Page updated 11 May 2001
This page contains two submissions:
The first is an edited version of an e-mail I received about the maximum dimensions of the Grand Union. The second, from a well known commercial user of the waterway, provides notes on the best approach for taking a pair of boats through the canal.
It is quite clear that the Grand Junction (i.e. Brentford to Braunston) was built for craft up to 4.36m wide (14' 3"). My recent posting on URW reporting my measurement of selected locks all along the route shows this. The canal definitely does *not* get narrower at Berko; it would have made no sense for it to do so. However, it is true that full-width craft with any sort of height near their edges are likely to have trouble at certain bridges for air draft. Headroom is notoriously difficult to specify, as it depends on both the shape of the bridges and the shape of the craft.
North of Braunston, the locks are quite a bit bigger (longer and wider), but the bridges are more constricted. Piling outside the towpath through a couple of the bridges near Stockton has actually reduced the maximum width to 4.20 (13' 9") (i.e. slightly less than a breasted pair). In fact, since the 1930s, the width figure has been 3.84m (12' 7"), because of the difficulty of two craft wider than that passing in rather too many places.
BWB is now recognising that there is a difference between the largest craft which can get through a route, and the maximum recommended size of craft for regular passages. This is, I think, a useful distinction. The northern GU is one of the best illustrations of the need for it. Perhaps a brief discussion of the point merits inclusion in Nicholson's?
I reported measured lengths for my selected locks, but since there is quite a bit of variation I'm not confident I have found the shortest one. I would be surprised if it was less than 22.5m (73' 10") though, as the shortest I found was over 0.35m (1' 1") longer. I'm sure it is longer than 21.95m (72' 0"), a commonly quoted length.
I have focused on this route, because I am sure that eventually there will be (broad) links from it to the Avon and Nene, that the Leicester summit will be open to broad craft (Foxton plane reinstated, and some sort of a lift at Watford). At that point, its broadness will have become vital, and so should not be lost now.
If working deep draught or loaded boats, it is best to do most of this route single. No problems up to 3ft.0ins.