Skin-on-frame canoe/kayak plan help

Discussion in 'Boat Design' started by Ruming Jiang, Mar 8, 2021.

  1. mitchgrunes
    Joined: Jul 2020
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    Location: Maryland

    mitchgrunes Junior Member

  2. Ruming Jiang
    Joined: Mar 2021
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    Location: Vancouver BC Canada

    Ruming Jiang Junior Member

    Frankly paddle and seating position doesn't make much sense to me but I'm not going to argue with ICF. I prefer double bladed paddles.

    I think kayak has more enclosed structure while canoe has most of the body (hull?) open.
     
  3. Ruming Jiang
    Joined: Mar 2021
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    Location: Vancouver BC Canada

    Ruming Jiang Junior Member

    That's beautiful.

    I was not sure if my goals are really achievable or not. Just find it exciting to do something challenging.
     
  4. Ruming Jiang
    Joined: Mar 2021
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    Location: Vancouver BC Canada

    Ruming Jiang Junior Member

    Wow!
     
  5. Quidnic
    Joined: Apr 2020
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    Location: Wales

    Quidnic Junior Member

    Plastic wrap kayak



    There have been many plastic wrap boats like this made

    my idea is to have an inner and outer skin then fill with expanding foam
     

  6. mitchgrunes
    Joined: Jul 2020
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    Location: Maryland

    mitchgrunes Junior Member

    The ICF, a competitive sports organization, is just one community within the larger paddling community, and their definitions aren't exactly what most of the recreational paddlers I have known used.

    Within the recreational and whitewater playboat scene, "canoes" (C1's, occasional C2's) have mostly just been "kayaks" (k1's, occasional k2's) whose seats have been replaced with saddles, so you kneel instead of sit, irregardless of the paddle form, though a few C1s and C2s have been specially made.

    If I remember right, one of Zimmerly's documentary books about qajaqs and baidarkas of the high arctic distinguished them by being closed or open. Artic qajaqs were paddled using both 1 and 2 bladed paddles, based partly on regional differences.

    In recent common usage, "kayak" have started to encompass a much larger class of paddled, pedaled, poled, sailed or powered craft, closed or open, or sit-on-top with an enclosed flotation chamber underneath, and/or stand-on-top.

    There is no reason for a recreational paddler to be concerned with the ICF. I may be wrong, but I think most of the boats that do well in ICF competitions wouldn't be nearly as stable as what the original poster appears to seek, nor could they carry much gear.

    "Canoe" has a pretty wide range of definitions too. E.g., the 100 or 200 person boats that it has been suggested were used to migrate Polynesians between distant islands during their era of expansion have hypothetically perhaps been rafts, and maybe had sails.

    The plastic wrap boats like that do not appear durable. It would likely have sunk the first time he scraped against something, or stepped in the wrong place, especially since he did not use any flotation airbags. Not suitable for most class 1 or 2 whitewater.

    The particular design in that video was a quite tippy - though a lot of the problem was that the paddler used untrained techniques to paddle and balance it. One of the best aspects of sit-inside boats is that you can lock your knees against the sides (or, though I don't like this, against a center pillar), and continually bend your body sideways to keep your center of gravity over the boat, for both balance and paddling technique. He overused elbows and shoulders. If you use spinal twists for power, together with the sideways bends you can maintain balance much more effectively. Perhaps the paddle was a bit short too, and had no drip rings, and he had no spray skirt. I'm not sure he was wet at the end because water rolled off that short paddle, or because it leaked. But you wouldn't want to take such a fragile design too far from shore to swim back to shore. Nor might it be an ideal boat in alligator infested waters. :)

    As near as I can tell, open canoes in which people usually sit unattached on the thwarts are harder to stabilize, unless the shape is stable to begin with.

    On the other hand, like a lot of similar videos with similar designs and materials, as a quick and dirty trial, he obviously had fun, and maybe learned something. Play around with the lateral positions of the plastic pipe stringers, and you could give it a flatter bottom and flatter shape in general, for a little extra stability. Replace the packing tape with duct tape, and it might last a little longer - though still not comparable to better materials. I have wondered whether such a simple design could be stiff enough to be reasonably efficient. I guess it is OK to flex in the waves, so you don't have to waste energy parting them, but the boat would also flex and waste some energy with every stroke.

    If it filled with water, a weak design would break if you took it out of the water to empty it. Flotation air bags that filled most of the boat would help a little.

    I guess an engineer would say it has all the major elements of a classic SOF design. A skin is stretched under tension over a compressed frame, made of flexible materials, including long-wise stringers and curved cross pieces. What rigidity there is, is obtained by binding (taping in this case) the stringers to specific positions on the cross pieces.

    I could be wrong there. If you had enough layers of packing tape, maybe it would be strong and duraable enough.

    I have wondered whether a crude take-apart boat could be made out of such a design, in which the stringers (plastic pipes) are threaded through tubular webbing, whose positions are stuck with tape to the cross pieces to force it to the desired shape. If you use long stringers, they wouldn't fit inside a car, but you could easily lift the stringers individually on top of a car, and everything would store easily inside, if you washed it off first. You could alternately sew tubular webbing loops to the skin, so the skin would hold the stringer positions, instead of the binding to the cross pieces. But maybe you still need cross pieces for rigidity - I'm not sure.

    The advantage of such a design is obviously that you can make it in a few hours or less, play with the design, and rebuilt it to the new parameters. And that the materials other than the long poles are cheap. I like that idea. I've been tentatively planning to use something along those lines for experimental purposes, in near-shore flatwater of course.

    If you made long stringers by attaching two or three short ones together (e.g., put a wider piece of tubing in the middle. Drill holes at the ends of each, on opposite sides of the tube, and fit a bolt or cotter pin through one hole in the wider pipe, both holes at the end of the smaller pipe, and through the other hole at that end of the wider pipe. Very simple design. (I'm not sure a cotter pin would be strong enough, but a bolt would be.) That said, rust happens. Use high marine grade stainless steel, aluminum, or titanium bolts, and maybe put grease in the threads. I've had stainless steel bolts and nuts used in roof racks and camper caps rust in place to the extent that the bolts had to be cut for removal. (Perhaps partly because I drove to the sea shore, where there was a salt wind.) I've even had aluminum nuts bolts corrode into place and be almost impossible to remove on adjustable foot pegs. I've concluded salt water and salt and moisture laden air are unfriendly environments for metal components. Is there is such a thing as plastic bolts and nuts, or something else truly salt-water proof, that are strong enough to do the job? Regardless, you might need to double nut, or use washers, so you maintain enough pressure on the nut and bolt threads, despite thermal size changes, that they don't come loose. Maybe you should even carry extra nuts and bolts, and duct tape, for emergency repairs.

    You would not be able to remove a packing tape or duct tape or shrink wrap skin from such a take apart boat, so you couldn't actually take it apart, and would need to cut off the skin, and replace it every time you disasembled it. But once you have the final design, you could replace that skin with a single piece skin made out of conventional SOF materials, so you could take it apart. Or maybe it would be light enough you wouldn't have to? You could still car top it.
     
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