Human Powered Boat

Discussion in 'Boat Design' started by SolomonGrundy, Feb 12, 2005.

  1. SolomonGrundy
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    SolomonGrundy I'm not crazy...

    Hi all,
    I'm in the early stages of developing an (HPC) capable of a trans-pacific voyage. Some of the preliminary parameters I'm working with are: 22' LOA, 2600 lbs. Disp., self bailing/righting, prop. propulsion. Made of aluminum.
    I am an experienced boatman, welder and boatbuilder. The major issues I'm faced with at this time are how to turn the prop. and the modeling of the hull.
    I thusfar envision a highly efficient prop. on a stainless shaft connected to some sort of rudimentary V-drive with a screw and pinoin or bevel gears or something similar.
    My main problems are that I don't know the best way to deliver power from the legs to the shaft, I prefer "stair stepper" type device as opposed to a crank and pedal set up.
    To facilitate construction, I plan to have the parts CNC cut, that means modeling and that is not exactly my forte' but I feel up to the challenge.
    I have found some helpful info at www.nauticraft.com and also some chain and sprocket drawings from a Seattle designer, but nothing I would consider simple and reliable enough to be suitable.
    I'm looking forward to hearing some ideas in those regards.
    Some other questions I have are: How much horsepower can a person consistantly make with leg power alone? What would be the proper shaft diameter for such power? How many rpm could be expected? What is the most efficient prop. for such?
    I hope those more knowledgeable can help answer some of these questions.
    Thanks in advance.
     
  2. Skippy
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    Skippy Senior Member

    Hi SG, welcome to the forum.

    Self-righting. Have you considered carbon for the upper half of the hull? And just to be sure, is this completely enclosed?

    Power delivery. Full-body power would be greater than legs only, if you could find or make some kind of "Nordic Trac" or similar setup. With the stair stepper, you should still have some way of clipping your feet to the stairs, so you use more muscles. Otherwise, you may find that muscle fatigue takes place below your cardiovascular capacity.

    Here are a couple websites I found:
    Human-powered Boats
    Power of a Human
    "The typical average continuous power that can be generated by pedaling is about one-sixth horsepower or 125 watts, more or less, depending on the weight, strength, and endurance of the person pedaling."
     
  3. sharpii2
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    sharpii2 Senior Member

    A herculean heresey. A Dromon for our dayz

    Hi solomen

    As for propeller diameter, I would go with as large as possible. It is almost always more efficient to move a lot a little than to move a little a lot. I would have to get my displacement boat prop book to come up with an actual diameter. My guess would be in the order of 24in if not larger. And probably just two blades. And the design rpm should be about 100.

    I'm wondering. Is this going to be a solo effort? Or are there going to be two aboard?

    I've always wondered if these 'human propelled' voyages were little more than controlled drifts. It seems that with only 0.14 hp per ton for only about 12hrs a day that you wouldn't make much progress except in a constant dead calm or an at least semi favorable wind and current.

    Might I commit the heresey of suggesting the addition of a small sail of say 50 to 60sft and a long shallow keel for lateral area to go a long with the human propulsion rig?

    The sail can assist when you are 'working' and work when you are not. Also, this way, the wind can be usually your friend rather than mostly your enemy. And this way, perhaps, even up wind voyages could be contemplated.

    I think only the orneriest, most cotentious, carmugeon would dare call such a craft a 'sailboat'. After all just about all the oared craft of ancient times, from the Greek galleys to the Viking long ships, had at least token sail rigs.

    Also, I think your stair stepper would need some sort of flywheel where as a peddle rig would probably not.

    That's my 2 cent$ worth.

    Bob
     
  4. JEM
    Joined: Jan 2004
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    JEM Senior Member

    Contact Tom, who owns www.tailboats.com . I bet he has some goods words of advice.
     
  5. SolomonGrundy
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    SolomonGrundy I'm not crazy...

    Human Powered Craft

    Wow,
    Now this is what I'm looking for...feed back. Much thanks to you three for the useful information.
    My intent is for human power only, however I do intend to provide for an emergency use sprit sail. The idea of the "Nordic Track" set up is quite appealing in its efficiency, but in order to perform the long hours of operation necessary, I intend to be semi reclined. So I guess the ideal set up could be a combination stair stepper/nordic track device. With such a mechanism however one comes up square against the most prolific axiom of seafarers K.I.S.S. (keep it simple stupid). As the distance to Hawaii is about 2200 nm. the propulsion system must be as reliable, efficient, repairable underway and simple as practable in that order.
    Another problem I notice immediately is that I dont see how it could be possible for a 24" prop. to turn 100 rpm or even 20 rpm with under 1/4 hp.
    I'm looking forward to seeing if Tom at Tailboats has any words of wisdom for me, those boats are sweet, but I'm not sure the power system could be adapatble for such a larger craft as I propose, I guess I'll have to ask him.
    Please continue with the feed back. Some questions are becoming more clear and some haven't been toutched. I plan to begin construction in mid August. Provided I have a model to generate the cutting files by then.
     
  6. JEM
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    JEM Senior Member

    The actual "tail" of Tom's propulsion system probably wouldn't be useful for your idea. His system has different goals in mind vs yours. But you share the basic concept of transmitting leg power to boat propulsion is the same. So kicking around ideas should, at the minimum, give you good food for thought.

    He's explored the prop option and has done some testing. We've discussed his trials in e-mails and he's absorbed a lot of the learning curve. He'll at least be able to tell you what to be careful about and what you need to over-come.

    I think a a leg powered prop would be fun!
     
  7. icetreader
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    icetreader Senior Member

    Solomon,
    All that's left for me to say is that it's an exciting idea, and the advice you got here is excellent.
    If I had to design such an HPV I would think along the lines of a twinhull, especially since whether pedaling or stepping - being upright is a more ergonomic position.

    Here's another possible source of inspiration: http://webpages.charter.net/rcgilmore/Illustrations.htm#WaterSites

    Yoav
     
  8. Eric Sponberg
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    Eric Sponberg Senior Member

    Solomon,

    I have a potential client that seeks to set the record for smallest sailboat to sail around the world. I won't at this point say how small it is as the project is proprietary at the moment, but we are considering human power as a back-up and for emergencies.

    If you start from the power available, and we are considering leg power to a bicycle type crank with chain drive to a propeller shaft, you will find that the propeller calculations work out to a very large diameter, 2-blade propeller with long narrow blades. The diameter and pitch come out of the calculations. Obviously, light weight is very important, so the propeller will be built out of carbon fiber. An alternative drive system would be a rubber/plastic belt similar to a car's timing belt running over similarly toothed cranks. All this equipment is readily available from McMaster-Carr (www.mcmaster.com).

    I think that the bicycle type of crank would likely impart the most power to the propeller because with every push of each leg, your rotational power at the crank translates directly into rotational power at the propeller shaft. The motion is the same, you don't have to convert motion from say up-and-down pedals into rotation at the shaft. The conversion is done in your legs and ankles. This is the most efficient.

    You may recall the flights of the Gossamer Albatross of the early 90s I think it was, a human-powered airplane and a flight across the English Channel. The propeller worked out for your boat, and the one that I am anticipating, would be similar to that used on the plane. They used a bicycle crank for power.

    Eric
     
  9. D'ARTOIS
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    D'ARTOIS Senior Member

    What Eric says cut's (a lot) of wood. Surely you have done it, but most forumers don't know the actual distance. Well to sail or pedal straight into Honolulu you'll need to wrestle through 2335 nautical miles measured in a straight course.
    In good condition, what will your average daily distance be? If you are lucky, 30 nm?
    So you 'll be at the minimum 78 days on the way. Haven't checked winds, currents and so. The 2300 lbs foe a 22' looks heavy to me, is that loaded or unloaded?
    Instead of drinkingwater, take a good non-mechanical desalinator. And prepare for a textile funnel to collect rain - if it wil rain. No idea about North Pacific circumstances.
    I wish you all the luck of the world.
     
  10. Skippy
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    Skippy Senior Member

    Just a couple more comments on power generation. I think one attraction of the stair stepper is that you're standing up, which uses more muscles. You use your back muscles by standing up straighter as you push with your leg. You can get a similar effect by standing up on a bicycle and shifting to a higher gear. You may lose that effect with either mechanism when reclining.

    I would agree that it's good to use your back as well as your legs. One simple reclined configuration would be a "skulling" style rowing machine, where the seat slides along a track. It allows you to use your back, arms, and legs to differing degrees depending on how they tire. It's kind of funny though. There you are in a boat, rowing without any oars -- fake rowing! :) But I still like it. In calm water, actual oars would be even better, although out on the ocean, I can see wanting to avoid windage and interaction with the surface.

    I agree that the fish tail might not work very well. If fish could live on the surface and be born with oars (or sails), I think they would. :)
     
  11. icetreader
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    icetreader Senior Member

    Skippy,
    We don't know much about the fishtail mode of propulsion, except it works amazingly well for fish (and marine mammals in a different angle). Since we all seem to agree that a propeller for such HP boat should be large and rotate relatively slowly it may not be such a big leap to a large fishtail going slowly from side to side (or up and down).
    Y.
     
  12. SolomonGrundy
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    SolomonGrundy I'm not crazy...

    Hpc

    Mr. Sponberg,
    Great information. Your reputation makes me take special note. If possible, could you answer just a few more questions I have?
    You mention a carbon fiber prop., what about aluminum? I ask because, in my experience, a carbon fiber spar is about 7 times the cost of an aluminum one. For economy, one could have a few spare props and still have some money left over.
    I understand your statement to mean that for the given hp output (aproximately 1/4), the (relatively) large prop. is apropriate. But wasn't the Gossamar Albatros geared up?
    Am I incorrect in my thinking that for a given hp, displacement, and prismatic coefficient there is an optimum shaft rpm that is dependant on the prop. pitch and diameter and to a lesser extent the shaft diameter? Could this then not be achieved by the proper gearing?
    If you say that pedal/crank rotation is most efficient, I am inclined to believe you, but the throw on a crank shaft/pedal doesn't take full advantage of a longer power stroke... I mean that when one is rotating a crankshaft, the leg comes up before it is fully extended and that it begins its downward travel well before the knees are bent enough for the maximum throw. Am I missing something simple?
     
  13. Skippy
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    Skippy Senior Member

    SG, most stock bicycles have somewhat short cranks. I think that helps for sprinting. And you can damage your knees if you overextend your legs. For distance cruising, you might consider using longer cranks.

    icetreader, you may be right about that. In fact, I wonder how much energy is lost to rotation by a prop. I remember maybe a decade ago, seeing a picture of an entire vessel shaped like a fish. Maybe on the cover of a science magazine or Mechanix Illustrated. It was manmade, but it had a large number of joints that curled just like a fish's tail. I think a lot of the reasons for any propulsion system are based on the nature of the generator rather than hydrodynamics. Motors rotate, so they use props. Fish don't, so they wag their tails. Both of these systems create unproductive sideways motion. A boat floats on the surface, so it can use either sails or oars (or paddlewheels). Sails get energy from the wind, and oars push more directly aftward. (Should that be "abaft"?) In fact, is there any reason paddlewheels shouldn't be considered? The axis of rotation is certainly more convenient.
     
  14. JEM
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    JEM Senior Member

    Would you need some sort of "coasting" clutch? Kinda like a 10 speed bike so you don't have to keep your feet pumping if you want to stop peddaling?

    I imagine you wouldn't have any need to go in reverse.
     

  15. SolomonGrundy
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    SolomonGrundy I'm not crazy...

    Hpv

    Geeze, In the time it took to write my last post, 3 people commented.
    Awesome.
    D'ARTIOS, my dimentions and weights are preliminary and not yet " etched in stone ", Mick Bird made it to Hawaii from California in 6? days rowing. If this proposed power system can't better that, than I probably save myself a few grand. I can probably turn out 20 hollow oars in the time it would take to fabricate the system that still has yet to be decided upon.
    You do bring up an interesting question however, namely the speed at wich said craft may travel. I'm assuming rations for 90 days, onboard integral H2O tank for 30 days, not to mention the power required for necessary systems, ie. VHF, 2 meter, GPS, and Iridium. I'm considering 3 Optima batteries charged by wind and photo electric chargers to power supplemental systems. And a mechanical desalinator is mandatory. But please all, I ask to remain focused on the issues at hand and not on outfitting except as it applies to actual displacement and hulshape.
    2200 lbs. is a target for loaded weight, but I figure I'm close, within 500 lbs. or so.
    My main problem with a multi-hull is that, looking at the stability curve, they are just as hard to right inverted as they are upright. Besides, I need to carry some volume for the displacement, not exactly condusive to a multi hull.
     
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