A-Class Catamaran Plans?

Discussion in 'Multihulls' started by Nordschleife, Jan 5, 2020.

  1. Nordschleife
    Joined: Jan 2020
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    Nordschleife Junior Member

    As the title says. I want to build a carbon fiber A-class catamaran and would like to know if there are any available plans. I would like it to be competitive as I wish to race it.
     
  2. patzefran
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    patzefran patzefran

  3. patzefran
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    patzefran patzefran

  4. waynemarlow
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    waynemarlow Senior Member

    Don't knock the Lindhal build method, its a very good method for 1 offs. The other nicety is that you can simply take a measurement of your own boat, change the design to your own needs and get going. We contemplated making asymmetric top halves of the hull to try and reduce weight at the back and give more clearance for the ton of string now needed + integrate a proper X beam type of system to stiffen the whole structure for future foils on the F16 we built, using the Lindahl system, its relatively easy to do. Weight wise you won't be too much over a proper prepeg type of factory boat.
     
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  5. Erwan
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    Erwan Senior Member

    To make things simple:)

    First: make a soft-wing, which does not required a leech tension pulley block nor a circular track on the rear beam.

    As the wingsail will have area in front of the "mast" just like a rudder with compensation, then the center of effort of the sail will move forward too, relative to the mast foot on the cross-beam.

    To match the change in sail's CoE you will have to move the foils casings closer to the main cross-beam just in front of the lateral stays.

    Since you achieve concentration of the main loads between the mast foot and the lateral stays (50cm)
    You just need to suss out a carbon cross-beam 50 cm x 228 cm which can take all the loads, with the foils casing "integrated".

    The remainings loads will come from the rudders & the front stay.

    A glass+carbonUD/foam technlogy for the hulls should make it for these "lower" loads.

    You will use bolt & nuts for the hulls/cross-beams so your boat will be very carbon-print friendly when shipped in container to Europe or AUS or NZ.

    In addition without pulley block for your leech tension, foiling gybes & tacks will be more affordable.
    a significant advantage when racing.

    And the cute Greta will send you many kisses for your climate friendly boat:rolleyes::oops:

    Happy New Year

    EK
     
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  6. waynemarlow
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    waynemarlow Senior Member

    Erwan, you obviously have this as a design you've been working on, do you have any drawings ?
     
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  7. Nordschleife
    Joined: Jan 2020
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    Nordschleife Junior Member

    Thanks everyone for their responses. I have emailed Mr. Lindahl inquiring about plans, and hope he responds quickly. I think Erwan's design is very interesting, and I was hoping to use a wingsail on the cat anyway, and I hope to use one. If I can't acquire a set of Lindahl plans, could I possibly design my own cat?
     
  8. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Nordschleife - what is you experience with high performance sailboats? Have you sailed an A-Cat? Have you considered buying a used A-Class cat? The cost may be less than the cost of materials and equipment to build a similarly competitive boat.
     
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  9. Nordschleife
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    Nordschleife Junior Member

    I used to own a DNA F1X catamaran, and can sail it decently. I am building a boat because I want to rather than for cost reasons
     
  10. Erwan
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    Erwan Senior Member

    Wayne,
    Sorry I have no design yet as it is not the priority and also the learning curve of CAD freeware like Blender is a bit discouraging, especially for just one project

    My priority is more on structural engineering for the wing structure, and I am pretty ignorant on this matter.

    The basic idea is today's foilers need very stiff (=costly ) plateform.

    When you sheet in the mainsail, you pull up the rear cross-beam, and the mast reaction will push down the front cross beam.

    If not stiff, the AoA of the main foils are likely to change each time you change the mainsail tension.

    So , a self-supported rig like a wing or even a windsurf/wishbone rig would make it.

    From this point, the logic is to concentrate the high tech on one piece: the main cross-beam.

    I have been using XFOIL to create a family of airfoils with camber changing from 0% to 6%,
    and so far, with NCrit=1 and transition set @1%, it provides better results than low drag airfoils (which were designed for some laminar flow).
    I don't know any wing section especially designed for turbulent flows, so these benchmarks are probably not that relevant, but I have nothing else.

    Thank you for your interest, I am very open, and do not hesitate if you have any extra questions, but remember I am not a professional in the cat industry.

    My best wishes for everybody and to Nordschleife ' s great project.

    Cheers

    Erwan
     
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  11. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Nordschleife,

    Regarding the hull shape, there is a very intersting interview of Guillaume Verdier which explains the reason for square hull section for the foiling cat, and more rounded ones for the floater.

    Long time ago, Martin Fischer, told me that the "flattish" keel line at the bow and at the stern of GroupamaC or ETNZ 72 aims to create dynamic lift for the bow, and reduces wetted area for the stern.

    Don't know if a freeware like Michlet would address these hull features?

    Keep us informed of your interesting project

    Cheers

    Erwan
     
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  12. Nordschleife
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    Nordschleife Junior Member

    So there are no commercially available plans?
     
  13. DCockey
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    Location: Midcoast Maine

    DCockey Senior Member

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  14. Nordschleife
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    Nordschleife Junior Member


  15. Nordschleife
    Joined: Jan 2020
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    Nordschleife Junior Member

    I'm waiting for a response from one of the officers. In the meantime are there any plans anybody knows of?
     
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