Tugboat with propellers in Tunnels

Discussion in 'Boat Design' started by phil brady, Jun 22, 2012.

  1. phil brady
    Joined: Mar 2012
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    Location: Louisiana

    phil brady Junior Member

    [​IMG]

    Hello again everyone, I was hoping I could get your opinions on this hull design. Generally what do you see as the pros and cons of the squared off tunnels. I am sorry that I don't have any more pics; I just pulled this one off the internet.
     
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  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    Not a comment on the hull design but about the boat pictured.

    That boat looks like what in the US are sometimes called "towboats" and which are used to push barges. The terminology is confusing because they usually "push" rather than "tow". Shallow draft appears to be a majro requirement. Towboats have very different requirement than tugboats.
    http://en.wikipedia.org/wiki/Towboat
     

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  3. phil brady
    Joined: Mar 2012
    Posts: 10
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    Location: Louisiana

    phil brady Junior Member

    I was wondering why the builder would not have opted to round off the tunnels. It seems like it would create smoother operation. What are everyone's thoughts?
     
  4. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    It's the longitudinal shape that really matters, since this is guiding the flow into the propeller. There are (or shouldn't be...) no significant transverse velocities or rotational movements before the propeller disc. The drawback of the "chined" tunnel is a collection of stagnant fluid in the inner corners, which in some circumstances may disturb the propeller, but that is of minor influence, compared with the importance of a correct and smoooooth longitudinal shape!
     
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  5. DCockey
    Joined: Oct 2009
    Posts: 4,237
    Likes: 183, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    I agree with baeckmo's comment, and would add that in the example shown there is considerable clearance between the propellers and tunnels. For that example at least rounded tunnels would be more expensive to build with little added benefit.
     
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