Small Kayak - Under 13 feet - Stability?

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

  1. millionswords
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    millionswords HomeMade Kayak?

    Alan regarding sea bee - it is a neat little boat, sufficiently can carry a 250lbs as the designer claims. I picked it up because it is a SOF design, and uses un conventional material just like mine.

    If i follow most of Tom's guidelines and make some necessary changes in the due course I think I will have a nice frame in hand.

    Now thinking of the strongback, and how to proceed.
    My first hurdle is to bend two bamboo Gunwales together and join them on the bow and stern to have the first base.

    Once this is done, I think I will be off to chisel the mortise for the ribs and deck beams in the gunnel. So I need the gunnel to be large enough, and at the same time not break the hollow bamboo.

    Because the sea bee is a multichine design, I'm thinking of not bending bamboo, but employing something like what Nansen does to his Arctic Kayak. Link: http://bp1.blogger.com/_yFfmvdFuhnI/SCdubOiAKxI/AAAAAAAABVc/EwNkpeeJOCY/s400/Bamboo Interior.JPG

    http://bp2.blogger.com/_yFfmvdFuhnI/SCdu0eiAK4I/AAAAAAAABWU/iUTOJMlBx_0/s1600-h/Stowage Below.JPG
     
  2. Guest625101138

    Guest625101138 Previous Member

    I would avoid any through notching of the bamboo. Once you notch it, groove it deeply or put a hole through it you create a stress raiser. You should devise a method of connection that avoids notching.

    I expect you could make a good connection with twine and some waterproof glue to keep it together.

    Rick
     
  3. ancient kayaker
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    ancient kayaker aka Terry Haines

    Bamboo can be straightened or indeed bent to surprisingly small radii: 10^6.swords has a video showing how it is done. If I could get 20 ft bamboo at all, let alone for $1 I would like to try it out for myself. The nodes are nobbly but are also, in my limited experience, strong points so shaving a bit off the outside to get a fair shape should not erode strength. I am looking forward to seeing how it turns out.
     
  4. millionswords
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    millionswords HomeMade Kayak?

    Bamboo some thoughts!

    Yeah AK,

    Today I just returned from the bamboo market, I was surprised to see so many varieties of them, same size but different weights. Some are hollow types some are solid types, green ones, yellow ones. All tall to the length of 22 to 30 feet.

    I saw a couple of them as tall as 25 feet and weigh just about 2 KG or so. Feeling them in hand was amazing, and promising. Tall 3 to 5 inch radius bamboo are very nice and not narrowing too much to the tip. Cutting out the 13 feet from the 20+ footers would give a very stable Gunwale.

    @Rick, the longitudinal chiseled do not bother the strength of the bamboo, they are surprisingly strong even if chiseled for mitering. This is because of the nodes that give strength to each nodal section.

    Every 1ft to 1.5 feet has a node, and so the strength is distributed throughout the pole. I have seen and used bamboo ladders, and they are as tall as 15 to 20 feet, all made from bamboo, and lashing with coconut-fiber ropes. These are brilliant cheap use of bamboo and coconut fiber.

    here are some pictures of Bamboo Ladders and how they are Joined!

    http://www.emilyreadettbayley.com/images/mirrors/bamboo-ladder.jpg
    http://www.symphonyproducts.com/assets/images/Ladder8.jpg
    http://www.symphonyproducts.com/assets/images/ladder3_web.jpg

    http://www.symphonyproducts.com/assets/images/ladder7_web.jpg
    http://farm1.static.flickr.com/56/184745637_7228404006.jpg?v=0
    [you can see it is being carried easily on a cycle, its not too heavy. In the background you can see the best Beer avaialble in India, Kingfisher Beer!!] :)

    http://farm4.static.flickr.com/3214/2656623383_a590a269ed.jpg?v=0
    http://farm4.static.flickr.com/3126/2628454890_fc97d0ca9f_b.jpg
    http://farm3.static.flickr.com/2063/2250786024_5b3d505602.jpg?v=1202487760
    http://www.istockphoto.com/file_thumbview_approve/2004143/2/istockphoto_2004143_bamboo_ladder.jpg

    http://www.bamboocraft.net/workshop/data/523/medium/03_10_20_Bzr_Escola_038_mod.jpg
     
    Last edited: Dec 24, 2008
  5. millionswords
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    millionswords HomeMade Kayak?

    see what can be done to Bamboo in a manufacturing process - http://images.andale.com/f2/122/113/25154637/2007/8/23/manufacturing_process_bamboo.gif

    Node removal, sanding and fumigating would be some process i would be interested in. :) - looks wonderful and promising.


    This is a small fountain made with bamboo and mitering, it is promising to see how the bamboo is placed in water throughout, and seems it does not bother the wood!

    http://www.newzealandwatergardener.com/content.asp?Category=373

    Here is a nice joint! - http://farm2.static.flickr.com/1273/1085165710_73e1969437.jpg
     
  6. millionswords
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    millionswords HomeMade Kayak?

    Lashing Bamboo

    Okay here goes the idea from today's pondering! and it answers Rick's concerns!

    I'm not going to make holes or chisels in the bamboo.

    Bamboo can be peeled.
    So I intend to cut the bamboo across to about 90 - 95% and then leave the peel to hang.

    [​IMG]

    The above cut is not made from a Hack Saw, so it is a little amateurish!

    This peel is fibrous and can be bent over the connecting pole. Now with the peel bent, start to lash like mad. :) Tight lashing using the right thread will enable a strong hold and no slipping.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    Now the Strong Back Issue: addressed!

    I think I was confused with too many articles and pictures on Strip Building and Conventional SOF kayak building! Now that what I do is not conventional, I had to pick up so many ideas from so many other construction methods and cook up a unique one...

    • The last picture is a drawing I made on paper to show how to proceed without Jigs of Plywood.
    • In this method, it is a slow process but certainly would work.
    • The two gunwales are lashed to a Bow piece/Stern first (may be a cross cut miter would help)
    • Then the first Deck Beam is lashed at the right interval one side at a time, to both the gunwale.
    • When this is done the gunwale start to take shape, and wont slip, I have shown two beams lashed in the drawing.
    • When all the beams are lashed, the gunwale will be a fully bent boat shape, lash it to the Stern.
    • What I propose is to also lash the ribs at this point at the same joints as the beams, leaving the stringer side hanging...
    • So what you will see will be some thing like that in the drawing..
    • And then I can lash the stringers to the Bow and Stern, then the hanging ribs should be lashed to it.

    This way a strong back is not needed. Only a couple of saw horses to mount the frame for easy lashing height.

    Ooof - that was what I wanted to do. Only now I come to a comfortable understanding.

    I do not know how this will be numerically correct. It can't be, it must be a very very ancestral way of building the water craft, this is what I can do now, without tools.
    I can't imagine how the Sea Bee's numeric would go into this sort of building?
    I have started to loft the offset table of the sea bee to poster boards, but still wonder how would that help me?

    1) Roughly I can follow the intervals of the ribs, and the beam of the sea bee.
    2) I may not have a multichine, though it is possible
    3) I cannot have a rocker, though it is possible remotely.
    4) Knee Beam could be bent and managed.
    5) Flooring can be a bit of plywood strips.
    6) No idea about the coaming! - two thin bamboos can be lashed together and coaming made!

    What do u people think? Alan, AK, Messabout and Rick?
     

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    Last edited: Dec 24, 2008
  7. alan white
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    alan white Senior Member

    Years ago I built a very resiliant and strong backpack frame of ash. I lashed it with cotton twine that was first immersed in Weldwood waterproof glue. Once dry all was sanded and varnished. The lashings were hard as steel cables and over years never failed. Very snowshoe-like but since cotton (compared to gut) absorbs so well (look at boat decks) it resists rot very well.
    Regarding node stick-out: Would it make sense to pad out the sections between the nodes? Maybe using strips of bamboo that are glued on the outer faces after the longitudinals are bent to the molds.
     
  8. millionswords
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    millionswords HomeMade Kayak?

    That is really promising, but how much of thread can I glue - sand and varnish? :confused:

    Will think about it after the construction of frame. When I try it with plastic sheet wrap/saran test I will get an idea of how the nodes stick-out bothers the boat.
     
  9. ancient kayaker
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    ancient kayaker aka Terry Haines

    3 to 5 inch radius bamboo sounds far too heavy for a skin on frame boat; more like what you would need for a small ship. Typical wood sections on boats I have seen are from 3/4 x 1 to 1 x 1-1/4 inches across. If bamboo is at as stiff and strong as the woods commonly used about 1-1/2 inches diameter should be plenty. The strength of the frame comes from attaching several light pieces together: most of the stiffness comes from the tightly stretched skin. If you put all the bamboo you plan to use in a bundle and pick it up you will get an idea of its weight: a skin on frame boat is second only to carbon composite for lightness; if it looks to be turning out more than 20 lb you are over-building it. A heavy boat is not likely to last longer, it gets banged about when handling it on land because it is clumsy. My 12 ft canoe is 20 lb, with no deck, including a rather fancy wooden slatted seat: it is made of 3 mm ply with 1 inch square gunnels, 1/2 x 3/4 wood strips along the seams and a 3/4 sq keel. A skin on frame boat of similar size should be lighter than that, around 15 lb is typical.

    I like the idea of using peeled bamboo for binding but I didn't see the advantage offered by peeling the end of the bamboo to create binding threads, compared with an accurately cut joint and separate binding. All it saves is the task of anchoring the binding to one of the bamboo pieces.

    If you build the boat "freehand" allowing the two gunnels to find their own shape you are likely to end up with an assymetrical boat rather than a more attactive and functional shape. To succeed you will have to match the opposite pieces of bamboo perfectly. While practice makes perfect you may have to make a lot of boats before you get it right, as you do not have ancestors to show you the methods developed over generations of boatbuilders.

    You should be able to make a serviceable strongback as follows:

    Take two sturdy bamboo pieces a foot or two longer than the boat will be, lash them together at both ends, then force a short crosspiece between them so they are bent into a kind of shield shape. Tightly stretch a piece of string between the ends. Then you have something strong to attach the boat to as it is built, and a straight line to ensure that is is symmetrical. Once all the parts are attached to the frame and securely lashed it should stay straight without support.

    I think your original idea of smoothing the nodes will work without need for padding; from what I have seen the bamboo does not tend to bend unevenly at the nodes. But try it out first: with something unusual it is always wise to experiment first.
     
  10. millionswords
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    millionswords HomeMade Kayak?

    AK - U the man!

    That tightly stretched string in the middle is a piece of cute tip!
    Just like the chalking line right?

    I saw a video yesterday night in youtube, and it was a bit different in approach like mine. They did not start from the ends, but made a ladder like structure first, starting from the middle beam, and then adding the beams towards the bow and stern. Then before adding the last beam pieces they lashed the ends. This way it would be symmetrical too.

    In your idea of tying the gunwales together and then inserting the middle beams would be a little slippery but still work.

    AK, You cleared a big doubt on the usage of larger diameter bamboo. I too thought it is unnecessary to use a large bamboo for the gunwales as this should be a light - real light boat. Strength is brilliant in a 1 inch bamboo and ease of working with it is to be considered too.

    I tried to carry the bigger bamboo and weigh them roughly, it was light - but bulky! Moving a 13 feet x 2 gunwales lashed would be a problem.

    I will check both options - will buy both sizes today the 1 or 2 incher and the 3.5 incher.

    Will come back with reviews.
     
  11. ancient kayaker
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    ancient kayaker aka Terry Haines

    The 3.5" sounds about right for the strongback. By bending a pair around a crosspiece you create a stiff base on which to build the boat. It would be convenient to fasten it securely to the ground at about waist height. However a flat surface to build on is convenient, a place to put tools and for small things you may drop to be found. If you do not have plywood for this, perhaps a canvas or tarp cover over the strongback would serve as well.

    Regarding bamboo size: boat design and biulding is an evolutionary process in which we build apon the experiences of others. Since there is not much of a dtabase for bamboo boat construction the key is to experiment, observe bamboo use in other areas, compare that to wooden constructin in the eame areas, and be prepared to make mistakes!
     
  12. ancient kayaker
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    ancient kayaker aka Terry Haines

    I have done some research on Bamboo using the Internet. There’s not much detailed information out there but these are the basics:

    Strength is proportional to density (like most woods). I have not been able to obtain any specifics.
    Stiffness: no data found.
    Structure is very different from wood which has cells: bamboo is essentially a composite of fibers and lignin, a natural resin. Lignin is a thermoplastic which is why bamboo can be bent using heat. As far as I can determine the only reason to use water in the process is for rapid cooling and to prevent charring, so steaming should have no advantage apart from temperature control.
    Density is high, specific gravity is about 0.95: compare this with oak at about 0.75 and cedar at about 0.4, spruce about 0.5. Bamboo is hollow: based on samples I have seen and handled the hole is about ½ of the outside diameter or 1/4 th of the cross section, reducing its average density to about 0.7 SG, similar to oak or ash.
    Resistance to decay is moderate to good, as far as I can establish. It should be protected like most woods, especially the end grain and hollow ends, but the natural enamel of the skin is very hard. Older bamboo (age when harvested) is more resistant.

    Use in a canoe is discussed first as I have more familiarity with wood canoes than with wood kayaks.

    The 4 most important considerations in my opinion are strength, stiffness, weight and ease of use. With no strength or stiffness data, but it is probably safe to assume that it is at least comparable with durable hard woods. Samples I have handled seemed lighter than hardwood (maple) doweling of comparable diameter and less stiff in proportion, presumably due to its hollow nature. Its most obvious feature is, it’s round.

    In canoe construction wood with a rectangular profile is commonly used, which has several advantages over bamboo. It can be cut to precise dimensions, it accepts screws and nails readily, most glues are designed for use with it, by varying the thickness to width ratio of the wood it is easy to optimize the ratio of resistance to bending in the 2 directions normal to the axis, and it is easy to fasten the skin by sandwiching between two strips of wood.

    When using bamboo you can use binding instead of fasteners and glue but binding can be stabilized with a coat of glue.

    You need to match the stiffness and strength of the wood you are replacing with bamboo. As you are stuck with using round section you must match the strongest direction and accept the unwanted extra strength in the other direction.

    Gunnels: 2 pieces of spruce are typically used with the skin sandwiched between, for a total dimension of 1 to 1.5 sq in. I would use bamboo 1.25 to 1.5 inches diameter here.

    Keel: typically a rectangular section 0.5 x 1 is used; I would use 1 to 1.25 inch diameter bamboo here.

    Stringers: I have seen typical stringers range from 0.75 sq to 0.25 x 1.25. I would use 0.75 diameter bamboo here. Usually a boat will have 3 or 4 stringers between the gunnel and keel on each side.

    Ribs: I have only seen one boat with bent ribs, these were about 0.4 x 0.8 steamed ash: I would use 5/8 to 3/4 diameter bamboo here provided it will bend easily. Steamed ribs are spaced about 6 inches apart. They are usually sandwiched between the 2 pieces of wood forming the gunnel; these joints are structurally important. When using a single piece of bamboo for the gunnel, you must join the ribs neatly to the gunnels. Rather than relying on a simple bound butt joint, I would drill the gunnel halfway through to fit the rib end, possibly tapering the rib to fit in a smaller hole, then bind. If this joint is drilled then it should be made water-tight.

    Hull shape: there is a nice looking skin on boat canoe featured in the Wooden Boat magazine numbers 205 and 206 (Nov/Dec 2008 and Jan/Feb 2009 issues), if you can get that in India. The boat is 11.5 ft long with a 28 inch beam. The magazine may sell you back copies or a copy of the article. E-mail woodenboat@woodenboat.com.

    Another source of hull design is the Adirondack Museum at http://www.adkmuseum.org/. I bought a plan for the Wee Lassie, a famous boat designed by Henry J. Rushton around 1886. It is a small boat, 9.4 ft long with a 27 inch beam, but could easily be made larger, 12 ft long with a 28 inch beam would be about right for your 220 lb weight.

    Skin: 9 oz nylon is often recommended.

    Waterproofing: water-based exterior grade polyurethane is recommended by several designers. In the past oil-based paint was often used. The paint should remain slightly flexible; any paint designed for use on wood should remain flexible for several years at least.

    For your application in calm waters a kayak has no advantage over a canoe, and will carry a lot more luggage without the complexity of hatches and deck straps. A canoe is typically lighter than a kayak of the same construction. However, if you prefer a kayak, a canoe design can easily be adapted. The difference between a canoe and a kayak is the deck and cockpit. Because of the deck a kayak is usually built lower; when adapting a design such as the Wee Lassie .the top plank could be left off to achieve this. A kayak is stiffer because the deck provides additional bracing. The deck should be strong enough to support your weight. Typically you will sit on the rear deck in order to enter the cockpit so this area should be well braced, a piece of plywood under the skin would be OK.
     
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  13. alan white
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    alan white Senior Member

    I've toyed (mentally) with using abs plastic (that hula-hoop material) to construct a tubular canoe/kayak frame. I don't know if it's been done but the technique would be the same as bamboo. Somehow, it would be lashed. at the ends, wood plugs would be inserted either to seal or to shape the ends.
    Abs isn't as stiff as bamboo and it's a lot like poly kayak hull material in terms of resiliance.
    I mention this because abs tubing is cheap and universally available. It provides some flotation and cannot rot. It could even be used to augment a bamboo construction, where smooth chines are desired.
    Apologies for changing the subject!
     
  14. messabout
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    messabout Senior Member

    Alan; you may be onto something with the plastic tubing. I am thinking in terms of PVC plumbing pipe. Cheap, and you can get all sorts of fittings and connectors, no rot, and if kept reasonably well protected from UV it will last for years. The adhesive is also cheap and very affective. It has the advantage over bamboo in that it is continuosly smooth and uniform in size.

    I have seen greenhouses and othr small enclosures made of this stuff. It had not occurred to me that it could be fashioned into a SOF boat skeleton. One of the features of PVC is that it will bend into a near perfectly smooth curve. The greenhouse structures are like a Quonsett hut. Just bent into an inverted U shape and the ends stuffed into a hole in the ground. What amounts to purlins or girts can be made useing straight lengths joined with X or T fittings of the same material. I once experimented with that concept in order to make a boat shed. It works.

    I think that a suitable ( define "suitable"?) boat could be made in the shape of a punt or spoon ended scow by using available PVC fittings only. No wood or other material required. The main drawback would be weight, no doubt. Using schedule 20 pipe as opposed to schedule 40 could keep weight more reasonable. Cheaper too.
     

  15. ancient kayaker
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    ancient kayaker aka Terry Haines

    No apologies needed for a good idea, Alan! I think it has come up before in connection with rafts or floating docks or some such thing, I'm not sure whether ABS or PVC was considered the best material, the consensus was that wood was cheaper but I didn't verify that.

    My previous post contained an error: the skin is not sandwiched between the 2 pieces of spruce comprising the gunnel, it's stapled to the gunnel and covered by the rub rail. In a bamboo canoe the rounded gunnel presents a problem which I did not address. If a flat is made along the outer edge of the bamboo gunnel to accommodate a half-round rub rail it may be seriously weakened, and there will not be enough material depth to hold screws since it is hollow. One method of anchoring the skin to the gunnel that might work would be to glue it, then protect and disguise the glue with a sewn fabric tube filled with suitable stuffing, kapok perhaps or closed-cell plastic foam.

    In a kayak the skin can be stretched over the gunnel all the way to the center of the deck for attachment to the king plank, but it will pose the same problem there and in any case it is unlikely that the skin will be wrinkle free.
     
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