Planing 10m Motor Yacht

Discussion in 'Boat Design' started by Simon_PL, Nov 3, 2019.

  1. Simon_PL
    Joined: Dec 2018
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    Location: Poland

    Simon_PL Junior Member

    Hi

    I am currently working on a concept of a 10m motor yacht.

    Basic data:
    Lenght: 10m
    Beam: 2,7m
    Draft: TBD
    Deadrise: 16.5 deg ( will be bigger once hull is finished ) 1.jpg 2.jpg 3.jpg 4.jpg

    The idea of this boat is to use is as daily boat with family and friends. Boat will accommodate small head behind port console and a small cabin begind drivers console. Comments are welcomed.
     

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  2. Yellowjacket
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    Yellowjacket Senior Member

    You need a transom. The following wave would come right through the boat when you come off a plane. The sides are too vertical all along the sides and toward the bow. You need some flare to keep splash and spray from blowing into the boat if you aren't running perfectly into or out of chop. You're doing things on the CAD program because that's the easy way to do it, but you're not developing surfaces that are going to work for a boat.
     
  3. bajansailor
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    bajansailor Marine Surveyor

    She looks rather similar to an Axopar - are you using a boat in their range as a reference to start off with?
    Axopar Boats - Range https://www.axopar.fi/range
    If this is just coincidence, then do have a look at the Axopars - lots of neat ideas on them, which you can always use as well.
    If I was interested in a boat like this, I think I would prefer if it had an outboard motor (or 2 even), like the Axopars, rather than an inboard engine with an outdrive leg as shown.
    Although I appreciate that an outboard engine does take up a lot of space that could be used by your swim platform.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    What do you mean by that ?
     
  5. gonzo
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    gonzo Senior Member

    It looks like a very tall boat for the narrow beam; particularly with a deep vee bottom. I would suggest you do a weights and stability calculation first. The weight is critical for the boat to float on her lines. The submerged volume must be equal to the displaced weight of the water. Also, planing hulls operate at a different condition because of the dynamic lift. The thrust vector should more less intersect the CG. Sterndrives, because they trim, have a fair amount of possible adjustment. However, they should not be counted on to correct a bad design.
     
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  6. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Why?.
    Not the weight but the CoG position.
    That's not correct.
    This is new for me. Any explanation on why?
    I don't want to troll the thread, just prevent the OP from geting incorrect conclusions.
     
    Last edited: Nov 4, 2019
  7. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Yellow, this is entirely in keeping with the modern form.

    Check out the Wally tenders to start with (photo below), and work from there.


    [​IMG]
     
  8. bajansailor
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    bajansailor Marine Surveyor

    TANSL, it might be easier for everybody concerned if we don't bother to argue about semantics, and instead just offer opinions about the design proposed by Simon?
     
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  9. TANSL
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    TANSL Senior Member

    @bajansailor, forget the semantics but, perhaps, it helps more by correctly advising the OP than by saying vaguenesses that are also incorrect.
    As for the project, I can't say anything, I would need to perform some calculations.
    As for the rendering, I do not like it although they are some forms that are very fashionable. Although I would like to help, if I had the ship's shapes, I cannot say, if I am honest, nothing more.
     
  10. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Gonzo (good to see you're still around!) I agree on the first - weights must be calculated properly, or at least estimated properly at this stage.

    Sentence 2 should read, "The submerged volume WILL be equal to the displaced weight of the water." Hydrostatics define it so. :)

    I have always noted that in a displacement boat, the thrust is better when aligned through CG, but on a planing boat the thrust must be such as to give some initial angle to the hull to initiate planing. Once "up", the effective CG moves aft due to lift, requiring the thrust line to stay such that it produces a nose-up moment to counteract the nose-down one from the centre of lift moving aft.

    Just my thoughts.
     
  11. TANSL
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    TANSL Senior Member

    Sorry to desagree but sumerged volume can not be equal to water weight. In everything else, I can't agree either.
     
    Last edited: Nov 4, 2019
  12. SailDesign
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    SailDesign Old Phart! Stay upwind..

    I'll re-write it...

    The weight of the displaced water MUST be equal to the weight of the boat. Science says so.
     
  13. TANSL
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    TANSL Senior Member

  14. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Well, Duh!, as they say over here.

    When planing, dynamic lift affects it, and when in displacement mode close too hull speed, there may be enough suction to INcrease the effective displacement.

    But no-one designs for those cases initially....

    Or, since we are being Heinlein's Fair Witnesses here, in 39 years of design, both commercial and pleasure, sail, power, planing and displacement, I have never designed for the dynamic case when examining buoyant displacement.

    Do you?
     
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  15. TANSL
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    TANSL Senior Member

    Well, I finished my studies in 1971, so I think I still have a bit of an advantage. And yes, I have taken into account the planning conditions when designing planing vessels. Perhaps it is that I am very obsolete and now designs are no longer rigorously made.
     
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