Pedal powered dinghy works at last

Hello from Lancashire, England. I've been building my mini boat, which is 7'3" at the waterline, since January. The aluminium hull was the easy part but getting it to go and steer were a nightmare. I'm a keen cyclist so thought that it should be pedal powered. A trolling motor would be too easy! Today I've finally had a successful trial, which I think may be my tenth time on the water. I wrote a blog post about it.
I promise you this my young friend……….. https://mountainbiker.online/2021/07/13/i-promise-you-this-my-young-friend/

 

Your opening sentence in your blog says it all.
Well done!

Have you seen this approach?
Centre canard for balance input from the handle bars.
Brake levers operate the rudder for steering.

Play-on!

 

Good effort!
If pedal powered boats is something you're interested in pursuing, I'm fairly local (Huddersfield), have built one in the past which I'm still quite pleased with and have investigated the subject a fair amount. Hoping to build another in the medium term future. Happy to chat, show n tell etc.

Best wishes

 

If the canal runs through Huddersfield I could drop in! Seriously it would be good to chat. I'll be doing a lot more testing and have a method to calculate efficiency. The great thing about pedal power is that legs give more power than arms so it can't be too hard to beat rowing.

 

Excellent work Andrew! And you managed to reach your 'hull speed' as well.
Your hull form is not ideal though for this purpose - it could be improved a bit, but this would only mean that you would reach hull speed with slightly less effort.

And thanks Bluebell for that video link above - here is a link to the follow-up video that explains how the water bike works. Very ingenious indeed.

Andrew, have you come across the front rower system for rowing with your legs? It is also very neat.
Forward facing rowing for canoes, rowboats https://www.frontrower.com/

 

This is my first build so ease of build was important. As Bajansailor says my hull shape is far from ideal but it's stable and I'm laying back in a relaxed position. Next I want to make sure it's totally reliable for longer distances though I have fitted some brackets so I can take the wheels with me rather than concealing them in the bushes. Efficiency? Some say that paddle wheels are as bad as 25% efficient but I just need to compare tip speed to actual speed on the water. At 1 revolution per second my paddle tip speed is 0.8 meters X pi so that's approx. 2.5 m/s or 5.5 mph. If I was travelling at 3 mph then my efficiency would be a little over 50%. I got this method from the internet. Does anyone know if it's accurate? Is it wrong?

 

Hi Andrew,
what you were calculating, is a kind of "slip". Output power divided by input power is usually called efficiency.

 

To fully calculate efficiency in terms of how much of your bio mechanical energy is converted into forward motion is quite a complicated thing, and to improve it means chasing down often many small losses at different points along the transmission, hull and rudder design etc. The leading proponent of efficient pedal powered boats is probably Rick Willoughby, who is no longer a member here, but is contactable.

Here is one of his typical recent very high performance designs:



The efficient, long skinny hulls are pretty easy to build, depending on material choices, if you wanted to explore that route in future.

There is a *very* long thread here that Rick set up, with a great deal of information (along with the usual amount of argument and red herrings!)

Pedal Powered Boats https://www.boatdesign.net/threads/pedal-powered-boats.23345/

Here's some film of my own boat, converted from a Dart 18, using second hand commercial sea cycle drives:



It is a heavy boat, but a great platform for cruising, fishing and mucking about generally. Also very manoeuverable.

The most efficient boats are likely to be using high aspect ratio two bladed propellors; model aircraft props can sometimes be used.

The pedal-powered boats thread explores transmissions, rudders etc. at length.

However, it absolutely depends on what you want the boat to do, and I would suggest that for a lot of canal work, where depth and shopping trolley count are unknown factors, a paddle wheel is a very sensible choice.

 

When I studied paddle wheels for a potential installation,
I found up to 80% efficiency,
but that was with considerable effort, design, and knowledge.

 

Yes, my paddle wheel doesn't "feather" for added efficiency but I might still be able to achieve a similar efficiency to the prop. of an electric trolling motor and could even have less drag because only the propulsive paddles touch the water. As a cyclist I'm good for 200 watts if the need arises! It's possible that a 400 watt trolling motor could get my boat to maximum hull speed but would never get it to plane so I might have quite similar performance.

 

I have been trying to find some examples of paddle track systems. Right now, I am building a forward rower powered track drive for a large sailboard converted to tri. Found a board for $10 at a reuse centre. I am getting severe cramping of the feet and toes while swimming, so had to give up my daily 2k swim. I hope the row boat will take up the exercise option

 

I’ve read, probably on this forum which I’ve lurked around for a while, that track systems are inefficient due to friction. Of course you have plenty of power in the legs to overcome friction so you may still be able to achieve good speed. Remember maximum hull speed before you get too ambitious in looking for speed. Today I cruised for 2 miles at an average, according to Strava, of 3.3 mph. It was about the same effort as walking but I could have put more work in. My speed, however, is never likely to exceed 4.16 mph which is my calculated hull speed.

 

@Saqa, the problem with track systems is that the second you quit applying power, the craft stops, like flooring the brake pedal on a car. I can't think of any way around that. Also, it's a lot of added weight.

 

Guys, do have to keep in context. An efficient cruiser is very different from an efficient exerciser! I have selected a heavy system deliberately

Also, the inertia of the heavy craft might allow some coasting between strokes and iron it out somewhat. Re the track blades, blades should be hinged one way, so they can fold back in the stream when applied power diminishes

 

Andrew
Do you have any interest in developing your boat further? I have an idea that might work very well with your existing setup