I’ll admit I haven’t been too thrilled with the performance of my homemade boat. On a positive note it doesn’t leak any water and it’s stable, especially when you consider it’s small size at just 2.1 meters at the waterline. Today I’d adjusted the angle at which the fishtail which propels the boat pushes on the water in the hope that I could get a little more speed out of it. I wanted to try a gentler technique on the treadles which move the fishtail up and down to reduce the bobbing which is an inefficiency. In the worse case it could allow water to splash over the top of the hull. I pulled the boat to the canal on it’s wheels which I then remove before launching. I climbed in with no wobbling, which had been my biggest fear on my first test. Now, my fourth time on the water, I was feeling relaxed and confident., I pushed off and started to push the treadles rhythmically. I once again noticed that it was far easier to push with my left leg than it is with my right. This shouldn’t be the case because the left pedal lifts around 1.5 kg of mechanism, whereas the right drops this weight down whilst the fishtail achieves a similar angle to the water in each direction.
I progressed under a bridge and turned around. I noticed that only the right pedal gave any significant forward motion but managed a full 180 degree turn without having to resort to my emergency paddle. I stopped back at the point where I’d launched to make an adjustment to the fishtail to try to make it harder to push with the left foot and get more forward movement. It made no discernible difference but I sailed on under another bridge to where some canal boats moor permanently.
I was enjoying being on the water but the lack of speed is frustrating. Strava is not precise enough for this application. It indicates spikes of speed in in the record. Today it said my maximum speed was 24.8 mph! I wish!
By looking at a small slice of my journey on Strava I believe my real speed is 1.7 mph, which is about half what I’d be satisfied with. A kayak, for instance, moves at about 2 mph with a beginner in board and perhaps 3 mph for a more experienced paddler. I feel that, since legs are far more powerful than arms, it’s not unreasonable to expect a leg powered boat to match or exceed this level of performance, even if it’s shorter and wider. I think I finally found the route of my problem today. My right leg pushes the fishtail down, which could lift the rear of the boat up. Due to the weight of the boat and myself, this doesn’t happen, which gives a firm platform from which to propel the boat forwards. When the fishtail moves upwards it bobs the back of the boat downwards, not providing a firm platform and wasting any energy which does pass through the system as waves in the water.
My conclusion is therefore that the fishtail method isn’t going to be sufficient on a small, light boat. Actuating it in a horizontal plane would just thrash the hull from side to side, so I imagine would be even less effective. Don’t worry, though. I’ve been thinking about a leg propelled boat for long enough to have a redevelopment in mind which I’ll construct over the next few weeks. It’s been a fascinating experience so far. And I’ve managed to stay dry throughout.