The hydrofoil designerhas in this area attempted to do more with less.

The general area of margins has hidden within it manypitfalls. Margins in weight, propulsion power, accommodations,and generator capacity can have a significant impact on thedesign particularly in a small ship. The impact of theshaft horsepower on the installed power plant and fuel

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storage capacity is significant. The variation in shafthorsepower margin by ship type, although in some casesapparently small, can be significant. The values presentedby Wilson and Lombardi [8] were used in this analysis in aneffort to be consistent with current practice. Margins inother areas were not addressed since for comparative purposesships were redesigned to a common set of standards andcriteria at the level of detail investigated.

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CHAPTER 3A COMPARATIVE ANALYSIS OF NAVAL HYDROFOILS

AND DISPLACEMENT SHIPS

The differences in design and construction betweenhydrofoils and displacement ships in areas other than themeans of sustension prevent a logical comparison of theadvantages and disadvantages inherent in these ship types.To allow a comparison to be made, the differences in theships are analyzed as they are presently constructed andthe differences in design criteria and standards are reducedto allow a side-by-side comparison.

The rationale for the ships selected for the study iscontained in Section 3.1, followed by the method of analysisand computer model in Sections 3.2 and 3.3 respectively.The comparative analysis of a small hydrofoil and a similarsize planning craft is contained in Section 3.4. A similaranalysis for a large hydrofoil and a displacement ship iscontained in Section 3.5.

3.1 Selection of ShipsThe desire to examine on an equal basis a hydrofoil and

its non-hydrofoil counterpart directly affected the shipsavailable for the study. The first criteria was that theships should be designed as combatants as opposed to testbeds for research and development purposes. This limitedthe hydrofoil population significantly. This restrictionhad two effects. The first was the imposition of the same

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warfare related standards required of a naval combatant tothe hydrofoil. The second was the elimination of a widediversity in apparent design criteria which appeared in theexamination of the hydrofoils whose initial purpose had beenas a proving ground for the technology.

Having limited the available number of hydrofoilssignificantly, it was determined that a side-by-side compar-ison of a hydrofoil and its displacement counterpart wouldyield the most useful information. The hydrofoil designsselected were then chosen for their diversity in size,performance, and mission capabilities.

At the small ship end of the spectrum, the 230 tonNATO HYDROFOIL (PHM) , a joint U.S. -NATO project, was chosen.It is a small, single mission area, gas turbine powered shipwith a small crew and limited endurance. For a larger ship,the Deepwater Escort Hydrofoil (DEH) , a product of designstudies by the Boeing Corporation and the U.S. Navy was usedA 1200 ton multimission ship with an endurance sufficientfor ocean crossings, it represents the conceptual design ofa large hydrofoil.

Having selected the hydrofoils to be examined, thecandidates for a displacement ship to use as a yardstickfor comparison were examined. To attempt to provide a one-to-one comparison of the current state-of-the-art indisplacement ship design with hydrofoil design the followingselection criteria were used:

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Similar SizeSimilar Mission Area Capabilities

Recent DesignBased on these criteria the PG-84 class of patrol boats

was selected for comparison with the PHM. A 240 ton hard-chine planning hull capable of calm water speeds of 40 knots,it provided a close match to PHM in both size and speed. Ithas the same mission capability as PHM and a similarendurance. Built in the period 1966 to 1970, the ships werethe first U.S. Naval combatants with gas turbine propulsionand aluminum hull construction. Other than a 10 yeardifference in technology, the ships are very similar

Selection of the counterpart for the DEH was not asstraightforward. There are no recent designs in the 1200ton range by the U.S. Navy. The result was the selection ofa current design with a gas turbine propulsion plant for thecomparison of current displacement ship design standardsand criteria with those of DEH. To provide a side-by-sidecomparison, a 1200 ton high speed displacement ship wasdeveloped from a standard series estimate and PG-84 designstandards.

The smallest current gas turbine design, other thanPG-84, is the new Patrol Frigate Class (FFG-7). 5 A current

5 The Patrol Frigate Class was originally designated thePF-109 class but was subsequently changed to the FFG-7class.

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design with multimission capabilities, it displacesapproximately 3500 tons. It has a large crew by hydrofoilstandards, three times the size of DEH, and a maximum speedof about 28 knots. The differences in size and speed led tothe selection of a 1200 ton series 64 hull form for the side-by-side comparison. This disparity in size and performancefor the same general mission capability provides a veryvisible indication of the impact of hydrofoil technology.The principle characteristics of PHM, PG-84, DEH and FFG-7are presented in Table 1.

The choice of ships permits not only a basis forevaluating the features which are characteristic of a rangeof ship sizes. It also provides the basis for assessingthe impact of gaining the hydrofoil's superior speed bothin calm water and in a sea state.

3.2 Method of AnalysisTo provide a basis for evaluating those areas in which

there is an apparent difference in the standards, criteriaor design philosophy between a hydrofoil and its displacementcounterpart, an analysis of the weight and volume utilizationof the two ship types was made. As a derivative of theweight and volume analysis, a collection of specificparameters was developed. The specific parameters areratios of weight, volume or other characteristics such ascrew size or shaft horsepower which give a quantitativemeasure of the ship's characteristics and design criteria.

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TABLE 1SHIP'S CHARACTERISTICS

PG-84 (19) PHM(19)Displacement(tons) 245 230Length (ft) 164.5 130Beam (ft) 23.8 29Draft (ft) 9.5 9.5Main Engines 2 Diesel/1 GT 2 Diesel/1 GT

CODAG CODAGPropulsor Propeller WaterjetSpeed (kts) 40+ 40+Range (N.M.) 600+

Complement 24 21Payload 3 /50 cal GunStandard Missileor 40MM Gun

7 6MM OTTO Melara GunHarpoon MissileMK92FCSMK87WCS

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TABLE 1 (continued)SHIP'S CHARACTERISTICS

Displacement(tons)Length (ft)Beam (ft)Draft (ft)Main Engines

PropulsorSpeed (kts)Range (nim)ComplementPayload

DEH (15)

12002004036

2 GT/2 GTCOGOG

Propeller40+

-2600 at 40+ kts82

Missile LauncherTorpedo Tubes76MM OTTO Melara GunTowed Sonar, FoilMounted SonarMK92FCS2 0MM CIWS

FFG-7 (19)

34504454524.5

2 GT

Propeller28+

4500 at 20 kts185

1-76MM OTTO Melara Gun1-Tartar MissileLauncher2-SH2D Lamps Helo2-Triple Torpedo Tubes1-20MM CIWSSQS-56 SonarMK92FCS

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The specific parameters provide a better indication of themagnitude of the difference in a selected area than weightor volume alone. They also provide the input for conceptuallyupgrading the displacement hull to hydrofoil design standards.

The weight analysis was based on the weight groupings ofthe Ship Work Breakdown Structure System Classification [9]

.

The weight groups and their definitions as used in thisanalysis are contained in Table 2. Payload weight was usedas the figure of merit in evaluating the respective platforms.The definition of payload is therefore significant ifconsistent conclusions are to be drawn. For hydrofoilsand other high performance ships, such as surface effectships and air cushion vehicles, payload is often defined asthe variable load (fuel, personnel, stores, water, ammunitionand aircraft) , Armament (Weight Group 7) and Command andSurveilance (Weight Group 4). This may be a valid conceptwhen comparing similar high performance vehicles. However,when comparing these high performance ships with ships out-side that category, a more restrictive definition of payloadgives a better indication of the platforms capability.Payload in the context to be used in this analysis is theportion of the ship's displacement attributable to itsprimary military mission, excluding mobility factors. Thisis normally used in the evaluation of displacement shipsand is defined as the weight groups for command and surveil-ance (Weight Group 4) and armament (Weight Group 7), and thoseitems in the variable load directly related to the military

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TABLE 2WEIGHT CLASSIFICATIONS [9]

Group 1

Group

Group 3

Group 4

Group 5

Group 6

Group 7

Loads

Hull StructureFraming, Shell Plating, Bulkheads, Decks,Deck House Structure, Masts, FoundationsPropulsion PlantPrime Movers, Transmission Systems, Propulsors,Propulsion Support Systems (Fuel Oil & Lube Oil)Electric PlantPower Generation Systems, Power Distribution

Systems, Lighting System, Power GenerationSupport SystemsCommand and SurveilanceCommand & Control Systems, Navigation Systems,Exterior Communications, Surface & SubsurfaceSensors, Countermeasures, Fire Control SystemsAuxiliary SystemsHeating, Ventilation & Air Conditioning Systems,Seawater Systems, Freshwater Systems, Anchor,Mooring & Boat Handing Systems, Foil Systems &ControlsOutfit and FurnishingsNon-Structural Compartmentation, Painting,Insulation, Deck Covering, Messing, Berthing &Sanitary Facilities, Furnishings and Fixtures,Commisary Equipment, Office Furnishings,Storeroom FixturesArmamentGun Systems, Missile Launching Systems,Torpedo Launching Systems, Ammunition Stowageand Handling SystemsPersonnel - Crew and Crew's EffectsStores - Fresh, Frozen and Dry FoodstuffsGeneral Stores -Fuel Oil - For Main Propulsion, Power GenerationLubricating Oil -Potable Water -Ammunition - For Ship's Weapons

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TABLE 2 (continued)

Aircraft - Aircraft Weight OnlyAviation Stores - Repair Parts and Tools for

Aircraft MaintenanceAviation Fuel -

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mission; ammunition, aircraft, and aircraft related storesand fuel. The impact of this definition will not be overlyapparent in the data presented since the items excluded fromthe high performance ship definition are derived from thesame set of requirements for the side-by-side comparison.The variation in these components of the variable load is areflection of the platform's characteristics in response tothe requirement. An excellent example of this is fuelweight. With displacement, speed, range and prime moverfixed, the fuel weight is a direct reflection of the plat-form's hydrodynamic efficiency. For a side-by-side comparisonwith equivalency in as many areas as possible, payload weightis a good quantitative measure of the platform's merit.

Since the scope of the designs examined ranged fromcompleted ships with returned weight statements (PG-84) tofeasibility studies (DEH) , the margin provided in the weightstatements varied significantly. To place all the designson a similar basis, the weight margin was distributedequally among the seven major weight groups.

A volume analysis was conducted to assess the volumetricimpact of hydrofoil technology. The volume categoriespresented in Table 3 are derived from the proposed NavySpace Classification System [10] and give an indication ofthe major functions requiring an allocation of space.Volume fractions were used as an indication of a ship impactin areas where there was no corresponding weight impact. Thisoccurs in the areas of access, voids, storerooms and other

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TABLE 3VOLUME CLASSIFICATION [10]

Military Mission Performance (Payload Volume)Communications Detection and Evaluation SpacesWeapons Systems SpacesAviation SpacesShip Control

Ship's Personnel (Personnel Volume)Living Spaces - Berthing, Messing, and SanitarySupporting Functions - Administrative, Food Preparation,Medical and Personnel ServicesStowage - Stores and Provisions Storerooms and PotableWater Tankage

Ship OperationMain Propulsion Machinery Spaces - (Machinery Box Volume)Main Propulsion Machinery and Auxiliaries, ElectricalPower GeneratorsAuxiliary Systems and Equipment - External to theMachinery Box (Auxiliary Systems Volume)Steering Systems, Ventilation Systems, DeckAuxiliariesStowageEndurance Fuel Oil (Fuel Volume)Stores and Supplies (Stores Volume)TankageBallast Tanks, VoidsPassageways and Access (Access Volume)

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service type spaces such as steering gear rooms, fanrooms, and deck machinery spaces.

To provide an indication of relative performance ina selected area, a set of specific parameters was developed.These parameters serve a twofold purpose. They are a moredirectly applicable quantitative measure of performance thanweight, volume, weight fraction or volume fraction. Theyprovide the basis for changing the design standards andcriteria in a conceptual redesign. The selection of theparameters was in many cases based on the weight estimatingcorrelations from Section 6 of Weight Control of Naval Ships,Volume 1 [11]. The selection of the volume parameters wasbased on a logical correlation between the volume requirementand the prime utilization of the space. The parametersselected and the definition of the parameters and terms usedare contained in Table 4

.

3.3 Computer ModelThe computer model was developed to permit an investiga-

tion of the impact of hydrofoil design criteria and standardson a displacement hull form and to give an indication of thesensitivity of the figure of merit to the variation indesign criteria and standards. The model was developed tobe a tool to provide comparisons between ships with knownparameters such as size, speed, shaft horsepower, and crewsize. Therefore, it is not a synthesis model and does notcheck for feasibility in areas other than weight and volume.

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ParameterVehicleDensityStructuralDensityPropulsionPlantSpecificWeightSpecificMachineryVolumePayloadDensityElectricalSystemSpecificWeightSpecificPersonnelVolumeArrangementVolumeFraction

AuxiliarySystemsVolumeFractionStoresVolumeFractionOutfit &FurnishingDensityAuxiliarySystemDensity

TABLE 4SPECIFIC PARAMETERS

Definition UnitsFull Load Weight/Total Enclosed Volume lb/ft 3

Hull Structural Weight (GP1)/ Total lb/ft 3Enclosed VolumePropulsion Plant Weight (GP2)/ lb/SHPPropulsion Shaft Horsepower

Machinery Box Volume/Installed ft 3/SHPPropulsion Horsepower

Payload Weight/Payload Volume lb/ft 3

Electrical Plant Weight (GP-3)/ lb/KWInstalled KW of Generator Capacity

Total Personnel Volume/Crew Size ft 3/MAN

Arrangement Volume/Total EnclosedVolume

Auxiliary System Volume/TotalEnclosed Volume

Stores Volume/Total Enclosed Volume

Outfit & Furnishing Weight (GP-6)/ lb/ft 3Total Enclosed Volume

Auxiliary System Weight (GP-5)/ lb/ftTotal Enclosed Volume

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3.3.1 Objective of the Computer ModelThe objective of the computer model was to reduce the

differences in design criteria and standards that existbetween hydrofoils and displacement ships. The intent wasto enable a comparison of ships with similar characteristicsin all areas except the hull type.

Since the sensitivity of the hydrofoil to designchanges prohibited the redesign of the hydrofoil down todisplacement ship standards. The more logical alternativeof designing the displacement ship up to hydrofoil standardswas undertaken. With this approach the impact of the hydro-foil's design criteria would be reflected in a change in thefigure of merit.

A secondary objective of the computer model was totest the sensitivity of the figure of merit to changes inthe design parameters both individually and collectively.This provides an indication of the relative importance ofthe design parameters. It also provides an indication ofthe range of parameters for which the conclusions are valid.

3.3.2 Description of the Computer ModelThe model was designed for analysis rather than

synthesis. It therefore utilizes a fixed ship size and typeand balances weight and volume to produce a balanced ship inthese two areas. The model is an itterative series ofweight and volume calculations based on a fixed displacementThe input to the model is the performance parameters of the

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hydrofoil with which the comparison is to be made. Theseare maximum speed in calm water, range at maximum speed incalm water, crew size, stores endurance period, and installedelectrical generation capacity. After providing the weightand volume necessary to support the functions required tomeet these performance requirements, the difference betweenthe weight utilized and the initial displacement is payload,the figure of merit. The sizing of the weights and volumesis based on the specific parameters from the analysis of thehydrofoil used in the comparison. This results in the up-grading of the displacement hull's standards.

The significant difference between the hull forms otherthan the foil system is the speed-power relationship. Sincethe displacement and speed are known, the required shafthorsepower for the maximum speed is also known from acharacteristic speed-power curve for the displacement hullform. This is used as an input to the program. Thecharacteristics of the prime mover also have an impact onthe model. For the hydrofoils involved, the prime moverwas the General Electric LM2500. The assumption was madethat the upgraded displacement ship would have the sameprime mover and thus the same specific fuel comsumptionrate characteristics.

3.3.2.1 Weight AlgorithmThe weight algorithm balances the specified dis-

placement with the categories of weight utilization otherthan payload. The weight which remains after all the

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containment, mobility, personnel and other miscellaneousweight demands are met is the weight available for payload.

The weight algorithm has three sections which areeffectively independent of each other relying solely on theperformance parameters and specific parameters for therespective area. The weights associated with containment,Group 1 (Hull Weight) , Group 5 (Auxiliary Weight) and Group 6(Outfit and Furnishings) are the only groups which arevolume dependent and as such are affected by the volumealgorithm. The prediction of these three weight groups isbased on an assumed volume and the respective specificparameter for the weight group. For the initial itteration,the volume is estimated from the displacement and vehicledensity. On later itterations it is estimated from thevolume algorithm.

The propulsion machinery weight, Group 2, and FuelWeight are computed from the inputs of required shaft-horse-power at maximum speed, shaft horsepower margin, the maximumspeed, and the range at the maximum speed. Closelyassociated with these weights is the electrical systemweight, Group 3, and the required fuel for its prime movers.The propulsion machinery weight is estimated from thepropulsion machinery specific density (lb/SHP) . Similarlythe electrical system weight is estimated from its specificdensity (lb/KW) . The fuel weight, however, is a function ofseveral variables, shaft horsepower, range, speed, electricalplant size, and specific fuel consumption rates. The weight

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of fuel is estimated in two parts. The fuel weight for theelectrical plant is estimated from the installed electricalgenerator capacity, the prime mover's assumed specific fuelconsumption rate, and the estimated length of operationbased on time at full speed. 6

Wf = [Hf X X * 34 H x SFCA x (^) ]/2240where

Wf = electrical plant fuel weightSFCA = electric plant prime mover specific fuelconsumption rateKW = installed generator capacityEFF = assumed generator efficiencyR = range at maximum speedV = maximum speed

The fuel estimate is conservative since it is based oninstalled generator capacity rather than the actualelectrical loads.

The propulsion plant fuel weight is predicted in aslightly different manner. In ships which have relatively

6Although this is the best case for the electric plantfuel, it is the worst case for the total fuel load. Theelectric plant fuel load would be a greater fraction ofthe total fuel load at a lower speed, e.g., the hullborneendurance speed for a hydrofoil. Due to the large fuelfraction required for the high speed endurance, theavailable hullborne endurance normally exceeds the requiredendurance even with the longer period of generator operation

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large fuel fractions the Brequet range equation is used. Itaccounts for the reduction in displacement and attendantreduction in required shaft horsepower as fuel is consumed.This reduction is presented as an increase in range since alower power requirement also implies a lower rate of fuelconsumption. The Brequet range equation reflects these facts

2240 , AV X , , A ,RB = SPC ( SHP ) ln (A=W^

WhereRB = Brequet RangeSFC = Propulsion Prime Mover Specific Fuel ConsumptionRateA = Displacement Full LoadV = Maximum SpeedSHP = Required Shaft Horsepower at Maximum Speed WithSHP MarginWf = Propulsion Fuel Weight

The difference between the range predicted by the Brequetequation and the standard range prediction without accountingfor fuel burnoff is significant. As shown in Figure 6, at afuel fraction of 25% the Brequet range is 15% greater. Thishas a definite effect on the predictions of the model. Thetotal fuel weight is then the sum of the propulsion andelectrical plant fuel weights with an appropriate tailpipeallowance.

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oz 1.3i-o StiAfir tJo*tPoue/L

l0 ,-20 -|0 +10 +20PERCENTAGE VARIATION OF PARAMETERFROM BASELINE VALUE

FIGURE 14 Sensitivity Analysis of Upgraded PG-84 toSingle Parameter Changes

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consumption rate, structural density, propulsion plantspecific weight, specific personnel volume and payloaddensity were all varied in one percent increments of theoriginal value. All the parameters except those sixselected were held constant at the original value. Theresults of this analysis are shown in Figure 15. Thisanalysis indicates that a 5% variation in these six majorparameters still results in a payload fraction greaterthan PHM. Thus with a 5% error in the estimates for theseparameters the redesigned PG-84 would still have a largerpayload.

3.4.5 Summary of the Analysis of PG-84 and PHMThe comparison of PG-84 and PHM point out differences

in several design areas. The areas of greatest apparentdifference are propulsion plant weight and volume, personnelvolume, and arrangements and access volume. In all theseareas PHM showed a marked advantage. There was a lesserbut yet significant difference in the areas of hull structuralweight and electrical system weight. The net result was theaccommodation of the foil system without an adverse effecron payload carrying capability.

To determine the cost of the foil system in terms ofpayload carrying capability, the PG-84 was conceptuallyredesigned to the same performance requirements, criteriaand standards as PHM. The only significant differencebetween the two is the hull form and foil system and thus

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PAYLOADWEIGHTFRICTION

+ 5 +10 -H5EQUAL PERCENTAGE CHANGE OF SIX MAJOR PARAMETERSFROM THE BASELINE UPGRADED PG-81* VALUES (%)

FIGURE 15 Sensitivity Analysis of Upgraded PG-84 toMultiple Parameter Changes

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the propulsive power requirement. The comparison was thenmade based on the weight of payload carried as the figure ofmerit. The results of the comparison of PHM and the redesignedPG-84 are summarized below.

PG-84 (redesigned) is capable of carrying 42 percentor 13.5 tons more payload than PHM. However, afraction of the additional payload weight may berequired to provide additional payload support suchas electrical power or air-conditioning.

The redesigned PG-84 is required to reduce speedfrom its maximum speed at approximately sea state 3to avoid excessive accelerations. PHM can maintainits maximum speed through sea state 5 and probablyinto sea state 6.

The redeisgned PG-84 requires more fuel to cover thesame endurance range at high speed due to its poorhydrodynamic efficiency compared to the hydrofoil.

This demonstrates the tradeoff between seakeeping ability asmanifested by the ability to maintain speed in the highersea states and the ability to carry payload. For the smallship case there is no obvious best. The selection must bepredicted on the ship's operating profile and area ofintended operations.

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3.5 A Comparative Analysis of A Large Hydrofoil and ADisplacement Ship

3.5.1 Analysis of DEH and FFG-7Unlike the comparison of PHM and PG-84, there are

significant differences in both size, a factor of three,and speed, a factor of two, between DEH and FFG-7. Althoughthis makes comparison of some features of questionablesignificance, it still lends insight into the wide gulfbetween the conventional surface combatant and a hydrofoilwith the same relative mission capabilities.

The overhead involved with the foil system is not asreadily judged due to the differences in size. The impactof the DEH's speed and endurance is much more apparent. Theanalysis of the two designs was conducted using the methodsdescribed in Section 3.2. The results of this analysis arecontained in Figures 16 to 19.

3.5.2 Comparison of DEH and FFG-7An inspection of the weight and volume utilization on

DEH and FFG-7 shows the marked difference between a displace-ment ship and a hydrofoil. Examining the relative weightsand volumes, the differences in size and speed must beconsidered. Although the mission areas are the same and thecapabilities are very similar, the effects of size and speedtend to bias the relative magnitudes in both the weight andvolume analyses.

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100

FOILS17.056

x

11.756

8.15680 k.2%

U.7561.2%7.9\M$.6%

37.8

60 _^6 ^ ^%

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AUXILLARI SYSTEMS

OUTFIT & FURNISHINGELECTRICAL SYSTEMPROPULSION MACHINERY

HULL STRUCTURE

PERSONNEL

FUEL

PAYLOAD

DEH FFG-7

FIGURE 16 DEH - FFG-7 Comparative Weight Fraction Analysis

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100-

80-

60-

VOLBME(*)

20-

3*0*8.0*k.o%

32.1%

21.0


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17.8 15.5

DEH FFG-7VEHICLE DENSITY (lb/ft3 )

5.72.6

DEH FFG-7HULL STRUCTURAL DENSITY

(lb/ft3 )

1lwU

3.3DEH FFG-7PROPULSION PLANT SPECIFIC

WEIGHT (lb/SHP)

1.U5.0

DEH FFG-7MACHINERY BOX SPECIFIC

VOLUME (ft3/SHP)

FIGURE 18 DEH - FFG-7 Specific Parameters

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The measure of effectiveness, payload weight is mostrevealing. DEH has a larger payload weight fraction thanFFG-7 with about the same volume fraction. The weightdifference is not disputable, for DEH has a significantnumber of weapons systems which are by necessity compact.FFG-7 has many of the same or similar weapons systems butalso has a large volume requirement imposed by twohelicopters. DEH is still significantly better in terms ofthe measure of effectiveness. It should be noted that atwelve percent payload fraction is representative of manyof the more recent displacement ship designs and thus FFG-7rather than DEH is a variation from the norm [16],

The effect of speed appears in two areas. The fuelvolume is a direct indication of the DEH's requirement forhigh speed. The large weight fraction alloted to fuel, 33%,reflects the requirement for both high speed and a longendurance range at high speeds. FFG-7 with a much lowerspeed requirement but longer endurance results in a lowerfuel fraction. The other area which speed impacts ispropulsion machinery. The machinery weight fraction forboth ships is small reflecting the impact of gas turbines.Examining the propulsion plant specific weight, however,shows that there is a significant difference. The impacton DEH is more apparent in the volume analysis where about33% of the total volume is propulsion machinery, electricalgenerators, and propulsion auxiliaries. The other point of

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interest is both ships have identical main propulsion primemovers and are fitted with propellers as propulsors ratherthan having a waterjet for the hydrofoil. The propulsioncomparison can be summarized as follows:

Propulsion WeightFractionMachinery VolumeFractionPropulsion PlantSpecific WeightMachinery BoxSpecific Volume

DEH

5.6%

32.7%

3.3 lb/SHP

FFG-7

7.3%

11.3%

14.4 lb/SHP (e)

1.0 ft 3 /SHP 1.45 ft 3/SHP

Examining the other weight groups shows the trends whichwere also apparent in the comparison of PHM and PG-84 inSection 3.4.2. There is again a marked reduction in both theweight fraction and specific weight in the areas of outfitand furnishings and auxiliary systems.

8 The factor of 4 difference in propulsion plant specificweight is an area of major impact at the horsepower levelsrequired by these ships (50,000 SHP) . The areas of weightsaving are numerous including lightweight reduction gearsand shafting, less sound isolation, and shorter lengthsof intake and exhaust ducting.

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DEH FFG-7Outfit & FurnishingWeight FractionOutfit & FurnishingDensityAuxiliary SystemWeight FractionAuxiliary SystemsDensity

4.2'

0.74 lb/ft

4.2%

0.70 lb/ft

8.0%

1.2 lb/ft

11.6%

1.75 lb/ft

Unlike the comparison of PHM and PG-84 in Section 3.4.2,there is a significant difference in the structural areabeyond the state of the art in lightweight structural design.FFG-7 with a steel hull and aluminum deckhouse is signifi-cantly heavier than the all aluminum DEH. This is reflectedin both the weight fraction and structural density.

Structural WeightFractionStructural Density

DEH

16.7'2.6 lb/ft

FFG-7

37%5.7 lb/ft 3

The very high structural weight fraction again reflects thecost of excessive volume. For most destroyer designs thestructural weight fraction is in the range of 26 to 32%(see Figure 4, Section 2.2). This impact cannot be over-looked if a high speed displacement hull is desired.

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The effect of size and more importantly volume isreflected in many areas. The first indication is vehicledensity.

Vehicle DensityDEH17.8 lb/ft 3

FFG-715.5 lb/ft 3

A large amount of unproductive space is the first indicationof the cause for the low vehicle density in FFG-7. Access,voids and tankage, and store's volume in FFG-7 all contributeto the low vehicle density as well as the large hangarrequired for the relatively light helicopter. This largelyunderutilized space is too costly to be allowed on a hydro-foil where volume carries with it a more significant weightpenalty. Similarly, the volume provided for the crew carriesa weight penalty and thus the hydrofoil reflects the impactof this volume in its specific personnel volume.

DEH FFG-7Specific PersonnelVolume 400 ft 3 /man 593 ft 3 /man

The cost of volume can be illustrated by assuming areduction in personnel' volume standards on FFG-7 to thestandards of DEH while making no changes in any of FFG-7 'sother design criteria. The net change in volume of

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200 ft 3 /man for the 185 man crew results in a 143 ton changein displacement or an equilvalent addition of payload assumingno additional payload volume is required. For FFG-7 thisrepresents approximately a 50% increase in payload weight.

The differences which might have been attributed to adifferent operating profile in the case of PHM and PG-84 arenot truly present here. Both ships are designed for longopen ocean transits and to be self-sustaining over extendedperiods of time. The significant differences other thansize and speed and their ramafications have been pointed outin this section. The result appears to be a smaller, fastership which has the same mission capabilities as a ship threetimes its size and half its speed. The overhead of the foilsystem appears to be well justified and has given the shipsignificant capabilities.

3.5.3 Redesign of A Displacement Hull Form to DEHStandards

The redesign of the FFG-7 was attempted with thecomputer model to provide an indication of the impact hydro-foil design standards would have on a displacement hull form.The FFG-7 *s original parameters and the ones used to upgradethe standards to hydrofoil standards are contained in Table 7.The model was used to predict two ships. The first was anFFG-7 with DEH's payload fraction searching for the maximumspeed. The second was a ship with FFG-7 's speed and searchingfor the payload fraction. The results are presented graphicallyin Figure 20.

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TABLE 7PERFORMANCE REQUIREMENTS AND PARAMETERS FOR UPGRADED FFG-7

DEH FFG-7 FFG-7 toDEH StandardsDisplacementMaximum SpeedRange at Maximum SpeedSHPAssumed Propulsion SFCGenerator CapacityAssumed Generator SFCCrew SizeStore's EnduranceVehicle DensityStructural DensityAuxiliary Systems DensityOutfit & Furnishing DensityPropulsion Plant Specific Wt.SHP MarginElectrical System Specific Wt. 61.5Machinery Box Specific Vol.Specific Personnel VolumeArrangements Volume FractionAuxiliary Systems VolumeFractionStore's Volume FractionPayload Density

1220 3450 3450~45 28.5 --2600 ~2000 260040,000 -32,000 0.43 [13] 0.43[13] 0.43 [13]1500 2000 20000.5 0.5 0.582 185 18545 45 4517.8 15.5 --2.6 5.7 2.60.70 1.75 0.700.74 1.2 0.743.3 14.4 3.3-- 1.25 1.2561.5 125 61.51.0 1.45 1.0400 593 4000.08 0.22 0.080.04 0.17 0.040.03 0.02 0.0311.7 11.7

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FOILS17.0*

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?7f%

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V=39 Kts V=28 Kts V=28 KtsSHP=1 1*0,000 SHP=li0,000 SHP=l40,000%mh%6.0$9.0*

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9.5*FFG-7 to FFG-7 to FFG-7DEH standards DEH standardsfor maximum for maxiirainspeed payload

AUXILLARYSYSTEMSOUTFIT &FURNISHINGSELECTRICALPROPULSIONMACHINERY

HULLSTRUCTURE

PERSONNEL

FUEL

PAYLOAD

FIGURE 2 Upgraded FFG-7 Comparisons

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For the first case the maximum speed was estimated atabout 39 knots with 140,000 shaft horsepower required. Inthe second case the resultant payload was about 1445 tons or42 percent of full load displacement. These results arenot intended to be accepted as feasible designs. They do,however, show the significant impact which hydrofoil tech-nology could have on the conventional displacement ship.

To provide a side-by-side comparison, a poweringestimate for a 1200 ton series 64 hull form was made. Thisestimate is contained in Appendix B. From the estimate of50,000 shaft horsepower for a 1200 ton ship at 45 knots, aship was conceptually designed to DEH standards. The inputsto the computer model for this analysis are shown in Table 8and the results in Figures 21 and 22 and Table 9. Again theonly major area of difference is fuel weight. This mayreflect the conservatism in the selection of shaft horsepowerrequired for maximum speed and specific fuel consumption rate.If this is the case a smaller required fuel weight would bealmost directly transferable to payload.

Even with the large difference in required fuel theSeries 64 hull form has a larger payload fraction and asizeable increase in payload.

Payload Weight Fraction Payload Weight (tons)DEH 0.131 160SERIES 64 0.159 191

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TABLE 8PERFORMANCE REQUIREMENTS AND PARAMETERS FOR

SERIES 64 HULL FORM

DisplacementMaximum SpeedRange at Maximum SpeedSHPAssumed Propulsion SFCGenerator CapacityAssumed Generator SFCCrew SizeStore's EnduranceVehicle DensityStructural DensityAuxiliary Systems DensityOutfit & Furnishing DensityPropulsion Plant Specific WeightSHP MarginElectrical System Specific Wt.Machinery Box Specific VolumeSpecific Personnel VolumeArrangement Volume FractionAuxiliary Systems Volume FractionStore's Volume FractionPayload Density

DEH SERIES 641220 1200~45 452600 2600-40,000 50,000*-0.43 [13] 0.43 [13]1500 KW 1500 KW0.5 0.582 8245 4517.8 17.82.6 2.60.7 0.70.74 0.743.3 3.3-- 1.125[8]61.5 61.51.0 1.0400 4000.08 0.080.04 0.040.03 0.0311.7 11.7

*SHP estimate contained in Appendix B.

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WEIGHTS

TABLE 9SERIES 64 WEIGHT AND VOLUME ESTIMATE

Group 1Group 2Group 3Group 5Group 6PayloadPersonnelStoresFuelDisplacement

Weight (tons)210.8173.6641.1856.7660.00

191.0010.9813.18

542.431200.00

Weight Fraction0.1760.0610.0340.0470.0500.1590.0090.0110.452

VOLUMES

Machinery Box VolumeAuxiliary Systems VolumeAccess VolumePayload VolumePersonnel VolumeStore's VolumeFuel VolumeTotal Volume

Volume Vol urn(Cubic Feet)56250 0.317265 0.04

14530 0.0837712 0.20832800 0.1815449 0.030

27615 0.152181620

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FOILS17.0*

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AUXILLARI SYSTEMSOUTFIT & FURNISHINGSELECTRICAL SYSTEMPROPULSION MACHINERY

HULL STRUCTURE

PERSONNEL

FUEL

PAYLOAD

DEH SERIES 6U

FIGURE 21 Comparative Weight Fractions for Series 64 and DEH

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1w 15.1 15.0

80-

60- 32.7 31.0

VOLDME

18.1UO- 21.3 15.2on 10.9n

20.0 208

AUXILIARY SYSTEMSACCESS & STORES

MACHINERY

PERSONNEL

FUEL

PAYLOAD

DEH SERIES 6U

FIGURE 22 Comparative Volume Fractions for Series 64 and DEH

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Although the increase in the payload weight fraction is lessthan that experienced with the PG-84 case, 21 percent asopposed to 42 percent for PG-84, the net increase of 31 tonsof payload is substantial.

The other important aspect of the large fuel fractionis the endurance at lower speeds. The large fuel fractionfor the Series 64 results in an endurance at 20 kts. inexcess of 5000 N.M. 9 This is about 1000 N.M. greater endurancethan estimated for DEH at 19 kts. [15] .

3.5.4 Sensitivity Analysis of the High SpeedDisplacement Hull Form

The large fuel fraction for the Series 64 hull formraised questions on the sensitivity of the figure of meritto small changes in the propulsion plant characteristics atthe high speeds and long endurance ranges required of thisship. To give some indication of the effect required shafthorsepower and specific fuel consumption rate have on thepayload fraction, a sensitivity analysis was made with thecomputer model for these two parameters. The results ofthe analysis are shown in Figure 23.

9 Based on the horsepower estimate in Appendix B of 7000 SHPat 20 kts. and a steady 1200 KW electrical load resulting inapproximately an additional 2000 hp, the maximum range isabout 5100 N.M. using a 0.5 all purpose fuel rate.

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A decrease in required shaft horsepower of 10 percentresults in a 20 percent improvement in payload fraction anda reduction of the fuel fraction to 42 percent. A similar10 percent decrease in specific fuel consumption rate resultsin a 13.7 percent increase in payload fraction.

The combined result of changing both the required shafthorsepower and the specific fuel consumption rate by 10 per-cent is a 31 percent increase in payload fraction. In thiscase the fuel fraction is 38.9 percent which is similar toDEH which is expected for ships with approximately thesame lift-drag ratio at this speed.

3.5.5 Summary of the Analysis of DEH and FFG-7The size difference between DEH and FFG-7 overshadowed

much of the comparison of the two ships. It did point outthe wide variance between displacement ship standards andhydrofoil standards, but it would not permit a side-by-sidecomparison. To provide a side-by-side comparison a 1200 tonSeries 64 hull form was used to provide a powering estimate.Utilizing this as an input, a 1200 ton displacement ship wasconceptually designed for the comparison.

The impact of hydrofoil technology on a large displace-ment ship was assessed by examining the payload fraction ormaximum speed arrived at by designing FFG-7 to DEH standards.The results were a 28 knot destroyer with a 42 percent pay-load weight fraction or a 39 knot destroyer with a 12 percent

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payload weight fraction. Neither case was examined forfeasibility. They do demonstrate the extent of the impactof advanced technology applied to displacement ship design.

The comparison of DEH and the Series 64 hull formpresented the cost of the foil system in terms of availablepayload for two ships of the same size. The Series 64 hullform designed to DEH standards has a greater payload carryingcapacity than DEH. The 31 ton gain in payload capacity andgreater endurance at low speeds for the Series 64 must againbe traded-off against the superior performance of DEH in aseaway.

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The impact of hydrofoil design criteria on displacementships shows the marked potential for improvement which isavailable from hydrofoil technology. The capabilities ofa small, fast, displacement ship such as the Series 64 hullform designed to hydrofoil standards exceeds the capabilitiesof many of the larger surface combatants.

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CHAPTER 5RECOMMENDATIONS

The following areas are recommended for further study.(1) The examination of other high performance vehicles

(SES, SWATH, ACV) in the same manner to evaluatethe potentials of the vehicles and the areas ofdesign innovation.

(2) A detailed study of the feasibility of a small,2000 ton or less, displacement ship for moderatespeeds, 40 knots, using hydrofoil design criteriaand standards.

(3) A cost estimate for the redesigned displacementships to indicate the cost implications of theapplication of high performance design standards.

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REFERENCES

1. Jewel, David A. Hybrid Fluid-Media Vehicles , NavalShip Research and Development Center Report No. 4247,August, 1973.

2. Mandel, P. A Comparative Evaluation of Naval ShipTypes , S.N.A.M.E. Transactions, Vol. 70, 1962.3. Taggart, R. , Hoyt, E.D. and Hawkins, S., PerformanceCriteria for Hydrofoil Craft , Robert Taggart Inc.Report No. 32301, April, 1971.4. Hoerner, S.F., Consideration of Size-Speed-Power in

Hydrofoil Craft , Gibbs and Cox Inc., Report 14131/S1/1(1-502), November, 1958.5. Heller, S.R. and Clark, D.J., The Outlook for LighterStructures in High Performance Marine Vehicles ,

MasUnz Technology, Vol. 11, No. 4, October, 1974.6. Altenburg, C.J. and Scott, R.J., Design Considerationsfor Aluminum Hull Structures , Ship Structure CommitteeReport No. 218, 1971, AD729021.7. Miller, R.T., Long, C.L. and Reitz, S., ASW SurfaceShip of the ' 80's' Study , Naval EnqlnzoAU Jou&nal,Vol. 84, No. 6, December, 1972.8. Wilson, W.B. and Lombardi , P.V., Interim Procedure forThe Calculation of High Performance Ship EnduranceFuel Requirements , Naval Ship Engineering Center,January, 1974.9. Naval Ship Systems Command, Skip Wotik Breakdown St/uictuAz,NAVSHIPS 0900-039-9010, March, 1973.10. Naval Ship Engineering Center, Proposed U.S. Navy ShipSpace Classification Manual , December, 1969.11. Bureau of Ships, WeMjht Con&iol ol Naval Skip6 Vu/Ung tha

VoXoaJL VeAlgn and Con6t/iucJxon ?&u.od, Volume. 7, NAVSHIPS329-0031.12. Lundgaard, B. and Mathers, H.M., PGM-84 Class AluminumGunboat Machinery and Controls , Paper No. 67-357,A1AA/SNAME Advanced Marine Vehicles Meeting, Norfolk,

VA, May, 1967.

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13. Basile, N. , Propulsion System Lecture Notes, ProfessionalSummer at M.I.T. , July, 1974.14. Savitsky, D. , On the Seakeeping of Planning Hulls ,

Marine Technology, Vol. 5, No. 2, April, 1968.15. Aroner, R. and Hubbard, R.M. , DEH, A High EnduranceEscort Hydrofoil for the Fleet , Paper #74-311, AIAA/SNAME Advanced Marine Vehicles Conference, San Diego,Calif., February, 1974.16. Grostick, J.L., Ship Mission Systems Analysis ,Comparative Naval Architecture (13.71), MIT,December, 1974.17. Yeh, Hugh Y.H., Series 64 Resistance Experiments onHigh-Speed Displacement Forms , Ua/U.ne TechnologyVol. 2, No. 3, July, 1965.18. Final Weight Report, PG-88 Series Patrol Boats ,Tacoma Boatbuilding Co. Inc., 10 November 1967.19. Moore, John E. , land, Fighting Shlpi> 1974-1975, McDonald and

Co. (Publishers) Ltd., London, England, 1974.20. Mandel, P., WateA, KiA and lnteA.io.cc Vehicle*, NationalScience Foundation Sea Grant Project GH-1. MassachusettsInstitute of Technology, MIT Press, Cambridge,Massachusetts, 1969.21. Schaffer, R.L., Veepwaten. Ebcoit HyaAofiott [VEH) Skip Vive

Conceptual VtelgnA (C), NAVSEC Report 6114-74-16,February, 1974.22. Patrol Frigate PF-109 Class Allocated Baseline WeightEstimate , Naval Ship Engineering Center, Departmentof the Navy, Washington, D.C., April, 1973.23. Hubble, E. Nadine, Resistance of Hard-Chine, SteplessPlanning Craft with Systematic Variation of Hull Form,Longitudinal Center of Gravity and Loading , NavalShip Research and Development Center Report 4307,April, 1974.24. Blount, D.L. and Fox, D.L., Small Craft Power Prediction ,Paper presented to Western Gulf Section, Society ofNaval Architects and Marine Engineers, 14 February 1975.

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APPENDIX ASHIP DATA

Weights, volumes and other information used for theanalysis of the ships in Section 3 are presented forreference in this section.

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TABLE A-lPG-84 WEIGHT AND VOLUME DATA

Weight Summary [18]Tons

GP1 66.6GP2 46.9GP3 8.7GP4 8.0GP5 20.6GP6 24.2GP7 13.2Light Ship Displacement 188.2

LoadsFuel 36.14Ammo 8.25Personnel (includingstores) 6.89Misc. 2.39Full Load Displacement 241.87

Volume Summary

Machinery Box VolumeAuxiliary Systems VolumeAccess VolumePayload VolumePersonnel VolumeStores VolumeFuel VolumeTotal Volume

Cubic Feet13,3201,2185,6827,093

11,9612,7122,416

44,403

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TABLE A-l (continued)

Additional DataCrew Size

Total InstalledHorsepowerInstalled KW ofGenerator Capacity

24(3 officers, 2 cpo ' s , 19 enlisted)14,750 HP200 KW

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Weight Summary [5]

TABLE A-PHM WEIGHT AND VOLUME DATA

TonsGP1 46.1GP2 36.2GP3 9.2GP4 10.5GP5 48.3GP6 16.0GP7 10.3Light Ship Displacement 176.6

LoadsFuel 41.3Ammo 10.7Personnel (includingstores) 2.71Full Load Displacement 231.3

Volume Summary Cubic FeetMachinery Box Volume 12,550Auxiliary Systems Volume 547Access Volume

comparative analysis of naval hydrofoil and dispacement ship design_john larsen grostick

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