For general interest, my 1918 edition copy of Bradshaw's "Canals and Navigable Rivers of England and Wales", written by Henry de Sallis, has the following extract taken from a longer section describing different types of vessels both narrow and wide beam, which I hope may be helpful:-
quote:-
"Principal types of vessels used in Inland Navigation.
a) non sailing vessels
"Narrow" boats or "monkey" boats are by far the most numerous class of vessels engaged in inland navigation. They are from 70ft to 72ft long by from 6ft 9in. to 7ft 2in. beam, and draw from 8in. to 11in. of water when empty, loading afterwards about 1in. to 1 ton.
The ordinary type of long-distance travelling narrow boat carries from 25 to 30 tons, and is built with rounded bilges. The narrow boats in use on the Severn and in a few other localities for short-distance traffic are built with square bilges, and carry up to 40 tons.This latter class of boat requires more power to haul, as it offers more resistance to the water, and also has the disadvantage of not being able to "carry a top", as the boatmen say, that is they become top heavy in loading sooner than a boat with rounded bilges.
A modification of the narrow boat is found in Yorkshire, where is a type of short boat about 58ft. long by 7ft. beam, made for the purpose of passing the short locks of the Huddersfield Broad Canal and Calder and Hebble Navigation and the narrow locks of the Huddersfield Narrow Canal. Another small type of narrow boat is found on the Shropshire Union Canals, being made to pass the small locks between Wappenshall junction and Trench; these boats measure 70ft. long by 6ft 2ins. wide, and draw, when empty, about 12.5 in., and when loaded with 17.5 tons, about 2ft. 8.5ins. ..."
Howard