Development of a Value Engineered NOMAD Buoy

DEVELOPMENT OF A VALUE-ENGINEERED NOMAD BUOY

GeraldTimpe (LT) William 0. Rainnie,Jr.

U.S. CoastGuard NOAA Data Buoy Office NOAA Data Buoy Office National Space TechnologyLaboratories NSTL Station, MS 39529 NSTL Station, MS 39529

ABSTRACT In July 1946, theBureau of Ships became involved in a program todevelop automatic weather station Sincethe mid-1970s, the National Oceanic andAtmo- buoys. As a perspectivepart of this program,they sphericAdministration (NOAA) Data Buoy Office requested DTM8 to conduct a preliminaryinvestiga- (NDBO) hasused Navy OceanographicMeteorological tioninto the feasibility of mooring a buoy, simi- AutomaticDevice (NOMAD) buoys as partof their lar to Buoy By in 3600 ft ofwater with a 3-kncur- oceandata gathering network. These U.S. Navy- rent.3This investigation concluded that a hull built,20-ft long, boat-shaped hulls, have proven thesize of Buoy B couldnot support the static to beextremely seaworthy buoys. The hullsare weightof an anchor lineof sufficient length to be reliable,easily transportable, and for many appli- moored in 3600 ft ofwater. To supportsuch a cations,they are an attractivealternative to the mooring, a similar shaped hull had to be 20-ftlong conventional40-ft and 33-ftdiameter discus-shaped and displaceapproximately 20,000 lb.This was to buoys. As a result, NDBO, inearly 1979,began become theprototype of the buoy now calledthe activelypursuing the idea of designing and con- NOMAD. structing a secondgeneration, value-engineered (VE) version of the NOMAD buoy. A consulting firm In 1952, thefirst NOMAD buoy, NOMAD-1, was built was contractedto redesign the NOMAD hull, and in accordinglyspecifications to prepared by June1981, construction was started on a series of DTMB,3,4 and was deliveredNationaltheto five new NOMAD buoys.This paper describes the Bureau of Standards (NBS), who was taskedwith the design and constructionof the VE NOMAD buoy, and jobof evaluating the buoy.5 From 1954 to 1971, detailsthe efforts of industry and government 20 additional NOMAD hulls were built and subse- workingtogether to produce a reliable,cost effec- quentlyoperated by the NBS, Naval Air System Com- tive data buoy. mand, and NavalUnderwater Systems Center (NUSC), withfavorable results.6-9

NOMAD DEVELOPMENT 20-ft NOMAD VS 40-ft DISCUS The NOMAD hullis we1 1-documented to have been develo ed fromthe "Roberts buoy" or "current radio In 1959, atthe behest ofthe Office ofNaval buoy."!-3 The Robertsbuoy was a 6.67-ft Research (ONR), theConvair Division ofGeneral long,400-lb, boat-shaped buoy developed inthe Dynamics (GO) Corporation was contractedto gener- early 1940s,by the U.S. Coast and GeodeticSurvey, atethedesign of a eneralpurpose telemetry to measure strongtidal currents. The buoy'sper- oceanographic buoy?lO,yl distancelong for formance was satisfactory,but its limited size (2500mi) transmissions of HF radiodata. The restrictedthe buoy's use inother areas. designcriteria called for the survival of the buoy inthe following environmental conditions: current The successortothe Roberts buoy was theNaval velocityof 10 kn, windvelocity of 150kn, 60-ft ResearchLaboratory (NRL)Mark 3 buoy.This hull highbreaking wave, and an unspecifiedice loading. was designed by NRL forhousing sono-radio equip- Model tests wereconducted on tencandidate hull ment,moored in a strongcurrent in deep water. It forms,with Preliminary indications showing that was 12.58-ftlong and displacedapproximately 4700 thetwo leading contenders were the 40-ft discus lb. The buoy resembledthe Roberts buoy, but with buoy and the NOMAD. In 1965, it was concludedthat increaseddimensions to accommodatea largerpay- the40-ft 200,000 lbdiscus buoy was thebest load.There were two tentative designs of the NRL choice, and, as a result,the "Monster Buoy" was Mark 3 buoy, designated Buoy A andBuoy B. The two developed. The NOMAD hull was rejectedprincipally designshad the same dimensionsin plane; however, becausethe buoy's excessive rollmotion resulted Buoy B had an approximately8-in. greater draft inhigh antennaradiation losses, and alsobecause than Buoy A. NRL taskedthe David Taylor Model thehull was notsymmetrical. Another problem with Basin (DTMB) to conductmodel tests on bothhull the NOMAD (althoughnot mentioned inthe refer- typ es to determinetypes to their performance.2 The ences) was thebuoy's relatively small displaced resultsof these model tests caused DTMB to recom- volume. Inthe mid-1960s when the"Monster Buoy" mend thefurther development of Buoy B because of was conceived,the vacuum tubeelectronics used for itsgreater load-carrying capacity. dataprocessing and transmissionrequired diesel or

605

US. Government work not protected by US. copyright. propanemotor generators to provide the necessary requiredforpresent and perspective NDBO buoy power. It wouldhave been impossibleto fit such a sites. These studiesconcluded that discus buoys powersystem intothe confines of a NOMAD hull. as large as49 ft mightnot survive on some north- Today, integratedcircuits and CMOS technologyhave ernPacific and northernAtlantic sites. drasticallyreduced the power requirements.This, coupledwith the use of the UHF satellite communi- cations, has eliminated,for NDBO's use, thepre- In December1978, NDBO sponsored a "SevereEnviron- viousobjections to the NOMAD hull. mentNorkshop" todiscuss the problem of discus buoy'scapsizing in a severeenvironment and to seek possiblesolutions.16 Among the many con- THE NOMAD AND NDBO clusions of theworkshop were that 40-ft buoys should be used inlieu of 33-ft buoys in severe InJuly 1974, NUSC transferredthree NOMADS to NDBO sites, and solidballast should beused inlieu of forevaluation and use, followed by thefive more waterball ast for 33-ft hulls on severesites. It hullsin June1975. NDBO has sinceacquired title was furthersuggested that the NOMAD buoy should be to 15 ofthe 21 NOMAD buoys built. Of these 15 considered as a possiblesolution tothe severe hulls,14 are still in use inthe NDBO buoyinven- environmentproblem. Intheir many yearsof use, tory. One hull,designated 6N9, brokeits mooring no capsizingof mooreda NOMAD has beenknown to offthe New Jerseycoast in October 1980,and was occur. subsequentlylost at sea.The final NOMAD buoy acquired came fromWashington, DC Navy Yard in NDBO fostered and seriouslypursued the possibility 1981, and isbelieved to be thefirst NOMAD built, of the NOMAD as a solutionto the severe environ- NOMAD-1. mentproblem. In 1979,a NOMAD was moored nextto a 40-ft buoy at 45.9"N latitude and 131.1"W longi- tude,the site of the first 33-ft buoy capsizing. The objective was two-fold:to test for the sur- The NOMAD hull has become a reliablepart of NDBO's vivabilityof the buoy and instruments and to check hullinventory. Infact, in many areas,such as theresulting data quality. A mooringfailure cut cost and ease oftransportation, the NOMAD is a shortthe experiment, but sufficient data were col- superiorhull to NDBO's 40-ft and 33-ftdiscus lectedto indicate that the NOMAD satisfiedboth of buoys. NOMAD hullsare smal ler and cheaper to thetest requirements. Subsequently, the NOMAD was buildthan the larger discus hulls. In 1981, the independentlydeployed at the site, and duringthat priceof a NOMAD hull was roughly 20 percent of periodsignificant wave heights as large as 33 ft thatof a 40-ftdiscus. In addition, the biannual wereencountered. This test, combined with mooring maintenancecost of an aluminum NOMAD isless than design changes that expanded the use ofinverse halfof that of the large discus buoys. There are catenarytype moorings,17 led theto tentative alsoeconomical advantages otherin areas. The conclusionthat the NOMAD buoy was capableof NOMAD'S smallsize makes the buoy transportable by replacing a 40-ftor33-ft hull anyon site. truckor rail, whereas thelarge discus hulls must Because ofthis, the decision wasmade notto build betowed or transported by shipfrom location to 40-ftor 49-ft hulls as severeenvironment buoys, location. The reduceddrag ona NOMAD hullpermits and instead go forwardwith the design and procure- theuse of smaller, moreeconomical mooring compo- ment of a second generation NOMAD buoy.However, nents.In spite of itsbeing an unsymmetricalbuoy onlyyears of experience with NOMAD buoys in severe withonly a 15-ftinstrument height, the NOMAD pro- environments will answer thequestion. ducesdata quality (including one-dimensional wave data)equivalent to the larger discus buoy. There may be limitations on directional wave measurement due tothe hull's being nonsymmetrical, but this VE NOMAD DESIGN problem is understudy. Due toits smaller size, the NOMAD isslightly more vulnerableto collision In June1979, NDBO contractedthe consulting firm and vandalismthan the larger discus hull; however, ofChi Associates, Inc., to examinethe original all-in-all,the NOMAD'S advantages faroutweigh its NOMAD buoydesign and suggestpossible modifica- disadvantages. tionsto the design to reduce the buoy's fabricationcost. The ChiAssociates work was performed inthree stages. First, given the operating environments theof buoys,Chi Associates was to SEVERE ENVIRONMENT BUOY developthe design criteria for the VE NOMAD. The resultantdesign criteria, detailed inTable 1, In a four-yearperiod, five of NDBO's discusbuoys followsthe same generallines as thedesign cri- havecapsized during severe weather events. Three teria developed for NDBO's VE 33-ftdiscus buoys. ofthese were 33-ftbuoys that capsized while Second, theoriginal structural design was modified moored inthe North Pacific. Onewas a 40-ft buoy slightly,after which the fabrication cost of the that becameunmoored and capsizedwhile adrift originaldesign was compared tothat of themodi- northeastof Bermuda. Onewas a 16-ft buoy, which fiedhull constructed of aluminum and tothat of capsizedwhile moored inthe Gulf Stream off the themodified hull constructed of steel. The cost coastof Florida. Environmental conditions associ- analysis showed that a substantialcost reduction atedwiththese capsizing were analyzed.12~13 was possible by alteringthe buoy's structural In addition,In in 1977studies14,15 were initi- design. The materialcost of the buoy accounted atedin an attemptto identify the capsizing mech- foronly approximately 25 percentofthe total anism,and fromthat determine the size of buoys fabricationcost of the buoy. As a result,the

606 fabricationcost of a steelhull was onlymargi- design. These modifications were all analyzed, and nallyless than that of an aluminum hull. Compar- ultimatelythe majority of themwere approved by ingthe two hulls on a lifecycle cost basis, the NDBO. The first two VE NOMAD buoys, hulls 6N16 and lowermaintenance and associatedtransportation 6N17, were deliveredin early 1982. The buoyswere costfavored the use of aluminum as thehull mater- modified,integrated withtheir meteorological ial;thus, the decision wasmade toprogress with packages, and weresubsequently deployed at the buoy redesignwith aluminum as thestructural National Weather Service (NWS) sponsoredstations material. The thirdpart of ChiAssociates work inthe Great Lakes. The remainingthree buoys in involvedthe actual design work ofvalue engineer- theAldi Corporation contract are scheduled to be ingthe NOMAD hullstructure. The effectof the delivered by early summer 1982. modifications,such as reducingthe number ofhull compartments,reducing the number ofstructural elements by increasingthe span length and plating PHYSICAL CHARACTERISTICS thickness, and using more economicalelement shapes and sizes, was enteredinto the design process and The VE NOMAD buoy is a boat-shapedhull, 20-ft analyzed. Once thehull design was optimized, a long,approximately 10-ft wide and 7-ft deep, with costanalysis revealed that the value-engineering exteriorlines virtually identical to thoseof the modificationsreduced thelabor cost associated original NOMAD buoy (Fig. 1). In its deployed withfabrication by approximately 50 percent and configuration,the buoyhas a displacementof loweredthe total fabrication cost by approximately 19,250 lb anda reservebuoyancy of 19,500 lb. The 40 percent. The ChiAssociates VE NOMAD design was buoy isconstructed of 5086 marinealloy aluminum, initiallydelivered in June 1980. Afteraltera- with1/2-in. thick deck and sideplating, and tions and revisionsthe design was accepted by 5/8-in.thick bottom and transomplating. In con- NDBO in March 1981.l8 trastto the original NOMAD'S eightcompartments, the VE NOMAD hasonly four main compartments -- threebattery compartments and one electronics com- Table 1. VE NOMAD DesignCriteria partment.

I. I. Hull Loading a) Deck Plating 450 psf b) Bottom and Side Plating 1,000 psf c) MooringForces 20,200 Ib maximum II. Superstructure Loading a) Wind Loading 37 psf (IO0 kn wind) b) InertialLoading Heave 2.0 g 0 Sway 0.5 g Surge 0.6 g Pitch 2.6 rad/sec2 SHEER PLAN BODV PLAN Ill. Buoyancy: Ensure that the buoy has sufficient reserve buoyancy such that any two compartments may be flooded, Length Overall 20.00 ft and the buoy will st1 II remain afloat. Width 9.66 ft Depth ft 7.04 Design Waterline (OWL) 5.00 ft DWL 302 ft3 Volume302 at DWL Once theChi Associates VE NOMAD design was delivered,work was begun toprepare the design for B lockCoef f entI cI CB 0.38 eventualprocurement. Working within the framework PrismaticCoefflcient Cp 0.51 ofthe Chi Associates design, NDBO's Engineering SectionArea Coefflcient CM 0.64 Divisionperformed the extensive detail design work WaterplaneCoefflcient Cwp 0.79 requiredfor the hull. Structural element inter- section and terminationdetails, structural mast Vertical Center of Buoyancy at DWL 3.54 ft Above Baseline Longitudinal Center of Buoyancy at DWL 8.78 ft Forward of foundations,handrail anddeck layout, buoya com- Transom partmentalventing system required by theair-de- Transverse Metacentric RadiusEMT 2.53 ft polarizedbatteries, anda revisedforward mast Longitudinal Metacentric RadiusEML 9.60 ft design were incorporatedinto the basic Chi Associ- ates work tocomplete the VE NOMAD design. Figure 1. NOMAD Hull Form In June 1981, aftercompetitive bidding, Aldi Corporation, a San Diegobased manufacturing and The VE NOMAD buoy is a volume constraineddesign; repairfacility, was awarded thecontract to con- therefore, it must be ballastedto its design dis- struct a series of five VE NOMAD buoys. The con- placementusing approximately 6,300 lb of bagged tractcalled for the basic hull and superstructure leadshot. Floor plates with access points were to be fabricated,with the battery racks and asso- installedin the bottom of eachmain compartment, ciatedmounting brackets for the buoy's meteorolog- making it possibleto secure the hull's ballast ical package to be installed oncethe buoyhas been intothe voids between the floor and shellplating, deliveredto NDBO's facilityat the National Space therebypreventing the ballast from shifting at TechnologyLaboratories (NSTL) Mississippi.in largeangles of buoy heel. Afterthe award ofthe contract, Aldi Corporation reviewedthe VE NOMAD design andrecommended sev- Inthe past years, there hasbeen an increasing eralmodifications that would improve both struc- concernabout ice loading onbuoys; thesuperstruc- turalefficiency and ease of fabricationofthe ture and deck layoutof the VE NOMAD reflectthat

60 7 concern. The cage-typeforward mast on theorigi- VE NOMAD 3.0 WI = 19,250 LB nalhull was replacedwith a hingedpipe mast in an 1 VCG - 0.29 FT P,,C"lWL"E SLOPE LCG = 106 IN. FORWARDT~n~son efforttoreduce the mast's projected area and 2.8 ~ KYy = 6.12 FT therebyminimize any possibleice accumulation on I n themast. In addition,the number ofobstructions on the deck ofthe VE NOMAD werereduced from that 2.4 2'6 I ofthe original hull.

Afterintegration, and justprior to its deploy- ment, an incliningexperiment was conducted on hull 6N16 to determinethe vertical center of gravity (VCG) ofthe VE NOMAD classof buoy. The experi- mentalresults corresponded very closely with the expectedresults calculated from the hull's fabri- cationdrawing and aretherefore viewed as reli- 1.0 1 able.During the same timeperiod, values of naturalperiod of pitch and roll weremeasured by 0.8 1 "sallying"the buoy,and fromthese values of naturalperiod, approximate values of longitudinal and transverseradii gyrationof were calculated.19Figure 2 listsnajorall physical parameterstheof buoy. With thisinformation, NDBO's frequencydomain hull and mooringresponse program20 was used generateto response ampli- tudeoperator (RAO) curvesfor the unmooredbuoy in the heave and pitch mode. As shown by thesecurves CONCLUSION inFig. 3, the VE NOMAD buoy exhibitsresonance in pitch(and to a lesserdegree in heave) at a fre- The VE NOMAD buoy was developed aas resultof quency of 2.6 rad/sec. However, thisis far to extensivedesign workby Chi Associates,Aldi theright-hand side of the spectrum in an areaof Corporation, and NDBO. The buoy incorporatedthe littleappreciable wave energy. provenperformance of the original NOMAD, such as itsreliability, reduced maintenance, and ease of transportation,with an optimizedstructural design,to produce a reliable,cost effective data buoy.Although somewhat limited,theexperience withthe VE NOMAD hasbeen good, and asa result, NDBO iscurrently planning construction of a second seriesof VE NOMAD buoys,with probable delivery in early 1983.

REFERENCES

1. E. 6. Roberts,"Investigation of Buoy Charac- teristics and theDesign of a Buoy forStrong Currents," U.S. Coast and GeodeticSurvey SpecialReport No. 130, February 1941.

2. R. Eisenberg,"Characteristics of the NRL Mark 3 Boat-Type Buoy and Determinationof Mooring LineSizes," David Taylor Model Basin Report No. 550, September 1945.

3. Roland A. Ebner,"The Development of Buoy a Displacement -- Delivered 8,300 Ib forMeteorological Set AN/SMT-1 and the Ground Oisplacement -- Bare Hull 9,400 Ib TackleforAnchoring,'' David Taylor Model Displacement -- Integrated (W/O Ballast) 12,700 ib BasinReport No. C-454, Decenber 1951. Displacement -- Deployed 19,250 Ib Metacentric Height (GM) --Deployed 1.70 ft 4. "Buoy forMeteorological Set AN/SMT-1,Assem- Vertical Center of Grav'ity-- Deployed 4.24 ft Above Base I i ne bly and Details,"David Taylor Model Basin Longitudinal Center of Gravity -- Deployed 8.78 ft Forward of Drawing No. S-10703, September 1951. Transom Rol I Period -- Deployed 3.5 5 5. WilliamHakkarinen, "Sea Operations with the Pitch PeriodPitch -- Deployed 2.4 s NOMAD Buoy," (privatecorrespondence) May Radius of Gyration About Longitudinal Axis 4.13 ft 1969. Radius of GyrationAbout Transverse AXIS 6.32ft 6. WilliamHakkarinen, "The World of NOMAD-1," MarineTechnology Society Buoy Technology Con- Figure 2. NOMADVE Buoy ferenceProceedings, March 1964.

608 7. Sydney 0. Marcus, Jr., "Evaluation of NOMAD-1 14. Anonymous, "An Evaluationtheof Capsizing Data Meteorologicalfor and Oceanographic BehaviorDiscusof Buoys Severalat Loca- Applications,"Marine Technology Society Buoy tions,"Hoffman Maritime Consultants, Inc., TechnologyConference, March 1964. Report No. 7883, July 1978.

8. R. E. Mattern,al.,et "The Meteorological 15. John H. Nath and S. TheodoreChester, Jr., Buoy Programme ofthe U.S. Navy," The Marine "Steep Wave SpectrumRelations and Buoy Relia- Observer,Vol. XXXVII, 1967. bility," NDBO ReportonContract 03-78-603- 0500, January1979. 9. James J. Gallagher, et a1 . , "NOMAD Buoy Opera- tions in Long Island Sound," NUSC, New London 16. Anonymous, "FinalReport of the NDBO Severe Laboratory TM No. TA131-11-74, April 1974. Environment Buoy Workshop," NDBO Report No. F-200-1, July 1979. 10. Anonymous, "Development of an Ocean DataSta- tionTelemetry Buoy ProgressReport," General 17. Anonymous, "NDBO Buoy Mooring Workshop DynamicsCorp., Report No. GD/C-65-018, May Report," NDBO Report No. F-320-2,September 1965. 1978.

11. Robert S. Devereauz and Feenan D. Jennings, 18. M. Basci, H. Yek, and M. Chi, "NOMAD Buoy "TheMonster Buoy," Geo-MarineTechnology, ValueEngineering," Associates,Chi June Apr i1 1966. 1980.

12.Glenn 0. Hamilton, "Buoy Capsizing Wave Condi- 19. J. P. Comstock, "Principles of NavalArchi- tions,"Mariners Weather Log, Vo.24,No. 3, tecture," The Society of NavalArchitects and May-June1980. MarineEngineers, New York,1967. 13.Glenn D. Hamilton,"Severe Buoy Wave Condi- 20. T. R. Goodman, P. Kaplan, T. P. Sargent, and tions,"press,in Mariners' Weather Log, J. Bentson, "Static and Dynamic Analysis of a 1982. Moored BuoySystem," Oceanics,Inc., April 1972.

609