Treddlecat powered raft

Discussion in 'Boat Design' started by pollacchi, Jul 1, 2013.

  1. pollacchi
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    pollacchi New Member

    I have an important raft race against my older smarter brother and I need to win this time, I think the treddlecat mechanism fitted to a raft would blow him out of the water. I think someone (vinnie) has already built one so if anyone out there has some advice or sketches, I'd be eternally grateful for their help
    Here's hoping. Theres a lot of pride at stake ..................
     
  2. Skyak
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    Skyak Senior Member

    I think the treddlecat would get trounced by a common rowing shell. The way to optimize performance is to determine your thrust generating capability for the length of the course and select the hull length to optimize speed for that thrust. Distribute the effort efficiently to a larger percentage of your muscles and use thrust generating faces that are closer to perpendicular to the direction you are going.
     
  3. messabout
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    messabout Senior Member

    If the boat must take the form of a raft, then make it narrow and long and row it.

    Sounds like a fun project. Keep us informed and tell us more about the rules of the game.
     
  4. pollacchi
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    pollacchi New Member

    Thanks guys but I was looking for some sketches ideas on how to build a treddlecat mechanism, any ideas?
     
  5. messabout
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    messabout Senior Member

    Here is an idea. Bulid a long skinney raft and forget the treadle cat notion. As stated above, a good rowing shell will humiliate a boat that uses some sort of treadle contraption to make it go. It is likely to do the same with a raft like boat.

    You must tell us what the boat is to be. The term raft can mean anything up to including Thor Heyerdahls straw boat. A raft could be anythng from a few logs strapped together to a few 55 gallon drums assembled into some sort of floating object.

    If you want informed advice then post details.
     
  6. pollacchi
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    pollacchi New Member

    there are no rules other than it must be powered by human propulsion, first over the line wins, and the usual safety requirements, hence my search request for a fast simple method of human propulsion, ie one that I can build without too much skill required. I'm pretty good at maths so I can do all that stuff, Im going with a twin hull 4.8m long and approx 500mm wide its the design and fabrication of a propulsion system. rowing is a bit obvious we get extra marks (pints) are for ingenuity,
     
  7. messabout
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    messabout Senior Member

    I have failed to find anything that describes a treadle cat on the internet. Treadle is a very old method for powering sewing machines, jig saws and such. I think it might be fun to contemplate that method of propulsion for a boat. It is most unlikely that it would yield high standards of performance. Fun to mess with but that is about all.

    Your mentioned 500mm width. Is that the width of each hull or the overall width including both hulls? Any propulsion device that is located between the hulls will encounter problems with the converging bow waves of the two hulls. The closer together the hulls, the closer to the front of the boat the wave interference. Five hundred mm is much too wide for 4.8 meter cat hulls. Shoot for a hull length to beam ratio of 10 or more.

    Cats almost always have more wetted surface than a monohull of the same capacity. At human powered velocities, surface friction is a major consideration. Minimize wetted surface area so that the sum of surface frictions are minimzed. If you are good at basic geometry, you can see that different shapes have varying surface area for a given contained volume.

    The fastest human powered boats are pedal powered. The boats use a propeller, driven by bicycle like mechanical elements. There is a huge long term thread here on the forum that goes into that subject in great detail. One of the main contributors to that thread is Rick Willoughby. Use that name in the search function. It will probably lead you to that thread. There is much to learn there. There is another thread that discusses boats powered by cordless electric drills. Good stuff in that thread too. Research some of this and I expect that you will rethink the treadle cat idea.
     
  8. Skyak
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    Skyak Senior Member

    The treddle cat is also for two with sideways seating. When you change this to one forward facing operator you will end up with a hobbie mirage drive.
     
  9. SamSam
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    SamSam Senior Member

  10. messabout
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    messabout Senior Member

    Thanks Sam. Now I know what a Treddlecat is.

    Not impressed, even though it looks like fun for a resort rental boat.
     
  11. SamSam
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    SamSam Senior Member

    Yes, from the little exposed in the advertising blurb, it looks like it's only a blade that must have a limited movement, allowing it to flop a few degrees back and forth, and the only mechanism involved is to be able to push it back and forth.
     

  12. SamSam
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    SamSam Senior Member

    After I posted the above I happened to look at the random gallery photos at the bottom of the page and thought that one posted by 'blared' would be a good solution. That random photo disappeared so I looked in 'blared's' photo gallery and found another solution to an important challenge by an older, smarter brother that one needs to beat.

    Being such a small time, localized rivalry it would hardly matter what mechanism was involved or even who crossed the finish line first if the propulsive force was an overall winner.






    I'm thinking panda power would work.















    [​IMG]
     
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