Hull Shape

Discussion in 'Boat Design' started by Northwindii, Mar 6, 2016.

  1. Northwindii
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    Northwindii Junior Member

    I am developing some initial ideas on a boat. And, based on my goals, I have decided that the full displacement, round bilge hull is the best type for my intended use.

    QUESTION: Is there a generally agreed upon "best" hull shape? Is this available in some kind od generic CAD file?

    My goal is 130 LWL, 28 Beam, 8 Draft. Goals are sea worthiness and economy.
     
  2. Stumble
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    Stumble Senior Member

    Best in what sense? A perfect cylinder will have the least drag, but be grotesquely uncomfortable since it has no initial stability.

    A long lean hull will be the most fuel efficient but have limited volume

    A stockier hull will have more volume and load carrying capacity

    The simple answer is no, there is no ideal or best hull design. Just a hull optimized for the specific role of the boat. If you can provide a copy of the SOR for the boat there may be places to point you for an optimized hull.
     
  3. gonzo
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    gonzo Senior Member

    No there is no ideal shape. Each set of requirements and owner/operator preferences and legal restrictions produce a particular shape. Setting a size as a goal is not conducive to a good design for the purpose, unless the purpose is to build a vessel of a particular size. Make a list of everything you want the vessel to do, where will it operate, how many passengers and professional crew are needed, materials preferences, interior ( artwork, how many cabins, etc), target speed, range, etc, etc. That is the first step. Seaworthiness and economy are biases (this is the general purpose). The second step is to set the constraints. These are quantifiable parameters. For example, it must operate in cold waters in #8 Beaufort conditions. The range must be 4500 miles, cruising speed 12kt, etc.
     
  4. PAR
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    PAR Yacht Designer/Builder

    As has been mentioned, boats particularly multi million dollar 140' vessels (I've never seen s 140' yacht that wasn't a multi million dollar project), are designed around a specific set of goals and the shapes employed reflect these requirements. Self designing a 140' yacht or vessel (I'm assuming a 10% overhang over the LWL) just is out of the question, based on your questions, thus far. I have plans for both a 130' ketch and a 150' powerboat, both now stock designs in the drawer.

    Maybe it would be best to list your SOR and other desires, so we can see where you're at and what you need.
     
  5. TANSL
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    TANSL Senior Member

    I believe that the same criteria that have led you to think that "full displacement, round bilge hull is the best type" will serve you to decide the "best hull shape".
    The two previous post can help. Read them carefully. If you explain to us how you got these initial findings, maybe we can help you better.
     
  6. jehardiman
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    jehardiman Senior Member

    Oh God that would be a pig! Too fat and too shallow.
     
  7. Rastapop
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    Rastapop Naval Architect

    I don't see how you can come to that conclusion based on the tiny amount of information offered so far.
     
  8. Ike
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    Ike Senior Member

    Would you try to design your own passenger jet? A 130-140 foot yacht is just as complex. You need to hire a professional. A naval architect will make you a Ststement of Requirements base don your needs and give you a preliminary idea of what you have in mind.
     
  9. PAR
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    PAR Yacht Designer/Builder

    John tends to hold back his feelings about things. I often have to get him to open up a bit, but it's a lot like work.

    He's quite correct, even with the absurdly basic parameters offered. My 65'er has over 8' of draft.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    And to think those 900 foot cruise ships draw as little as 28 feet. How do the props stay in the water ?
     
  11. Rastapop
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    Rastapop Naval Architect

    I assume you're talking to me? (You didn't quote)

    It's not possible to accurately make judgements like that without an SOR (and more data on the vessel). There are plenty of vessels that length or longer with less draft, plenty that length or shorter with more beam (you don't even know whether the quoted beam is at the waterline or not), and plenty with a higher B/L ratio.
     
  12. Heimfried
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    Heimfried Senior Member

    The TO didn't state a unit. Maybe it's 130 mm LWL ;)
     
  13. Skyak
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    Skyak Senior Member

    Wouldn't you start with Delft Systematic Yacht hull series? The characterization of many or most typical hull shapes has been quantified to the extent possible. You determine which is best for your application. If you don't find what you need there proceed to CFD.
     
  14. jehardiman
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    jehardiman Senior Member

    Actually it is easy to come to that conclusion, especially because seaworthiness was specified.

    It's not the L/T geosim, it's the size.

    So lets turn this into a learning opportunity... can anyone offer a reason why you would or wouldn't want a vessel of the dimensions Northwindii proposed (135 ft x 28 ft x 8 ft because 135 m is not a "boat")? FWIW, there are a lot of vessels near those dimensions, almost all of one type and hull form. A quick look at those will tell you all you need to know about his selection of dimensions.
     

  15. Rastapop
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    Rastapop Naval Architect

    I note you haven't given even a single reason why you think your judgement is valid.

    Without an SOR and more data on the vessel you can't accurately assess whether it's " too fat", etc, etc
     
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