Catamaran kayak basic shapes and dimensions help.

Discussion in 'Multihulls' started by DeaninMilwaukee, Nov 21, 2016.

  1. DeaninMilwaukee
    Joined: Nov 2016
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    Location: milwaukee

    DeaninMilwaukee Junior Member

    Hi, I've have been lurking and learning here for a while, and I'm hoping for some basic dimensions design help for a catamaran kayak I wish to build.

    I found the Wavewalk 700 online ( http://wavewalk.com/blog/new-700-series/#Dimensions) and it seems close to what I want, but am hoping to optimize the design for my specific use. ( and have the fun of making it myself. )

    My design needs: Will mostly be used 2 up to explore creeks and small rivers, so maneuverability is important, and it needs to be as easy to paddle as possible to make up for two non-athletes to be able to cover reasonable distances with some measure of speed.
    So criteria in order of importance:
    1) Stability ( hence catamaran )
    2) ease of paddling ( to allow as much speed as is practical )
    3) maneuverability

    I will be using glass over foam construction and have a hot wire cutter, so I can literally make any under waterline shape that is needed.

    Here's what I think would work:

    I believe I would get better results by stretching the Wavewalk design from 12'10" to 14 ft long to compensate for the displacement loss from changing the underwater section to perfectly round with a 5 inch radius, allowing about 500 lbs displacement before it goes deeper than the rounded hull bottom.

    This will give a fineness ratio of about 16:1. At 5mph ( achievable? ) and 14 ft long, I calculated sp/length of 1.163 and a cp of 0.56. With my limited knowledge I believe this means the ends should go from sharpish tips to full hull width ( 10" ) in a fairly short distance, say perhaps only 18 inches.
    For maneuverability, I think no rocker at all will be needed due to the round hull bottom. ( please correct me if I'm wrong! )

    As for the the ends, since the hulls will be so close together ( 16" between them ) I think that I should follow the wavewalk example and have them asymmetrical at both ends.


    So am I on track here or way off? At this point I can change any dimension or shape, I just want to do it right the first time.

    Thanks in advance for any help.
     
  2. DeaninMilwaukee
    Joined: Nov 2016
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    Location: milwaukee

    DeaninMilwaukee Junior Member

    97 views and no comments? Have I posted in the wrong forum? Perhaps I should have posted in boat design instead.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you are looking for maneuverability a double paddle canoe may be more suitable.
     
  4. DeaninMilwaukee
    Joined: Nov 2016
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    Location: milwaukee

    DeaninMilwaukee Junior Member

    I did consider the canoe route, but they are just too tippy for my weak swimmer wife to feel comfortable. She does just fine in our cheap n slow kayaks however.
     
  5. redreuben
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    redreuben redreuben

  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Canoes don't have to be tippy. It depends on the design. If they have a chine and rather flat bottom, there are quite stable.
     

  7. DeaninMilwaukee
    Joined: Nov 2016
    Posts: 21
    Likes: 1, Points: 3, Legacy Rep: 10
    Location: milwaukee

    DeaninMilwaukee Junior Member

    Thanks for the input everyone. I was hoping to design and build my own boat ( for the fun of it ) rather than just purchase something.

    The catamaran design is appealing in that I can make it fairly small and light yet able to easily carry two people like a canoe, with potentially more speed than a canoe while greatly exceeding a canoes stability.

    I had planned to make each hull removable with no tools using a plug and socket design locked in with hitch pins.

    As I mentioned, the Wavewalk 700 is close to perfect for me, but has a few problems for my use including a fairly deep draft at max load of 8 inches, a bit heavy at 88 lbs ( I think I can come in closer to 60 ) and is not able to be taken apart for convenience of transport and storage.
    I could just copy it for a lighter disassemble-able home built version, but I thought why not optimize the hull shape and size for paddling use at the same time.

    Thanks again for the help and different viewpoints.

    Dean
     
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