4.0 x 2.0 meter polyethelene catamaran

Discussion in 'Boat Design' started by foilcats, Jan 11, 2009.

  1. foilcats
    Joined: Mar 2007
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    Location: Auckland

    foilcats Stephen Snedden

    4.0 x 2.0 meter polyethelene catamaran

    Im looking for any design ideas for a small runabout to suit a diesel 10hp engine 65kg,

    the boat needs to plane easily and not be too ugly,

    must be open boat with no cabin,

    stable and be able to carry the outboard load of up to 25hp manual or helm,

    any good ideas to help and design features that one would expect to be on it please coment,

    will give praise to who ever helps,

    any sugestions be appreciated,

    have a student to draw it over 500 hrs in next 3 months and will show it as it progresses,
     
  2. HJS
    Joined: Nov 2008
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    Small catamaran

    Please, have a look to this one.
    Close to what you are looking for?
    Let me know.
    Don't built this one!
    There are some bugs in this design.
    This is not the final design.

    JS
     

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  3. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    10hp inboard on an easy planing cat in polly is cutting it a bit thin. And that on a 2m thing ?

    The smallest planing boat I have seen was a 2.8m baby cathedral hull with a 15hp outboard on it.

    You left safety out of the equasion. Don't give students the idea they can design / build a boat without doing the safety thing, one of them may go off and build something and not come back to class the next day. Unless it's only a model boat.
     
  4. foilcats
    Joined: Mar 2007
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    foilcats Stephen Snedden

    thanks looks interesting

    trying to keep to the basics and more a cat design with more deck room,
    looks good though any back end views?

     
  5. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Cat hulls have less buoyancy than mono hulls. You have to calculate the booyancy, take into consideration the weight of the boat as well as the rest of the stuff, motor, person, fuel etc.

    Keep in mind the boat cannot float at deck height, there has to be reserve buoyancy left. To achieve this the hulls have to have some depth. If the hull height exceeds a certain height to boat width ratio to get enough buoyancy the cat is going to become top heavy and difficult to keep upright.

    My opinion is such a small cat is going to be unstable never mind getting it to plane easily.
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I don't think it would be that difficult to develop a cat hull to fit those needs, though a good working understanding of yacht design would be especially helpful. This wouldn't be one for a student of design, you're going to want a real designer.

    I'd personally recommend a "sea sled" design for this size range to gain capacity and more usable internal volume. If you're not familiar with a sled, then picture a cat bows attached to an inverted V, mono hull, stern section. I have an 18' sea sled design that works very well, especially in shallow water on low HP. The sled design will plane more easily than a cat too. Contact me by email (click on my name) if interested.
     
  7. HJS
    Joined: Nov 2008
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    Planing a cat

    It is very important to check up the total weight on a planing cat
    check up the planing area - total weight relation
    one hull planing area must have the ability to carry the total weight
    when planing in rough sea it can be that one hull has to carry the total weight
    and if the planing area is to small it goes down in displacement mode
    with much more drag
    while the other hull is still planing with less drag
    this way the cat can go into an uncontrolled sharp turn
    or capsize
    thats also why the over all beam has to be moderate

    if you need more deck space
    made the boat bigger

    the suggested design can go 30 knots with 15 hp
    so 10 hp is my recommendation

    js

    multihull designer since 1966
     

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  8. foilcats
    Joined: Mar 2007
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    Location: Auckland

    foilcats Stephen Snedden

    4.0 x 2.0 Catamaran

    Here is a basic idea of what i want it to be like its double skin and has top and bottom mould parts, the hull design im working on now and appreciate the imput,
     
  9. foilcats
    Joined: Mar 2007
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    Location: Auckland

    foilcats Stephen Snedden

    Sketch of 4.0M x 2.0M Cat

    heres the picture i forgot to attach it,
     

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  10. sabahcat
    Joined: Dec 2008
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    Location: australia

    sabahcat Senior Member

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