Pedal Powered Boats

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

  1. Submarine Tom

    Submarine Tom Previous Member

    Well, there you go.

    Good plan.
     
  2. I57
    Joined: Feb 2008
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 62
    Location: Melbourne, Australia

    I57 Senior Member

    GMR
    Great to see your boat on the water, looks good. Bad luck with the prop, need one a bit more robust. That old prop I've got made of fibreglass is still on offer if you can handle the cost of shipping. Its sized at 1:8 which is close to your 1:7.4 ratio, if it feels hard to pedal you can trim it off a bit at the prop tips.
    Pic is of the prop fitted to my first boat.

    Ian
     

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  3. GMR
    Joined: Sep 2011
    Posts: 54
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Nova Scotia

    GMR Junior Member

    Thanks Ian , I would gladly give that prop a try if you think it is appropriate for my boat. Going out again tomorrow with a lowered frame, pattern prop, gps, and camera. Also will add a couple of boards for me to stand on while my buddy pedals. Then I can take pictures of the wake. I have a kite that I tried out on dry land last night and it seems to pull quite hard but I don't expect to try it on the boat yet. I'll be back on here Sunday with a report!
    Cheers, Glen
     
  4. GMR
    Joined: Sep 2011
    Posts: 54
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Nova Scotia

    GMR Junior Member

    I brought the the frame down about 5 inches using short pieces of square tube and hose clamps. This week I will make new frame extensions but will keep the old ones. Not being comfortable with a completely unsuspended shaft/prop I made up a rod that allows almost no restriction to any movement of the prop and shaft except for limiting the depth. It worked quite well so now I am deciding what the lowest drag wiould be for a support. Probably 1/16 cable with a hair fairing....... I was holding the boat while Jane pedalled and the prop moved at least 8 inches forward as the shaft bowed down enough to touch rocks on the bottom!
    I had started with a 16x12 APC elecric prop which broke. Then I switched to a 16x14 pattern prop and found that with one person on the boat it took a lot of work to keep anywhere near the cadence I like and I don't know how long I could do that. Then when I added a heavy temporary 2 x 6 spruce deck and another 200 pound person it got significantly more difficult. So I didn't have another 16" prop so I tried a 16x 12 that had been cut down to about 13 inches and that worked much better for two people. With two pedalling it would probably be too light. And with just one person on board it was too light.
    I bought a few larger props but unless I change my gearing I doubt that I will use them. I have heard/read that there are advantages (efficiency) to spinning a larger prop at a lower speed. Do you think this is a worthwhile experiment?
    Lots of noise compared to a sea kayak so I can see myself making some sort of enclosure for the drive stuff as well as keeping a little of the splash away, mostly a noise thing. Isolating the drive from the main frame will help too.

    My mobile phone GPS wasn't cooperating so I don't have any performance figures yet. I did get some pictures of the wake and will put them up in a couple days. For now it is back to dry dock to firm up some of the changes.

    Glen
     
  5. Submarine Tom

    Submarine Tom Previous Member

    Good progress.

    Consider trimmimg the trailing edge on each blade instead of taking off diameter.

    Javaprop is brilliant in determining diameter and RPM.

    You can assume 100 - 125 watts at the prop for extended periods.

    Looking forward to those pictures.
     
  6. portacruise
    Joined: Jun 2009
    Posts: 1,114
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Hope my comments above are useful.

    Porta
     
  7. Liighthead
    Joined: Jul 2012
    Posts: 88
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Girgarre aus

    Liighthead Junior Member

    hey was thinking im about to make a small boat ( one sheet of plywood job, easy cheap just to play around with trying few things )
    where/how can i get my hands on one of those 90* sprocket to shaft things, not sure what it would be called haha sorry..
    would be nice todo something like I57's setup in this pic
    [​IMG]

    but not sure where to find all the parts ect? anyone lead me in the right direction or any tips todo something like this? lol
     
  8. portacruise
    Joined: Jun 2009
    Posts: 1,114
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Light:

    Scrounge parts from used bikes at Charity donation stores, angle grinder gears, model RC props, electricians flex drill spring steel drive shaft or 10mm Al etc. Or spend big bucks to buy new parts on internet, read the archives for sources and hints.

    Porta
     
  9. Coach Dave
    Joined: Jun 2011
    Posts: 70
    Likes: 4, Points: 0, Legacy Rep: 40
    Location: Malabar, FL

    Coach Dave Junior Member

    GMR Nice job on your boat. It looks like you have a good starting point that gets you on the water and you can modify for your intended use. You used a 16x14 prop and a 1:7.4 ratio. Let's say you want to spin at 70 RPM. Without any prop slip that equates to 6.9 MPH. For your size boat you have to put a lot more than 100 watts into the pedals to get that speed. If you move to the middle chain ring (which looks to be about 42T) instead of the big chain ring (52T) it would probably put you into a more comfortable torque / RPM range at a 1:6 ratio.

    When you added a heavy deck and a passenger you dropped your speed and increased your required thrust. One option is switching to your small chain ring that looks like about 30T giving you a 1:4.3 ratio. I suspect your chopped down 13x12 prop was slipping quite a bit under load. A larger diameter prop would slip less and be more efficient. Bigger is not always better. If the prop gets too big you need more draft, drag goes up and your drive shaft becomes too flimsy to handle the torque. So there are always tradeoffs to consider.

    Here some reading material for you on prop sizing for human powered boats. http://www.umwelteinsatz.ch/IBS/propsim.pdf Here is a link on prop slip. http://www.boatdesign.net/forums/diy-marinizing/what-propellor-slip-26982.html Check out Rick's post #5

    Coach Dave
     
  10. Liighthead
    Joined: Jul 2012
    Posts: 88
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    Location: Girgarre aus

    Liighthead Junior Member

    yeah can get my hands on all the other parts, just that gear to drive shaft ( sorry again not sure what to call it haha. )
    any idea where to get one of them? :/
     
  11. GMR
    Joined: Sep 2011
    Posts: 54
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Nova Scotia

    GMR Junior Member

    Hi

    I bought a piece of 1/2 inch aluminum and I will see how it does compared to the 3/8. I wanted to put a keyway into some of the couplings and hubs so making it the same size as the gearbox shafts makes sense. One concern I have is that this may put a larger side load on the bearings in the gearbox. I could go with a fixed shaft, or at least a fixed bearing close to the prop so that the motion is limited to fore and aft as the shaft bows (but not as much as it used to). As you have suggested Porta. This could be foil shaped to reduce drag.... In that case I could use a u-joint as well but that means the prop will no longer be lined up with the current at any time. My buddy took a fair bit of video of the wake but I can't tell you what the speed was. I have a GPS to use for this weekend so I hope to have some numbers. The videos will be up on my blog as soon as I figure out how to get them there.
    I am going to do some testing using the second chain ring (yes, 42 teeth)Coach and try using the larger props. See, this just one more reason to have different gears available!!
    Tom, when you talk about trimming the trailing edge of the prop, do you have a suggestion about what persentage to remove? I'm gessing this requires the edge to be reshaped as close to the original as possible.

    I chopped up the tube mounting all the drive train last night for several reasons. One, to get it to sit between the frame tubes instead of on top of them which will drop the height another two inches. This will also make it shorter and easier to manage, plus, knock off a fair bit of weight. The gearbox will now sit just forward and below the crank but behind the forward main frame tube. I will weld some 1/8 angle on the ends to clamp on the main frame and attach a thin rubber strip to dampen some of the noise.

    Should have the lowered frame extentions done tomorrow and I don't think I will bother with plasic bushings until I test them. I can also see that I will need a comfy office chair with armrests and cup holders but I may elect to remove the wheels.
    Not ready to wire up the rudders just yet so I will contine with a hard linkage for now. Sure hope I can get this stuff at least tack welded together before this long weekend.

    Cheers, Glen
     
  12. GMR
    Joined: Sep 2011
    Posts: 54
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Nova Scotia

    GMR Junior Member

    Lighthead

    My gearbox is a 90 degree unit with a 2:1 ratio and half inch shafts that I purchased directly from Mitrpak. Seems like a quality product but mine isn't even broken in. Others on this site have had good results.

    Glen
     
  13. Liighthead
    Joined: Jul 2012
    Posts: 88
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Girgarre aus

    Liighthead Junior Member

    thanks for that :)
    proably lean towards a electric motor setup for that price though :/
    then can move to my fishing boat if needed.
    though maybe sometime later :)
     
  14. Submarine Tom

    Submarine Tom Previous Member

    GMR,
    Sorry, only just saw your question.
    It depends on how wide it is to start with.
    Can you trial and error taking off 10% at a time?
    A pic of the prop in question would help.
    Maybe you've already posted it, hard to keep up sometimes.
     

  15. GMR
    Joined: Sep 2011
    Posts: 54
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Nova Scotia

    GMR Junior Member

    Oh oh.......I think I spoke too soon about the gearbox....feels like a pin sheared off inside. Just suddenly went to free wheeling while it was being driven at a comfortable pace....Gearbox is really smooth, no connection inside so I will take it apart tomorrow. Good thing it happened a kilometer from where I put in. So I didn't get to try anything new....

    Glen
     
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