Pedal Powered Boats

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

  1. hoytedow
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    hoytedow Wood Butcher

  2. Tiny Turnip
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    Tiny Turnip Senior Member

    Hoyt - awesome! Many thanks!
     
  3. jehardiman
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    jehardiman Senior Member

    No planes, that is...unusual. Also notice that that is an at pressure chamber, more like Sea Trek helmets and BOB units so you are still limited to 4'/sec ascent rates and standard bottom time calculations. Ascent rate was one of the big things we needed to control with human powered subs as their speed could easily exceed those rates.
     
  4. El_Guero

    El_Guero Previous Member

  5. JonBoat
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    JonBoat Junior Member

    I can't say i have read thru all 129 pages of this thread but i would like to do something like the attached.

    I have an aluminum flat bottom boat and fish some lakes where you aren't permitted power. Thought this would be a good way to move about and a good home project.

    I would like to do a water hydraulic system since I think it would be the neatest with just a couple bulkhead fittings going thru the transom. I suppose i am looking to source some pumps/motors. Preferably bidirectional fixed displacement but could be unidirectional cause who uses reverse anyways. Anyone have ideas on this? Plastic, Brass, supplier?

    [​IMG]

    http://www.princessauto.com/pal/en/Drill-Pumps/Metal-Drill-Pump/5770250.p
     
    Last edited: Nov 10, 2013
  6. hoytedow
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    hoytedow Wood Butcher

    You should find this very interesting. Lurvio made a masterpiece of one. http://www.boatdesign.net/forums/wo...ation/building-small-trolling-boat-32364.html

    See Post #117 for pedal mechanism.
     
  7. icetreader
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    icetreader Senior Member

  8. Lurvio
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    Lurvio Mad scientist

    Jonboat
    An interesting idea but there are some problems. First you need to get the prop rpm up to over 500 if you don't want to fit a 40 cm dia. propeller. The draft quickly becomes a problem on shallow water and launching/landing the boat. A hydraulic system will have all sort of frictions in it so you lose a lot of power. There is somewhere between 100 and 200 watts of power in an adult man so everything counts.

    I had an idea of an outdrive for my pedal boat when I was designing it. It would have had a belt drive from the power shaft to the prop shaft and a simple U-joint at the steering/trim pivot point. I ended up with a straight shaft design with a tunnel that fits half of my 200 mm diameter propeller. There is still a bit too much friction even in this simple setup (the shaft seal mostly).

    To give you some usable help, maybe you can give some details about the boat in question. Length, beam (at chine), weight and if you have a picture of the bottom inside or out. What sort of water your boating in.


    Hoyt
    Way cool thing that subo kayak. I want one.

    cheers
    Lurvio
     
  9. portacruise
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    portacruise Senior Member

    Hi, Jon:

    A flat bottom boat is great for stability and fishing, but not too great for pedaling because of the water friction of the shape. They work well with petrol motors but it would be hard to make headway against wind and waves by pedal power. The best shapes/ arrangements with the tiny amount of power available from a human will keep losses low, and are something like this:
    http://www.youtube.com/watch?v=tMw8q5g4DsE
    Weed/debris tangling will be an issue with props so it might be best to have easy access to the prop. The video example would allow this and so do some of the side prop designs by Rick Willoughby.

    Hope this helps.

    Porta

     
  10. JonBoat
    Joined: Jul 2012
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    JonBoat Junior Member

    Lurvio,

    I have a 12' flat bottom boat about 50" wide at the base. Its got a big footprint.[​IMG]

    This is primarily a stillwater fishing boat and while i don't mind paddling from one location to the other or even trolling, i thought this would be a cool idea. The biggest obstacle in my way would be some headwind.

    I thought of using bicycle gearing to get the prop up at a good speed but i could also use a large source pump and a small prop motor to multiply the speed if i could find a suitable pump. Any ideas on pumps?

    http://www.princessauto.com/pal/en/Drill-Pumps/Metal-Drill-Pump/5770250.p

    JonBoat
     
  11. Jeremy Harris
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    Jeremy Harris Senior Member

    The problem with using hydraulics is the very poor efficiency at low power levels. Hydraulics have a fairly high fixed loss, which means that much of the 100W or so from the pedals will get absorbed by the hydraulic system losses.

    If you want to test this, then get a couple of those pumps hooked up in a closed circuit and feel how stiff the input shaft is to turn, even with no load. Compare it to a bike crank and chain system, which has may be 2 or 3% lost power. I suspect you'd find that the hydraulic system will lose maybe 20 to 30% or more, which is an unacceptably high loss when you've only got so little power to start with.
     
  12. Scheny
    Joined: Feb 2012
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    Scheny Junior Member

    Hi guys!

    I didn´t spend much time in the forum for the last months, but I got really interesting news. After spending weeks in studying Godzilla, I now understand how to fully use its capabilities.

    Until now, there was consens, that parabolic shapes with elliptic cross sections are fastest for HPB´s. Godzilla proves this and calculates a perfect parabolic hull for 5m/s target speed:
    • 7.8m length
    • 98kg weight
    • 357W @5m/s

    Resizing to 5.5 meters length, the required energy increases to 366 watts. But here comes the big surprise! After resetting nearly every value to simulate semigliders (a displacement boat with high L/B ratio like fast cats sometimes have it) I got following values:
    • 5.5m length (restricted by me)
    • 98kg weigth
    • 352W @5m/s

    So this means, that semigliders can be faster than displacement boats, even for HPB´s.

    I will post resistance charts in the near future. My modular drivetrain has also evolved very far, so that I will build a prototype soon. Currently I got an 88% efficient Raceprop and an 81% efficient weedshedding prop which can be 3D printed very cheap.

    Cheers, Andreas
     
    1 person likes this.
  13. hoytedow
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    hoytedow Wood Butcher

    Do you have an illustration of that?
     
  14. Scheny
    Joined: Feb 2012
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    Scheny Junior Member

    It looks like an olympic rowing shell with the tail cut off. Actually a 7.8m parabolic hull cut down to 6.2m seems to be the new benchmark:
    350W @5m/s

    Still couldn´t beat that value... :cool:
     

  15. MLampi
    Joined: Aug 2008
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    MLampi Junior Member

    Hi Scheny,

    How about a parabolic hull cut down and flattened toward the stern? This would provide more of a planing surface.

    I suspect it would look a bit like a Cadence hull from the waterline and below.
     
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