I notice that the maximum speed of unpowered wooden barges and narrowboats seems to be 7km/h, whereas the maximum speed of the steel and composite hull types are 11km/h, which matches the speed of steam tugs (etc.). Is there a reason for this lower speed for wooden barges and narrowboats? I don't think that the hull type made a difference to how fast that they could go, did it? The fly boats were wooden, after all.
I tnought I got that from the data you gave me. Possibly I misread?
Hmm - I don't think that I distinguished between the speed of the wooden and composite/steel types, did I? Incidentally, where did you get the 11km/h from? It might be that that is where the error is. I do recall reading that intermediate speeds between the plodding speed of the single horse narrow boats and the positively zephyr-like fly-boats caused a bough wave which damaged the banks.
Reading again it looks like I misread a few bits. Will fix.