Scale: 1:96. Plan showing a profile of a boat built at Boston for Lord Percy in 1774 with one long sliding keel; a profile of a boat fitted at Deptford with three sliding keels in 1789; and a profile, sections, upper deck, and part framing for 'Trial' (1790), an 8-gun Cutter, as built and fitted at Plymouth with three sliding keels. The plan also shows how these sliding keels can be used depending upon the angle and strenght of the wind.