Humber keel

[2] Early keels were designed to work in waterways which were only 3.5 feet (1.1 m) deep, but could still carry 40 to 50 tonnes of cargo.

The after part of the hull, in the region of the structural keel, was shaped to give a slightly concave run[a] so that water flowed efficiently past the sternpost and the rudder.

In stronger winds, the yards would be hoisted with the sails furled to them with light yarn that would be broken when the sheets were pulled.

The mainsail could be doused by hauling on the slabline – a rope from the deck, up to the hounds (the mast at the level of the main yard) and then to the foot of the sail.

[3] Lateral resistance was provided by a huge pair of leeboards, since the structural keel protruded below the flat bottom of the hull by only a few inches.

[6] The dimensions of these craft were influenced by the gauge, or width, of inland waterways created or modernised during that period.

In comparison to the widespread use of the Narrowboat standard, far fewer inland waterways were designed to accommodate the larger Humber Keel gauge vessels.