Mini6.5 design

Discussion in 'Boat Design' started by Alik, Dec 29, 2003.

  1. Alik
    Joined: Jul 2003
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    Location: Thailand

    Alik Senior Member

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  2. Alik
    Joined: Jul 2003
    Posts: 3,007
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    Location: Thailand

    Alik Senior Member

    More...
     

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  3. sylvain
    Joined: Oct 2003
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    Location: Quebec

    sylvain New Member

    Hi Alik

    i'm interest in bulding your boat, How much is your plan??

    Could you please give me information about it !!

    Regards

    sylvain_l@hotmail.com:)
     
  4. Alik
    Joined: Jul 2003
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    Alik Senior Member

    More_pictures...
    heeled_waterlines_(15_degrees)
     

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  5. Alik
    Joined: Jul 2003
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    Location: Thailand

    Alik Senior Member

    And_3D...
     

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  6. K4oc

    K4oc Guest

    Hi,
    comments on your mini design.
    * Too big cockpit, you need it small for solo or max double persons. All the rest is just exposing the driver and making a lot of space so you can fall.

    * Boat is way too round, or to put it different - the hull has not enough form stability to be powerfull enough. With minis, forget everything about reducing wetted surface because the only thing that matters is POWER. Magnens and Manuards are flat, powerfull and fast boats, that will roll over everything. Even the new Lombard went for a wider water line to add power to the boat.

    But that is just my oppinion, right?

    Be cool, and happy new year.

    Kristian (www.4ocean.si)
     
  7. Andy
    Joined: Aug 2003
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    Location: Edinburgh

    Andy Senior Member

    Id agree with the last post - the hull needs more form stability. This in turn will mean the keel needs to be canted further to achieve the same (limited to 10 degrees?) heel angle, so you gain a lot more power on both counts.

    The heeled picture of your hull currently looks like the wetted surface area of the hull will remain fairly constant as the boat heels, and the round sections are one way of achieving hull balance through a useful range of heel angles. This is how the hull of the TS2 one metre skiff works. BUT, the way most of the new minis work is different. As the hull heels, it ends up sailing on a new axis from the bow to somewhere on the leeward aft quarter. This axis should, I think, be as straight as possible or I'd imagine the boat will start to have steering problems. The large flat underwater area is a drag when upright, but as the boat heels it starts to sail more on the turn of the bilge, and thus wetted area is also reduced. Most open class sailors will deliberately heel their boats with the canting keel in light weather to make use of this mode.

    The cockpit seems ok in size for an all around crewed/solo boat - maybe you could draw a smaller cockpit for those who want to use it for solo sailing only.

    Finally, if you go for the big waterline beam design then I would recommend using 2 asymmetric daggerboards over a single gybing board, as the violent motions of a mini make any ventilation problems you might experience with a single board a great deal worse!!!

    I am working on a mini design of my own at the moment, so will try to post something to compare with your ideas.

    Keep up the good work!!!

    Andy
     
  8. SailDesign
    Joined: Jan 2003
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    Location: Jamestown, RI, USA

    SailDesign Old Phart! Stay upwind..

    Alik,
    Don't listen to them - I like it!
    Steve ;-)
     
  9. Alik
    Joined: Jul 2003
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    Alik Senior Member

    Thanks_all!
    What I want is multipurpose boat, for day sailing as well.
    About high initial staility hull: Andy, what is RM10 for your design?
     
  10. danielro
    Joined: Jul 2003
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    Location: Spain

    danielro Junior Member

    more on hulls

    Hello alik, i'm trying to design a mini too, i had designed a hull very similar to the showed in your drawings, the mine had Bwl:2.04; Draft: 0.235 m; Wetted surface: 9.33 m2; Cp:0.538 and LCB; 4.6% aft for a fully, fully, loaded condition of 1200 kg,... but thinking in the replies of this topic i designed a second beamy hull with bwl: 2.20 m; Draft: 0.212 m, Wetted surface: 10.13 m2, Cp: 0.553 and LCB: 5.5%aft been the metacentric height KMt (for KG = 0, baseline in the bottom of the hull) 2.535 m, for the wider and 1.975 m for the narrower,
    I heel the hulls and post a picture showing the results. As you can see in this, the waterline heeled has the same angle to the centerline, seven degrees, but only two things.
    1) the wetted surface is quite similar. 8.88 and 8.75 m2.
    2) the BWL, and the KMt has a closer difference too. 1.711 and 1.653 m.
    I suppose that the change on the hull data will vary linearly (more or less) with the heel, then with more heel less difference in wetted surface, Bwl, and Kmt...
    Seem to be best a wider hull.
    What do you think about this?
    ohh and it's is a nice job, very beautiful drawings
    Daniel
     
  11. danielro
    Joined: Jul 2003
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    Location: Spain

    danielro Junior Member

    picture

    trying to post the picture...
     

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  12. Alik
    Joined: Jul 2003
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    Location: Thailand

    Alik Senior Member

    That's really interesting
    My boat has: LOA=6.50m; LWL=6.50m; B=3.00m; BWL=2.00m; Tc=0.202m; FM=0.77m; DSPL=1030kg; WS=8.97m2; CP=0.536; CB=0.384; LCB=-6.6%LWL
    BM=1.941m (upright) BM=1.594m (heeled 15)
     
  13. Alik
    Joined: Jul 2003
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    Location: Thailand

    Alik Senior Member

    I suppose we can only decide better "slender" or "skimming dish boat" using VPP :) Here is my sail plan.
     

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  14. danielro
    Joined: Jul 2003
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    Location: Spain

    danielro Junior Member

    Yes Alik, as you say the VPP will give us a measure of the importance of the form stability on the overall performance, but i need to define more my design
    Looking at your profile, and other modern designs, i see the keel placed nearer the transom.
    If the weight of the ballast is around 200 kg, over 1030 kg of maximum displacement and the LCB is 6.6% Aft the midship section, how it's possible that the waterline was the one showed in the picture? and other question, which are the benefits of this location?
    Regards, Daniel
     

  15. danielro
    Joined: Jul 2003
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    Location: Spain

    danielro Junior Member

    Well, i am thinking that it's possible to build a ballast tank to set the desired trim, but then if the tank has a capacity of 125 or 150 litres the 1030 kg displacement seems to be to low...
    ...I dont have enough money to build a mini with carbon fiber... :)
    DAniel.
     
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