Small Kayak - Under 13 feet - Stability?

Discussion in 'Stability' started by millionswords, Dec 16, 2008.

  1. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Incorporate thinner bamboo sections

    You will get a much more rigid structure if you slice the bamboo into say 1" strips, and bend them in U shapes to join gunell, chines and keels together.

    Sigurds suggestion of diagonals is valuable - you can run these strips in U shapes that run from the centre frame to either end.

    From experience, I would be inclined to use the current shape as a "base" to build an almost "woven" frame of thinner bamboo slices, and not even use the current frame as part of the finished boat. Use thin hemp rope to lash it all together.

    Boats have been built sucessfully that way for years in different parts of thw world.

    A rough drawing is attached to illustrate some options.
     

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  2. millionswords
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    millionswords HomeMade Kayak?

    thanks for the suggestion rwatson, this has been discussed in length previously with ancientkayaker and alan, then we decided to go on with this type of lashing, if this does not give me desired results I would not mind ripping apart the frame and using the 1" strips technique, sure the bamboo strips method would work, but the bend will be "U-shaped" rather than a "flat bottom U". I have to source a jig to cut bigger dia bamboo into strips of same width. [see these Jigs used in Brazil - http://www.bamboocraft.net/workshop/showphoto.php?photo=806&size=big&cat=

    http://bamboodirect.com/bamboo/photobooks/4Xsplitter.gif
    http://www.bamboogardener.com/tools-pictures/4-way-splitter.jpg ]
     
  3. millionswords
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    millionswords HomeMade Kayak?

    ** --- for my reference ----

    --------------------------------------------------------------------------
    Here is the list of wood we see out here:

    1. Aini/Aangili 595 Kg/m3 [Artocarpus hirsutus, locally called Pala in Tamil, it is the Jackfruit tree most used for boat making in Kerala]

    2. Bean Teak - 675 [ Lagerstroemia parviflora Roxb. Kaccaikkattai or Chenangi in Tamil]

    3. Jack 595

    4. Saj/Lauraceae - 880 [Cinnamon verum, Ilavangappattai in Tamil]

    5. Red Cedar - 450 Kg/m3 [Cedrus deodara, this is Indian Cedar, locally called Deodar, Devadaru or Karuppu Tekku in Tamil means Black Teakwood]

    Other than this, without any density data, we get Palak, Thekku, Vengai maram, puliya maram, silver oak, Kongu[Sal], Burma teak, Paduk[ Pterocarpus], Rubber wood, beech wood.

    ---------------------------------------------------------------
     
  4. rwatson
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    rwatson Senior Member

    The splitting and the U shape are things to think about, thats for sure -

    I dont think you will achieve the stiffness you need with the current technique. You still have a lot of "infill" to create, in the way of lengthways sections to support the fabric. Doing this in large section bamboo will make for a very cumbersome and hard to fasten structure.

    You certainly dont want to have a pronounced U in the bottom section, which would be the case if you bent thinner strips for the framing moulds.

    I had better success using very thin strips in longitudinal directions only, bent over frames that were hardchined (small straight bits fastened together). I predict this would give you much better results.

    Using strips will make the fastenings way easier and more robust. You can even 'pin' through two or more thinner strips as well as lashing them.- something hard to achieve on bigger diameter sections.

    Without a lot of back tracking to find out the reason for the shortness in this design, I cannot stress too highly the advantages of going as long as is feasible. I had to manually carry my canoes up and down a very steep hill for about a kilometre to get to the beach. I started off with an 11 ft canoe.

    The final and best solution was a 21ft kyak, made of quite a few 5mm x 7 mm longitudinal wooden strips. It was very light, and when it was in the water, the ease of paddling was phenonenal compared to the shorter versions. You may have storage and transport limitations of course.
     
  5. sigurd
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    sigurd Pompuous Pangolin

    10^6words, are you implying you can't get thinner bamboo?

    If bamboo or bent wood is used for transverse framing, it is possible to get a flatter U if you skew it off from the vertical plane.

    Cane can be bent very sharply but like I said it gets soft when wet. You can get it from furniture makers but it was kinda expensive.
     
  6. millionswords
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    millionswords HomeMade Kayak?

    @sigurd - Cane is not right choice. Cane can be bent like we need, but useless, it rots soon, even after a lot of varnishing it will get soft when wet, I have many cane furnitures at home. Cane retains its bent shape without much effort either, but not for water craft!

    PS: you seem to have been to India and stayed long enough :) you are invited to Chennai, India any time! again.
     
  7. millionswords
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    millionswords HomeMade Kayak?

    My Understanding...

    Please check the bold words below:

     

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  8. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    "- You say I have less Chine Stringers?"
    Not quite sure what you mean in this question, but I had a lot of much thinner lengthways strips (about 6 inches apart) , with quite a small number of frames. This meant that the fabric was well supported, and the shape of the fabric was quite streamlined under water pressure. Without good support for the fabric, it will form ugly hollows, no matter how hard you stretch it over the frames.

    " Mine as is is Hardchined. You advocate to use a couple of more Longitudinal Chine Stringers to assist the skin? [in form of thin 1" strips of longer bamboo?]"

    Yes, even with a single hard chine, I would be inclined to lay a lot more of the thinner strips lengthways, and reduce the bulk of the main chine with a smaller section. In the process, you could "soften" the very flat bottom, and get a little bit of a curve happening, which will make it more manouverable and easier to paddle.

    It will also provide that rigidity you are seeking.
     

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    Last edited: Mar 6, 2009

  9. millionswords
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    millionswords HomeMade Kayak?

    Hmmm - that is something interesting, and worth the effort. I'm now in the process of finding the right sized bamboo culm for the Keel. Still hunting, not yet found something that will work., I need a smaller diameter bamboo that is either straight or little curved to give it a natural rocker. Summer has started to peek in, and finding bamboo is getting harder these days.,, lets see!
     
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