Pedal Powered Boats

Discussion in 'Boat Design' started by Guest625101138, Jul 14, 2008.

  1. clmanges
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    clmanges Senior Member

    That doesn't sound very good to me. Have you looked at the hull shapes of canoes and kayaks that are meant to be heeled over to assist in turning them? No protrusions, no hard chines, very smooth curves. And a transverse wave would be more apt to flip a boat with the flares you describe (or just chuck you overboard) than it would a traditional canoe or yak. You're putting a sudden brake on secondary stability.

    As to the flipper drive, well, at least you've got a more simplified mechanism than I've ever seen, but that mostly rigid fin is likely just going to stir the water more than move you forward. There are some pretty decent fin drives out there, but they all use complex linkages and pivots to try to emulate the way a fish-tail actually moves (very hard to do, since the motion starts at the fish's head). Have you considered just using a Hobie Mirage drive? Expensive, but the new ones are even reversible.
     
  2. Sockmonkey
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    Sockmonkey Junior Member

    The hull flares were supposed to be like an abbreviated version of the concave hull shape clipper hulls use. You're probably right about the transverse waves though.

    The Hobie drives are done like penguin flippers, which are essentially prop blades that reciprocate instead of spinning.
    By all accounts on here, while they're not bad, they're far from great.
    Complex linkages are part of the problem. Every time you redirect or alter force/distance trade-off, the efficiency suffers from mechanical losses.
    It's one of the reasons the racing pedal-boat drives limit themselves to a single 90 degree gearbox.

    Most of the flexing of a fish's body is due to them needing to use their body to counterbalance the side forces of the tail, and the need to keep water flowing smoothly over the whole body while doing so.
    For a fish-tail drive, the boat hull is more than long enough to provide a stable pivot point.
    while more joints would refine the motion a little, it's only the second joint at the base of the fin that's actually critical to making thrust instead of churning water as shown in my crappy drawing.
    [​IMG]
    It's not perfect, but the mechanical losses between leg and fin are minimized.
    A slightly fancy third class lever.
    Legs put out intermittent force, and a tail runs on intermittent force.
    As long as the fin connection has some flex to it, it will self-adjust the angle of the fin from the water pressing against it during the swoosh.
     
  3. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Thought of doing this with existing foot controlled kayak rudder. Just tack big long horizontal fin on existing typical kayak rudder. Only issue is existing cables routing through holes in boat if fine for steering but not really up to pushing power through with 10,000 cycles over an hour or more at a time. But that could be upgraded with a few little pulleys and still keep normal kayak rudder system intact for normal use.
    It was thinking even a limited system could be handy for kayak fishermen to be able to both steer and propel a kayak hands-free, and in very shallow water, when Fish On! happens and you want both hands free.
     
  4. Sockmonkey
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    Sockmonkey Junior Member

    Swooshy drive can steer too. Just don't extend one of your legs all the way when pushing and the thrust is aimed to the side a bit. That, plus the reversability means it does all the things you would need mechanisms for, and it doesn't tangle in weeds.
     
  5. portacruise
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    portacruise Senior Member



    There was a company that made a commercial Pedal Power version sometime back by the name of (Pacific?) tail boats?
     
  6. portacruise
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    portacruise Senior Member

  7. Sockmonkey
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    Sockmonkey Junior Member

    Pretty neat, though that initial version does make the mistake of being surface piercing.
    I've noticed many of these designs complicate the drivetrain with lots of levers and rotary motion costing them the efficiency they're trying to get by using a fin.
    In the electric one shown, they should be using a pair of linear electric actuators that act like solenoids or something to move the fin back and forth.
    Same reason most pedal boats use twisted chains instead of a short vertical driveshaft.
    Granted it's just a prototype, but you see it in supposed production models too.
    I figure you guys have seen every wacky idea ever made on here, so if there's some critical flaw in my reasoning let me know.
     
  8. portacruise
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    portacruise Senior Member

    "It was thinking even a limited system could be handy for kayak fishermen to be able to both steer and propel a kayak hands-free, and in very shallow water, when Fish On! happens and you want both hands free."

    The system link below can be hands-free or powered, and may work better than kayaks in some situations. There are some one man inflatable hulls that weigh as little as 3.5 lb, which are much easier to pack in with back straps, transport by air travel, or portage compared to kayaks. Some are rated for class III rivers, and have been customized to float in as little as 4 inches of water. Float tubes are much slower than a kayak, but that might not matter as much, if you use a River current to power you downstream only. I am not endorsing this particular brand, they just have pretty good videos.

     
  9. Squidly-Diddly
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    Squidly-Diddly Senior Member

    that thing in the kiddie pool looks pretty good, both efficient and user friendly.

    I was wanting a stand-up system with two "foil"(not so much paddle) oars that would flap in the water more or less like wings as you work them from mid-calf height to fully extended over your head, turning them slightly on each stroke to keep the foil going the right way. Thats about 5ft of motion so the oar locks and oars would be pretty long. Oars could also be turned 90 deg and rowed, probably from seated position.
     
  10. Sockmonkey
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    Sockmonkey Junior Member

    The motion would be like you were doing deadlifts then? Or do you mean from a seated position?
     
  11. Squidly-Diddly
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    Squidly-Diddly Senior Member

    pretty much, and then "pull downs". both work most of the body. I'm thinking the pull down stoke would be the main power stroke but with less control due to less foot traction on deck, but you'd also get power on the upstroke and more control due to more down force on boat. you'd also be able to control how your weight was effecting the boat it rode waves on either stroke, or more likely have waves factor into what your body was doing.

    by "seated" I mean a different mode and position, like a normal rowboat.
     
  12. Sockmonkey
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    Sockmonkey Junior Member

    So a setup like this?
    [​IMG]
    Oscillating Fin under the hull going up and down in guide rails secured to the hull.
     
  13. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Interesting, but no, more like this except the oars would stay the water and act as foils being manually turned about 45degs (total, so about 22.5 off flat) each stroke. Something that could be done while keeping the boat more or less still normal, and still have a conventionally useful set of oars.
     

    Attached Files:

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  14. Sockmonkey
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    Sockmonkey Junior Member

    Snag the flippers off a Hobie drive and stick them on poles? They likely sell replacement flippers.
    In terms of efficiency, I think you would be best off having the oarlocks jut from the sides a few inches, have the oars oriented vertically, and move your hands together and apart.
    The up and down flapping of your initial idea would have the paddle-ends breaking the surface unless you were being super careful, which would waste energy creating turbulence.

    Hmm, you know the oscillating fin pic I just posted could also be operated by doing reclined bench presses, leg presses, or squats. It's a full body workout machine. ;)
     

  15. Squidly-Diddly
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    Squidly-Diddly Senior Member

    main concept is full body workout.
    I was thinking of just shaving one edge of existing longest wooden oars paddles (and shafts near the paddles that will be in the water) I can find to create foils. Hobie flippers will be optimized for tips moving several times faster than the base, due to small diameter of motion VS size of flippers.

    I'm not too worried about breaking the surface because that would happen at extreme down-stroke as you almost touch your toes, and people would only do that if "forcing themselves".

    You could work the bench press (and rowing machine) muscles by keeping legs straight and bending over and using just arms.

    Biggest problem would be streamlining the oar shafts while keeping them strong enough.
     
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