Well we are certainly going onto tidal rivers and we need some safety equipment, something to stop the boat in the event of engine failure. The anchor that came with the boat is this puny 10 pound effort.
Now I know that our knowledge of all things boating is next to nothing. In fact when we bought the boat the surveyor said that we would be on a steep learning curve and sure enough we were for the first month as we learned manoeuvring through open lock gates and to avoid mooring on the tow path. Since then we have built up a steady relationship with the boat and some of us have gained immense knowledge of the intricacies of boat painting, red oxide and rust inhibitor, especially around the contact regions of the side of the boat, the gunwales. It seems that it is only with the onset of our epic journey around the cut of England that we have stepped up the search for knowledge again of all things to do with narrow boats.
Anyway the point is even with our level of boating expertise it was obvious to us that the anchor that came with the boat would be struggling to do anything with a 16 ton boat rushing towards a lively weir, so after extensive searching through google and the internet we found that we needed an anchor of somewhere between 12 and 16 Kg. The general consensus was that it was more important that all crew members could deploy the thing in an emergency so we bought a 14 Kg anchor. The chain attached to the anchor should weigh about the same and this should be attached to a rope called a warp which should be somewhere between 5 and 10 times the depth of the river.
The diameter of the warp needs to be 18mm for this anchor and chain.