Scale: 48. A cotemporary full hull model of a shot proof mortar boat as proposed by Sir William Congreve in 1805-9. The central battery on deck is covered by an angled roof which is removable on the model to show the interior layout. There are also a number of smaller gunports from which either small arms fire or rockets could be worked. The double-ended hull has rudders at either end, both of which can be locked in line with the hull, which are supposed to prevent tacking while bombarding a target ashore or afloat. At this scale, the model represents a vessel measuring 120 feet in length by 30 feet in the beam.