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Building USS Cairo: A 1:35 Scale Scratch Built Scale Model

. . . . .

By C. A. Raven

History

USS Cairo (pronounced kay-row)was an 1862 City class ironclad for theUnion Navy. Designed for river use, it car-ried a large battery of assorted weapons,featured a steam-powered center paddle-wheel, and became famous for two very dif-ferent reasons. USS Cairo was the first

vessel in history to be sunk by an electri-cally detonated mine. Its subsequent rais-ing some one hundred years later becamenotorious as one of America’s greatest nau-tical archaeological disasters. Truly, a veryinteresting vessel that comes with a realbonus for the model builder: one may actu-ally visit what is left of this ship at its per-manent home at Vicksburg NationalMilitary Park in Mississippi.

Figure 1. All photographs by the builders.

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Plans

The decision to scratch build USSCairo at 1:35 scale was influenced by twofactors: the model would present a niceviewing size to reveal an elaborate gundeck, and further detail enhancements,such as figures and small caliber weapons,would be readily available. This very con-venient scale produced a model of aboutsixty inches in length. (Figure 1)

Research took over a year before wewere ready to start the model of USS Cairo.The value of detailed research cannot beemphasized enough. The five different setsof plans available all differ, and all requirecorrections. We took a set of plans and cor-rected the many inaccuracies. Theseincluded errors in cannon port cover sizeand height, beam width, and smokestackheight as the major issues.

Once corrected, a trip to our localprinting store was in order. Utilizing a largescale printer we created a full set of plans

at actual scale for about twenty dollars.The large sheets allow for a perfect matchwhen taking measurements to create themodel’s various parts. (Figure 2) Full sizeplan sheets further allow one to test thelocations of assemblies, such as weapons,and their subsequent rigging and recoilpaths.

Basswood Lay Up

We chose to build USS Cairo frombasswood as it closely resembles scale oak,when stained properly, while being easierto carve. Using full size plan sheets and apounce wheel, the outboard lines of theship were traced to the basswood blank.The profile of the ship’s lower hull is prettysimple with a slightly curved deck sheer.Cutting was done by quartering the bowand stern blocks so that each block may bepassed through a standard band saw.(Figure 3) First, each block was cut the cor-rect side profile of the ship. Setting the

Figure 2.

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sawtable at a twenty-seven degree bevelangle allowed cutting the ship’s shape asseen from above. The angle produced thesignature flared hull shape found in CityClass iron clads. Once all four quarter sec-tions were sawn to shape they wererejoined and coupled to the side rails.(Figure 4) Then we fitted the framing forthe center paddlewheel’s raceway. Thewaterway was planked using scale sheetplanking. A layer of eighth-inch apple plywas attached to the bottom of the hull.

The complete hull blank was glued, stapledand screwed together and faired.Applications of putty, followed by sanding,brought the lower hull to its final shape,ready for primer. We decided to paint thelower hull at this point, due to its largesize, since it seemed easier to flip the hullupside down to lay paint. The paint wasallowed to cure for two weeks before tapingand papering off to protect it during furtherconstruction. (Figure 5)

Figure 4. Figure 5.

Figure 3.

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Figure 6.

Figure 7.

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Weapons

USS Cairo carried a total of fourteenlarge guns, although, only thirteen weremounted for use. The variety of heavyweapons required the creation of two typesof gun carriages. Based on actual measure-ments from the carriages aboard the shipwe constructed wooden masters. We castsilicon molds of the carriage masters,allowing for many copies. (Figure 6) Resincastings were painted and detailed withhardware and compound blocks. (Figure 7)

Four separate types of gun barrelswould be required: Dahlgrens, forty-twopound rifles, thirty-two pound smooth-bores and one small Parrott rifle. Weturned to our good friend in Germany,Burkhardt Masch Kleinserien of BMK, fora full set of accurate, turned brass barrels.(Figure 8) Each barrel was then chemicallycolored using gun bluing, which in thiscase produced a brown tint to give a nicebronze patina. Cannon were mounted totheir carriages utilizing tiny threaded bolts.Each of four holes was drilled, tapped andcapped with strips of brass for the capsquares. (Figure 9)

The Wheel

Cairo‘s massive paddlewheel wasconstructed of four individual hoops withseventeen spokes each. These “spiders”were made of iron with oak paddles. Eachpaddle made from two boards apiece. Thespiders were further braced to each otherwith interlaced spokes like a bicycle.

Construction of this wheel beganusing a simple geometry computer pro-gram to generate a scale pattern drawingfor the hoops and spokes. The pattern wasused to fabricate a jig into which wereplaced .060-inch square styrene rod for thespokes. Rings were cut from .030-inchsheet styrene stock with a circle cutter.

(Figure 10) Once four spiders were com-pleted they were mounted together on abrass axle with spacers between them. The

Figure 8.

Figure 9.

Figure 10.

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Figure 11.

Figure 12.

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next task of weaving and installing theindividual woven spokes between thewheels was time consuming but the resultswere very good. The metalwork of the pad-dle wheel was airbrushed with an iron-col-ored acrylic paint prior to the installationof the two stained basswood boards perwheel float. (Figure 11)

Cairo was powered by a two-cylindersteam engine. Each of the large Pitmanarms was made from sectional basswood,then bolted through styrene “iron” bracesand connected to two eccentrics at ninetydegrees to each other. (Figure 12) Steamboilers and drives were installed on theplatforms under the gun deck and alignedto the wheel eccentrics. (Figure 13) Theremainder of gun deck was planked at thistime.

Decking

All deck planking was cut by handon a miniature band saw. This left a rough

texture that lent itself well to this applica-tion. Two sides of each board were black-ened with a permanent marker, doing onlyone long and one short side, to simulatecaulking. Marking all four sides wouldresult in too much buildup and ruin thescale effect. The gun deck was covered with1/8-inch plywood, glued and stapled.(Figure 14) There was no need for filling onthis deck as it was completely covered withthe deck planking. Cutouts were made forthe waterway and hatches to the deckbelow. Starting at the exact centerline ofthe boat, planking went quickly on the gundeck. Pencil markings on the plywood indi-cate where deck beams would be and theplanking was laid so that the plank endsterminated at these lines. Coamings werefitted around hatches, which also receivedtheir covers. (Figure 15)

At this point installation of theupper bulwarks required a table saw set tocut a bevel both top and bottom. To addlongitudinal strength in this model we

Figure 13. Finishing frames to the correct thickness.

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Figure 14.

Figure 15.

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opted to keep the upper sides as singlepiece construction. Because of deck edgecurve and sheer it was found necessary topre-shape the walls and kerf the forwardten inches. Cannon ports were cut using ascroll saw, incorporating the same bevel asapplied to the top and bottom edges of thebulwarks. The forward and aft pieces weremeasured freehand and shaped to fit. Priorto installation of the four walls, styrene“cladding” was applied to their outside sur-faces. (Figure 16)

This model was built to display theinterior through a partial opening along theport side. The walls were cut and bracesplaced for the opening. (Figure 17) Smallmagnets hidden in the braces keep thecover in place. The gun deck was complet-ed with the cannon placed in their stationsand the steam boilers mated with theirstacks. Further joist work and installation

of the hogging braces were completed priorto upper deck placement. (Figure 18)

Lighting also was added to themodel interior at this point, utilizing LEDtechnology hidden in the bottom of theupper deck. The lighting simulated thecolor and flicker of several kerosene lamps.This allowed the interior detailing to beseen clearly without looking unrealistic.(Figure 19) A small mercury switch shutsdown the lighting when the side cover is inplace. This model was designed to beinstalled into a lighted case. The supplywires for the interior lighting were rundown the inside of the hull and throughthe mounting pillars. They pick up powerfrom the same low-voltage supply thatlights the case. Lighting is individuallycontrollable through a dual button key fobremote control unit.

Figure 16.

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Upper Deck and Wheelhouse

The upper weather deck was con-structed as an independent assembly.Starting with a piece of ¼-inch plywood,

we made through cuts for the stacks,wheelhouse, skylights, and, of course, thepaddle wheel. Taking measurements fromthe plans, we finished the edges of deckand cutouts with mahogany. This was

Figure 18.

Figure 17.

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Figure 19.

Figure 20.

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strictly an aesthetic decision that made for amore interesting model. (Figure 20) The sky-light was constructed off the model, thenglazed and installed on the deck. (Figure 21)The large curved structure covering the pad-

dlewheel was made from thin aircraft plyover shaped frames. (Figure 22) Window gal-leries port and starboard look through to thepaddle wheel below and are covered withbrass rakers. (Figure 23) The remainder of

Figure 21.

Figure 22.

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Figure 23.

Figure 24.

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Figure 25.

Figure 26.

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deck was then planked as with the gundeck. After checking the lighting and theunit’s fit, the upper weather deck wasinstalled.

Final assembly included construc-tion of the multi-sided wheelhouse. Thiswas constructed on a basswood frame andcovered with styrene “cladding.“ (Figure 24)Hogging braces were added to their verticaltimbers. Masts, railings, cannon port cover,and rigging were then applied to the model.A signal flag cabinet and rocket station for-ward were added, along with an anchor.(Figure 25) Detailing aft included covers forthe chain drives that operated Cairo‘s dualrudders. (Figure 26)

In a moment of whimsy, a cage ofducks was installed on the aft weatherdeck. Ducks or geese were sometimes usedin port as alarm animals as well as provid-ing food for the crew. This model depictsthe cages open showing the fowl escaping.(Figure 27) This was done because every-one “Lost their Quackers!” both in in thedamage done in the raising the actual USSCairo and in building this model on com-mission.

Final Assembly

Construction of a custom cherrywood freestanding case was completed,

Figure 27.

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including custom-made overhead no-heatlighting. The model was then installed andthe display photographed. The beauty ofwarships most certainly can be a debatablepoint. However, this model USS Cairopresents a most impressively elegant dis-play. (Figure 28)

Three years in the research andbuilding, USS Cairo was a most challeng-ing model project. The unique design,combined with a variety of interestingdetails, made this a model ship builder ’sdream. The chance to view the real vesseloffered the opportunity for great realism inthe build. Our sincerest thanks go to allthose at the USS Cairo museum for their

input and support and to the SmithsonianInstitution for its assistance.

Acknowledgments

Vicksburg National Military Park 3201Clay Street, Vicksburg, MS 39180-3495Historic Naval Ships Association, (JeffNilsson, Executive Director) PO Box 401Smithfield, VA 23431-0401Smithsonian Information Center, PO Box37012, SI Building, Room 153, MRC 010Washington, DC 20013-7012BMK Brass Barrels, Germany

Figure 28.