Several features of the vessel's hull make it unique from most of those that preceded it. Steel was chosen for the primary building material. This allowed the vessel to be both lighter and stronger than older wood and iron yachts. The frames, spaced on 20-inch centers, were fashioned from bulb angle steel and supported a hull that was built flush and smooth, with straps fitted at the edges and butts. Joints below the waterline were overlapped for additional strength.  Ten-pound steel was used in areas that might encounter exceptional stress, particularly the garboard streak, where the hull met the keel. Lighter, seven-pound steel was used elsewhere. Unusual features for the time were the hull's seven watertight compartments, with a steel bulkhead dividing each. Four of the six bulkheads were fitted with watertight doors similar to those used on contemporary torpedo boats.

At least a portion of the vessel was double bottomed and designed to carry fresh water, for both consumption and to provide ballast. Further examples of the vessel's stout construction are found in the upper, quarter, and forecastle decks, which were plated with steel stringers. Indeed, the Rosinco was representative of a type of vessel built by American yachtsmen who wanted their boats to serve as naval auxiliaries. Built in 1916, this yacht could have been quickly retrofitted for coastal patrol service during World War I.