help me...concrete canoe

Discussion in 'Boat Design' started by Anna Paul, Feb 13, 2013.

  1. Anna Paul
    Joined: Feb 2013
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    Anna Paul Junior Member

    hi,im civil engineering student and im doing project on construction of concret canoe using lightweight aggregate concrete.For the project to move on i have to do the modelling and design of canoe, im using ANSYS software for it.Ive craeted the model,but now i dont know what all forces has to be considred and how to calculate it.I dont have any background knowledge on boat designing,so want to make it as simple and understanbale.i have assumed the canoe to be symmetric in all direction, load etc and thought considering to just float,not moving.Im not sure these assumptions are right too...

    Please help me with project....please tell me about the forces to be considerd and its calculation.
     
  2. Submarine Tom

    Submarine Tom Previous Member

    Google <concrete canoe project> and go from there.

    Good luck and welcome to the forum.
     
  3. FMS
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    FMS Senior Member

  4. kerosene
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    kerosene Senior Member

    and as this is an annual contest I believe there is also an old thread about the topic. Use search.
     
  5. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Several groups have used Michlet to estimate the calm-water resistance of the canoes,
    and IIRC they have put their findings on the net. Google is your friend :)
     
  6. Anna Paul
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    Anna Paul Junior Member

    thanku everyone for your reply...i hope i could go forward..:)
     
  7. alan craig
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    alan craig Senior Member

    Anna, I've just witnessed a beam test of a concrete sample containing random steel fibres; it failed very gradually. Fibres would stop a catastrophic failure if your rules allow it
    Alan
     
  8. Pericles
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    Pericles Senior Member

    Silica fume would be a good additive to the concrete.

    Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance. These improvements stem from both the mechanical improvements resulting from addition of a very fine powder to the cement paste mix as well as from the pozzolanic reactions between the silica fume and free calcium hydroxide in the paste.

    Addition of silica fume also reduces the permeability of concrete to chloride ions, which protects the reinforcing steel of concrete from corrosion, especially in chloride-rich environments such as coastal regions and those of humid continental roadways and runways (because of the use of deicing salts) and saltwater bridges.

    http://en.wikipedia.org/wiki/Silica_fume
     
  9. Petros
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    Petros Senior Member

    Anna,

    Sounds like a fun project. Canoes are not really "analyses" in the engineering sense since they are traditional craft their design details have evolved over many centuries, much of traditional boat building is done this way. Unless this is part of your project assignment the best thing to do is to look at popular traditional designs and do a back analyses the strength of the structure, and than choose allowable stresses of your proposed materials.

    If you need to do this as part of your presentation than this is how I would model it since I have done so with the 12 or more kayaks and canoes I have designed and built: treat the length of the canoe as a uniformly loaded beam, but inverted. If you will have say 2 crew in the hull, it is two load points with the water pressure supporting the hull as the uniform load (do not forget the weight of the hull which will not be insignificant). Also, look at a worse case scenario with most of the carrying capacity at the center, with the water supporting the hull. the load diagram inverted would look like a beam balanced on a point (like a teeter-toter), with a uniform load along its length (the water pressure supporting the hull).

    The structure of the canoe can be treated like a truss or I-beam, the gunwales are the compression members and the bottom is the tension side, the sides are the web of the truss. Use a fairly generous safety factor of about 1.5 or more, also consider maximum load the total displacement volume of the hull with no freeboard (water level right at the gunwale height), this should give adequate strength. they do not really travel fast enough to be concerned with dynamic loads, canoes are not usually designed for whitewater river running. for normal flat water travel you will want 4 or more inches of free board at your design load of course (for kayaks I usually figure much less, but for a canoe I would want a dryer ride).

    Also consider the side loads on the hull, since it is open top you will have the water pressure pushing the sides inward. Again take the max pressure as the water pressure with the canoe with the water at the gunwale height, and than a safety factor (might consider going as high as 2.0 for this condition).

    It depends on your design rules and allowed materials but I would design several floor stringers of either metal or composite that has good tensile strength, and than design the gunwales for compression with at least one metal stringer in each gunwale. watch out for buckling of the gunwales, you will need thwarts to brace the gunwales about every three feet or so. If possible I would use number three rebar as stringers, welded into a frame (or wired into place), and than use a metal mesh on bottom and sides to form the web/side wall strength. there are many other ways to do this, I think I have seen it done with several layers of metal mesh and only use stringers at the gunwales. And of course make the concrete thickness as small as possible, you just need enough to make it reliable water tight, and to stiffen the structure. Use lots of paint to waterproof the concrete if the rules allow.

    About the hull design, the fastest shapes are very narrow beam with a round bottom (low wetted surface), the problem with that is a hull like this is very tippy and unstable. So you will want a fairly flat bottom and enough beam to keep everyone comfortable that will be your crew.

    Also, search the internet for what others have done, there are lots of examples to learn from. This contest was old when I was in engineering school 35 years ago. Our team at CSULB (Cal state Long Beach) won the design and presentation award, though the quality of the build was rather poor and way too heavy and it did not perform well.

    Do your homework on it and win or lose, you will learn a lot and have lots of fun.

    Good luck.
     
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  10. messabout
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    messabout Senior Member

    Annna; I will not add to the excellent design commentary posted above.

    A tid bit of advice:
    When you do the build, there will be a lot of messy concrete work, much of it with your hands instead of trowels. Beware. The stuff can cause painful lesions on body parts in frequent or continual contact with the concrete mixture. Among those who work in concrete, they are unaffectionately called strawberries. Not a danger if you use nitrile gloves while making those mud pies.


    Good luck with your project and keep us informed about your progres.
     
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  11. Submarine Tom

    Submarine Tom Previous Member

    Anna,

    What attention you're commanding!

    I'll have to remember that when I reincarnate in my next on-line entity.

    Think female.

    You are a woman, right?

    I hope so, I like that in a person.
     
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  12. Leo Lazauskas
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    Leo Lazauskas Senior Member

    That's a very classy pick-up line, Tom!
     
  13. hoytedow
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    hoytedow Senior Member

    Yes, by all means, protect your skin. It can leave your skin with vitiligo.

    http://en.wikipedia.org/wiki/Vitiligo

    [​IMG]
     
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  14. messabout
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    messabout Senior Member

    I did not mean to refer to vitiglio. The strawberries that I warned about are bleeding sores and have no affect on normal pigmentation.
     

  15. Anna Paul
    Joined: Feb 2013
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    Anna Paul Junior Member

    sir,ive read about silica fume and thought of using it.But , as ive heard , it is not available in my place,(im from kerala,India) so i had to drop it. Thankyou for your suggestion :)
     
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