Trying to design my own cat.

Discussion in 'Multihulls' started by Richard Atkin, Aug 12, 2007.

  1. bobg3723
    Joined: Aug 2005
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    Location: Crystal, MN - USA

    bobg3723 Senior Member

    Heck, even a 9 meter water weenie for the third hull would be even more portable. Just inflate and pile on the bodies.:cool:

    Cheers,
    Bob
     
  2. Ikarus342000
    Joined: Mar 2007
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    Location: FRANCE

    Ikarus342000 Ikarus342000

    Do not fool around with the DUO 900

    Hello

    As designer of the DUO 900 are strictly against any changes on this design.
    A-symmetrical catamarans are very weight sensitive. This boat is meant to stay light. So do not fool around with the design without consulting me.

    Bernd Kohler
    K-designs
    France
     
  3. bobg3723
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    bobg3723 Senior Member

    My apologies Bernd. Thank you for correcting my foolish lack of understanding of the Duo900's design parameters.

    Sincerly,
    Bob
     
  4. bobg3723
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    bobg3723 Senior Member

    Hypothetically speaking as it relates to symetrically shaped hull forms, could not the bridgedeck beams of a catamaran be so designed to accept a third hull to function as a degraded performance trimaran? One might wonder why bother, but the idea is to take a high performance catamaran of light displacement and modify it to accept more displacement in trimaran mode. This might come in handy for when a group of extra passengers might be accomodated onboard on a family outing 'on the lake' with the increased displacement capacity of the added third hull that would normally be beyond the safe operating limits of the light displacement cat alone. Is this paradigm wrong?
     
  5. rayaldridge
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    rayaldridge Senior Member

    A good tri will have much wider overall beam than a cat of similar length.

    Of course, if you built new beams, as well, it might work. This is the essence of the kits that were or are sold to convert a beach cat into a tri.

    Ray

    http://slidercat.com/blog/wordpress
     
  6. bobg3723
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    bobg3723 Senior Member

    That part about having to increase the beam overall makes things not too much more complicated to excecute, on the face of it. But on further examination, the added expense of another set of properly engineered crossbeams along with the added central hull does force one (me, in particular) to ponder whether it made more sense to stick with a higher displacement design from the very start. A cat to tri retrofit does stray from the KISS principle....

    Note to self:
    What I learned today: Try not to make a silk purse out of a sow's ear.:( :D


    BobG
     
  7. Richard Atkin
    Joined: Jul 2007
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    Hi Bob and Ray and Mas and French dude Bernd

    I've given up on the whole idea of making a small heavy cat for choppy seas. No matter how you build it, the reliance on lateral stability means it will always feel like a washing machine when sailing in 2 or 3 ft waves, especially in light wind...and that is very typical conditions in LA. The 'gliding cat feeling' that I enjoyed in the past, was always on a very flat sea. It's taken me a while to wake up to this point.

    I realise that a monohull with that 'stupid' big lead keel dragging through the water is not such a bad thing after all. I won't say no to the nice big cosy cabin too.....and slightly better payload. I will enjoy the 'mono feeling' instead.

    I'm looking at pocket cruisers at the moment. As much as I like the fresh open deck feeling of a small cat....I am also attracted to the opposite. Super-cosy, very strongly built offshore pocket cruisers appeal to me (even though they are incredibly slow). A good one will get me and about 5 other people through really shitty conditions....so it could broaden my sailing experiences. Maybe I will develop an appetite for bad weather.

    I will have two boats if my LA property and my bank account will allow it. Mono for the rough, and cat when it's flat. That way I get the best of both worlds.
     
  8. rayaldridge
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    rayaldridge Senior Member

    I feel the opposite way, Richard. When it's rough, I like the idea of being aboard a boat that won't sink, and doesn't beat me up until I get too tired to make good decisions.

    One thing I haven't understood about your design efforts is your urge to take so many people sailing at the same time.

    Ray

    http://slidercat.com/blog/wordpress
     
  9. Richard Atkin
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    Richard Atkin atn_atkin@hotmail.com

    Ray,
    I agree the sinking factor is a big negative. But I have no intention of sailing from one country to the next.

    Not sure why you think a monohull will beat you up any more than it's multi equivalent. Monos are less weight sensitive aren't they? More immediate reactive buoyancy? Surely that makes them better for dealing with large wind waves, if we are talking about small cruisers. When a cat is big enough, the waves are not so much of a problem...but I don't want big.

    As for so many people...
    a couple is very romantic,
    4 people is like inviting your neighbours over for a cup of tea,
    6 people is a small gathering...the boat starts to feel very lively, but it's not really a party
    8 people makes the boat feel closer to a party...you start to get multiple conversations, and couples can be with each other away from the crowd without looking like snobs.

    I want all those options. I like camping with many people.
    Up to 6 is more realistic though
     
  10. Leo Lazauskas
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    Leo Lazauskas Senior Member

     
  11. Guest625101138

    Guest625101138 Previous Member

     
  12. ropf
    Joined: Aug 2008
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    Location: Germany

    ropf Junior Member

    Richard, don't give up - just start from the right end! Buy a small boat, mayby a sailing dingy with a tent.

    All it need is to keep you afloat and allow some kind of movement. Dont care abot speed, pitching, pointing or whatever.

    Then go out and sail for some months. This will change your mind completly about what you want and what you need. Always look out how the different boats behave under different conditions.

    Now you have a idea what kind of boat you really want as well what all the design numbers an computer generated pictures mean in practice.

    You are ready for the next one. You will find boats of all classes and styles in the second hand market and usually cheaper than building by yourself.

    You are now sailing again. In the evening on anchor you may start to draw your dreamboat.

    The only place to design a boat is a boat!
    good luck
    ropf
     
  13. Richard Atkin
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    Richard Atkin atn_atkin@hotmail.com

    Ropf,
    The only boats I have ever sailed are the P class, Phase2, Sunburst, and hire cats. I did many years of sailing when I was a kid. I am not completely new to the ocean, but I have never sailed a larger boat.
    I agree with you though....I need to start sailing again. Getting past the worst of winter now, in Wellington, I'd like to get on the water soon.
     
  14. Butch .H
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    Butch .H Senior Member

    Richard get the mono cats suck!
     

  15. Richard Atkin
    Joined: Jul 2007
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    NASA designed a space shuttle with wings....the worst concievable design for re-entering the earth's atmosphere. They did it because they thought that the idea of picking up a little capsule in the ocean 'sucked'. They might tell you that the wings were for war strategy reasons, or national security, or something like that....but I think they just thought the floating capsule 'sucked'. :D
    Now they have gone back to the more sensible design. Well, they are trying to, but they keep getting confused between imperial and metric.
     
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