A discussion on different hull shapes in regards efficiency and safety

Discussion in 'Boat Design' started by donncha, Jun 3, 2008.

  1. donncha
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    donncha Junior Member

    The advantages and disadvantages of different kinds of hull shapes and profiles in regards efficiency and safety in mono-hull sailing yachts

    I am writing a short essay on this subject (3000-5000 words) and I would appreciate any help or comments. I know this is a huge topic and to tell the truth I have only a basic understanding of yacht design. I do have an interest in the subject and would hope to go on to do it later in life. I myself am just finished secondary school (high school) and hope to do mechanical engineering next year in university.

    I have as resources Skene's "Elements of Yacht Design" and Larsson and Eliasson's "Principles of Yacht Design". I also have various books on building and plans.

    Main questions:
    Is this idea viable at all?
    What have I left out of the equation?

    These are the primary titles for the different sub topics I hope to cover:

    The basic variables


    Displacement
    Displacement/length ratio
    Overall Length/Average Width

    Stresses and forces:
    Stability/Lateral plane
    Resistance
    Physical stress on hull shape
    Forces form sails/rigging

    Lay down the basics of each popular hull shape


    Long Keel
    Fin Keel
    Bilge Keel

    Keel-hung rudder
    Skeg

    Multi chine
    Round chine
    Flat bottomed

    Different stern profiles
    Different bow profiles


    Practical considerations such as materials and building

    Materials:
    Wood
    Aluminum
    Steel
    Fiberglass
    Ferro-cement
    Other
     
  2. PAR
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    PAR Yacht Designer/Builder

    The sub topics you've listed will require a hundred page essay to just touch on the basics of these subjects. You may want to limit the scope of the discussion.
     
  3. donncha
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    donncha Junior Member

    Thanks, any suggestions on how to?
     
  4. Knut Sand
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    Knut Sand Senior Member

    What about:

    • Displacement hulls
    • Planing hulls (here you can consider flat bottom, v-bottom, deep v-bottom)
    Try to show some examples for use, rescue, ambulance, leisure, fast vs slow, fuel economy. Should be enough there.

    If you get below 3000 words, you can throw in (the b'stard) Semi Planing hulls, neither fish nor bird....
     
  5. Tiny Turnip
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    Tiny Turnip Senior Member

    tackling big subjects with small word counts.

    When writing a paper on a large subject area but with a limited word budget/scope of project/time or energy available, a classic approach is to do case studies.

    By considering a number of well chosen examples, which illustrate the range of the subject you wish to explore, AND have plenty of data / information easily available to you, your analysis and evaluation can be focussed on the examples, yet illustrate the scope of the issue. For as big a subject as this, within your word count, you may find that as few as 3 or 4 examples (i.e. popular boats!) well chosen and used, could provide you with the makings of a good paper.

    You have already identified CRITERIA which you can use to analyse examples. The really interesting bit is the evaluation; having picked the examples apart with your analysis, so you can demonstrate an understanding of the designs, you can then find some way of assigning VALUE to the different case studies. This allows you to make a useful comparison. Some steps of assigning value are objective, and might come straight from the analysed data, e.g. hull speed. You can also talk about the interplay of different aspects of your analysis – e.g. how the hull works with the rig, how different rigs change the performance of the same hull, how comfort and performance affect each other. However, some parts are subjective, and this means your INFORMED opinion. For the example in hand, extended sailing experience with each case study boat might be the best authority for providing an informed opinion. If your authority (i.e. experience, expertise, training, knowledge, publications) are limited, It is perfectly O.K.and in fact gains academic credit to support your arguments by referring to other publications or papers.(always reference/credit the authors, otherwise its plagiarism) However, If I were marking your paper, I would be looking for something more intelligent than *just* regurgitating boat reviews out of magazines! Often comparing opinion from different authors who have different perspectives on the same subject can be very helpful, especially if you understand where the authors are coming from. You see this clearly of course, on internet forums…
    I say that evaluation is the really interesting bit, because a bald figure, like say, hull speed for a boat, is very limited. The design BRIEF, or intended use is very important here.
    For an out and out record breaking attempt, the speed the boat can attain on a single point of sailing, under very particular conditions may well be the principle important factor. For a boat designed to race round a course, the ability to sail fast at all points of sailing, in wildly differing conditions, and gain fractions of a knot in boat speed is likely to be more important. For a cruiser, safety in a wide range of conditions, and comfort are likely to be more important than improving boat speed by the odd quarter of a knot.

    If you thought this would be a useful approach, I’m sure you would find help here in selecting case study examples, and tackling the analysis and evaluation, but use other sources as well, and don’t expect everyone to do all the work for you. If you have questions, often having a stab at an answer yourself first, and asking for opinion gets the best responses.

    I have virtually no authority in the subject area, btw, just enthusiasm!

    Best of luck with it!
     
  6. Tiny Turnip
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    Tiny Turnip Senior Member

    I would add that the choice of examples for case study would depend on the nature of study you are interested in - the examples in my earlier post (record breaker, racing yacht, family cruiser) might be good for discussing broad or gross principles, but choosing different designs fulfilling a similar brief, e.g. the selection of gaff rigged 20ftish trailer sailers compared in May's 'Classic Boat' magazine, would allow you to discuss finer points of design within that narrower field.

    My apologies if I'm trying to 'teach grandmother to suck eggs' too - I always tend to err on too much information - if its helpful great, If I'm banging on about what you already know, please forgive me!
     

  7. donncha
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    donncha Junior Member

    Thank you very much for your lengthy response Tiny Turnip. As a matter of fact I read that review of the gaff rigged trailer sailers, it was in PBO uncharacteristically. As it happens I also buy Classic Boat, I wish there was a "Practical Classic Boat Owner", but I'll be careful to avoid quoting too much from the magazines. Your advice is certainly helpful and you idea of using examples as a primary building block certainly makes a lot of sense. The evaluation certainly is the important stage in the essay and the conclusions drawn from the the examples would form the basis for this. Thanks again for your help and I certainly appreciate you taking the time to write that reply.

    Thanks Knut Sand for pointing that out, I completely forgot about planing hulls.
     
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