the case of the square/rectangular kayak

Discussion in 'Boat Design' started by john5346, Jul 16, 2010.

  1. john5346
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    john5346 Junior Member

    Thank you :) I will try that.
     
  2. messabout
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    messabout Senior Member

    John; If you wish to build a very simple, angular section, cheap, quick, and easy to build, but entirely adequate canoe/kayak....then take a look at the Six Hour Canoe. Google that name for details. It may be just what you are looking for. You could actually build it in six hours if you have a little bit of woodworking experience. Two sheets of plywood is all the material you will need.
     
  3. rwatson
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    rwatson Senior Member

    Found it - http://members.shaw.ca/brad.clarke/boats/fanny1.htm

    Nice beginners project - if John finds that a bit daunting, he can just join two side strips at each end, and spread the middle. With this boat shape, add a flat bottom. You can even cut the "boat shape" out of a flat bit of ply, and "wrap" the two sides along the edges. Fibreglassing seems a bit scary at first, but just have a play with a few "test bits" first. Its surprisingly forgiving even when in-expertly applied.

    Try it with cheap materials and only plan on it lasting a few months. Its a good fun learning experience in safe water areas.
     
  4. lewisboats
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    lewisboats Obsessed Member

    Here is what I did for/with my son.
    [​IMG]

    It is an enlargement of a single sheeter that I did with some cub scouts.

    The entire boat is done by laying out one of these and using it as a template for all the rest. Two of these per side and using the shape of the curve provided the shape of the bottom panels.

    [​IMG]

    It even did a stint as the center hull of a tri:
    [​IMG]

    The entire build is here:

    http://www.angelfire.com/ego/lewisboatworks/html/ScoutCanubuildfront_a.htm
     
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  5. daiquiri
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    daiquiri Engineering and Design

    @Lewisboats:
    I presume you have added some kind of rudder or a false keel (?), because it doesn't look to me like a hullform which will keep the straight course very well (flat bottom plus a considerable rocker).
     
  6. lewisboats
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    lewisboats Obsessed Member

    It has a small skeg extending along the bottom. It actually did quite well as a paddler. You can just see it under the hull in the first picture.
     
  7. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Ok, just saw it on the page 7 of your blog. Nice little boat. :)
     
  8. magwas
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    magwas Senior Member

    Daiquiry: I suggest to post developments as well. It would show how small the difference between them wrt building effort.
     
  9. lewisboats
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    lewisboats Obsessed Member

    I expect we (I) had it from plywood sheets to in the water with less than 20 hours total work (not including curing times of course). Quick and dirty...and I still have it in the back yard on horses. Needs to have the Skeg replaced and a few spots of delam fixed but it is still usable.
     
  10. sharpii2
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    sharpii2 Senior Member

    The last suggestion (the six hour canoe) was far more sensible than what I’m about to propose.

    Attached are drawings of two ultra simple kayaks, or ‘boxyaks‘, as I like to call them.
    The first one is just a box drawn to kayak proportions with a raised deck on either end. As you can see it is all square except for the angle for the end of the stern raised deck. As drawn, it will displace just under 204 kg, fully loaded. It has a draft of just under 8 cm at that displacement. It is 61 cm wide and 4.59 m long. The raised decks are just under 8 cm above the freeboard of the sides and are just upward extensions of them.

    The second ‘boxyak’ has only two changes.

    The bottom slopes up at both ends forming a very shallow ‘V’ lengthise. Its draft is a little over 15 cm with the same displacement. The end decks are pitched rather than raised. They are pitched up just over 15 cm high, so they will have the same volume under them as the first ‘box yak’.

    I would proposed building a scale model of each to exactly same scale. Then I would propose two tests.

    The first would be a drift test. Both models would be weighted to the correct scale displacement (down to the scale waterline), set in a pond with a gentle breeze blowing and watched to see which one drifts away the fastest. This would be in effect sailing sideways. My guess is that the first one would drift the fastest.

    The second test would be the propulsion test. Each would be given a small sail set far forward. The sails, of course, would be of exact same design and area. The two ‘boxyaks’ would be watched to see which one sailed away the fastest. My guess is that the second one would be the fastest.

    You could then compare how much faster they drifted and sail compared to one another to see how much better the more complicated design is than the simpler box.

    Then, if you are really enterprising, you can build one of the boxyaks full size and take it to various small boat meets. When they see either one of these, their jaws should dropJ. At this point you might be able to make some money. Get them to place bets on how much faster a real kayak is compared to your crude ‘box yak’. Then get two paddlers, who each get rewarded if the boat they paddle wins the bet, and get them to do a several mile race. Hopefully the bettors will grossly over estimate the superiority of the real kayak.
     

    Attached Files:

  11. hoytedow
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    hoytedow I'm not a cat.

    Some of us should wear a helmet all the time. :D
     
  12. peter radclyffe
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    peter radclyffe Senior Member

    you guys are hilarious
     
  13. rwatson
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    rwatson Senior Member

    and you would be right - I have tried both, and the flat keel is definitely the fastest, but a bugger to turn.

    This simplistic stuff is definitely "hilarious", but I remember well the first tentative steps into the floating world. If you havnt tried the simple stuff, then slightly complex stuff seems really hard - ie walking is simple, but when you are crawling, it seemed tricky.

    Mind you, after you do a couple of simplistic boats, you soon see that the proper plans are really easy as well.
     
  14. john5346
    Joined: Jul 2010
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    john5346 Junior Member


  15. hoytedow
    Joined: Sep 2009
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    hoytedow I'm not a cat.

    Wasn't the rectangular kayak developed from a flat board, to begin with?
     
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