Design of canal boats

Discussion in 'Boat Design' started by Tadworth, Aug 13, 2005.

  1. Tadworth
    Joined: Jan 2005
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    Location: Milton Keynes

    Tadworth New Member

    I'm drawing up plans for a new cargo carrying canal barge ( or narrowboat as we call them in the uk ) 21m long x 2m wide, i wonder if an underwater bulb would work on such a slow, 4mph max boat, drawing 3ft empty, and 4ft loaded ?

    I'm aiming at maximum effecientcy, and minimum wash.

    There's been a boom in building new canal boats in the uk, but there's only been one new attempt at design in the last 40 years, and the best, most expensive boat is a copy of a 1930's design, the vast majority are fabricated by welding firms who have no knowledge of boat design, hence a very low standard of effecientcy, and handling.
     
  2. Thunderhead19
    Joined: Sep 2003
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    Location: British Columbia, Canada

    Thunderhead19 Senior Member

    Speaking strictly from second and third hand knowlege, 4 kts is really too slow and your boat is too small. Bulbous bows interfere with the formation of the bow wave at certain Froude numbers, this means they have one speed range that they work in, and you have to run at that speed for days, non-stop to see any noticeable savings. They increase the surface area of the hull under water and create more friction too. The size and design also appears to depend on the length, draft, beam and speed you want to travel. Basically, it looks like adding anything underwater to a small, slow barge like this will actually INCREASE drag by increasing your wetted surface area and have little affect on the wavemaking resistance which in your case will be very small anyway. Some other member might disagree, and I know your question will attract a response from a peculiar person trying to sell an idea of his about a high speed waveless boat, just ignore him. Long slender barges are very efficient. You may be able to reach an optimum trade off between shallowing up your draft, reducing your wetted surface and still having a resonably long slender barge. This might improve the handling and over all efficiency. Because I'm Canadian, I'm going to suggest you study a few canoes. The big fur-trading type have been designed to pack a great deal of cargo, travel great distances and handle fairly well.
     
  3. gggGuest
    Joined: Feb 2005
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    Location: UK

    gggGuest ...

    If you're designing a genuine cargo carrier there are very few options... Your draft is very limited by depth, and your beam by locks of course, so that mandates a rectangular section for the vast majority of the craft for carrying capacity. Now you have got a more or less constant speed, so you can design for that. Big scale wavemaking isn't an issue, so its just a question of whether you can do anything to minimise bow and stern waves that has a big enough pay off in wash reduction and the like at your chosen speed to make up for the wetter area. This is probably serious test tank stuff because I bet that the narrow beam great length and high prismatic co-efficient puts it out of the normal range. There's a (very) brief discussion of the same issues of great length to beam/draft and high prismatic in "The Athenian trireme", Morrison/Coates/Rankov, isbn 0 521 564190. Not of great use, but interesting if you can borrow a copy from a local library. The upside is that the task (flat water, steady speed etc) is probably the easiest to model in a test tank.
     
  4. waveless
    Joined: Jul 2005
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    Location: Amsterdam

    waveless Junior Member

    I know your question will attract a response from a peculiar person trying to sell an idea of his about a high speed waveless boat, just ignore him.
    ============================================================
    Why?

    Could you give some reason.
     

  5. Thunderhead19
    Joined: Sep 2003
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    Location: British Columbia, Canada

    Thunderhead19 Senior Member

    HAH! I knew you'd visit!!! I sure got your attention!!! HAH!
    reason 1. I'm a friendly guy, and am trying to have fun with you. Ha HA! I predicted your appearance here ha ha!

    reason 2. I've noticed you trying to attract interest in your idea, (it's a good idea) your english is inelegant and seems to be TELLING people what THEY want instead of inviting them to look at your idia and it's possible applications. Have you ever been to a store and had a pushy salesperson that tried to sell you something you weren't looking for? it's a little irritating.

    reason 3. It's a good idea, but it's not fully developed. It's incomplete. What if there are some unmitigatable difficulties? You've told a bunch of people that it's the idea of the future. What if it fails to meet your claims? They're not going to like that.
     
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