Read Copenhagen Plans of Fulton's "Steam Battery": Blockship and Catamaran , free online book, by Howard I. Chapelle, on ReadCentral.com.

In 1960, Kjeld Rasmussen, naval architect of the Danish Greenland Company, was requested by the author to inspect in the Danish Royal Archives at Copenhagen a folio of American ship plans, the index of which had listed some Civil War river monitors. Mr. Rasmussen found the monitor plans had been withdrawn but discovered that three plans of Fulton’s Steam Battery existed, as well as plans of the first Princeton, a screw sloop-of-war.

Copies of the Steam Battery’s plans were obtained at Copenhagen in September 1960 through the courtesy of the archivist, and were found to consist of the lines, copied in 1817, an inboard profile and arrangement, and a sail and rigging plan. From these the reconstruction for a scale model was drawn and is presented here with reproductions of the original drawings upon which the reconstruction is based.

It is apparent that Montgery’s description is generally accurate. The vessel is a catamaran, made of two hulls, double-ended and exactly alike. The outboard sides are “moulded,” with round bilges, the inboard sides are straight and flat, as though a hull had been split along the middle line and then planked up flat where split. The hulls are separated by the race, in which the paddle wheel is placed at mid-length. The topsides are made elliptical at the ends, and the midsection shows a marked tumble-home over the thick topside planking but less on the moulded lines.

The lines plan agreed rather closely to Montgery’s description of the hull. After careful fairing it was found the lines drawing would produce a vessel 153 feet 2 inches overall outside the stems, or about 151 feet over the planked rabbets, with a moulded beam of 56 feet and extreme beam of 58 feet. The moulded depth was 22 feet 9 inches and the width of the race was 14 feet 10 inches, plank to plank. The room and space of framing shown was 2 feet. The designed draft appears to be 13 feet and this would bring the port sills 5 feet 6 inches above the loadline and the underside of the gun-deck beams about 2 feet 9 inches above the loadline.

The lines plan is a Danish copy, probably of the building plan by Noah Brown, and may be based on the plan Montgery obtained from Brown. The spar deck has the iron stanchions (Gurley translated these as “chandeliers”) which are set inboard 4 feet from the plank-sheer. This gives room for cotton bales, outboard the stanchions, to form a barricade. As will be seen by comparing the original Danish drawing with the model drawing, the construction indicates that the iron stanchions should be carried around the ends of the hull in the same manner as along the sides, since the lower ends of the iron stanchions pass through the spar deck and are secured to the inside of the inner ceiling of the gun deck. The rudders are as shown in the Danish drawing, and it is supposed that they were operated ferryboat fashion, one at each end of the vessel. Hence, each pair of rudders was toggled together by a cross-yoke. This was probably operated by a tiller (possibly the cross-yokes and tillers were of iron) pivoted under the beams of the gun deck close to the ends of the ship. Tiller ropes led from a tackle under the gun-deck through trunks to the spar deck, where the wheels were placed. This allowed proper sweep to the tillers and operation of each pair of rudders. The paddle wheel was apparently of iron, with wooden blades, and agrees with Montgery’s description. In the plan for the model it is shown raised 18 inches above the original design position, to agree with trial requirements.

It should be observed that the close CL-to-CL frame spacing created a hull having frames touching one another, at least to above the turn of the bilge, so the vessel was almost solid timber, before being planked and ceiled, from keel to about the loadline. The sides are not only heavily planked but, after the frames were ceiled with extraordinarily heavy, square timbering, a supplementary solid, vertical framing was introduced inboard and another ceiling added. The sides scale about 5 feet from outside the plank to the inboard face of the inner ceiling at the level of the gunports.

The hulls were tied together athwartship by the deck beams of the gun deck and spar deck, except in the wake of the paddle wheel. Knees were placed along the sides of the race at alternate gun-deck beams. In addition, the 12 1-foot-square timbers, crossing the race at the rabbets of the hulls, (mentioned by Montgery) are shown. These must have created extraordinary resistance, even at the low speed of this steamer. The deck details shown are the results of reconstruction of the inboard works.