Rigged model of an English Chalk Barge

Rigged model, Scale 1:24, of an English Chalk Barge (1768), by Frederick Raban Williams, British, 1930-1937. The hull of this model has been taken from the earliest known plan of such a vessel, entitled 'An English Chalk Barge' which is published in Chapman's "Architectura Navalis Mercatoria" of 1768.

The Thames sailing barges, of which only a very few now survive, were perhaps the best-known craft of the Thames Estuary. These barges evolved from lighters which were used on the Thames at least as early as the 17th century.

The lighters were constructed with sharply raking ends and a flat bottom so that they could rest conveniently on the mud at low water. Vessels of this type are employed to this day as dumb-barges, or lighters, throughout the estuary and lower reaches of the Thames; and, although steel has now largely displaced timber and iron for their construction, the traditional design remains.

This model of a mid-18th century barge has been made from the earliest-known plans of an English sailing barge, which are contained in Chapman's 'Architectura Navalis Mercatoria' of 1768. The hull was designed with the same flat bottom, meeting the sides at an angle known as a chine, and the same sloping now and stern as a lighter; but there was more sheer and the sides inclined outwards. In the 18th century, Thames barges were rigged with a spritsail and fore-staysail, as shown on the model. These sails had gradually replaced an earlier rig consisting of a single square sail.

Thames barges were fitted with port and starboard lee-boards. When tacking, the board on the lee side was lowered into the water to decrease the drift to leeward.