propulsion for 12.5' caster kayaks

Discussion in 'Boat Design' started by caseycola, Feb 3, 2010.

  1. caseycola
    Joined: Jan 2010
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    Location: pascagoula ms

    caseycola Junior Member

    I have read a lot of the pedal powered boat thread and otherthreads here but still am trying to get a plan together for what would work best for what i want to do. I have three perception 12.5' caster kayaks. I am looking to do 2 things.
    The purpose will be for recreation/fishing rivers, lakes, bays.
    Determine best propulsion method individually and I want to fabricate some sort of trimaran out of the three with aluminum/stainless tubing.
    Individually, how long does a trolling motor battery last usually? I think I would be satisfied with the speed but would be concerned with running a battery dead after a couple of hours.
    I like the ratchet gear and stairstepper style pedal system with some type of gear box (from mcmaster etc.), or would a regular bicycle pedal and gears setup work better (for being able to get 10-15 different speeds) if I was going to be out for up to 6 or 8 hours? pedaling from the seat in the reclined position.
    Or would a pedal powered battery charger pushing a trolling motor be more efficient than directly pedaling a prop all day?

    As for making some type of trimaran:

    Should I use stainless or aluminum or carbon fiber tubing? I need 1'' diameter. Which is cheapest?
    I am looking at the hollaender.com fittings to join them together, still looking for any other sources also.
    What is lightweight for decking/? any sources? or would a trampoline hold up?
    I wanted to have two kayaks in the back and in the one offset forward like a triangle or would this work better with all three side by side?
    I am thinking a 5hp motor on this setup would be easiest but does anyone know how good pedal power would work with three people +(maybe a sail for open water) on a rig like this. Also Id like to know cost wise would it be worth it. Seems like a good 5hp motor would be hard to compete with cost+performance+ease of installation.


    Thanks in advance for any help
     
  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    You are asking a whole lot of questions in a single posting.

    12 foot kayaks will have a practical limit to the speed you can reasonably expect regardless of the power that you might apply. Less than 5 MPH. A five horse outboard is more power than you can use on such a rig. Something like the 2HP Honda will be enough. If you pedal power the boat you will not be able to develope more than a half HP even if you are a very good athlete.

    Battery power has time limits as you mention. You might get 4 hours run time from a large deep cycle battery if you have a modest sized motor and you do not run it a maximum speeds. Charging the battery with a pedal powered generator is a very inefficient way to go. Abandon that idea.

    One inch tubing is too small to tie all those boats together, Two inch tubing is more practical. Two inch carbon fibre will be cost prohibitive. Use aluminum for weight saving, ease of machining, and moderate cost.

    Multiple short boats configured as a trimaran will work but not as well as you might like.

    If you wish to human power the boats, then recumbent pedal powered propellor is the most promising method. Propellors are more efficient then the various flapper methods. A very simple scheme might be arrange the boats in a tee shape with the middle boat extending forward of the other two. Get a rowing rig such as the Piantidosi and row from the front boat. Occupants of the other two boats can help by paddling if there is a headwind or opposing tidal flow.

    The overall best plan is to abandon the whole scheme and build, buy, or steal a very long, lightweight, skinny boat. Then you can power it any way that you might choose. It will be much easier to manouver, much faster for a given power input, easier to transport, and generally a lot easier to live with. Probably wont cost much more than the three kayak arrangement and it will certainly work better.

    The forum has several very informative threads that address human powered vehicle questions. Use the search function to find them.
     
  3. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    From practical experience, the speed in a 12 ft canoe, versus 16ft, to 21 ft was a huge difference.

    All Rick Wllougbys pedal powered boats were at least 18ft.
     

  4. thudpucker
    Joined: Jul 2007
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    Location: Al.

    thudpucker Senior Member

    I met a guy in Sitka AK, as he beached his Kayak.
    He'd made the Journey form San Francisco. He was headed on up to the top of the world, and down the other side.

    His Kayak was a two holer, with his shroud tied up around his chest.

    It was a 14' as I recall. He had a Double ended Paddle that came apart in the middle. Two more stashed on the side of the kayak. All the same so the parts could be interchanged.

    He had quite a story. But never once did he mention a need for any other source of power.
     
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