boat design

Discussion in 'Boat Design' started by adriano, Apr 20, 2014.

  1. adriano
    Joined: Aug 2009
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    Location: italy

    adriano Junior Member

    Hi there,
    Am sure there are skilled guys in this forum who could give me some good advices.
    Am aiming to reshape an old Italian rowing canoe shaped boat "Gozzo-Cornigiotto"(5 mt. length, mt.1,60 max beam), see attatched original picture, for costal use into an outboarder (approx.10-15 HP) driven craft.
    As you can see from my attatched efforts I moved aft the main section and added more volume aft with some V-shaped forward sections.
    Free board hull planking (cold molded) approx. kg. 1,5 per m2
    wetted surface hull planking approx. kg, 2,5 m2
    Draft 10 / 12 cm.
    Is anybody kind enough to suggest eventually how the immerged sections could be properly improved?
    I appreciate any comments.
    Adriano:)
     

    Attached Files:

  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Well the image doesn't offer enough information about the hull shape to make any real suggestions (I don't have FreeShip or DelftShip), can you post a JPG image of the lines? You have a lot more HP than necessary for a 5 meter craft of likely displacement speeds. A boat like this would need only a few HP to achieve hull speed, with 5 HP being more than enough to overcome chop and currents.

    If you're looking to make her get up on plane, then the shape will likely need considerable alteration, particularly, as you've guessed, aft. Getting a double ender shape up on plane can be problematic, mostly because they lack bearing area for it's "plane patch". The addition of :wings" such as those used on the Bartender could work, as will straightening out the run, possibly with a flat panel down the centerline. It all depends on how fast you want to run, but if exceeding more than 1.5 speed/length ratio speeds, you'll need buttock angles 3 degrees or less and a crisp exit.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't open it either, and is that boat pictured 1.6 m beam, it looks slimmer.
     
  4. gonzo
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    gonzo Senior Member

    Hobbles or planing boards can help, but they were used on older boats to get a bit more speed out of them. It is not a real solution to a design limitation. That model would work fine with a 3HP. Starting by using a design that is not adequate for the target speed is not a good choice. A wider and flatter aft section would help, but would also destroy the sweet lines of that model.
     
  5. adriano
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    adriano Junior Member

    thanks all,
    yes a 5 hp outboarder is definitely enough, she doesn't have to reach planing speed! The key is to maintain as much as possible the original lines (canoe body)
    at least at the free board area. Attatched pls find a screenshot (jpg file) of the original lines, I am told, although used for many years as rowing fishing boat on the north Italian Riviera costal area (Genoa region) sometime used used with latin sail, shesn't stable. No wonder she looks designed ruther for calm waters!
    Attatched (pdf file) my bottom suggestion moving aft the main section, increased aft water surface, but do not know whether this can be further improved?! Keel extention has to be added of course.
    Adding a kind of aft wing at the water line could be an alternative and I do not think it would spoil the whole look that much, at the end of the day some compromises have to be met?!
    Thanks for any further suggestions
    Adriano:)
     

    Attached Files:

  6. PAR
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    PAR Yacht Designer/Builder

    I see no advantage to moving volume aft on this hull. She's a pretty fat puppy, so you'll be limited to displacement speeds. Her buttocks are too steep and BWL to narrow aft to consider anything else, without major revisions to her aft sections. She looks like she'll do well under oar, not so well under sail and under power, she's all but limited to speeds of about 5 knots. A 2 HP engine will easily push her to this speed, though in some rough conditions, you might want a little more. 5 HP would be more (a fair bit) than she needs, plus if an outboard, she'd have reverse, which is a big plus.
     
  7. adriano
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    adriano Junior Member

    OK Paul
    If I correct understand
    due to her double ender shape it would be better to leave her original wetted surface lines (you're referring to?!) and be happy to be moved by a 2-3 hp outboarder for whatever speed can be achieved?
    my further questions :

    a - No need to move aft (from the middle) little bit her main section?

    b - No need to improve entrance (more V-shape) in the forward sections?
    Would these alterations make any sense in this case?

    Thanks for yr further comments
    Adriano:)
     
  8. PAR
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    PAR Yacht Designer/Builder

    I'm not sure what her original shape is, but this could be refined to improve her efficiency if desired. If playing with FreeShip or similar, target her Cp to her displacement speed. This might require some alterations to her shape, but I'll bet you can't get much more out of her original lines, maybe a few percent.
     
  9. adriano
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    adriano Junior Member

    Well.. the speed is not the main issue. Due to costal area use I would ruther think about stability/safty and am wondering that, by adding an outboarder, whether the bottom should have more v-shaped sections than flat ones ?!
    Adriano:)
     
  10. rwatson
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    rwatson Senior Member

    The cynic in me thinks "First he starts with a bad interpretation of an elegant traditional design, then decides to hack it into some sort of dogs breakfast of vaguely considered changes .... Why doesn't he just get a totally different professional design ?"

    Then the kind diplomat in me thinks - " let someone else suggest that he consider a properly designed different type if boat"

    I just don't know which thought I should post :confused:
     
  11. adriano
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    adriano Junior Member

    ohhh.... great idea Watson!
    There some clear reasons behind this project and at some stage you could. may be. also think someone being in a learning process??!! It's not matter of an airforce carrier?! right?
    Anyhow thanks for yr valuable suggestion!
    Have a good day
    Adriano
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    It is a rowing boat, without much prospect of being either a sail or power boat, really. It just needs a couple of pretty Italian girls for decorative purposes, one at each end, while you row in the middle.
     
  13. adriano
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    adriano Junior Member

    Hi mite
    That idea was already "on Board"! Unforunately no more than two girls due to limited space!
    Have good day
     

  14. Mr Efficiency
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    Mr Efficiency Senior Member

    OOh la la !
     
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