Sun Fast 30 OD

Discussion in 'Sailboats' started by myszek, Jan 26, 2024.

  1. myszek
    Joined: Jan 2013
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    Location: Lodz, Poland

    myszek Junior Member

    Hello

    A friend of mine called my attention on this boat:
    Sun Fast 30 One Design | Jeanneau Boats https://www.jeanneau.com/boats/sailboat/1-sun-fast/694-sun-fast-30-one-design
    and her unusual hull shape.

    The hull sections are almost triangular, clearly intended to plane on the leeward panel of the bottom when heeled. Without a heel, i.e. at light wind, the immersed area remains small. At least so I see.
    Many years ago I thought about such a layout for a small skiff, but was not courageous enough to try in in bigger boats.

    Do you know about any other boats with their hulls built around this principle?
    It will be very interesting to compare the performance of the new Sun Fast with more conservative designs.

    regards

    krzys
     
  2. skaraborgcraft
    Joined: Dec 2020
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    skaraborgcraft Senior Member

    This Mini from some years back.

    [​IMG]

    Seemed like a good compromise between upwind sanity, and downwind surfing.
     
  3. CarlosK2
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    CarlosK2 Senior Member

    Screenshot_2023-08-18-16-16-50-29.jpg

    I was very struck by the profile: the aft curve without fear of low pressure, suction.

    To a lesser extent it is also observed in the Dehler 30 OD, but here this trend (?) away from pure planing shapes is more pronounced.
     
  4. CarlosK2
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    CarlosK2 Senior Member

    Screenshot_2023-08-18-20-34-06-51.jpg

    The funny thing is that it seems that thanks to CFD it will be possible to reach 1925 in 2025

    Sailboats that quickly adopt a bow-up, stern-down attitude
     
  5. CarlosK2
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    CarlosK2 Senior Member

    Screenshot_2024-02-04-13-59-56-20.jpg

    When looking at this type of profile there are two things to keep in mind:

    (1) it hoists an astronomical amount of sail: about 45 square meters per Ton

    and

    (2) the crew can easily trim the hull attitude
     
  6. skaraborgcraft
    Joined: Dec 2020
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    skaraborgcraft Senior Member

    I had not noticed that seemingly abrupt aft angle on the Baroudeur. Does the reduced wetted bow surface actually make up for the excessive aft squat and drag induced by the transom? No doubt from video evidence the boat surfs and tracks well, probably assisted by a well submerged rudder.
     
  7. Paul Scott
    Joined: Sep 2004
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    Location: San Juan Island, Washington

    Paul Scott Senior Member

    almost looks like a multihull stern treatment? At least in profileā€¦. The shape has lurked for a bit for ballasted monohulls, but look at recent NS 14 hull design, with the flat planing surface looking like it was savagely ( (was that the word?) cut out of a normal rocker foil. I suppose with water ballast, some dinghy crew weight location change could be had, but I keep waiting for centerboard type weighted keels to show up so weight could be shifted fore and aft while under sail, much like dinghy crew weight. Keel bulbs have not been friendly to this approach, but Julian Bethwaite has been reducing the bulb size on his latest opus, so perhaps a move back to bulb less monohull keels?

    The move towards planing on the side of the hull seems kind of like plank on edge? But piling on the sail area is here, for good or ill. Fa fa fa fa fashion?
     

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    Last edited: Feb 9, 2024
  8. CarlosK2
    Joined: Jun 2023
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    CarlosK2 Senior Member

    Screenshot_2024-02-15-11-07-38-75.jpg

    How a motorsailer turned into a prodigious Surfboard reaching 20 Knots

    (1) a Longitudinal balance that we could call "classic": Longitudinal position of the Center of Gravity at or aft of the Pitch Axis (that pass through the Center of Flotation) In other words: there is no huge stern (in relation to the bow or a sharp bow) inviting the Wave to sink the bow.

    (2) Careene Profile: High pressure at the Bow and Low pressure (Suction) at the stern.
     
  9. CarlosK2
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    CarlosK2 Senior Member

    Screenshot_2024-02-11-23-06-07-91.jpg

    A handful of "Transat 6.50" (Mini Transat) move the lead ballast aft to Surf and forward to go upwind.

    One of them had the mechanism break down and the keel stayed in the aft-most position, and they found that it sailed very well, which is what I think. Even to go upwind it deserves the Center of Gravity at (or a little aft) the Center of Flotation.
     
    Paul Scott likes this.
  10. CarlosK2
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    Location: Vigo, Spain

    CarlosK2 Senior Member

  11. CarlosK2
    Joined: Jun 2023
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    Location: Vigo, Spain

    CarlosK2 Senior Member

    Screenshot_2024-02-15-13-21-48-14.jpg

    Aqua Quorum performed very well both downwind and upwind.

    Longitudinal position of the Center of Gravity at Longitudinal position of the Center of Flotation

    A good longitudinal balance is Essential.

    And if the daggerboard has to go far aft, then we can fit the sails to the daggerboard with a 3/4 rig and there is no need to install an additional daggerboard forward.

    ---

    All Beauty

    Antonio Puig Aqua Quorum Eau de Toilette Spray 100ml https://www.allbeauty.com/antonio-puig-aqua-quorum-eau-de-toilette-spray-100ml/14683844.html
     
  12. skaraborgcraft
    Joined: Dec 2020
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    skaraborgcraft Senior Member

    Good info. The Harrison Butler theory has a lot skeptics, but it is true his sailing boats do self steer very well compared to some that do not adhere to his "meta-analysis". More than one way to skin a cat. The fore-n-aft calculation at rest is one thing, heeled areas another. Many old boats had "cod heads and mackeral tail" shape, similar to the Barouder, and handled well, according to those that worked them.
     
    Last edited: Feb 15, 2024 at 8:21 AM
  13. CarlosK2
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    Location: Vigo, Spain

    CarlosK2 Senior Member

  14. CarlosK2
    Joined: Jun 2023
    Posts: 297
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    Location: Vigo, Spain

    CarlosK2 Senior Member


  15. CarlosK2
    Joined: Jun 2023
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    Location: Vigo, Spain

    CarlosK2 Senior Member

    Longitudinal Balance

    Longitudinal Position of Center of Buoyancy (LCB and Longitud Position of Center of Gravity, LCG) =

    = Longitudinal Position of Center of Flotation (LCF)
     
    skaraborgcraft likes this.
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