First Czech A-Cat

Discussion in 'Boat Design' started by Vector77, Apr 14, 2014.

  1. Vector77
    Joined: Apr 2014
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    Vector77 Junior Member

    Hello guyes,
    I work on design of first czech A-Cat. Here are some pictures of actual design... What do you think?

    Thank you


    Attached Files:

  2. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    Unless it is a hydrofoil cat, with such zero reserve buoyancy forward it will be a very wet ride.
    In addition to that, with such a small waterplane area forward it might often end up as an underwater ride too - regardless of whether it is a displacement or hydrofoiling cat. :)
  3. Vector77
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    Vector77 Junior Member

    Hydrofoil cat will be second part... at this moment cat is going to be for standard sailing with C boards.

    So do you think that cat would have bigger buoyancy forward reserve then yet?
  4. messabout
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    messabout Senior Member

    Fast cats, like the A class, need to have slender hulls in order to make best speed. The problem is that very slender boats can easily bury the bow. It is usually the lee bow that dives and threatens to pitchpole the boat. Forward bearing is obviously important.

    If the boat is to tack well, the forward ends should have some rocker so that the bow does not resist turning. Rocker means that the keel line rises upward toward the waterline. When it does that, within reason, you can get away with slightly broader and a little flatter forward sections. All the while considering bow entrance angle. All this is subject to experimentation of course.
  5. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Is this just an exercise or are you planning on building it?

    The reason I ask is that with what is going n in the A Cat class right now anything not designed to foil is going to have a useful racing life of about two years. There are already designs in the works to make the most of J foils, and as soon as DNA comes out with a stable foiling boat everything else is going to be non-competitive.

    I was actually looking at buying a new A Cat this year, but am instead buying an old junker just to get some experience, and holdi off for the first generation of true flyers.
  6. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    I'll confess I don't know much about Cat design though I've sailed a few - Tornado, Darts and others, even a C Class. It looks like the forward topsides would exacerbate any bow 'diving' characteristics along with the lack of forward volume noted by Daquiri. If that upper surface went into a wave it would go down and down, likely enough pitchpole the boat. So called reverse bows might be trendy but they allow a bit more buoayncy to be carried low down far forward. However the above shape sheds water - fast and in a way that does not contribute to nose diving.

    Don't worry too much though, the first couple of dinghies I drew, fortunately did not build, were too fine up front, under the W/L. Go look at a few more cat hulls. Note stuff like the ETNZ and Oracle too, there is quite a lot of buoyancy up front there especially on ETNZ.

    Mmm note that edition of Rhino is Educational.....are you a student?

  7. Vector77
    Joined: Apr 2014
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    Vector77 Junior Member

    SukiSolo - Yes, I'm student of Industrial design at Czech Technical university...

    I would like to build my own small Cat just for my self....
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