What have I done?

Discussion in 'Boat Design' started by wardd, Aug 10, 2010.

  1. wardd
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    wardd Senior Member

    suggestions and criticisms.
     

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  2. wardd
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    wardd Senior Member

    pic

    lines plan
     

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    Last edited: Aug 10, 2010
  3. lewisboats
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    lewisboats Obsessed Member

    Double ender or double ended at the waterline...fairly narrow for the length, shallow draft so it might be a fixed long keel or centerboard or combination or perhaps a leeboarder. You didn't adjust the midship location so it may or may not be correct. Your curve of areas shows only a teensy bump just aft of the midship area so it is very symmetrical at the waterline at level flotation. It has a bit of a hollow entry but not much but it is very sharp. It has almost no flare to the topsides and doesn't loose very much length on the waterline so it is fairly short ended.

    Its long, narrow shallow and low...
    Some kind of double ended sharpie perhaps? That would mean a nice big centerboard. Perhaps a Ketch rig?












































    Perhaps you shouldn't have put it in your AS29 folder...:rolleyes: :D
     
  4. lewisboats
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    lewisboats Obsessed Member

    Cross post... Guess I was wrong with my guess now that I see a picture.

    Tippy without lots of heavy keel down low...center for a tri perhaps?
     
  5. wardd
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    wardd Senior Member

    It's meant for a 10 - 20 hp diesel and trailerable.

    A keel can be added and this shows a 1' 6" draft, would it be better with 2'?
     
  6. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Check out the beam, it is too narrow, imho. You will have stability problems, unless you add some ballast at the bottom. But then, you'll have to see if the final weight is still compatible with design hydrostatics data.
    In fact, your design beam is more practical (8.5 feet), but somehow you have ended up with a much narrower boat (6.76 ft).

    I say the final boat in the spiral will be beamier and perhaps heavier. ;)

    The concept is dimensionally similar to this electric launch:
    http://www.elcomotoryachts.com/36-foot-elco-electric-launch.shtml
    so you might use that one as a guideline for preliminary weights, and main dimensions - for example.
     
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  7. lewisboats
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    lewisboats Obsessed Member

    you need more beam...you initial stability is below your proposed shearline... not good. You would need about 2 more draft feet of heavy keel to stabilize it as it sits. If it stayed upright you would be puking your guts up with the roll in anything but a millpond because you have no flare to stiffen it up as it heels. You can trailer 8.5 ft...the beam you started with...I suggest you go back to that and work from there.
     
  8. wardd
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    wardd Senior Member


    it was meant as 8.5 feet

    I'm new with the program
     
  9. lewisboats
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    lewisboats Obsessed Member

    daiquiri...great minds???? Nice launch.
     
  10. wardd
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    wardd Senior Member

    latest iteration
     

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  11. terhohalme
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    terhohalme BEng Boat Technology

    Check your prismatic coefficient Cp, it seems very low. As a displacement motorboat (speed near to hull speed) it should be somewhere around 0.60.
     
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  12. daiquiri
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    daiquiri Engineering and Design

    I would also add some rocker to the chines, they are too flat and too close to the surface, imho. When you arrive near "hull speed" you will have two wave crests (bow and stern) and a wave through amidship. This might leave your chines dry, with a consequent loss of transverse stability.
     
  13. wardd
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    wardd Senior Member

    Here it is with a 2' draft
     

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  14. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    And now? What's the goal of the design? :)

    P.S.
    The attached fbm file cannot be read by Freeship+. you should post a pdf print.
     

  15. frank smith
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    frank smith Senior Member

    What is it that you want ? I cant tell from what you have posted so far .
     
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