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

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1 Building USS Cairo: A 1:35 Scale Scratch Built Scale Model..... By C. A. Raven Figure 1. All photographs by the builders. History USS Cairo (pronounced kay-row) was an 1862 City class ironclad for the Union Navy. Designed for river use, it carried a large battery of assorted weapons, featured a steam-powered center paddlewheel, and became famous for two very different reasons. USS Cairo was the first vessel in history to be sunk by an electrically detonated mine. Its subsequent raising some one hundred years later became notorious as one of America s greatest nautical archaeological disasters. Truly, a very interesting vessel that comes with a real bonus for the model builder: one may actually visit what is left of this ship at its permanent home at Vicksburg National Military Park in Mississippi. NAUTICAL RESEARCH JOURNAL 81

2 Plans The decision to scratch build USS Cairo at 1:35 scale was influenced by two factors: the model would present a nice viewing size to reveal an elaborate gun deck, and further detail enhancements, such as figures and small caliber weapons, would be readily available. This very convenient scale produced a model of about sixty inches in length. (Figure 1) Research took over a year before we were ready to start the model of USS Cairo. The value of detailed research cannot be emphasized enough. The five different sets of plans available all differ, and all require corrections. We took a set of plans and corrected the many inaccuracies. These included errors in cannon port cover size and height, beam width, and smokestack height as the major issues. Once corrected, a trip to our local printing store was in order. Utilizing a large scale printer we created a full set of plans at actual scale for about twenty dollars. The large sheets allow for a perfect match when taking measurements to create the model s various parts. (Figure 2) Full size plan sheets further allow one to test the locations of assemblies, such as weapons, and their subsequent rigging and recoil paths. Basswood Lay Up We chose to build USS Cairo from basswood as it closely resembles scale oak, when stained properly, while being easier to carve. Using full size plan sheets and a pounce wheel, the outboard lines of the ship were traced to the basswood blank. The profile of the ship s lower hull is pretty simple with a slightly curved deck sheer. Cutting was done by quartering the bow and stern blocks so that each block may be passed through a standard band saw. (Figure 3) First, each block was cut the correct side profile of the ship. Setting the Figure Vol. 57, No.2 SUMMER 2012

3 Figure 3. Figure 4. Figure 5. sawtable at a twenty-seven degree bevel angle allowed cutting the ship s shape as seen from above. The angle produced the signature flared hull shape found in City Class iron clads. Once all four quarter sections were sawn to shape they were rejoined and coupled to the side rails. (Figure 4) Then we fitted the framing for the center paddlewheel s raceway. The waterway was planked using scale sheet planking. A layer of eighth-inch apple ply was attached to the bottom of the hull. The complete hull blank was glued, stapled and 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 the lower hull at this point, due to its large size, since it seemed easier to flip the hull upside down to lay paint. The paint was allowed to cure for two weeks before taping and papering off to protect it during further construction. (Figure 5) NAUTICAL RESEARCH JOURNAL 83

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5 Weapons USS Cairo carried a total of fourteen large guns, although, only thirteen were mounted for use. The variety of heavy weapons required the creation of two types of gun carriages. Based on actual measurements from the carriages aboard the ship we constructed wooden masters. We cast silicon molds of the carriage masters, allowing for many copies. (Figure 6) Resin castings were painted and detailed with hardware and compound blocks. (Figure 7) Four separate types of gun barrels would be required: Dahlgrens, forty-two pound rifles, thirty-two pound smoothbores and one small Parrott rifle. We turned to our good friend in Germany, Burkhardt Masch Kleinserien of BMK, for a full set of accurate, turned brass barrels. (Figure 8) Each barrel was then chemically colored using gun bluing, which in this case produced a brown tint to give a nice bronze patina. Cannon were mounted to their carriages utilizing tiny threaded bolts. Each of four holes was drilled, tapped and capped with strips of brass for the cap squares. (Figure 9) Figure 8. Figure 9. The Wheel Cairo s massive paddlewheel was constructed of four individual hoops with seventeen spokes each. These spiders were made of iron with oak paddles. Each paddle made from two boards apiece. The spiders were further braced to each other with interlaced spokes like a bicycle. Construction of this wheel began using a simple geometry computer program to generate a scale pattern drawing for the hoops and spokes. The pattern was used to fabricate a jig into which were placed.060-inch square styrene rod for the spokes. Rings were cut from.030-inch sheet styrene stock with a circle cutter. Figure 10. (Figure 10) Once four spiders were completed they were mounted together on a brass axle with spacers between them. The NAUTICAL RESEARCH JOURNAL 85

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7 Figure 13. Finishing frames to the correct thickness. next task of weaving and installing the individual woven spokes between the wheels was time consuming but the results were very good. The metalwork of the paddle wheel was airbrushed with an iron-colored acrylic paint prior to the installation of the two stained basswood boards per wheel float. (Figure 11) Cairo was powered by a two-cylinder steam engine. Each of the large Pitman arms was made from sectional basswood, then bolted through styrene iron braces and connected to two eccentrics at ninety degrees to each other. (Figure 12) Steam boilers and drives were installed on the platforms under the gun deck and aligned to the wheel eccentrics. (Figure 13) The remainder of gun deck was planked at this time. Decking All deck planking was cut by hand on a miniature band saw. This left a rough texture that lent itself well to this application. Two sides of each board were blackened with a permanent marker, doing only one long and one short side, to simulate caulking. Marking all four sides would result in too much buildup and ruin the scale effect. The gun deck was covered with 1/8-inch plywood, glued and stapled. (Figure 14) There was no need for filling on this deck as it was completely covered with the deck planking. Cutouts were made for the waterway and hatches to the deck below. Starting at the exact centerline of the boat, planking went quickly on the gun deck. Pencil markings on the plywood indicate where deck beams would be and the planking was laid so that the plank ends terminated at these lines. Coamings were fitted around hatches, which also received their covers. (Figure 15) At this point installation of the upper bulwarks required a table saw set to cut a bevel both top and bottom. To add longitudinal strength in this model we NAUTICAL RESEARCH JOURNAL 87

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9 Figure 16. opted to keep the upper sides as single piece construction. Because of deck edge curve and sheer it was found necessary to pre-shape the walls and kerf the forward ten inches. Cannon ports were cut using a scroll saw, incorporating the same bevel as applied to the top and bottom edges of the bulwarks. The forward and aft pieces were measured freehand and shaped to fit. Prior to installation of the four walls, styrene cladding was applied to their outside surfaces. (Figure 16) This model was built to display the interior through a partial opening along the port side. The walls were cut and braces placed for the opening. (Figure 17) Small magnets hidden in the braces keep the cover in place. The gun deck was completed with the cannon placed in their stations and the steam boilers mated with their stacks. Further joist work and installation of the hogging braces were completed prior to upper deck placement. (Figure 18) Lighting also was added to the model interior at this point, utilizing LED technology hidden in the bottom of the upper deck. The lighting simulated the color and flicker of several kerosene lamps. This allowed the interior detailing to be seen clearly without looking unrealistic. (Figure 19) A small mercury switch shuts down the lighting when the side cover is in place. This model was designed to be installed into a lighted case. The supply wires for the interior lighting were run down the inside of the hull and through the mounting pillars. They pick up power from the same low-voltage supply that lights the case. Lighting is individually controllable through a dual button key fob remote control unit. NAUTICAL RESEARCH JOURNAL 89

10 Figure 17. Upper Deck and Wheelhouse The upper weather deck was constructed as an independent assembly. Starting with a piece of ¼-inch plywood, we made through cuts for the stacks, wheelhouse, skylights, and, of course, the paddle wheel. Taking measurements from the plans, we finished the edges of deck and cutouts with mahogany. This was Figure Vol. 57, No.2 SUMMER 2012

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12 Figure 21. strictly an aesthetic decision that made for a more interesting model. (Figure 20) The skylight was constructed off the model, then glazed and installed on the deck. (Figure 21) The large curved structure covering the paddlewheel was made from thin aircraft ply over shaped frames. (Figure 22) Window galleries port and starboard look through to the paddle wheel below and are covered with brass rakers. (Figure 23) The remainder of Figure Vol. 57, No.2 SUMMER 2012

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15 Figure 27. deck was then planked as with the gun deck. After checking the lighting and the unit s fit, the upper weather deck was installed. Final assembly included construction of the multi-sided wheelhouse. This was constructed on a basswood frame and covered with styrene cladding. (Figure 24) Hogging braces were added to their vertical timbers. Masts, railings, cannon port cover, and rigging were then applied to the model. A signal flag cabinet and rocket station forward were added, along with an anchor. (Figure 25) Detailing aft included covers for the chain drives that operated Cairo s dual rudders. (Figure 26) In a moment of whimsy, a cage of ducks was installed on the aft weather deck. Ducks or geese were sometimes used in port as alarm animals as well as providing food for the crew. This model depicts the cages open showing the fowl escaping. (Figure 27) This was done because everyone Lost their Quackers! both in in the damage done in the raising the actual USS Cairo and in building this model on commission. Final Assembly Construction of a custom cherry wood freestanding case was completed, NAUTICAL RESEARCH JOURNAL 95

16 Figure 28. including custom-made overhead no-heat lighting. The model was then installed and the display photographed. The beauty of warships most certainly can be a debatable point. However, this model USS Cairo presents a most impressively elegant display. (Figure 28) Three years in the research and building, USS Cairo was a most challenging model project. The unique design, combined with a variety of interesting details, made this a model ship builder s dream. The chance to view the real vessel offered the opportunity for great realism in the build. Our sincerest thanks go to all those at the USS Cairo museum for their 96 input and support and to the Smithsonian Institution for its assistance. Acknowledgments Vicksburg National Military Park 3201 Clay Street, Vicksburg, MS Historic Naval Ships Association, (Jeff Nilsson, Executive Director) PO Box 401 Smithfield, VA Smithsonian Information Center, PO Box 37012, SI Building, Room 153, MRC 010 Washington, DC BMK Brass Barrels, Germany Vol. 57, No.2 SUMMER 2012