Small electric sternwheeler catamaran

Discussion in 'Boat Design' started by YotaTruck, Mar 30, 2016.

  1. YotaTruck
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    YotaTruck Junior Member

    I've been searching around for information on sternwheelers and found mostly threads on riverboat type projects much larger than what I'm looking for. I came across this the other day and it got me thinking:

    http://www.youtube.com/watch?v=_J41e_uGevw

    These folks essentially take a pontoon boat, put a paddlewheel inside a housing in between the logs, and power it with an electric motor. No idea on pricing but I'm sure it's a pretty penny. The simplicity of it all intrigued me as I've wanted to build some sort of small electric leisure cruiser for a while. Electric only lakes are quite common in my area.

    With regard to sternwheelers, it would seem (to a layperson) that a catamaran or pontoon type of boat lends itself well to that type of propulsion. When searching for information on small sternwheelers, one tends to find contraptions like this one slapped on the rear of some sort of conventional monohull:

    [​IMG]

    http://www.boatdesign.net/forums/propulsion/do-they-exist-articulating-paddle-wheel-19475.html

    With a catamaran, the wheel can be located neatly between the hulls and covered with a housing. Also, once draft is established, the "dip" of the wheel could be tweaked for maximum power and efficiency simply by shimming the axle mounts. Depending on the size of the hulls vs. the draft it may even be possible to have the wheel mounted slightly higher than the undersides of the hulls, allowing for very shallow operation. I got some very basic guidelines on wheel design here and started playing around:

    http://www.americansternwheel.org/Boats/articles/the_paddlewheel.pdf

    I also found this plan from William Atkin for a 28' LOA, 9'-8" beam scow. This boat is 4' longer, over 1'-6" wider, and a great deal heavier than what I would intend to build, but it at least gives a sense of scale. He specifies an engine making 35HP @ 1800 RPM (indicating about 102 FT/LBS at the shaft), geared down to 60 RPM (30:1)-this gives a max speed of about 7 MPH-plenty for my purposes. I'd be quite happy with 5-6:

    http://www.atkinboatplans.com/Misc/LadyOfTheLake.html

    Here she is in action:

    http://www.youtube.com/watch?v=6aPTl0Sfwzk

    What I'm trying to get a sense of whether or not a golf cart type motor would be able to supply the power needed to move a smaller, lighter craft 5-6 MPH and still have a practical range. The Griffin electric boats boast of a 6 hour runtime before recharging is needed, but they don't indicate whether that is 6 hours of running at max speed, etc... Looking forward to some discussion on this.
     
  2. gonzo
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    gonzo Senior Member

    What is the purpose of propelling a boat with a sternwheel?
     
  3. YotaTruck
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    YotaTruck Junior Member

    Novelty, something different, etc... I know that a lot of this forum is devoted to professionals and real-world projects, but there are a fair amount of us backyard tinkerers here as well who enjoy messing around with different ideas. Not saying that a paddlewheel is necessarily better or worse than anything else, just looking to get the input of those more knowledgeable than myself. I do feel as though the low RPM of a paddlewheel lends itself well to electric power. I've seen a lot of electric outboard adaptations, but in order to really take advantage of electric power you need to be able to fit a pretty large prop because of the RPM limitations.
     
  4. gonzo
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    gonzo Senior Member

    Electric motors can run at whatever RPMs you need. Depending on the design they can be slow or fast. Paddlewheels need a lot of reduction because their large diameter means that the tangential speed at the edge of the blades is high. Power is the same regardless of source. In other words an HP from an electric motor is the same as an HP from a gas engine or, for that matter, from a horse.
     
  5. YotaTruck
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    YotaTruck Junior Member

    They can run at whatever RPM you need-the question is, at what voltage and for how long? There are electric motors that will produce the power needed to turn a small outboard prop at 5000 RPM, but the battery bank needed becomes exceedingly expensive and heavy and the runtime is still going to be low. The most practical electric boats out there are displacement hulls that swing big, slow moving props.
     
  6. gonzo
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    gonzo Senior Member

    Electric motors are rated in Watts. The RPMs they turn at does not affect the amount of watts they consume from the battery.
     
  7. fredrosse
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    fredrosse USACE Steam

    Electric plus Paddlewheels

    I have built a fully electric cruiser, very inexpensive, from an O'day Javelin sailboat hull, fitted with a common (although large for a 14 ft hull) 14 inch three blade propeller. 3/4 horsepower, just right for cruising with 4 adults aboard, for a few hours. This boat has very good propulsion efficiency because of the large, low speed propeller. It would be easy to arrange the same thing between catamaran hulls, with the prop shaft adjustable for submergence, shallow water could easily be accommodated.

    The setup and build of the O'day is detailed on the Yahoo Group, Electric Boats. Propulsion efficiency with a paddlewheel is several points lower, but still a workable arrangement.

    Articulated Paddlewheels? I have also built a steam sidewheeler, operating with fixed floats initially, but converted to articulated wheels after a few years running. The articulated wheels are definitely more efficient, although I ended up with 72 working pivots in the water, definitely high maintenance. Details for this boat are well covered on thesteamboatingforum.net

    While both boats are somewhat "eccentric" I have enjoyed them very much, quiet cruising, with very shallow draft for the steamer.
     

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  8. TANSL
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    TANSL Senior Member

    Allow me a question from someone not very expert in this field. What can consume/absorb a motor from a battery are amps (not watts), right?
     
  9. Skyak
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    Skyak Senior Member

    Watts are the unit of power and are what is important. Because batteries are a voltage source it is common to talk about amps as if they are a measure of power. It's wrong but power is amps times voltage so it is proportional in a battery circuit.

    Just an example if how amps should NOT be used to indicate power -a duty cycle that has high amperage for short bursts will deplete a battery far sooner than predicted because of resistance internal to the battery.
     
  10. Stumble
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    Stumble Senior Member

    Watts = amps * voltage

    Voltage from a battery is fixed (roughly) so the change is in amps. But the amount of power is in watts.

    Change from a 12v system to a 24v system and the amps drop but the watts stay the same.


    What Gonzo is saying is that rpm doesn't change the watt draw, the amount of work done does. So a 1kw motor operating at 100rpm draws the same amount of power as a 1kw motor at 10,000rpm. As rpm goes up torque goes down, but the energy usage stays the same.
     
  11. Skyak
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    Skyak Senior Member

    The reason smart people don't build electric paddle wheel boats is that battery storage is vastly more expensive than common petro fuel and one of the wonderful benefits is silence. So wasting the output of expensive batteries making noise and splashes is pretty far from desirable.
     
  12. Skyak
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    Skyak Senior Member

    Beat-cha by a minute!
     
  13. YotaTruck
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    YotaTruck Junior Member

    Maybe so, but I would be interested in the real world performance of the Griffin boats that initially turned me on to the idea.
     
  14. SamSam
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    SamSam Senior Member

    I have no idea about the electric motor stuff, but the boat in the youtube is not the one in the Atkins, Lady Of The Lake plans. Or if it is, they didn't follow the plans too closely. In the youtube boat, which looks to be made from steel, the bottom of the hull at the stern doesn't curve up like in the bow. That allows water to easily feed into the paddlewheel, makes the boat move through the water easier and makes for better steering. Also the youtube boat sides don't flare out, as seen from above. I don't know why Atkins would put that boat on their site and say it was from their plans.

    This one is from their plans... https://www.facebook.com/media/set/?set=a.414780978591897.92329.414369185299743&type=3
     

  15. Skyak
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    Skyak Senior Member

    Well the 'good' news is that your boat would likely be the only one of it's kind for a very long time.

    I understand the desire to do something unique (my goofy propulsion is a steam powered sculling oar, swims like a fish powered by sticks), but here you go looking for performance. The answer you seek can only come from the owner of that unique boat, and he may not be able or inclined to give you an accurate answer.

    I don't see any big advantage to pairing a paddle wheel to a cat or mechanically moving the wheel to adjust power or speed -they are just inefficient, too slow for rudders to be inefficient, and insensitive to disturbed water because they are drag based. If you are interested in efficiency in a paddle wheel there is a more complicated design that keeps the paddle perpendicular to the flow so it doesn't waste as much energy throwing water in directions of no value -search 'feathering paddle wheel'.

    http://www.boatdesign.net/forums/boat-design/concerning-feathered-paddlewheels-46313.html
     
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