A contemporary half model of the experimental yacht 'Problem', built at a scale of 1:6, as designed by Mr Henry Dempster, Newcastle upon Tyne in 1848. Mounted on a backboard, it would appear that it is constructed in the ‘bread and butter’ fashion but in the vertical plane as opposed to the normal horizontal. It was probably the extreme design of the hull shape that led to this style being used.

Dempster was an employee of the Honourable East India Company and was a prolific inventor of maritime ideas. This vessel was actually built since contemporary accounts exist of its sailing trials on the Tyne. The rig and hull shape enabled it to sail in either direction and it attained speeds of up to seven knots. The rig consisted of a central mast setting three square sails, and two smaller masts either side setting a single triangular sails sheeted by outriggers..