Scale: unknown. A contemporary full model of a sailing vessel fitted with two revolving masts. This model is known to represent a design proposed by Lieutenant Molyneux Shuldam in 1821–27 for a fore and aft sailing rig, which was mounted on turntables. The masts are made up of four individual spars on which are mounted fixed yards, which would set square sails similar to the type used on a lug rig. The idea was that by being able to revolve the whole rig, the vessel would be able to sail using wind blowing from any direction. At a scale of 1:12, the model illustrates a vessel measuring 36 feet in length by 9 feet in the beam.