Box barge hull shape - which is better?

Discussion in 'Hydrodynamics and Aerodynamics' started by Justaguy, Jan 30, 2016.

  1. cor
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    cor Senior Member

    Better at what? Construction ease, resistance to impact damage, looks, efficient use of material, drag (at what speed), ability to land on a shallow beach, etc.

    C.O.
     
  2. TANSL
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    TANSL Senior Member

    Among other things, sharp corners cause the flow becomes turbulent, rather than laminar, and that energy used to form the vortices is subtracted from that used in ship propulsion.
    The resistance of a plate perpendicular to the flow is much greater than if the plate forms an angle to the flow direction.
    Anyway, there are several reasons.
    Instead, a bilge angled slightly reduced the magnitude of the transverse swinging.
     
  3. Justaguy
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    Justaguy Junior Member

    Covered that in my first post and more so in my second. However, rather than heading down the path of greater specificity, sticking with general concepts and their explanations is what I need. See replies from TANSL for an example. Thanks.
     
  4. Justaguy
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    Justaguy Junior Member

    That's the kind of info I need at this stage.

    What about the basic differences due to downward deflection of water and the resulting lifting effect on the bow? I imagine that those forces would be greater with 45 vs curve. Does any of that really matter?
     
  5. JRD
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    JRD Senior Member

    As long as we are still talking about a barge it doesn't matter.
     
  6. waikikin
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    waikikin Senior Member

    Perhaps the opposite will happen, did the deck retain the same area or the waterplane when you cut away at an angle? Your pics show a similar overall length so by cutting away a swim end at 45 both ends from the deck edge you've changed so much.... there's always room for improvement.....

    Jeff.
     
  7. Justaguy
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    Justaguy Junior Member

    Thanks for the info, JRD.

    I hesitate to add this because I've tried so hard to stick to concepts vs. specific recommendations on specific designs. However, it would be a self-propelled barge/scow; sometimes motor, sometimes sail.

    Other than big flat iron things to carry coal or timber, etc. (which this would not be), people seem to mix and match the terms barge and scow, with nothing being definitive. While talking about hulls, I don't use scow as that tends to get people thinking about high-speed racing scows, which is the wrong direction.

    I'm talking more about a boring, rectangular thing, optimized as much as makes sense without carving it to the point that it looks like a canoe. Also, if it were "optimized" to the point that it negated most of the benefits of sheet building, that would be too much.

    Bending plywood from bottom up a bow or stern is not a big deal and is still within the "sheet building" category, in my opinion. However, headlog not included for the moment, if building with a simple 45 degree angle provides 90% of the benefits of a simple curved bow, than the greater simplicity of the 45 would seem to win out. That's really what I'm trying to get at here.

    At the end of the day, we're talking about a displacement hull speed of 7-8 knots maximum.
     
  8. waikikin
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    waikikin Senior Member

    OK, you could even call it a "lighter".. if you're talking sheet & not prepared to make some very slight concession to profile then that is what you'll get, very plain & simple you'll get a sheet boat that burns more than it could otherwise, may even run bow down if you're looking for jogging speed.
    Jeff.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Still no mention of size ? Saving that up for later ? If 7/8 knots and the length of it had been mentioned from the outset, some useful answers might have been forthcoming.
     
  10. Justaguy
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    Justaguy Junior Member

    Confusion reduction

    Although complaints regarding my initial post related to insufficient information, in fact, I provided too much. That drawing was only supposed to quickly convey differences in shapes to launch a discussion about concepts (which I called maxims). Instead, it distracted (and is still distracting) people who decided to design a boat and found the info lacking for that endeavor. Of course it was lacking. I wasn't trying to design a boat at that point. I was trying to understand the forces at work on a single feature -- something that should be easily and quickly obtainable in a forum on hydrodynamics.

    Had I provided the new attachment below, instead of the one I did, it might have avoided some of the confusion. It might now give others the opportunity to focus on and comment on what it is I'm really asking about.

    Justaguy
     

    Attached Files:

  11. waikikin
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    waikikin Senior Member

    No one aspect works alone.... without a greater purpose of design the maxims are irrelevant, you did define goals.
    If you don't like content in the forum feel free to click a name then engage "ignore" function, may save distraction, responses are for the benifit of the many, not just one guy.


    All the best from Jeff.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Probably the first principle of boat design, you cannot focus on one aspect while studiously ignoring the rest, a more holistic approach is essential. So how long is it proposed to be, then ?

    holistic/həʊˈlɪstɪk,hɒ-/
    adjective
    characterized by the belief that the parts of something are intimately interconnected and explicable only by reference to the whole.
     
  13. Justaguy
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    Justaguy Junior Member

    No, I'm not saving it. As I've tried to painstakingly point out, this thread is not about that.

    It might be important to mention that nothing can be efficient unless it is first effective.
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    Do you think Mr Boeing designs the nose cones on his planes, and then later worries about what to put behind it ? Thankfully not ! It can be seen that your query is straying into that kind of absurdity. For your boat to run effectively at 7 to 8 knots, it will need to be at least 40 feet long.
     

  15. Justaguy
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    Justaguy Junior Member

    There are other threads to read

    While this thread is not only for me, it is initially for me, otherwise, I never would have started it.

    I don't want to ignore anyone, especially if they are on point. However, if a person does not want to answer the question that I posed, in the thread that I started, in a way that helps me, then that person could unsubscribe from the thread and/or stop responding to it. That would make a lot more sense, especially after I've made it clear that they are not helping and in fact are cluttering up the thread with undesired, off-topic replies.

    The irony here is, after I tried to be polite and clear, and got unsatisfactory responses, and then I tried to initiate a Take 2, and the unhelpful responses just kept coming, I am the one who gets downgraded behind the scenes. I guess I didn't lay the necessary number of pineapples at their feet or earn the right to join the "cool kid club" so I can use cool words like "bote". So, lacking that, I get a bunch of flak when I asked my question instead of help.

    Mostly this boatdesign forum is good, as I've made abundantly clear in the past. Sometimes, however, it's back to junior high school. Unfortunate, as I thought this forum was above that nonsense.
     
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