What type of 4-8 metre hull for speed around 30-35 knots in calm water?

Discussion in 'Boat Design' started by nqb12179, Mar 14, 2014.

  1. PAR
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  2. Pericles
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  3. Boat Design Net Moderator
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    < threads merged to consolidate individual pieces of information into one discussion >
     
  4. PAR
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    PAR Yacht Designer/Builder

    You 'da man, Jeff . . .

    There are exceptions to the LWL governed S/L rule, but I think the original poster just doesn't have sufficient grasp on the basics, so . . . Simply put, any hull will do just fine in a "calm sea". The whole point of yacht design is to generate shapes suited to the owner's requirements, which often contrast with "calm sea" attributes.
     
  5. Pericles
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  6. nqb12179
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    nqb12179 Junior Member

    Sorry for the ambiguous question. I m a naval architect student.
    For the owner requirement is to serve the speed around 20 to 30 knots and the LOA (8m) which has to make a yacht stable enought to accommodate his family. I mean for the rolling and trimming conditions.
    The yacht will be use in a shot distance for holiday. That why I was asking any hull series which may be suit to for this type of the yacht.

    Thank you for all ur help
     
  7. DCockey
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    DCockey Senior Member

    Are your questions related to an assignment or project which is part of your studies as a naval architecture student?
     
  8. PAR
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    Before tackling this sort of thing, maybe a much longer look at some of the basics of hydrodynamics, possibly some developmental history study as well, as this (your questions) would be only something I'd expect from a NA student, in their first month of study, as with very little study, obvious hull choices become very apparent.
     
  9. rxcomposite
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    rxcomposite Senior Member

    8 meter, 5 people? Kind of tight but for a daycruiser it will work.

    For the speed you are looking at, 20 knots is a little just over the hump for a planing boat. Kind of a hard ride for anything above "calm" seas. Evaluate a semi disp monohull instead. Hull lines and test data are vailable from SNAME or PNA.
     
  10. rxcomposite
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    rxcomposite Senior Member

    Did a quick check. You are not into the recommended design lane.

    The speed to length number is 20knot/26'^0.5=3.92

    With a planing hull, it is just after the hump speed. With a semi disp, you are into steep curve. Attached graph of range you need to work at and evaluate.
     

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  11. rasorinc
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    rasorinc Senior Member

    I would refer you to the Glen-L marine site. Over 300 plans.
    click on outboards and look and see if any would work out for you. They post a fair amount of data for each plan on the site-- all designed by NAs
     
  12. raffshore
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    raffshore Junior Member

    in my (humble) opinion a deep V hull that goes from 30°/35° to 21°/24° with a little help from some (2or 3) 2 to 4 cm lift strakes will always work
     
  13. PAR
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    PAR Yacht Designer/Builder

    Considering the OP's requirements, a deep V (as has been previously pointed out) wouldn't be a wise choice.
     
  14. frank smith
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    frank smith Senior Member

    Hickman sea sled.
     

  15. nqb12179
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    nqb12179 Junior Member

    I m thinking about using series 62 planning hull with deadries angle at 12.5 degrees.
    There will be two spray rails rubbed below and parallel along the waterline from section 0 (FP) until the midship. The chine rail will be located from midship section to Ap Have u had any suggestion? Thank you
     
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