Raft down the Mississippi

Discussion in 'Boatbuilding' started by qwist04, Jan 18, 2005.

  1. qwist04
    Joined: Jan 2005
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    Location: Twin Cities, MN

    qwist04 Junior Member

    pedal-powered raft?

    Since I'm back on here and thinking about it, these are my latest plans for a raft. Everything is very tentative.

    The raft will be modeled (unsurprisingly) after the Neutrinos' Vilma B. Two pontoons at 4' wide, 18' long, 1' deep, filled with Styrofoam. With cross pieces and a plywood cover, total dimensions will be about 16' wide by 18' long. Intending to fit four people on the raft, with a small shelter used mostly for storage.

    Here's the catch -- I don't want to do the whole trip with an outboard engine. I'm tentatively thinking of rigging a bicycle to a propeller (probably a large model airplane prop). I know there have been a few pedal-powered boat threads, but I have not found any information on anyone building a pedal-powered raft. Is this a bad idea? Is there too much drag for this to effective on a raft? Are the dimensions on the raft too big for a pedal-powered prop?

    With four people on the raft, everyone could take turns doing 30 minute shifts, so the pace of the biking would be pretty quick, I would imagine.

    At this point, I'm not too worried about the technicalities of rigging the bike/propeller. Just trying to find out if the idea is feasible.

    By the way, I do plan on having a 5hp-9.9hp outboard motor as a backup.
     
  2. kengrome
    Joined: Jul 2006
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    kengrome Senior Member

    For economy I would use surplus 5 gallon polyethylene drums to make my pontoons. They are almost 2 feet wide and they are 3 feet long each. Fasten 6 of them together end-to-end for each pontoon, and use two pontoons per side to give you the 4 foot wide floats you're planning to use on each side of the raft.

    One good thing about polyethylene barrels is that they are individually replaceable if they get damaged. Another is the fact that they are relatively cheap since lots of liquids come in them and are basically 'leftover containers' and sold cheaply when the contents are removed. They also flex and bounce off things without damage most of the time, which may come in handy when you bang into things in your raft.

    Sorry of this was already mentioned previously, I haven't read the entire thread yet ... :)
     
  3. BarendGrobler
    Joined: Mar 2007
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    BarendGrobler Junior Member

    Propper rafting trip

    All you guys talking about how adventurous it would be rafting down some river, it sounds quite nice (kinda like driving miss daisy!)
    Have a look at a book called "THE KON-TIKI EXPEDITION" written by THOR HEYERDAHL about 6 guys rafting across the Pacific Ocean!
    Now there's a real adventure and there is at least a real goal: ending your adventure on some Polynesian Island!
    :D
     
  4. Guest625101138

    Guest625101138 Previous Member

    You could plan on a fit individual pumping out 150W for a couple of hours at a time. With careful design you could get some useful motion with this power level. I have not analysed your proposed hulls but I suspect they are not easily driven.

    If you actually want to make useful progress under pedal power I would suggest you determine likely total displacement, design the optimum boat and then look at how you can get close to that with available materials.

    You can make some nifty multiple station drive arrangements so all four could pedal at once driving a common shaft. The best I have seen of this are raced in South Africe and they hold about 8kts. I have attached a photo of Vel'eau 12. I believe it has 12 cycle stations, 6 aside, and solar power. You could sit sideways like this with simple bike chains onto the shaft to swing a decent prop. With 18ft hulls you might hold over 5 kts with all four cranking steadily at an all-day pace of say 120W. Rotate meals, plenty of water and leave the outboard motor behind to reduce weight. This would be an adventure and you do your bit to leave a little more oil in the ground.

    Rick W.
     

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  5. qwist04
    Joined: Jan 2005
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    qwist04 Junior Member

    Thanks for your responses, Ken and Rick. I planned to base the raft on the Floating Neutrinos' because it seems like really knew what they were doing. Information about the Vilma B can be found here. I have considered barrels, too, but I was under the assumption that this would be less efficient than the pontoons. Seems like this was a wrong assumption? I do like the fact that barrels would be able to fixed/replaced way easier than a pontoon.

    The multiple station drive arrangement is an excellent idea. I am unsure how I would design and build it; might you know of somewhere I can find plans for something along those lines?

    Also, if anyone could point me to other raft plans that might be more efficient than the Vilma B, I would greatly appreciate it.

    Now, time to read through the 21 page thread on the human powered boat.

    Thanks again.


    Here's a picture of the Vilma B in progress, which was the same dimensions as I gave in my last post:
    [​IMG]
     
  6. Guest625101138

    Guest625101138 Previous Member

    If you make an estimate of the overall weight of the boat and items you want to transport then I can do some hull designs that would be easily driven and very simple to make from ply.

    Making the drive stations is not too hard if you have basic engineering skills like welding or brazing. The cheapest way to get parts is to get hold of some old bikes and start from there. These will provide bottom bracket, pedals, chainring, chain and sprockets.

    If you can keep the weight to about 1 tonne then 4 fit pedallers could make surprising progress.

    The boat design could be refined based on the building materials you want to use. Your budget will also come into play. You never know you might get some sponsorship if you stress the eco friendly aspect of the adventure.

    Rick W.
     
  7. djwkd
    Joined: Jul 2006
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    djwkd Senior Member

    I'm going without a motor.The dimensions are 22'x11'.

    It's sorta odd that your using nearly the exact same design as i am,and basing it on the same raft.I think the vilma b is a faveourite of non-barrel raft builders because it's a simple design,and can be easily extended.

    I'm planning to turn the heels of the bike i am using into a paddle wheel,with the rear wheel being attached to an extended chain (3 together?!).

    Does this sound like a bad idea?I know it mightn't be incredibly efficient,but i might make two.Depends what you guys think!

    Thanks again,dominic.
     
  8. Guest625101138

    Guest625101138 Previous Member

    Dominic
    There is nothing inherently inefficient with a paddle wheel in smooth water. They went out of fashion on ocean going vessels because they did not cope as well with sea conditions as a prop. They are probably more efficient for shallow water operation compared with say a jet - particularly at low power level. I have attached some photos of modern examples.

    You need to keep it big though so it operates at low slip. I would go for a diameter that you just put cranks on rather than gearing up. In fact if the boat is slow then actually gear down so it goes slower than your cadence.

    I also think you would be better off making hulls with pointy bow and stern rather than the bluff ends of Vilma B. The section can be still be rectangular so it is easy to build. This will give less resistance with the narrow sections on entry and exit.

    If you make an estimate of the total weight I can give you designs for optimum rectangular section hulls.

    Also how many people will be used to power the raft. Will it be just one or will there be more.

    Rick W.
     

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  9. qwist04
    Joined: Jan 2005
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    qwist04 Junior Member

    I truly appreciate your help. With some quick estimates on weight it seems like I can easily keep everything under 1 tonne. The sponsorship idea is something we are considering; we're also thinking about doing the trip as a benefit so we could try to get companies to donate things we need. People could pledge money to an organization for every 50 miles we go, or something along those lines.

    Anyway, I'll put together a more specific weight estimate pretty soon.


    djwkd -
    It is very interesting that we are considering very similar trips on a similar raft (just on a different river). I'm definitely going to go with Rick's advice about the pointy bow and stern. With about 1700 miles of pedaling to do if I go to NOLA, I want the best efficiency possible in a raft. It will be fun to compare our trips when they actually happen.
     
  10. Guest625101138

    Guest625101138 Previous Member

    I have attached a lines plan for hulls of a 23ft catamaran. Each hull is 2ft wide and raft overall beam is about 9ft. This boat is designed for 1 tonne and speed of 5 kts.

    Two average males could hold 4.6kts at an all day pace. Three people could get up to 5.4kts. Four people will not do much better, only 5.6kts. That is because it is optimised for 5kts so wave drag gets significant above this. It would do better with 4 people if the design speed was higher.

    The hulls could be simplified even more but this is just what Godzilla produced for a square chine and length constraint. It is to give you an idea of what pointy ends look like.

    The paddle wheel idea is a good one but you need to think big with this but make it light. Think in terms of it sitting between the two hulls toward the stern. Blades say 6ft wide and 6 to 8" deep on a wheel about 3ft in diameter. This should work OK at normal cadence.

    The hulls could be made from light material, maybe 3/8" weatherproof ply, but fill them with expanding foam and add some rubbing strips to give them impact and wear resistance.

    Rick W.
     

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  11. djwkd
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    djwkd Senior Member

    Thankyou for your advice rick,i will go with your advice.I now know how to bend wood so i can scrap the bicycle wheel idea!So glad!

    Qwist-the difference between our trips is that mine is of roughly 10 miles-yours is more than 100 times that!:p
     
  12. djwkd
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    djwkd Senior Member

    No response?!oh and-i think it's this theread-guppy-could oyu post a larger picture of your avatar?
     
  13. tomtom2
    Joined: Jul 2007
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    Location: CA

    tomtom2 New Member

    Is anybody familiar with the fishing rafts found along the wolf river in central wisconsin? These are small docks, usually no larger than 14x14, supported by 55 gallon drums. On top of a wooden platform are small shacks, some simply thrown together to keep out rain, others resembling small houses more than shacks(one that i'm familiar with has bunkbeds for 5, cabinets, a large counter space, and an outhouse). These are used primarily for fishing off of during spring and summer, and are towed/pushed by flatbottom boat to a location along the river shore, where steel pipes are sunk into the mud to hold them in place, along with ropes attached to trees. They may be used elsewhere, but to my knowledge ive only heard of or seen them used along the wolf river. I'll try and get some pics up if possible.

    If anybody knows what I'm talking about, would this type of raft, possibly enlarged, make a suitable vessel for going down the mississippi? I was thinking of something about 18x12 feet, propelled using push poles similar to skiffs one might see in bogs or salt flats. For navigating the locks and dams, I would mount an outboard to the back for greater maneuverability, however on open sections of river and in situations where I wonbt need to avoid barges, running the engine non stop seemed a waste of fuel. Any thoughts on this?
     
  14. djwkd
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    djwkd Senior Member

    That should be OK but i'm not at all familiar with that river,being in england.I don't know if you've read the whole thread but raft-builders (including myself)favour the designs of the floating neutrinos-http://www.floatingneutrinos.com this is one of the best raft sites because it has pics of the build of 10 rafts,not just one like Miss Rockaway Armada- http://www.missrockaway.org
     

  15. qwist04
    Joined: Jan 2005
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    qwist04 Junior Member

    Rick,

    Thanks so much for the help. Sorry for the delayed response: I've been out of town for the past couple weeks.

    djwkd - Regarding length of our trips... touche. But that's only if I do decide to go the whole way. I still may only do Minneapolis to St. Louis. Still considerably more than 10 miles, but not the 1800 miles it takes from Minneapolis to NOLA.
     
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