Kath complains that you have to subtract one time from another to get the time between intermediate points, so I started thinking about something simpler to use. So here is mark one of my canal easycalc disc.
This one is for a trip from our base at High Line Yachting (HLY) in Iver, to Paddington basin - about five and three quarter hours usually. I picked this one because there are no locks to make it simpler.
The outer pink ring shows elapsed time in hours and the inner yellow disc, which is free to rotate shows places along the way. I worked out the angle for each place in 360ths of the whole journey time , then just used a protractor to draw them on.
So looking at the first picture you can see it takes about one and three quarter hours from the start to get to Bulls Bridge. Easy. Now the really cool bit comes next. By rotating the yellow disc, I can easily see that it will take two hours to get to Kensal Green when I am at the Back Horse. Neat.
The idea is to make a set of these discs for typical journeys we take e.g from Iver to Marsworth. This particular version uses the whole journey time to make up the 360 degrees, but next time I might just make a 6 hour outer disc (or a 6 day outer disc or whatever), without necessarily taking up all the circle on the total distance. (If you get my drift - don't worry if not :-) )
What do you think?