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THE SOCIETYOF NAVALARCHITECTSANO MARINEENGINEERS74 Trinitylace,ew York,N.Y.,0006Paper.bepresentedttheShiptructureYmposl.mWashl@m,.C.,October8,1975

Structural Developments: Inland WaterwayTowboats and BargesJames O. Gundlach, Visitor, Canal Barge Company, Inc., New Orleans, La.

0 Copyright975byTheS.C#ety NavalArchitectsndMar!..ng,neersABSTRACT

The harsh, exacting environmentof the inland waterways requires acentinual search for safer, moreefficient and more reliable equipmentand methods. While traditional research and development efforts haveaccounted for much of the progressthus far, parallel headway has been madeby innovative operators seekizg higherlevels of productivityy and reliabilityy.

Many improvements have occurredin the past and many are yet to come,hut this goal ca be reached far moreexpeditiously by free md easy exchangeof informat ion between designers,builders and operators. It is in-cumbent upon designers and buildersto follow their creations into therivers and canals to ie.uthem inservice, looking for flaws amweaknesses. It is ecpally importantthat we operators share experiencesand ideas, not only with one another,hut with the design and buildimgcommunity, as well. With an open andreceptive exchange of information wecan effectively utilize real-worldoperations as a research and development envircmment for future growth,INTRODUCTION

Developments or improvements inany system usually come as the resultof research and development efforts orthrough iovations based on fieldexperience. In the past one hmdredand fifty years river equipment in theUnited States has experienced manytechnological adXnCemets which cameby way of the former. By contrast,this report deals with several re-finements, most of which are theproducts of the latter. Canal BargeCompany is an operating barge line andnot a research and development enterprise. aut we, like so many others, havemade significant developments by aninquisitive and analytical search forbetter utilization of the equipment weoperate. The credo which guides us issimply stated: when solving a problem,

find and cure the cause; treat just notthe symptom.What are the incentives that produs to solutions? Obviously, increasedproductivity and safety of the equipmentis dominant, but this goal is reachedby a dual path. Surely higher operatingperformance characteristics, i.e., speedand tonnage, improve productivityy. Butjust as important in this quest is theminimization of equipment idleness forcedon the operator by needed maintenanceand repairs. Fortunately, sizeable gainshave been made in both areas, withclassic research and development account-ing for most of the performance improvements and field developments generatingmost of the increased utilizationthrough better ,,maintainability.,Tbe current rules and regulations prodweriver equipment designs quite adequateto perform their expected tasks safelyand efficiently. Why then tbe need forinmrovisat ions? For one. comuet itionsp~rs us to achieve higher le~els ofefficiency and lower operating costs.Unforeseen operating requirementssimilarly dictate a need for change inequipment characteristics. And of nosmall importance is the economic pressureto create equipment capable of with-standing the countless impacts andabrasions during a full lifetime ofriver service.Technology has brought the inlandwaterway industry to its present high

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clegreeof proficiency. It has not beensheer luck, or accidental, or only theproduct of trial-and-error experiencesthat has carried us from the flatboatsand keelboats of the eighteenthcentury, past the steamboat and packetboat era, and through tbe developmentof the diesel-powered towboats andspecialized barges of today. Thisprogress bas been the result ofsystematic development based on soundtechnology, and nothing less.

Of utmost importance in anydiscourse on river equipment technologyis the understanding of their uniqueservice conditions and operatingrequirements. Quite often we operatorsfind marine researchers, boat andbarge designers, and our regulatoryagencies do not fully understand theuniqueness of the rivers and canals.In fact one might generalize by sayingthe only thing common to river andocean equipment is that both float inwater and transport freight. Beyondthat there is little commonality.Ships are built, sail the oceans fordecades, and barring grounding andcollisions, the only things they touch,save water, are piers when docking (andusually these with the aid of tugs)Conversely towboats and barges are builtand from that moment to retirementtheirs is a life of repeated impacts,grounding and abrasions.

On tbe other band, ships mustendure the ravaging effects of stormyweather at sea, while river equipmentseldom is exposed to any severe waveaction Obviously, the basic hullstreng,h required of ships is fargreater than that of river boats andbarges. By the same token ships needvery little localized stiffening, addedstrength or abrasion protection, whileon river equipment these are absolutelyessential.TOWBOAT DEVELOPMENTSIncreased Power: Todays towboats arerefinements of those which came on thescene in the decade prior to World WarII. The diesel engi~e prompted theshift from steam, and with it came im-proved reverse-reduction gears andclutches. With a relatively low-weight and compact power train available towboats have progressed steadilyfrom a few hundred horsepower to the10,000 horsepower brutes now inservice. But the changes have not allbeen in increased power. There ishardly a.system on a boat that has notbeen improved many times in tbe recentpast Bt what changes have occurredin boats structures?

One readily apparent change hasbeen the capability of increased horse-power with no increase in overall boat

size. In fact, some modern higher powerecboats are smaller than their lower powere,predecessors.Packing more power into a towingessel implies the need for greater hullrigidity. But as power levels have in-creased, the propellers have grown indiameter up to about 10 feet. With;;~czl water depths in the range of 9the propellers must be recessed

into tunnels,under the stern. Thesetunnels have the effect of reducimg hulldepths in this critical location which,unless compensated for, would lessenrather than increase the rigidity, Onecommon correction has been to raise thedeck near the stern, thereby returningthe vital section modulus by deepeningtbe bull. Another is to utilize thestructure of the deck house in thisarea to provide the additional stiffnessrequired. A third method has been tomodify and enlarge the structural mem-hers of the hull, especially those intbe after parts of the vessel.To those who have not experienced

a high-horsepower towboat in service,when the vessel is moving abead at fullspeed and suddenly the propellers arereversed with the >lanking (or reverse)rudders turned to one side and thesteering rudders to the other, theviolent vibrations then encountered aredifficult to describe adequately. Ithas been said this is perhaps the mosttortuous maneuver one can ask of anyboat , and yet it is a common occurrencewith almost all river towboats. Sincethis maneuver is an operational necessityit is likewise necessary the hull struc-ture be designed and built to accommodateit. This has been achieved in part bythe same techniques outlined before,but,as the entire vessel is subjectedto the violent shaking, the structurethroughout has had to be strengthenedand stiffened. Hull plate thicknesseshave been increased; bulkheads, trusses,and frames are made continuous throughintersecting bulkheads; and machineryfomdations made heavier and a part ofthe hull structure where possible.Kort Nozzles: From a structural viewpoint, the most complex portion of manytowboats, especially tbe higher poweredones, are the Kort nozzles enshroudingtbe propellers. These devices enhancethe thrust production under load significantly and are quite common onvessels in excess of 4000 horsepower.But,the advantages of the nozzles didnot come cheaply. Early nozzles werehigh maintenance items. Inadequateinternal framing, insufficient welding,thin shell plating and weak hull attach-ments combined to produce nozzlesneeding frequent repairs. Rather quickly,designers and builders modified andstrengthened this critical structure toa point where now one can usually expect

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nozzles to perform for years with littleor no repairs. One significant change,which surely has heen of great importancehere, has been to eliminate from thenozzlPs the pintlt!pins and gudgeoplates commonly used to support boththe steering and flanking rudders. Theviolent and turbulent forces imposed othe boat ,s rudders would be transmitteddirectly into the nozzles through thepintle pins, and thereby imposed con-tinual high-energy vibrations into theirstructure. It is no wonder early nozzleswith rudder bearings attached were suchproblems.Skin Coolers: One novel use of the Kortnozzle that has been tried, albeit s-uccessfully, is that of a skin coolerfor engine cooling water. Notwith-standing the wroblem of keenin.zthenozzle ~atert~ght , it would be-an idealcooler. The high external watervelocities would produce heat transfercoefficients sufficient to reject anyengine, s requirements. But e;en todiyit is practically inqms.ible to dependon tbe nozzle as a vm.tertigbt vessel ,and so it has bee abandoned as a cooler.

Kort nozzles are not the onlylocation found to be undesirable for theplacement of skin coolers, however Nottoo many years ago, it was a very commonpractice to place the skin coolers onthe bottom of towboats, These were oftwo basic types. One was an internalcooler with the hull ,.sbottom plate for-ming the exterior side of the cooler.The other was an external cooler affixedto the outside of the bottom plate. Ineither case the location bas proved tobe very undesirable! especially aftera few years of service. The abrasiveaction of rubbing the river bottomsin shallow w~ter thins the plate, u-ltimately resulting i failures ad leaks,Even a small skin cooler leak must berepaired promptly and this is anotherpoint of contention with bottom coolers:when repairs nmst be made, they arevery difficult and expensive. The re-pairs require overhead welding whiletbe welder is usually i a prone positionTo complicate the problem, the verydocking of the boat frequently damagesbottom coolers. Large towboats weighseveral hundred tons, and may be spport-ed on hut a few blocks. The loadingon the hull in way of tbe blocks issufficient to distort and upset tbeplate. Should it be weakened de toreduced thickness from abrasion, thedocking load can, and has, caused platefailures which are usually found cmlyafter the boat is returned to the water,

h obvious solution to the coolerlocation problem is to place them elsewhere. This is now easily accomplishedby mounting tbe coolers on tbe bullsides. To provide the surface areaneeded one must use a separate extruded

tubular exchanger or a formed plate ol-channel-t ype cooler, Either choice isacceptable, but each type must be givensome protecticm from impacts and rubbingalong lock walls and docks. If repairsshould be necessary, boweer, they arerelatively easy and accessible.Retractable Pilot-House: To one unfa-miliar with inland river towboats, thesight of a retractable Dilot.house boatmu~t give a strange imp~ession. Hereis a vessel, its deck house confined toa single level, with only its pilot-house extended atop a bydralic. ram,sometimes approaching an elevation of40 feet above water level. If notblessed with the beaty of the swan ,surely these boats bze its style andgrace. Only they can lower their ,,heads,,to pass low fixed bridges which wouldbait most of their fixed pilot-housecounterparts. Tbe upper reach of theIllinois River near Chicago has seweralof these bridges, but as most of youare aware many of tbe riers we plyexperience some extraordinary changesin water leels. It is not at all ararity, therefore, for high fixed pilot-house boats to find otherwise pass~blebridges on the Ohio River and otherstemporarily blocking passage becausethey are too near tbe wxter surface.

Some might ask then, why not buildonly ,,retractables?,, A good question,but many boats are built to ply only theMississippi River, and of that , onlybelow St. Louis, Missouri or even Cairo,Illinois at the confluence with the OhioRiver. This part of tbe Mississippihas no bridge which would impede eventbe highest fixed pilot-house boat oftoday These limited-route boats thoughgenerally are the highest powered vessels,But what of the great number of otherboats which may see service on anynavi=able stream? Would not tberetractable design be the most versatileand functional ? In my opmlon, anytowboat built to see unrestricted serviceshould be of this type, simply becausea retractable pilothouse towboat cando anvthine a fixed Dilot-house boatcan, iut tiiereverse statement cannotbe made.If retractable are a desirabledesign, do they present any unusualstructural problems? Yes, some, but notoverwhelming ones. Basically, their

bulls are much like any other, the onlydifference being in the supports forthe lifting ram and guides. Perhaps thebiggest structural difference is in thedeck house. Since the retractable hasonly a single level house, its contribu-tion to overall hull rigidity would beless, if compensations are not made forextra stiffness.Towing Knees: Another noteworthy field-conceived improvement in towboat structure


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is in the towing knees, These triangularshaped appendages on the bow decks of alltowboats provide the boat 1s contact sur.face when pushing barges. Obviously,they must be of great strength and theyare. From a strength point-of-view, Ithink all builders have solved thisproblem. But the towknee is mm-e thana pushing surface. When pushing bargeswhose decks are higher than tbe fore+deck of the towboat, the towknees alsoserve as stairways. Most all areequipped with steps up their rear slopingsurfaces. Tbe problem thus created isif the barge deck is lower than thetop of the towkee, crewmen must climbto the top and then step or jump downto the barge. Ideally the empty bargedeck would be even with the top of thetowknees, while loaded barge decks wouldbe flush with the foredeck of the boatUnfortunately, the wide variance inbarges often places their deck at amintermediate level, forcing one toeither climb up or down. With riggingor other heavy loads in hand thisprestmts a hazard. The solution :construct the knees with an additionalsloping surface with steps from thetop, extending inboard, adjacent tothe headlog down to the deck. Then,providing the knees are at least ashigh as the highest barge decks, nomatter what deck elevation is encounter-ed thereafter one can step acrosssafely and comfortably.BARGE DEVELOPMENTSGeneral Considerateions: The concept ofbarging as we know it todzy began almost150 years ago when wooden keelboatswere lashed to steamboats. Over twentyyears passed however before the firststeamboat was built ad operated ex-pressly as a towboat for barges. How-ever, another twenty years were to passbefore barges in numbers became acommon sight. The technology of bargedesign moved ahead in the latter Dartof tiie19th century and the first30years of this century, bt with thecompletion of the Ohio River improve-ment project in 1929, this industryspurted ahead to a new level of activity.Other rivers were then improved and thebarge business continued to expand andit is still growing today.

This growth i size should otovershadow the tecbical growth i bargedesigns brought on by the wide varietyof commodities shipped. Structurally,the barges of today are highly developed,and though some might wish them to bestronger, more damage resistant and lessvulnerable to spilling their cargoes, itshould be acknowledged they are thesafest vehicles for bulk commodities inuse. Yet each one of those desirablegoals is sought by every barge operator,and as everyone kmws we now can makebarges stronger and more damage re-

sistant, But to do so almost alwaysimplies more displacement (light) andless cargo weight to be carried. In tbeextreme we can produce structures thatwould be practically impenetrable, btthis is economic foolishness. No, wemust search for compromises in theseattempts at improving barge structures.And it should be emphasized stronglythat a structure which appeals to oneoperation may be unacceptable to another.Certain situations may allow for bargesto be removed temporarily from servicefor repairs, but when in service demandmaximum cargo tonnages aboard. Othersmay allow almost no dovmtime, but emtolerate small reductions in cargotonnage. The point here is that it isnot possible to generalize and makeblanket statements on what is the ,,est,,design for all.In our operation, we have only tmkbarges, many of which are highly special-ized. Their capital Requirements arenatu.ally nmch higher than typical dry-cargo hopper barges. Since the capitalcost of a barge is E prime factor in

determining allowable downtine, we havefound it prudent to incorporate severalfeatures in our barges which add totheir weight (and reduce cargo tonnages)in order to avoid costly prematureidleness and repairs later.Bilge Knuckle Modif ications: One itemfound to contribute significantly tohull maintenance in ow scope ofoperations was the bilge knucklewearing thin prematurely due to abrasion.That this area is one of high wear shouldcome as no surprise. If one imagines +barge of rectangular cross-sectionfloating in a stream whose bottom pro-file is somewhat elliptical in shape,the point of Contact , should a grOdingoccur ,,is at the knuckles. Surely notall river beds are elliptical in shape,but the wear patterns we see indicatethe knuckles rub the bottom more thandoes the flat section in between. Oursolution to this is to add a wearingallowance to the plate thickness re-quired by the ABS rules. In a bargemeasuring 25o feet long,,the requiredthickness is about 3/8 Inch. Our stand.ard Practice is to use 3/4 inch, so wehave an additional 3/8 inch wearallowance. In this barge we sacrificeabout 10 tons of cargo capacity becauseof this, but we know these knuckles willgive at least 20 years of almost troble-free service, whereas the required 3/Binch knuckle will usually require majorrepairs or replacement after eight toten years service, depending on routestravslled.

A feature we include in the use ofthe extra-thick knuckles is a lap-jointattachment to tbe side plate and bottomplate rather than the customary bttweldconnection. The advantage of the lap,


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with the knuckle outside both bottomand side plates, is it acts as acontinuous 3/4 inch thick rubbing stripprotect ing the adjscent plating.Reduction of Hard-Spots: Anotherpractice adopted in tbe design of bilgeknuckles is to eliminate hard-spotsas much as possible. Hard spots arethose areas where a strone transverseor vertical member attacb~s directlyto the side or bottom plating. If sucha frame or member is attached to theknuckle it surely will create a spotfor concentrated wear. When the knucklesimpact severely with the bottom theyflex inward, often taking a permanentdeformation. But at the point of rein-forcement behind the knuckle, it willusually prevent or reduce tbe deformat ion. This causes the ,,ard-spots,,to protrude out from the surrmndingplate. From this time on these spotswill wear thin much faster tbam tbeplate around them.

The use of the thicker knucklesalso did create a minor problem i tbeadjscent hull structure of some barges.In double-sided or double-skin bargesemploying transverse wing tank stiff-ener plates in lieu of builtup trusses,it was found a minor impact from tbeside on the stiff ! thick kmcklewould pull the thinner bottom plateaway from the stiffener plate if thisplate was not welded to the bottomplate at the lap joint. (See Figure 1)

Early designs faced the toe of tbeouter bottom longitudinal frame inboard.With this frame placed directly overthe lap joint, tbe notch cut in tbestiffener plate to allow passage ofthis frame caused the bottom plate tofirst contact the stiffener plate severalinches away from the lap. Upon impactat the knuckle its stiffness caused theadjacent bottom plate to flex downward.If even a moderate impact occurred tbebottom plate might tear away from thestiffener plate and fracture itselfin tbe process thus creating a leak.The solution here is fortunately simple.We have found by only revei-sing thealignment of the outer bottom longitudinalso itS toe faces outward (rather thaninward) , the stiffener plate can beattached easily to tbe bottom plate inway of the lap joint. The bottom platethen does not have the flexibility tobend and tear. Tbe forces imposed onthe vulnerable weld attachment are moreparallel with the weldment rather thanacross it, (as in the earlier method)and the unit stresses are reducedporportionally.

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Spot of Sottom FailuresEARLY DESIGN

LATER DESIGNBILGE KNUCKLE DESIGNS

FIGURE 1

The problem just described surelymust appear to a designer or builder astrifling, but to tbe operator it can bea major and very expensive nuisance.We view this problem as an example oftbe lack of understanding by designersof the unique character of the riverenvironment mentioned before. Unfortun-ately this character is not always appar-ent on the drawing board. It is onlyfully revezled in the barsb world ofbarges banging into each other, smackingand sliding along lock walls, landingagainst docks and piers, smashing intoice up to two feet thick, and rubbingshallow river bottoms.Another subtle improvement we havemade in double-side or double-skin barge

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designs is to reduce to a minimun memberswhich may, if impacts or collisionsoccur , cause a penetration of the cargotank bulkhead. Even if the outer hullshould remain tight, cargo spilled intoa wing void can be a costly problem.Some designers feel the wing tank trans-verse framing, stiffener plates andbulkbeads should be stiff ad stout inthe transverse direct ion. Certainly,there must he transverse strength,btto make inflexible structures will onlylead to wing bulkhead failures, In ourexperience, we would much prefer toreplace z bent or buckled plate or framein a ,Sclean,wing tank than to repair afractured cargo blkbead which haddeposited its product into the void.

The varieties of frame and bracketarrangements are many, but the designerand builder should be mindful of thesepotential problems when piecing togethera hull c+trctre. Remember j it isusually better in low to moderate pactsto let the structure flex and deformif it Must, rather than be extremelystiff, especially in concentrated spots,Longitudinal vs. Transverse Framing: Adiscussion of river barge hull structm-eswould not be complete witbout comparingthe two basic framing msthods, fordoubleskin designs, longitudinal versustransverse. Our fleet has severalof each, and in our opinion the longitdinally framed barge is the betterchoice, Recall, the service of atypical river barge consists of muchrubbing against fixed objects, and mostof this rubbing is in the longitudinaldirection. Therefm-e, a longitudinallyframed barge creates fewer ,,ardspots


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So much for structural improvementsto enhance the serviceabilityy of barges.No doubt there are many others deservingrecognit ion, but I should like to turnmy attention to a subject of particularinterest to many barge operators today.Most of you are probably aware thereare several cargoes commonly shippedwhich are heated, either enroute orprior to Ioadig and discharge. A few,like liquid sulpbr, command mmchattention and are usually carried cmlyin very specialized barges having in-devendet cargo tanks. free to ex!xindunder the hig~ operating ternpertit;e(2750F) Others like residual fuel oil,coal tar, waxes and asphalts have otattracted much technical attention, btI hope this will change, especially theones requiring higher temperatures.Fuel oil and coal tar normally arebeated to no more th?.1500F and 125FiS more common, but waxes require about200F and aspbatls, while unloaded atabout 250F, may be loaded at near 400F.Since these products, especially asphalt,are fairly low-reenue cargoes, mostbarge companies have not seen fit tocarry them in expensive and sophisticatedbarges. In short, the towing rates haveprohibited simg the type equipment tbecondit ions warrant. If this situationcontinues, is there a way to redesignthe lower cost barges (doublesides anddouble-skin) to accommodate the tempera-tures and not be p=one to tank failuresfrom tbe high stresses developed?

The double-skin barge gies themost protection from cargo spills intothe water, but with the carriage ofasphalt in these barges if the cargotank should allow the product to leakinto the innerbottcwn, the repairconsequewees are enormous. And sincethe temperature differential betweenthe cargo tank and the outer hull maybe as much as 350F, this calamity isa real possibility.The double-sided barge offers aninteresting prospect with this service.The possibility of product leaking intothe wing voids certainly exists, butif it shcmld, it is much easier to remove than from the inerbottmn of %double-skin barge. What can be done toprevent this from happening thcmgh?.4swe view it, the most likely zonefor wing bulkhead failures in doublesided designs is near tbe connection

with the bottom plate. The bottom plateis cooled by the river, while the hotproduct may raise the bulkhead fstemperatures to almost 4000F. It seemslogical then this is where to expecttrouble. It appears there is nopractical method of constructing thisbulkhead to allow flexibility along thiscritical juncture. One idea whichseems to have some promise here is toprohibit the lower portion of theselongitdina.1 bulkheads from exposure

to tbe high loading temperatures, Wefeel one practical way to accornpolisbthis is to construct a ,,dam,,a fewinches inboard of the bulkhead andparallel to it. During the firstloading the product would spill oerinto the isolated area and be trappedindefinitely, As the barge is unloadedthis small amount of cargo would remainin place. During subsequent unloadingit will act as an insulator to reducethe temperature on the lower part ofthe bulkhead proper. Surely, thebulkhead will receive heat hy conductionthrough the plate itself and even convection of the product trapped behindthe dam, but if this notion will reducethe temperature in the danger zonesufficiently, the stresses may becometolerable. To my knowledge this ideahas never been attempted in practiceand before it is, I think some researchis required, Should it prove to be aworkable solution it will hae gone t+lone wav toward solvine one of thepuz;les-of today< s bar~e operations.(See Figure 3)

WING BULKHEAD DESIGNCARGO INSULATING LOWER PART

FIGURE 3

CONCLUS IONI have alluded to many technicaldevelopments in our area of the marinetransportation field. Much of what hasbeen discussed has been the result ofinnovations based cm operational ex


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periences. Not discussed in detail,but certainly deserving acknowledgement,is the vast amount of fruitful researchspanning more than a century which hasdeveloped the inland waterway towingindustry into tbe safe, efficient andreliable system we have today. But wecannot stop here. To do so is to movebackwards. We need to continue ourefforts to improve reliability to makeour operations more safe, and to makebetter use of the resources availableto us. These goals can only beachieved if all of us, the researchcommunity, the designers and buildersand we operators coordinate our effortsand work together. Tbe opportunity tohave presented some of our thoughtsand ideas today is a fine example ofthis much needed spirit of cooperat ion.We thank You for allowing us to contri-bute.

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