Yard Patrol From 108' Concept to Delivery

ROGER H. COMPTON, HOWARD A. CHATTERTON, GORDON HATCHELL & FRANK K. McGRATH

THE U S . NA VAL ACADEMY’S NEW YARD PATROL CRAFT:

FROM CONCEPT TO DELIVERY 1 r This paper was delivered at the Flagship Section Patrol Boat Symposium 13-14 March 1986, Arlington, Virginia

L

THE AUTHORS

Roger H. Compton is a Webb graduate who, since 1966, has been a part of the naval architecture faculty at the U.S. Naval Academy. Since accepting the appointment to the Academy, he has been instrumental in establishing the ABET accredited major program in naval architecture, in the conceptual design and operation of the Naval Academy Hydromechanics Lab- oratory, and in the conceptual design of the 10s-ft yard patrol craft. Besides hi3 Naval Academy involvement, he serves as an adjunct professor with Virginia Polytechnic Institute in its N A VSEA Institute graduate program at Crystal City. He is an active member of both ASNE and SNAME and has published technical papers with both societies.

Howard A. Chatterton began his career as a Navy coop student at the Boston Naval Shipyard in 1960. He received his bachelor’s degree in naval architecture and marine engineering from Massachusetts Institute of Technology in 1966, and his master’s degree in 1968.

He was employed by the Preliminary Design Division of BuShips in the submarine design and hydrofoil design groups until 1972, when he joined the Coast Guard’s Naval Engi- neering Division. He remained with the Design Branch until 1981, when he accepted a faculty position at the U.S. Naval Academy as the research director for the Academy’s hydromechanics laboratory.

He has recently returned to Coast Guard Headquarters as the assistant chieJ Naval Architecture Branch, Office of Merchant Marine Safety.

Gordon HatcheU is a naval architect at the Naval Sea Combat Systems Engineering Station, Norfolk, Virginia in the Com- batant Craft Engineering Department. He served as lead-ship YP project engineer from its inception to delivery and con- tinues to serve as project coordinator on follow-up ship procurements. He has worked on other boat procurements as well as serving as weight and stability coordinator. Mr. Hatchell began his engineering career in the Design Division at the Nor- folk Naval Shipyard in Portsmouth, Virginia after receiving a BS in civil engineering from Virginia Polytechnic Institute and State University. He is a member of ASNE and SNAME.

Frank K. McGrath holds a bachelor of science degree in naval architecture and marine engineering from the University of Michigan, 1964: He subsequently served on active duty in the U.S. Navy. for thirteen years as an engineering duty officer. During this period, he received a master of science degree in mechanical engineering from the Naval Postgraduate School, 1972, specializing in fluid dynamics. While in the Navy, Mr. McGrath served in various commands ashore at naval ship- yards, supervisor of shipbuilding and fleet stafJ He has had sea duty as main propulsion officer aboard the U.S.S. John F. Kennedy (CV-67). Subsequent to his naval duty, Mr. McGrath has been employed at Peterson Builders, Inc. as chief engineer and program manager, directing the detailed design of the

PGGJI I class aluminum gunboats, ARS-50 class steel rescue/ salvage vessels, the MCM-I class wooden mine countermea- sures ships and the YP-676 class patrol boats for the Naval Academy.

ABSTRACT

The design of the new 108-ft yard patrol craft (YPs) for the U.S. Naval Academy is described from its beginnings as a senior midshipman design project, through its preliminary and contract design development at the U.S. Navy’s small craft design team headquarters, Naval Sea Combat Systems Engineering Station, Norfolk, Virginia (NAVSEACOMBAT- SYSENGSTA-Norfolk). During preliminary and contract design the Naval Academy Hydromechanics Laboratory (NAHL) provided experimental data to support NAVSEA- COMBATSYSENGSTA-Norfolk’s design analyses in powering, seakeeping, and maneuvering. Several tradeoff studies of interest to patrol craft designers are presented. Major events in the detail design and construction of the first boat are described from both the designer’s and the shipbuilder’s points of view. The launching, builder’s and sea trials of the first boat are described. A modification to provide an oceanographic research capability for the Academy’s Oceanography Depart- ment is outlined. The model data acquired at NAHL and the full scale data acquired during sea trials provide an unusual opportunity for correlation analyses for small patrol craft.

INTRODUCTION

A n important and unique aspect of the U.S. Naval Academy’s mission “to prepare midshipmen morally, mentally, and physically to be professional officers in the naval service” requires hands-on, real-life exposure to the complex, mechanical systems that are the stuff of which navies are made - ships. Midshipmen obtain underway seagoing experience through year-round local operations on small open power launches and small sail- ing craft, more extensive summer cruises on operational U.S. Navy ships, and active year-round operation of a dedicated fleet of twin-screw yard patrol craft (YPs). YPs are used for training in navigation, ship handling, shipboard command organization, fleet tactical maneuvering principles, rules of the road, shipboard military procedures, and to gain “an appreciation for seagoing.” The on-the-water training is thus technical, sociological, military, and motivational.

Since 1958, the aforementioned training has been accomplished using a 15-boat fleet of specially designed 80-foot YPs described pictorially in Figure 1, with major characteristics listed in Table 1 [I]. While some elements of the YP fleet were built in 1968, most were built between 1958 and 1961. During the 28 years since their

37 Naval Engineers Journal, January 1987

USNA YARD PATROL CRAFT COMPTON/CHATTERTON/HATCHELL/McGRATH

Figure 1. 80-ft USNA yard patrol craft (YP).

Length Over-all Extreme Beam Draft (light load) Displacement Main propulsion

Generator

Propellers

Fuel Oil Capacity Lubricating Oil Capacity Fresh water Maximum Speed Cruising Speed Maximum Safe Capacity

Table 1. 80' USNA YP Characteristics

80'5" 18'9" 5 4"

69.5 tons (4) GM-6-71 diesels, 165

horsepower each (1) 120-volt, 20 kilowatt,

A.C. generator (2) 3-bladed, 36"-diameter

screws 2,070 gallons

15 gallons 420 gallons 13.5 knots

10 knots 60 people

Rudder angles (twin rudders) Standard Full

Heights Top of mast to boot top Yard arm to boot top

Radar antenna to boot top Vertical distance between

Height of eye (6-foot man) sidelights and masthead light

Main Deck (forward) Main Deck (aft) Signal bridge

13%" 25 35"

37' 10" 25 ' 6"

with stadimeter 28'

13'1"

12.8' 11.6' 19.6'

delivery, the YPs have been modified to meet the changing requirements of Naval Academy (and U.S. Navy) programs. Major among these changes was the admission of women to the Academy in 1977. As a result, much of the after end of the deckhouse was converted from a CIC (combat information center), to berthing space. This reduced the navigational training ability of the YPs. In addition, stores and lifesaving equipment were required for the increased complement, and this led to adverse changes in displacement and center of gravity. A post- conversion stability analysis of YP-660 indicated that the margin of safety for offshore operations was minimal at


best [2], thus placing a significant geographical limit on the YPs operational area.

Recognizing the YP fleet was fast approaching the end of its service life, the Naval Academy superintendent (then Vice Admiral Kinnard McKee, USN) requested cost estimates for replacing in-kind the 80-ft wooden YPs. A $3M per boat cost estimate, coupled with the restriction to coastal operation for safety, so concerned Adm. McKee that he requested input from the naval architecture faculty at the Academy. The initial charge to the "in house" naval architects was to investigate ways to get a fleet of boats incorporating current design and

COMPTON/CHATTERTON/HATCHELL/McGRATH USNA YARD PATROL CRAFT

equipment concepts less expensively, and without impos- ing such severe constraints on their operational area. Adm. McKee wanted “blue water” experience for the midshipmen - if the cost could be kept within reason. Cost savings were expected by considering a structural material other than wood and by using commercial instead of military electronics.

DESIGN PROBLEM DEFINITION

An in-depth analysis of need and a quantification of the capabilities needed in a replacement training craft were initiated by the naval architects of the Department of Naval Systems Engineering and representatives of the Department of Seamanship and Navigation. From an

Table 2. Replacement Yard Patrol Craft Operational Requirement (OR) Summary

General

To provide basic realistic professional afloat training to the midshipmen 10-1 1 month per year operation Craft to represent current fleet standards Will be strictly a noncombatant training craft Instruction to include watch station evolutions, fleet operating procedures, deck seamanship, rules of the road, practical navigation, piloting, ship handling, tactical steaming, basic engineering, damage control, operations and communication training, and basic oceanographic training Inland and open-ocean environments Maintained and supported at Naval Station, Annapolis, Maryland

Characteristics

Design emphasis on habitability, training space, maneuverability, stability 1,400 NM range at 12 knots Unrestricted operations in sea state 3; restricted operations in sea state 5 At-sea endurance of 5 days unreplenished Complement of 24 midshipmen, 2 officers, 4 enlisted personnel Training and habitability facilities for both male and female midshipmen (12 each assumed) Reflect, insofar as practical, the configuration and equipment of current Navy destroyer/frigates - including underway replenishment capability

Table 3. Replacement Yard Patrol Craft Design Requirements Summary

Limiting dimensions:

L I 120ft B 5 28 ft limitation due to berthinghaintenance T I 10 ft at Naval Station, Annapolis, Maryland A I 120LT

Diesel propulsion Galley seating: 15 Two combat information centers (CIC) with a total of 18 training positions CIC to be sound isolated from engine noise Enclosed engineering operating station (EOS) Pilot house to accommodate 8 persons; ship fully operable by 2 enlisted; 360” visibility; direct access to open bridge wings Signal bridge Walk-in damage control locker Anchors in hawse pipes Commercially available, state-of-the-art electronic equipment Capable of towing or being towed by another YP No overboard discharges in coastal/inland waters in compliance with current and anticipated federal standards Operational scenarios - during academic year: 9 hours per day, 5 days per week for short, repeated training evolutions - during intercessional period: two 5-week cruises along Atlantic Coast; six 10-day cruises

- 0-5 knots (maneuvering) 20% - 5-12 knots (transits, etc.) 60% - 2 10 knots (tactics) 20%

Speed-time profile

Annual operating time: 2,000 hrs per ship Estimated acquisition cost (1978 dollars) $2.5M per ship Required upgrading of YP support facilities

Naval Engineers Journal, January 1987 39


initial set of requirements drafted in December 1976 to the formal operational requirement (OR) and final design requirement document sent by the Superinten- dent (USNA) to the Chief of Naval Operations (CNO) in December 1978, the details of the requirements changed very little. The major operational requirements are shown in Table 2, and those features thought to be required to accomplish the mission are shown in Table 3. These tables represent a distillation of characteristics desired by the operator.

Some of the more significant matters considered in arriving at the OR and design requirements included:

1) The lack of consistently motivational and educa- tional assignments to operating fleets units for midshipmen summer professional training - especially for third class cruise (between freshman and soph- omore year). While a more capable YP fleet would solve this problem because of total control by the Naval Academy, it would also reduce real-world, real-Navy experiences - especially the sociological and the “see the world” ones.

2) The unavailability of most naval ships to female midshipmen.

3) The reduction of expense of transporting large num- bers of midshipmen to and from many widely separated ports.

4) Optimum YP fleet size - trading off increased training capability versus operating cost, maintenance procedures, and YP berthing.

5) The preference of both the ship handling instructors and maintenance personnel for wood hulls in lieu of steel, aluminum, or glass reinforced plastic - even though wood’s high cost of construction was one of the causes for the design problem’s existence!

6) Maximum YP speed. Seamanship and tactics instructors originally wanted 17 knots, but maintenance personnel wanted to retain 71-series diesel engines because of familiarity, dependability, and logistics simplification. Thus, the model 12V71N and 12 knots (vice a larger bore or turbocharged/intercooled engine and 17 knots) was ultimately specified for the new craft. It should be noted that the 12V71 is the largest of the 71 series engines.

As is so often the case, the problem definition specified characteristics not mandated by stated design constraints. While this was undoubtedly pragmatic - at least in the near term - it philosophically stifled a designer’s creative freedom. For example, in the YP case, twin-screw propulsion was specified in the OR. That the ship have “at least twin-screw propulsion” was a requirement of the training mission, but why eliminate the cost-benefit analysis of a triple-screw scheme in which the centerline screw would be used for single-screw ship handling training?

Thus, from the first official statement of need to the complete definition of the problem and its submission through the chain of command for review, approval, and funding, something as simple (relative to other naval ships) as a noncombatant training ship took two years. Technical, fiscal, and political dialog among naval architects, operators, maintenance personnel, and management were required to define this design problem.


APPROACHES TO SOLVING THE Y P DESIGN PROBLEM

The initial approaches to developing a replacement YP were explored by the naval architecture faculty of the U.S. Naval Academy beginning in December 1976. Four possible alternative concepts emerged. They were:

1) Reconfiguration of the 80-ft YP, presently in use at the Naval Academy, (and at other officer training establishments) to suit the stated mission (See Figure 1).

2) Reconfiguration of a “successful” U.S. Navy hull to suit the stated mission - for example, the 100-ft tor- pedo weapons retriever (TWR).

3) Reconfiguration of a “successful” commercially available hull to suit the stated mission - e.g., an offshore yacht like MV Silverudo built by Willard Boat Company [3], or an offshore crew boat/supply boat like those used to ferry personnel and supplies to offshore oil rigs.

4) A new design based totally on the developed design problem statement.

The logical viability of this list of alternative concepts was established several years later when NAVSEA- COMBATSYSENGSTA-Norfolk developed inde- pendently the same set of alternatives [4]. In early 1977, the late Cdr. Henry Schmidt, USN, undertook an active program to study the “commercially available hull” alternative. Prof. Roger Compton began study of the 100-ft TWR conversion and acted as faculty advisor for two teams of midshipman designers (senior students majoring in naval architecture) who developed original solutions to the problem directly from the current design requirements.

MIDSHIPMAN CONCEPTUAL DESIGNS

The YP design problem is ideal for midshipmen to undertake since the YP is of a size and complexity that make its conceptual design tractable in a short time frame (16 weeks) and it is a ship with which midshipmen have considerable operational experience. Of special concern to the midshipmen designers were the extreme structural loads encountered in the “seawall bumper drills” ex- perienced when students are at the helm. The team of Midshipmen Ron Miller and Mike Wertz decided to develop a glass reinforced plastic hull whose shape was a derivative of Beys’ Series 63 [5 ] round-bilge parent form. Their design featured twin-screw diesel propulsion, and accommodation spaces widely separated, but completely below the main deck. Working from the same design requirements, the team of Midshipmen Corey Glab and Rich Maurer developed a steel hull/aluminum deckhouse design featuring triple-screw propulsion (so that both twin-screw and single-screw ship handling could be taught) and widely separated accommodation spaces on and below the main deck. This latter hull was a modified (beamier) version of the TWR discussed earlier. This design project was entered in the 1977 American Society of Engineering Educators’ (ASEE) National Design


____ __

30

ze

26

24

Y z 5 22

5 : - a m N

ZC

18

- -- ~

THIINl!lt CRArT - TNO 425 SHP ENGIMES

- .z B a

-

5gure 3. Design study sizing plot - length versus beam (8V71TI engines).

VOLUME

LJ - . ..

Competition and was awarded Second Prize in the Senior Division.

While providing an ideal problem for fledgling naval architects to cut their teeth on, the Y P designs produced as student projects could not replace professionally produced ship designs. The midshipman design teams of the Class of 1977 were neither the first nor the last to choose a replacement YP for their senior design project. During and after the spring semester of 1977, much technical

Table 4. Alternative #I - 80-ft YP FY 77 YP673 Series

Length (overall) - 80'-5" Beam ( m a ) - 17'-9%" Draft ( m a ) - 5 1-41!

Displacement (light) - 57 tons Displacement (full load) - 68 tons Speed ( m a ) - 12.6 tons Range (at 12 knots and full load) - 400 N.M

Structure: - Planked wood hull with aluminum deck

Systems: - Engines: Two 12V 71N diesel engines (340

Propellers: Two 36" diameter x 24 " pitch. Generator: One 30kw diesel.

house; round bottom.

shp) with a reduction of 2: 1 .

Training Facilities: two independent CICs. pilot house with flying bridge and

Habitability: Crew: 2 officers, 8 midshipmen, shared

bridge wings over.

washrooms. Messroom: seating for 5 .

150

140

130

120

110

30

25

30

25

20

15

T R A I N I N G C R A F T YP wltwo 425-HP DIESELS

T-IT (PAYLOAD 6000 Ibl

PA RENT' A l.&F: -

- - __-__ .-.-

STEEL ij XLUMIN

LENGTH O V E R A L L (11.1

Figure 4. Design study sizing plot - various hull characteristics versus length (8V71TI engines).

dialog continued within the Naval Academy staff about the need of replacing the Y P fleet. As a result in January 1979 the CNO issued the operational requirements to NAVSEA requesting a full-fledged technical study of the replacement YP. The midshipman projects were treated as initial conceptual studies for the ultimate designers of the YP, NAVSEACOMBATSYSENGSTA-Norfolk.

NAVSEA PRELIMINARY AND CONTRACT DESIGNS

NAVSEA PMS 300 authorized NAVSEACOMBAT- SYSENGSTA-Norfolk to begin the concept exploration phase of the YP design process in August 1979. The design team, led by Gordon Hatchell, developed four feasibility alternatives [4]. Before developing any one of the concepts, however, those features required by the OR which primarily impact craft size were identified for analysis. It soon became apparent that the design would be volume-limited because of the internal space required for training functions and habitability.

An analysis of the internal volumes required for major functional spaces (i.e., operational, pedagogical, habitability, and machinery) was performed to arrive at an estimate of the total enclosed volume needed to satisfy the stated operational requirements. When this



analysis was performed initially, a maximum speed of “at least 14 knots” was specified by the operators. Two diesel propulsion system configurations were considered initially - twin turbocharged and intercooled 8V7 1TI engines, or twin naturally aspirated 16V149 engines. The former required that the craft have a total enclosed volume of 23,800 cubic feet and a maximum speed of 14 knots, while the latter resulted in a craft having a total enclosed volume of 25,000 cubic feet and an estimated maximum speed of 16 knots. While adequate internal volume is a necessary measure of size, it is not alone sufficient. Compartment length and beam minima for certain systems must also be considered (e.g., machinery spaces). The foregoing volume analysis was based on extensive experience with similar small craft, as are the design rules-of-thumb which suggest that, for a given craft length, there is a minimum beam below which stability problems are likely. When such fruits of design experience are combined with the physical and political constraints unique to the current design problem, plots like Figures 3 and 4 can be constructed which show clearly the bounds on certain gross ship characteristics. Such plots reduce the designer’s choice of major sizing parameter values to a more tractable range.

Having the required internal volumes estimated, the four conceptual solutions to the design problem could be quantitatively evaluated for feasibility.

ALTERNATIVE #1: RECONFIGURATION OF THE ~O-FT Y P (see Figure 1 and Table 4)

The most recent version of the 80-ft Y P falls short of meeting the OR in many areas. It would require an increase in volume of 2,925 cubic feet to fulfill mission requirements. Much of this added volume and its associated weight would be above the main deck with a portion above deck house level. Any increase in the vertical center of gravity of the existing craft would result in loss of seakeeping/stability characteristics which are presently marginal [2] and is, therefore, unacceptable.

ALTERNATIVE #2: A MODIFICATTON OF THE 1 0 0 - ~ ~ TWR

The 100-ft TWR hull structure and propulsion plant would satisfy the OR; however, its hull length and shape would severely restrict arrangement, habitability and operating spaces. The mission of the TWR required potable water and consumables for a complement of 15 men. To accomplish the longer duration cruises, and larger mixed complement required of the YP, additional storage, berthing, and sanitary spaces would result in the need for about 2,700 cubic feet of added internal volume. Major modification of the bow would be necessary to accommodate hawsepipes for anchor handling. The TWR has adequate stability (without ballast) to just satisfy an 80-knot beam wind criterion with its full load of torpedoes and its present sail area. It does not have margin to allow for growth. Use of the TWR hull for a YP would require an increase in sail area. This increased sail area and the requirement to satisfy an 80-knot beam wind criterion precluded the use of the TWR as a new


YP. Also, on the basis of operational experience, the 100-ft TWR greatly exceeds recommended maximum roll amplitudes for new designs. Considering the above, the TWR modification was eliminated as a viable alternative.

ALTERNATIVE #3: A MODIFICATION OF A SUITABLE COMMERCIALLY AVAILABLE HULL

Several commercially available hulls having lengths in the 85-120-ft range were considered. At least one example of a steel hull, aluminum hull, fiberglass hull, and wooden hull were studied. Both diesel and gas turbine engines were included. When evaluated in light of the OR, those listed in Table 5 [4] had adequate internal volume, but did not meet the U.S. Navy’s intact and damaged stability criteria for coastal operation. All of the hulls would require extensive internal rearrangement - including changes in structural bulkheads - to meet the requirements in the OR.

Structural adequacy with the revised bulkhead loca- tions was not investigated. The anchoring systems would require modification to more closely resemble Navy operations. Full electronic installations would be required for mission and training requirements and an underway replenishment kingpost added. Also, engines currently used have not been service approved. As with any stock design of the size required, these hulls are not “off the shelf,” but are built to customer needs and op- tions. The hull forms studied are listed in Table 5 . Of these, the most likely candidate seemed to be the Wil- lard Company’s MV Silverado. However, this approach was considered to possess the highest technical risk of all commercially available hulls because it was, at the time, the only large fiberglass craft constructed in the United States and it was untested with respect to the effects of impacts likely to occur in YP operations.

ALTERNATNE #4: AN ORIGINAL DESIGN

The development of a new design allowed for the most efficient incorporation of all the capabilities and characteristics spelled out in the OR. NAVSEACOMBAT- SYSENGSTA-Norfolk began the development of the new design by undertaking a study to determine which of the four most popular structural materials - steel, aluminum, fiberglass, or wood - would be most suitable. By the nature of its intended use, this craft would have to withstand repeated impact loadings resulting from ‘bumper drills.’

The bow sections and transom corners would have to be reinforced and properly fendered. In selecting the material one had to consider these drills, the requirement for minimum care as it relates to appearance, repairabili- ty, weight, and cost. The results of a careful engineering analysis of the relative merits of the four major structural materials considered are summarized in Table 6. NAVSEACOMBATSYSENGSTA-Norfolk rec-

ommended that a steel hull with aluminum superstruc- ture be used for this new craft. The order of priority for the remaining materials was fiberglass, aluminum, and wood.


I Figure 5. 108-ft steel hull, hard chine YP design - outboard profile.

I igure 6. 108-ft steel hull, hard chine YP design - platform

deck.

The next major decision was configuration of the propulsion system. Two approaches were taken. The first involved the use of two 16V149 diesel engines (880 SHP each), giving a maximum speed, with a steel hull, of 16 knots. The second involved the use of two 8V71TI diesel

---

i i ___

Figure 7. 108-ft steel hull, hard chine YP design - main deck.

engines (425 SHP each) giving a maximum speed, with a steel hull, of 13 knots. The 16V149 engines are four times heavier and twice as long as the smaller 8V71TI engines, but the latter are more complex due to turbocharging and intercooling.

After evaluation of the data and maximum speeds of each available option, the design based on using two 8V71TI engines in a twin-screw, twin-rudder configuration was considered most acceptable. This was based on a decision by operating personnel (USNA) that a cruise speed of 12 knots would be satisfactory.

With these two major systems decisions made, the hard-chined steel hulled design shown in Figures 5 through 7 and Table 7, was developed. This 108-ft "optimum " steel, twin 8V71TI powered craft was recommended to NAVSEA PMS 300 as the best alternative to develop further. At this point in time, a major review of the project was conducted by the Acquisition Review Committee (ARC). NAVSEA and USNA representatives

Table 5. Commercial Hulls Examined for Alternative 3

Manufacturer (Model) Designed Use Material

Peterson (P.B.I.) (MSI-15) Minesweeper Wood

St. Augustine Trawlers Shrimp trawler Wood

Steiners Fabricators Trawler Steel

Tacoma Boatbuilding Co. (PBMM) Patrol Boat Alum.

Feadship America Yacht Alum.

Progressive Shipbuilders Party fishing & Fabricators, Inc. Crew/Supply

Crew/Supply Patrol boat Crew/Supply Mini cruise ship Passenger ships

Blount Marine Corp.

Rockport Yacht & Supply Crew/Supply Burger Boat Co., Inc. Yacht

Willard Boat Works, Inc. Yacht Swiftships, Inc. Patrol/Comm'l

Patrol/Comm'l.

Alum. Alum. Alum. Alum. Alum. Alum.

Steel Alum. Alum. Alum. Fiberglass Alum. Alum.

Halter Marine, Inc. Crew/Supply Steel *Approximate

Displacement Length Beam (Full Load)

111'9" 23'"" 220 Tons

88'-0" 22'"" 127 Tons (Gross)

97'"'' 24'"" 172 Tons (Gross)*

(W/Minesweep gear)

86 Tons (Net)

117 Tons (Net)*

116'-0" 21" 105'-8" 21'4'' 114'"" 22'"" 120'-2" 24'-2" 90'-0" 26'-0" 100' -9" 22' - 10" 110'-0" 26'"" 115'-3" 26'"" 120' 22'"'' 116'-0" 27'"" 112'-148' varies 112'-0" 28"" 961-7" 19J-4" 991-9'' 221-9'' 125"O" 24'"" 122' -0" 25 ' - 1 K " 105 ' -10" 23 ' -9" 125 '-0" 23 '-3"

125 Tons 136 Tons* 147 Tons* 153 Tons* 88 Tons* 114 Tons* 126 Tons* 123 Tons* 138 Tons* 140 Tons* varies 154 Tons* 120 Tons 127 Tons* 156 Tons* 165 Tons 101 Tons 140.6 Tons

110'-0" 26'-0" 156 Tons*

Designed Conditions

Speed Draft (Max)

8.65' F.L. 14 7.6' L.L. 9 ' -0" 13* 9 ' -0'' 10 ' -0" 13'

7"-0" 37 8 ' -2" 13.2 6'-7" 14 7 ' -2" 14

17* 18* 16*

3 '-6" 32 16*

51-31' 17' varies 7 ' -6" 16* 5 ' -4" 18 6"-0" 14 6 ' 4 " 16 8 ' 4 " 18

8'-2%" 24 14

8 -0" 16*

7'-0-1/8" 18



Table 6. Summary of Hull Material Properties

Attribute Steel FRP Aluminum Wood

-Relative Cost of Material

Least Expensive. More expensive than steel. About same as wood. Most expensive.

-Formability Shaped using light metal working machinery.

Molded to any shape, rela- tively simple tooling required.

Shaped using light metal working machinery.

Can be made to conform to most surfaces.

-Appearance Smooth finish obtainable; some distortion possible during welding.

Smooth surface finish when made in a well finished female mold.

Smooth finish; distortion during welding likely.

Smooth finish with sanding and glazing.

-Effect of Minor Impacts

Little or none. Minor surface cracking (crazing)

Denting. Minor cracking

-Effect of Major Impacts

Denting. Penetration and breaking away of material.

Severe denting and possible support member distortion.

Shell penetration and cracking of support members.

-Abrasion Characteristics

Resists abrasion. Coating system requires renewal.

Abrasion will severely damage.

Moderately resistant to abrasion.

Abrasion will severely damage.

-*Weatherability Coating requires careful maintenance to limit corro- sion.

Excellent weather resistance, minimal maintenance required.

Good weather resistance, no coating system required above waterline.

Poor resistance to weather effects, requires continual maintenance.

-Fire Resistance Essentially fireproof. Fire retardant resins, will burn with heat source but self-extinguishing.

Distorts and melts at rela- tively low temperatures.

Poor fire resistance.

*If coating is applied for cosmetic appearance of the craft, then all hull materials will require some amount of maintenance time.

presented the ARC with the technical and cost tradeoffs developed in alternatives one through four recom-

mending the original design described in Figures 5 through 7 and in Table 7. However, representing the ultimate users and maintainers of a new YP, the USNA attendees expressed their preference for wood as a hull material. To the surprise of both NAVSEACOMBAT- SYSENGSTA-Norfolk and USNA naval architects, the ARC recommended to the CNO that a new design (alternative four) - 108 feet in length, soft chined, conventionally planked wooden hull, twin screw powered by 12V71 diesel engines, with an “economical cruising speed” of 12 knots - would be the best solution to the Naval Academy’s YP problem. NAVSEA was directed to proceed with such a design in April 1981. Responding quickly t o this unexpected direction, NAV- SEACOMBATSYSENGSTA-Norfolk presented a 112-ft wooden hull design to NAVSEA PMS 300 for review. The increase in length from 108 feet to 112 feet was considered necessary to compensate for the internal volume lost due to wooden construction. Arguing on the basis of increased cost for the added length, NAVSEA PMS 300 rejected the longer design in favor of a wooden hull of the original “optimum” length of 108 feet, which was within the size and cost constraints approved by the ARC. The rationale behind this decision is still unclear since a 3.5% increase in length should result in a minimal

Table 7. Original NAVSEACOMBATSYSENGSTA- Norfolk Design Characteristics for Replacement YP

Optimum Minimum

Length Overall 108 ft 102 ft Length on DWL 101 ft 95 ft Beam 24 ft 23 ft Draft (Navigational) 7 ft 9 in 7 ft 3 in Steel Hull Aluminum Deckhouse Hard-Chine Hullform Propulsion - Twin-screw fixed pitch propellers driven by 8V71TI engines Electrical - Two diesel generators; 24V batteries Berths - 30 (4 crew12 officer14 six-person spaces for midshipmen) Messroom Seating - 16 Sanitary Spaces - Isolated unisex spaces with 4 WC, 4 lav, 4 shwrs; holding tanks HVAC for living spaces, messroom, galley, passage- ways, waterclosets, CIC, EOS



I 1

Figure 8. Abbreviated lines sketch of 108-ft yard patrol craft (YP-676).

increase in hull cost (which only represents about 17% of the craft cost).

An interesting, if esoteric, interpretation of the YP lines drawing eased the internal volume problem: the molded lines were taken to represent the outside of the frames (inside of the wood planking) as would be done for steel hulls.

The controversial selection of wood as the hull material despite its high cost (the impetus for the design problem in the first place) can be attributed to several factors. Among them are:

1) Preference of existing small craft maintenance facility personnel.

2) Consideration of “bumper drill” problems. Wooden hull cosmetic repairs are tractable and the damage done to the seawall from impacts by wooden hulls will be less severe than from steel hulls.

3) Perhaps OPNAV wanted to preserve and strengthen the capability of U.S. builders to produce wooden craft with an eye toward rebuilding the Navy’s mine warfare fleet. This is purely conjecture.

The decision to specify the 12V71 naturally aspirated diesel engines instead of 8V71TI engines was influenced strongly by maintenance concerns over the added mechanical complexity of turbocharged/intercooled machinery. The operators satisfaction with a 12 knot “maximum economical speed” also favored the 12V71.

The major factors that dictated hull form configuration were speed, seakeeping, stability, training requirements and hull material. Seakeeping required operational capabilities in sea state 3 and survival in sea state 5. The governing stability criteria were an 80-knot beam wind and the ability to survive two-compartment flooding.

A model testing program, jointly developed by NAHL and NAVSEACOMBATSYSENGSTA-Norfolk, pro-

vided insights to the design team as to which hull characteristics best satisfied the major design goals. Original lines were developed based on achieving roll reduction at low speed. This called for a deep-vee shape, a small bilge radius and a large skeg. The resulting deep transom immersion created a serious powering penalty in the YP’s operating speed range. This powering penalty, intuitively logical, was borne out by the model testing program.

Although the large skeg provided excellent directional stability, good maneuverability was also a requirement. Radio controlled model tests of the new design and full scale trials of the 80-ft YP were used by the Norfolk designers to select a twin-rudder configuration which would provide good maneuverability in the tight areas of the Severn River [6,7]. Planked wood construction made hull producibility difficult for a deep-vee craft with as small a bilge radius a.4 was desirable for roll damping.

Based on the above considerations and NAVSEA independent design review board comments, the original lines were revised. Deadrise at amidship was reduced to 15 degrees, transom immersion was greatly reduced and bilge radius was increased. Model tests indicated that at the design speed, the 108-ft YP transom would be dry - i.e., separation of flow will occur as desired. The molded hull form which emerged after both preliminary and contract design is shown on the lines drawing, Figure 8. Hydrostatic analysis of the hull form defined by the lines was accomplished using the Navy’s Ship Hull Characteristics Program (SHCP).

A wave profile based on model tests showed that, as designed, the anchor had the potential to be in the bow wave at the design speed of 12 knots. The anchor hous- ing was consequently modified to reduce this possibility. The tapering of the trailing edge of the skeg was also a result of model test analysis. Powering estimates to eval-



I I Figure 9. YP-676 Structural midship section.

uate the adequacy of the selected engine configuration were extensive. Both analytical estimates and model tests results were considered.

The ARC decision was to build the boat out of wood, conventionally constructed, in lieu of using the wood- epoxy-saturation-technique system. Once wood was established as the hull material, various studies were conducted from which it was decided that Lloyd’s Rules would be used for designing the basic wood structure.

Material was selected for various structural components using Lloyd’s Rules and Wood: A Manual for its use as a Shipbuilding Material (NA VSHIPS 250-336). Primary members of laminated white oak are the keel, stem, trans erse frames, floors, clamp, shelf and hull

plank sheer, sheer strake, doublers and sheer blocks. Bilge stringers, midguard backing, deck beams and bulkhead stiffeners are of Douglas fir. The inner planking is Alaska yellow cedar (AYC) for its superior rot resistance due to fresh water in the bilges. Long leaf yellow pine (LLYP) was selected for outer planking because of its superior abrasion resistance and resistance to splitting. During construction, the planking material had to be changed due to material availability problems. Outer planking was changed to dense grain, Douglas fir. Silicon bronze hogging straps were provided. Using Lloyds, a frame spacing of 18 inches was selected with a total planking thickness of 29’4 inches. The general configuration of the hull structure can be seen in the midship section in Figure 9. The material for the deck house was chosen as aluminum, 5086-H116/H117 for plating and 5086 H l l l for stiffeners. Design loads were: front 1.74 psi, sides 1.04 psi, and top 1.39 psi.

Hull structural ruggedness has been verified in the short time since delivery. During an unexpected “bumper drill,” when a screw had backed off the gear linkage, YP-676 hit a pier head-on and crashed through four feet’of pier before hitting a cement wall. The only damage to the hull was a slight dent in the CRES sheathing which wraps around the stem.

The 12V-71 dieselengine and the 514 marine gear have both seen considerable application in Navy craft and have proven to be a durable combination. They are fully supported by the U.S. Navy Supply System. The engine is available at four power levels: 340 SHP @ 1800 RPM,

46

longitudina ! and deck girders. White oak is used for the

Naval Engineers Journal, January 1987

400 SHP @ 2100 RPM, 437 SHP @ 2100 RPM, and 480 SHP @ 2300 RPM. These power levels are determined by injector selection and engine timing adjustment. This flexibility provides means for upgrading the crafts’ performance to meet future requirements. The performance curves for the 12V-71N with N65 injectors and the 437 SHP at 2,100 RPM rating selected for the 108-ft YP are shown in Figure 10.

Propeller selection was based on achieving the best efficiency at the 12 knot operating speed in a sea state 3 with an engine RPM of 2,100. The largest propeller which could fit the stern without extending below the skeg and which satisfied a 20% clearance criteria with the hull was chosen. The K d J 2 method [7] of selecting the pitch/diameter ratio (P/D) was employed using standard propeller.series data of Gawn-Burrill[8] and Hankley [9]. This method has the advantage of eliminating propeller RPM from the early stages of analysis. The choice of propeller RPM was made by selecting a reduction gear ratio which optimized efficiency while providing maximum gear life and minimum torsional vibration. The selected propeller/gear system included a set of 52-in. diameter, 3 bladed, outboard turning propellers with a P/D of 1.05 and an expanded area ratio (EAR) of 0.65. The reduction ratio was 5.16: 1.

Both propulsion engines and diesel generators exhaust through the side of the hull just above the waterline. Both are wet exhaust systems featuring stainless steel mufflers designed to meet a silencing requirement of 85 dBA at 20 feet. The fuel system consists of two aluminum 3,500 gallon tanks, one 25 gallon stripping tank, supply and return manifolds, knife edge strainers, secondary filters, water separators and emergency fuel shutoff valves. All fuel system piping is steel. A fuel oil

440

400

360

5 320 2 280

p 240

L. 4 5 200

LGO

120 28

so 24

e 20 g . 16 5 12

-1

2 Y

3 2

4

I I I I I I I I I I I I I I I I I I I I I I I I I ( I I l l l l l l 1 1 l l l I l I I l I l I 0

1200 l iou 1600 Is00 2000 ENCIm SPEED - R P h l

FIGURE 17: YP676 Diesel Engine Performance Curves

Figure 10. YP-676 model 12V-71N diesel engine performance curves.


cooler is provided for each engine and a solenoid valve is provided on each engine to prevent fuel leaking into the engine cylinders when the engines are shut down.

The electrical system consists of two 50 kva, 45Ov, 60hz diesel driven generators with transformers to provide the 12Ov, 60 hz, power, two battery charging rec- tifiers to supply 28 vdc, and one 400 hz converter. The estimated electrical load, as indicated by the load analysis is 57 kva for cruising, 49 kva for functional loading, 52 kva at anchor or pierside and 43 kva while cruising and not preparing meals. Further, the 3-71 engines were selected because of commonality with propulsion engines. The 60 amp battery charging rectifier was selected over engine driven alternators because of reduced maintenance requirements. The 400 hz static inverter was selected over a motor generator set because of its small size, light weight and longer mean time between failures.

The electric plant is configured to allow for three modes of operation:

Single generator operation with one generator in

Parallel operation (primarily used for transfer of load

Split-plant operation (both generators running with

Each generator has a lo%, 2 hour overload rating that will satisfy peak loading conditions. Each generator has an 8% growth margin with one generator carrying the total load and the other in standby. Because of weight and space limitations, it is considered that selection of two 50 kW (62.5 kva) generators was the best engineering compromise.

The electric plant is designed to be controlled and monitored from the EOS. The generator engines can be monitored from the pilot house. The distribution system consists of an electric plant control panel (EPCP) located in the EOS, Navy type circuit breaker distribution panels fed from the vital and non-vital bus of the EPCP, transformer banks for 12Ov power, and isolated receptacle circuits. All vital auxiliaries for the propulsion plant and navigation are supplied from the 24 vdc system via the emergency supply battery bank. The shore power hookup provides for 440 volt 3 phase power input only.

Command, control and communications equipment and facilities consist of the items listed in Table 8.

The EPSCO electronic plotter and tracking system was selected to replace the extremely expensive gear- driven dead reckoning tracers (DRT). The plotter has the capability of receiving data from either Loran or SAT- VAV and provides various navigation displays in addition to serving as a DRT plotter.

Equipment required for both YP operation and for training evolutions is listed in Table 9.

The heating, air conditioning and ventilation (HVAC) system was designed utilizing the criteria and guidance of “A Guidance Manual for Designing Heating, Mechanical Cooling and Ventilation Systems on Small Craft of the U.S. Navy,” of January 18, 1978, with the

standby

from one generator to the other)

each carrying a portion of the total load).

exception that the criteria for cooling the galley is 90°F vice 105’F. The heating/air conditioning system is a reverse cycle system which is divided into discrete temper- ature controlled zones. The reverse cycle cooling/heating system was chosen over a chilled/heated water system after a tradeoff study was conducted. The pilot house has its own %-ton cooling/heating unit. The heating cycle receives thermal energy, with the raw water loop closed, either from the generator jacket cooling water or from immersion heaters.

At the present there are only three approved marine sanitation (MSD) systems. The GATX system was chosen and has proven to be satisfactory in service. The system has facilities to discharge sewage to port and starboard deck connections and overboard in non-restricted waters. Provisions are made to permit use of a vacuum system to remove sewage from the holding tank. One commode is arranged to permit flushing directly overboard for emergency operation.

The potable water system provides for onboard storage, onboard production and shore side supply of potable water. The system is arranged to allow selective water heating and distribution depending on cruise length and space occupancy. The onboard storage is sized to provide 25 gallons per day per man for 2 days for a 30 man crew. Onboard production of fresh water is provided by a 1,OOO GPD reverse osmosis (RO) desal- inator. Chemical treatment is accomplished in the storage tanks by a recirculating bromination system of the cartridge type.

Table 8. C3 Equipment and Facilities

Radio Navigation Suite - Loran “C” - 2 Electronic plotters and tracking systems - SATNAVIOmega

Depth sounder MK 27 gyrocompass with 7 repeaters lMC/6MC announcing system with 22 speakers, announcing system with collision, general and chemical alarms, and a loud hailer. The master control will be located in the pilot house with talkback capability from all speakers. 21MC intercommunication system HF/VHF AN/URC-94 transceiver VHF bridge-to-bridge radio AN/SPS-64 surface search radar with 2 repeaters lJV, JW, 21JS and JX sound powered telephone

Electrical alarms, safety and warning Yard-arm blinkers Air horn with integral compressor Voice tubes between bridge wing stations and helms- man and between pilot The master SATNAV/Omega is located near the chart table with remote readout in the chartroom at each plotter. The master Loran is located in the pilot house with remote readouts provided at the plotters. The Loran is provided with filtering for operations in and around Annapolis.

system

UHF AN/ARC-159 transceiver Bilge alarm panels connected to the 24 vdc electrical system, are provided in the EOS and in the pilot house.



Table 9. YP-676 Equipment List

Pilot House Damage Control Locker Integrated console (similar to those on on new USN ships):

Helm Steering jog valve Navigation and exterior lighting controls Siren and navigation horn actuators Engine RPM indicators Master gyro compass Magnetic compass Rudder angle indicator

Engine controls for operation by permanent crew Engine order telegraph Radar (master unit) Radio HF/VHF and radio UHF Radio VHF (bridge-to-bridge) Satellite navigation receiver Loran C Fathometer display Chart table Sound powered phone circuit Remote Halon release/alarm panel Anemometer display Voice tubes List and trim clinometers Intercom station Gyro compass repeater Quartermaster’s desk Remote diesel engine gauges and alarm panel -

Clock (main engines and generators)

Port and Starboard Bridge Wings

Gyro repeater with pelorus Sound powered phone circuits Voice tubes Rudder angle indicators

CIC Chart Room

Plotting and tracking systems (2) Radar repeaters (2) HF/VHF/UHF radio transceivers remotes (2) Plotting tables (2) Gyro Repeaters (2) Status boards (edge - lighted) (2) Sound powered phone circuits (2) Intercom stations (2) Speed indicators (2) Fathometer displays, remote (2) Clocks (2)

Oxygen breathing apparatus DC Equipment Shoring and patching material

Signal Bridge

Double banked flagboard Sound powered phone circuits Voice tubes Signal search lights Intercom station

Forecastle

(2) Independent windlasses (directional and 2 speed

(2) Anchors Fittings required for being towed Sound powered phone Intercom station

with deadman controls)

Fantail

Towing bollard Sound powered phone

Underway Replenishment Station

Kingpost Suitable unrep equipment for transfer of 50# load

between YPs only (no requirement for personnel transfer)

Sound powered phone

Miscellaneous

Standard watertight fittings Fire main system Halon system in engine room and fuel tank space Connections and sufficient hose sections to dewater

itself or another YP tied alongside with P-250 pump

Seawater for engine cooling is supplied to each pair of propulsion and generator engines through port and starboard sea suction fittings and strainers. Seawater is discharged from the propulsion engines through a piping network which divides the seawater between overboard discharge fittings, the shaft logs for bearing lubrication, and the muffler for cooling and noise abatement. Sea- water is discharged from the diesel generators through a piping network which divides the flow between over-


board discharge fittings and the muffler. Each diesel generator is equipped with a heat exchanger which ex- tracts waste heat for use by the heating system during cold weather.

The Wagner steering system was selected due to its reliability and current use on other similar boats. It consists of a ram system with two electric motor driven pumps, helm pump, manual pump for emergency steering (same as helm pump), jog valve, 30 gallon tank and


Figure 11. YP-676 inboard profile and 01 level.

associated valves. The system will move the rudder from 35"s to 35"P in 6 seconds with either motor-driven pump. Normal steering requires one motor-driven pump (other pump is standby). The jog valve has the same normal steering capabilities as the helm pump. The automatic changeover valve (located on the ram) shifts to manual upon loss of hydraulic pressure.

The bilge system is designed to dewater the craft with a system of pick-up strainers, piping, manifold and bilge pump. A pick-up strainer is located in each watertight compartment except the forepeak. The forepeak is drained into the adjacent compartment through a bulkhead valve. Bilge alarms are provided in each space and are monitored from the EOS. The P-250 pump can be used for back-up service.

The fire fighting systems provide both water and automatic Halon capability. The water fire stations are located on the main deck and the engine room. Each station has a Navy all purpose nozzle and a foam appli- cator. Firemain pressure is provided by a 180 GPM pump which is belt driven from a clutched power takeoff unit on the starboard engine. The Halon system provides protection in the engine room and fuel tank spaces only and can be controlled from the EOS or the pilot house in either the automatic or the manual mode. The automatic mode is activated by sensors located in the engine room and fuel tank space. Audible alarms are provided at both the EOS and pilot house consoles. Audible and visual alarms are provided in the en- gineroom. The EOS console has a fire detector test capability. The Halon system can be manually activated

.......... ............... .... ..._... ---'

Figure 13. YP-676 outboard profile.

Figure 12. YP-676 main deck and platform deck.

by mechanical pull handles located in the EOS and at the.engine room access.

Due to the fact that the berthing and messing facilities would generally not be used, and, when used, would be used for 5 days or less, minimum habitability standards were considered to be satisfactory. One 12-person bunkroom and two 6-person bunkrooms were selected to accommodate the midshipmen. A 2-person stateroom was provided for the officer instructors and a 4-person bunkroom was provided for the crew. Two unisex washrooms are on the platform deck, each with one shower, one watercloset and one lavoratory. An additional washroom was provided on the main deck adjacent to the officer-instructor stateroom which is close to the chart room and pilot house.

The messing facilities provide for the food to be pre- pared at the Naval Academy mess, frozen and placed in the craft refrigerators, defrosted and reheated and served family style as required. Seating for 15 persons was requested but, due to compromises that included an inclined ladder into the engine room, seating space for only 14 was provided.

Two 25-man Mark-6 inflatable life boats with manual and hydrostatic release modes are provided. Four life- rings outfitted with light reflective tape, beepers and float lights are also provided.

The anchors were originally requested to be recessed into the hull. However, with the decision to construct a

Halon Cvllndern

Figure 14. YP-676 machnery arrangement.



O O 2 f L a m /z M / L /a

Figure 15. YP81-1 with and without skeg and bilge keels. >H/P SPaD (/Gvors)

EXPERIMENTAL STUDIES IN SUPPORT OF DESIGN

Both the Naval Academy Hydromechanics Laboratory (NAHL) and the David Taylor Naval Ship Research and Development Center (DTNSRDC), Carderock, MD provides support to NAVSEACOMBATSYSENGSTA- Norfolk in the form of experimental results relating to powering, seakeeping, and maneuvering performance. As early as the spring of 1977, NAHL evaluated the resistance characteristics of one of the possible commercial hull forms [lo].

The major experimental contribution of NAHL to the YP design effort was borne of the designers' need to be able to improve early-stage powering estimates for patrol-type craft in the 100-ft length range at sub-planing and semi-planing speeds. The idea of a small systematic series of transom stern hulls in which certain major shape

wooden hull, it was the consensus that this requirement and operational parameters would be varied was propos- was not practical. Two 300-pound Navy lightweight an- ed to NAHL by Donald Blount and Gordon Hatchell of chors are provided. NAVSEACOMBATSYSENGSTA-Norfolk in August

A damage control stowage locker is provided on the 1980. The resulting series covered the following ranges of main deck. Figures 11 through 14 show the final config- parameters and evaluated their effects on still water uration of the 108-ft YP. resistance:

Figure 16. Soft and hard chine EHP and running trim comparison



Section Shape: Hard vs. Soft Chine

Slenderness: 4.0 I Lpp/B I 5.2

Loading: 105 I ~ A I 150 OIL)^

-0.13 I LCG/Lpp I -0.02 (aft of amidship)

Speed: 0.35 I V/JLWL I 2 . 0 0.30 I F N ~ I 1.50

still water for speed-resistance performance [13]. This series of tests provided the powering estimates used to select the propulsion engines. An example of the effective horsepower variation with speed for the selected hull is shown in Figure 18. Engineering estimates of appendage resistance, service allowance, and propulsive coefficient were made at that time and Table 10 is a sample of the powering estimates provided by NAHL. Also provided [13] for the selected hull are a wave-hull intersection estimate at 12 knots, a streamline prediction in way of the proposed bilge keels, and a rough estimate of the added power needed to achieve 12 knots in a sea state 2.

The lines for the series hulls were developed to represent realistic shapes, not optimum resistance shapes. Model size (nominal 5-ft length) was chosen to suit NAHL facilities. The six series models were built by Alfred Seebode. The first model to arrive at NAHL was the soft-chined hull having the middle of three slenderness ratios. This model (later designated YP81-1) was extensively tested at the midrange loading to establish the turbulence stimulation methods to be used o n the series. The resulting configuration, consisting of three vertical rows of cylindrical studs, was selected for all members of the series. Resistance tests of this first hull included the bare hull configuration and appended configurations in which a centerline skeg (square ended version and tapered version) and bilge keels were added. Typical results are shown in Figure 15.

When the corresponding hard-chine hull (having the same slenderness ratio) was delivered, it was ballasted to the same condition as YP81-1 and tested to assess the effect of section shape on resistance. Typical results are shown in Figure 16. These two models were then tested in long crested beam seas at zero forward speed to answer questions relating to how section shape would af- fect rolling behavior - all other things being equal. The results, for one loading condition, are summarized [ 111 in Figure 17. These results while intuitively reasonable, raised many questions, the answers to which await per- forming similar tests on the entire six hull series with variation in loading (displacement, height of center of gravity, and roll gyradius).

As the other models of the series arrived from the model maker, they were outfitted for testing. Since each of the six models was to be tested over the entire speed range at three displacements at three longitudinal weight distributions (a total of 54 tests), it took several months to complete the series. Although intermediate results were available to the designer as described earlier, the report summarizing the entire test series [12] was not published until after several of the new Y P class had been delivered to the Naval Academy.

After the ARC had provided program direction and the NAVSEA independent design review committee had presented its recommendations, NAVSEACOMBAT- SYSENGSTA-Norfolk developed the hull lines shown in Figure 8. These lines were used to build a seventh 5-ft model for testing (YP81-7). This model, outfitted as were the six series models except that it had an integral external keel/skeg, was tested at three displacements in

Table 10. Shaft Horsepower (SHP) Estimates for YP81-7 at 162 Long Tons (Faired Trailing

Edge on Skeg) (30% Service Allowance)

Ship Speed (V, [knots]) Effective horsepower (EHP)

for bare hull Appendage allowance: for

bilge keels, shafts, struts and bossings; assume 10% of EHP

Barehull Roughness, fouling, and

weather allowance; assume 30% of EHP

Barehull

Total effective horsepower (EHP)

Total

Estimated shaft horsepower SHP @ P.C. = 0.50

P.C. = 0.55 P.C. = 0.60

10 12 14

125 271 562

12.5 27.1 56.2

37.5 81.3 168.6

175.0 379.4 786.8

350.0 758.8 1573.6 318.2 689.8 1430.5 291.7 632.3 1311.3

While this activity was underway on the 5-ft model at the Naval Academy, a 1/6 scale model (about 18-ft long) was constructed for radio controlled maneuvering testing at the Maneuvering and Seakeeping Basin (MASK) at DTNSRDC. As with the Y P series, the results obtained [7] should be of value to the small craft designer in general - not just the YP designer. The effects of rudder size, hull displacement and trim on directional stability, maneuverability, and roll caused by rudder action were determined, and rudder size was based on these tests. When the radio controlled testing programs was completed at DTNSRDC, the 18-foot model was sent to NAHL for subsequent use.

The availability of test models of the new YP at NAHL caused great interest among the naval architecture students of the Brigade. In the senior course, Ex- perimental Naval Architecture, the models (5 ' and 18') of the new YP have been put through more tests than any small craft designer could afford. The resistance results reported by Compton [ 131 have been validated repeatedly by midshipmen. The midshipmen have ex- tended the experimental investigations to include:


USNA YARD PATROL CRAFT COMPTON/CHATTERTON/HATCHELL/M&RATH

1) Shallow water resistance (Figure 19). The increase is dramatic as critical speed [14] is approached. These findings have operational significance since more than 75% of the Chesapeake Bay is less than 10-ft deep.

2) Beam sea rolling. Studies with varying center of gravity heights and with the addition of paravane roll stabilizers (made of threaded rods and coffee jar tops) have been performed in still water to obtain the coefficients for the damped equation of free roll motion - and in long crested beam seas. See Figures 20 and 21.

3) Motion responses in long crested head seas. Pitch, heave, and relative bow motion (at station 1) have been measured at various speeds using both the 5 ‘ and the 18’ models. Correlation has been excellent as can be seen from the motion response amplitude operators (RAOs) shown in Figure 22. The RAOs when combined with irregular sea spectra via the principle of linear superposition [ 141 have been used to predict (statistically) the YP’s responses in more realistic seaways of varying severity. See Figure 23 for example.

4) Open water propeller performance. Figure 24 shows the open water propeller curves for the three bladed propeller used to run self propelled tests on the 18-ft model in the 380-ft tank of NAHL.

5 ) Propeller-hull interaction. A self-powered test has been conducted over the oDerating meed range to de-

I Figure 18. EHP versus speed for 108-ft YP expanded from 5-ft model data (YP81-7).

52

termine the quasi-propulsive coefficient, QPC. The results for the tests run by the Class of 1986 are shown in Figure 25.

Naval Engineers Journal, January 1987


Figure 19, YP performance in shallow water estimated from model tests.

' 0 I 2 3 4 s G 7 6

Figure 20. Curves of declining roll angles for 5-ft YP models.

6) Open water rudder performance. Rudders built to 1/6 scale by Don Bunker of the NAHL staff were tested in the circulating water channel. The results shown in Figure 26 are at least qualitatively reasonable.

7) Overall intact transverse stability. Experimental de- terminations of the curves of statical stability (right- ing arm versus angle of heel for fixed displacement

igure 21. Roll RAO for YP at zero speed in beam seas based on 5-ft model tests.

3 K75)

Figure 22. Head seas RAOs of pitch and heave in long crested regular waves.



P€€d Figure 23. Short term responses to long crested head seas.

ADVANCE GEFF/C/~NT; J 1 ‘igure 24. Open water performance curves for model YP pro-

peller.

and weight distribution) have been performed during laboratory exercises in the ship stability course under the direction of Professor Bruce Nehrling. Such curves, showing the effect of section shape, are given in Figure 27.

During the spring semester of 1986, an interesting study was performed by Midn. Matthew Ware, USN, in which he compared the performance and cost characteristics of streamlined versus the “as installed” externally stiffened flat plate rudders. While the peak lift-to-drag ratios were as much as 2.5 to 3.0 times higher for the streamlined (NACA 0015) rudder at an angle of attack


Figure 25. SHP test results for 108-ft based on 18-ft model tests.

ANqLE O f ATTACK (DE~RSS)

Figure 26. YP rudder characteristics in open flow.

of 5 ” , the obvious hydrodynamic advantage of the streamlined rudder must be weighed against the estimated $8,000 increase in acquisition cost for the streamlined rudder. Fuel savings, improvement in turning


~~~~~ ~

Figure 27. Experimentally determined curves of intact static stability for YP hull forms.

ability and differences in maintainability over the craft’s operational life must be traded off against the higher up-front cost.

LEAD SHIP DETAIL DESIGN, CONSTRUCTION, LAUNCHING, AND

BUILDERS TRIALS

With the completion of contract design, NAVSEA issued requests for proposals from shipbuilders who had been identified as possible lead yards for the new YP class. The first seven boats were to be built by the lead yard with the remaining thirteen to be built under a separate, subsequent contract. Peterson Builders, Inc. (PBI) of Sturgeon Bay, Wisconsin, emerged from a field of six responding shipbuilders as the winner of the lead yard contract.

As can be expected from any lead ship of her class, the YP-676 detail design had its fair share of engineering problems. In the case of outer planking lumber, a problem was encountered due to the fact that the species called for by the specifications (long leaf yellow pine) was not available. A change to Douglas fir outer planking was agreed upon. However, since Douglas fir is less dense than long leaf yellow pine, the total planking thickness had to be increased from 2 inches to 2% inches to satisfy “Lloyd’s Rules and Regulations for the Classification of Yachts and Small Craft,” which were imposed by the specification. This problem was further complicated by the question of whether the outer planks should be mill- ed with flat grain or vertical grain. Traditional wood shipbuilding practice calls for flat grain (grain runs parallel with the width of the plank as viewed from the end), being that it is more conformant to the ship’s curves and has less tendency to split. Vertical grain (grain runs parallel with the thickness of the plank as viewed from the end) planking on the other hand is stiffer and holds paint better although its cost is higher and is harder to work with. It was finally decided to go with the flat grain.

The specifications called for an analysis of the new YP-676 airborne and structureborne noise levels and a report outlining the predicted levels as compared to the

specified allowable levels. The report revealed that specified maximum noise levels would be exceeded in almost every compartment. Recommended solutions to the problem ranged from adding insulation to the boun- daries of compartments to extensive structural and machinery changes. To fully meet the noise specification would have been extremely expensive and disruptive to the design and construction schedule, involving such treatments as “floating” the deckhouse and constructing special high transmission loss areas into the hull in way of the propellers. These treatments would also add to the craft’s weight. Intensive trade-off discussions were held between all parties concerned. The final decision was that the most cost and schedule effective noise reduction measures would be employed, even if the maximum specified noise levels were exceeded slightly. This amounted to adding and/or changing insulation, adding mass loaded (lead vinyl) noise barriers, and vibration isolation of the main engines and diesel generator sets. As it turned out, the treatments were highly efficient and the end results well justified the decisions made during the fast paced tradeoff efforts.

One problem encountered was bolting of the keel at its deepest section. The contract design called for two keel bolts to be driven side by side at each frame through the keel, frame and keelson, which totals over 5 feet deep in places. At those depths, the drill bit has a tendency to wander and exit the side of the keel. As a solution to this problem, “windows” were cut into the keel just below the connection where the bolts were terminated. After nuts were installed, blocks were fitted and glued into place for a watertight seal, as shown in Figure 28.

Hull construction was performed indoors and, during the heating season, special measures had to be taken to prevent excessive drying, shrinkage, and checking of the wood. For this reason, a humidification system was maintained in the construction building to keep the am- bient humidity at an acceptable level. The deckhouse, being of all aluminum construction, was fabricated and partially outfitted as a separate module and then installed on the hull just before launch. All components were lofted and cut using numerically controlled equipment. Control of warpage was an ongoing problem, requiring constant attention to welding procedures and sequencing.

Launching proved to be a challenge. The YP in launch condition was too heavy for the yard cranes to sling launch, and the launching ways were occupied at the time by other construction. A plan was subsequently devised whereby the YP was rolled on aircraft wheel dollies onto a barge which transported it to a neigh- boring shipyard. There, a gantry crane lifted it off the barge and set it in the water. The launch was entirely successful, but follow-on launches were accomplished directly off the dock at the contractor’s yard.

Once in the water, propeller shafts were aligned and the vessel inclined. The inclining experiment verified previous predictions that the new YP would be a very stable boat.

Builder’s trials were held on 15 August 1984, and acceptance trials were held one week later. Propeller trials and fuel consumption tests were run in conjunction with



Face

L I

3” x 6” Access Windows Plugged & Sealed After Nuts Installed

Figure 28. Modifiid keel bolting arrangement. builder’s trials. The propeller trials showed that the propellers were not absorbing full torque of the main engines at rated rpm and would require repitching from 54.6” to 58”. As a further complication, it was dis- covered during trials that the propellers were “singing” over a 400-500 engine RPM band. The problem was analyzed and a recommendation was made to grind the trailing edges of the blades to a sharp chisel edge as shown in Figure 29. This was done and the problem was solved. Another major problem that surfaced during builder’s trials was that the port rudder would not achieve full 35” travel during full power turns. This was traced to flexing of the rudder stock and remedied by the addition of a bearing at the top of the stock. A second acceptance trial was run in November to demon- strate correction of these discrepancies. During these trials, the YP was highly maneuverable and stable.

igure 30. Model-full scale power and RPM correlation plot.


Original Profile

inging.

TURNING CHARRCTERISTICS FOR 108 FOOT YP 676

. ‘m 20 I0 10 20 M

RIGHT- - LiFT RUOOER ANGLE - OEGREES TACTICAL DIANETER AS A FUNCTION

OF RUDDER ANGLE AND SPEED

DThISRDC MOD€L D A T A (-A=&

M43K A C l L l i - Y

A = /6Z L r u,. 7 K r

Figure 31. Model-full scale maneuvering correlation plots; a) Trial data, b) Model data.


YP-676 departed on her delivery trip via the St. Law- rence Seaway on 14 November 1984. This was a true test of her seaworthiness, having encountered 20-foot seas in the North Atlantic off Nova Scotia. Although the boat rolled as much as 45" and took solid waves over the bow, the only ill effect suffered was to some copper ice sheathing which came loose from the hull. This was later replaced, and the follow hulls' attachment method was modified to prevent a recurrence of the problem.

IMPACT ON SUPPORT FACILITIES

The Small Craft Facility of the U.S. Naval Station, Annapolis, whose job it is to maintain and dock the new class of YPs, faced as acute problem with the decision to acquire a fleet of 20 108-ft YPs, since only 15 were formerly supported. The new craft were of conventionally planked wooden construction to prevent any major skills shift among Naval Station civilian and military workers, but the major impacts on workload, berthing slips, craft handling systems, and shops could not be avoided.

Major improvements to accommodate the larger fleet include:

Reconstruction of YP convenience berthing facilities

Construction of a repair berth. Acquiring a IargeTravelift and a new repair building in which major work can be accomplished under roof. Construction of finger piers to support the Travelift during lifting and launching operations. Upgrading of supporting shops space and equipment.

and upgrading of shore-to-ship utilities.

Naval Station military personnel increases will be required because the complement of the 108-ft Y P is four (one more than 80-ft YP) and there are to be additional craft. Civilian personnel increases are expected to num- ber between 10 and 15.

MODEL-FULL SCALE CORRELATIONS

The first set of full scale data from trials conducted by NAVSEACOMBATSYSENGSTA-Norfolk on YP-676 became available in March 1986. These included power, maneuvering, and seakeeping trials. YP-676 was instru- mented with torque and RPM meters and ran a measured course to develop a SHP versus speed curve. These data (identified by square plot symbols) are compared to the one-sixth scale model SHP test data (identified by solid circle plot symbols), collected by midshipman naval architects during the fall of 1985, in Figure 30. The degree of correlation is encouraging. At the design speed of 12 knots, model predicted DHP exceeds trial SHP by 4% while model predicted engine RPM (as- suming installed gear ratio of 5: 16: 1) is about 3 % lower than the trial RPM. Figure 31 shows how the radio-controlled model test maneuvering data, acquired in the large rectangular basin in the Harold Saunders facility, correlates with the NAVSEA trial data. It should be noted that the model was fitted with streamlined rudders while the full scale YP was fitted with flat plate, ex-

ternally stiffened rudders. In Figure 31(b), the indicated interpolation refers to linear interpolation on speed to match the 7-knot condition modeled at DTNSRDC.

It is hoped that the correlation of model data with full- scale trial data can be the subject of several technical reports yet to be written by authors from both NAVSEACOMBATSYSENGSTA-Norfolk and NAHL.

SPECIAL SERVICE MODIFICATIONS

Among the first departments at the Naval Academy to ponder a special modification to the 108' YP was the Oceanography Department. The present research vessel is an 8O-foot YP (YP-654) modified to carry oceanographic equipment. The modification is constrained to installations which can be removed on short notice to allow the ship to be used for seamanship and navigation training. There are additional constraints of deck space and electrical power which limit the usefulness of the

A design study [16, 171 completed in 1974, proposed a modified offshore supply boat to meet the mobile laboratory needs of the Naval Academy. Although this concept went no further than the design report, certain information collected for that effort has found use in the present 108-ft YP design process.

The procurement of the replacement YP provided a potential opportunity to improve oceanographic research vessel capability by either:

a. extensive modification of an existing 80-ft YP for use as a dedicated resource for oceanography.

b. building an enhanced capability into one of the

The first option was thoroughly explored. The existing craft are old, but are very well maintained.

However, in spite of many advantages, the 80-ft YP has one serious flaw. The wind heel stability of the vessel is less than 50 knots in any of the proposed configurations. This makes the vessel unsuitable for training up to 200 miles offshore. No combination of proposed arrangement and equipment could solve this deficiency.

The potential use of a new YP is being explored by the Oceanography Department, starting with a list of support equipments, as shown in Table 11. One possible arrangement, shown in Figure 32 was found to present some difficulties. The new vessel is provided with equipment removal soft patches which inhibit the location of major deck equipment. The standard oceanographic winches require a mix of single and three-phase power. The winches could be modified (at an unspecified price), but the electrical load would still exceed the installed generating capacity. Finally, the new craft are twin engine, without hydraulic or air systems installed. Use of a power takeoff from the main engines would make it difficult to maintain precise maneuvering RPM while handling the varying pressures and flow demands of various pieces of oceanographic gear.

80-ft YP.

108-ft Y Ps.

ACKNOWLEDGMENTS The authors wish to acknowledge the many people

whose dedicated efforts made the transition from con- 57 Naval Engineers Journal, January 1987


_-- Figure 32. 108-ft YP oceanographic configuration.

cept to operating patrol craft a reality. With genuine apologies to contributors whose names are not listed, we thank most sincerely, Superintendents McKee and Law- rence and Cdr. Henry Schmidt, USN (deceased) from the Naval Academy; Don Bunker, Steve Enzinger, John Hill, Jeff Hough, John Hoyt, and John Yashin of the NAHL staff; Jack Reynolds from the U.S. Naval Sta- tion, Annapolis; Don Blount, Robert Hamilton, and Bill Reynolds from NAVSEACOMBATSYSENGSTA- Norfolk; Ken Hum from NAVSEA PMS 300; Leo Gard- ner from Supervisor of Shipbuilding, Sturgeon Bay, WI; Tom Soik and Dick Wilcox from Peterson Builders, Inc.; Helen Wanbaugh, Mary Palombo, and Sandy Whitcher for invaluable assistance in readying this report for presentation.

Table 11. Proposed YP-676 Modification Desk Area Weight Height

Sq. Ft. Lbs. Ft.

Bow Thruster Deck Equipment Deck Shelter Crane Deck Winch Portable Towing System Salinity-Temp-Depth Rig U-Frame (Deck-Edge) A-Frame (Deck-Edge) Stage (Deck-Edge) Hydrographic Winch

9 4000 8 10.2 9OOO 18

9 2000 5 6 2000 3 6 1400 4

4000 16 2000 8

6 2000 4

Lab Equipment

Laser Range Finder Loran C Miniranger and Raydist

Capability Omega Satellite Navigation G .O.E. S. Receiver Data Reduction Computer and

Plotter Depth recorder Geological Sparker Rosette Sampler

Lab benches and sink Current meter

REFERENCES

(11 Henderson, R. and B. Dunbar, Sail and Power, U.S. Naval Institute, Annapolis, MD, 1967.

[2] Compton, R., S. Enzinger, R. Miller, and B. Nehrling, “An Intact Hydrostatic Analysis of YP-660,” U.S. Naval Academy Division of Engineering and Weapons Report

[3] Wilson, T., “MV Silverado,” Marine Technology, Vol. 15, No. 2, April, 1978.

[4] Hatchell, E. and R. Hamilton, “Afloat Training Craft for the U.S. Naval Academy,” NAVSEACOMBAT- SYSENGSTA-Norfolk Report No. 6660-7 Jan. 1981.

[S] Beys, P., “Series 63 Round Bottom Boats,” Davidson Laboratory, Stevens Institute of Technology, Report 949, April, 1963.

[6] Spangler, P., “Turning and Maneuvering Characteristics for the 80-ft YP - Full Scale Trial Results,” NAVSEA- COMBATSYSENGSTA-Norfolk Report No. 6660-94, August, 1982.

[7] Rossignol, G., “Maneuvering Characteristics of the YP-676 Class Seamanship Training Craft as Represented by Radio-Controlled Model 9022,” DTNSRDUSPD- 1082-01, April, 1983.

[8] Blount, D. and D. Fox, “Small-Craft Power Predic- tion,” Marine Technology, Vol. 13, No. 1, January, 1976.

[9] Hankley - Unpublished data on a series of commercial propellers.

[ 101 Watkins, R., “Experimental Prediction of EHP Require- ments for a Proposed YP Hull Design,’’ U.S. Naval Academy Division of Engineering and Weapons Report EW-7-78, March, 1978.

[ l l ] Compton, R., J. Hoyt, and J. Hough, “USNA YP Re- placement Model Test Program: Zero Speed Beam Seas Rolling Tests,” U.S. Naval Academy Division of Engi- neering and Weapons Report EW-3-81, March, 1981.

[I21 Compton, R., “The Resistance of a Systematic Series of Semi-planing Transom Stern Hulls,” SNAME Hampton Roads Section Paper, October, 1985.

[13] Compton, R., “USNA YP Replacement Model Test Pro- gram: Effective Horsepower Tests for YP81-7,” U.S. Naval Academy Division of Engineering and Weapons Report EW-20-82, July, 1982.

[ 141 Comstock, J. (editor), Principles of Naval Architecture, SNAME, New York, 1967.

[ 151 Blount, D., “Resistance and Propulsion Characteristics of a Round Bottom Boat,” DTMB Hydromechanics Lab- oratory R & D Report No. 2000, March, 1963.

[I61 Compton, R., “A Mobile Marine Laboratory System for the U.S. Naval Academy: Analysis of Need and Specifi- cation of Requirements,” U.S. Naval Academy Division of Engineering and Weapons Report EW-5-74, July, 1974.

[17] Compton, R., “A Mobile Marine Laboratory System for the U.S. Naval Academy: Conceptual Design Study,” U.S. Naval Academy Division of Engineering and Weap- ons Report EW-6-74, July, 1974.

EW-6-77, July, 1977.


Yard Patrol From 108' Concept to Delivery

Documents

Transcript of Yard Patrol From 108' Concept to Delivery