24ft power cat design

Discussion in 'Boat Design' started by ecojet, Jan 20, 2017.

  1. ecojet
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    ecojet Junior Member

    Thanks Zulu40, I'll check it out.
     
  2. guzzis3
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    guzzis3 Senior Member

    Oow. Where did you find that photo ? I've not seen that before...

    I can understand why someone would build a trailer with sliding beams but do consider the swing wing alternative. It throws up some design challenges but you won't get binding as you do with sliders (ask anyone with an international 23, seawind or those sliding trimarans they built about 15 years back). Also if you use a parallelogram to lift the bridgedeck (see a sango/wizard trailer) you can use the trailer winch.

    Good luck.
     
  3. shipwright
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    shipwright Junior Member

    Hull Form

    ECOJET: I have designed many commercial pleasure cats. others have mentioned drag betwteen hulls, quite a few designers of note have used assymentric hull form to help reduce this problem, have seen this used on power and sail.
    Shipwright:cool:
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I think Richard Wood's "skoota" boats are asymmetrical, which of course does not mean there isn't still some "shape" on the inward facing sides.
     
  5. ecojet
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    ecojet Junior Member

    Asymmetric hulls will be used in the design.
     
  6. shipwright
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    shipwright Junior Member

    A good example are the couger cat hull forms, having said that they need a bit more power. The shape of the tunnel and design of bridging structure is as important as the hull shape.
    Nelson
     
  7. ecojet
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    ecojet Junior Member

    Hey shipwright I know you probably meant the aussie built Cougar cats but here is an interesting boat, Cougar cat from the UK, 26ft x 13ft.

    At the moment it looks like 2 possibilities 7.6m x 3.8m demountable or 7.6m x 3m would be a wide load trailer job.
     

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  8. shipwright
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    shipwright Junior Member

    cat.

    Yes mate meant the qld couger ,the assymetric hull form extended right thru their range. I would only consider the 3m model, the cat has to be strong enough to withstand the twisting forces at sea. this is usually dependant on the tunnel shape,water clearance in the tunnel,also has to resist the slamming loads at sea.
    If can Find out 10m model I will post.
    Shipwright:cool:
     
  9. shipwright
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    shipwright Junior Member

    9.5m Comet

    This lines plan for a 9.5 cat, she was designed around the new Fiat=Cummins-Volvo engines at the time.
    sections will give you a fair idea of powered catamaran details.
    a pair of 330hp shaft drives usually around 30kn.
    the Volvo 220hp with a leg drive 28kn, exhibited great load carrying capacity.

    Shipwright:cool:
     

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  10. Mr Efficiency
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    Mr Efficiency Senior Member

    Shipwright, he wants a displacement cat, which means slender hulls and strict weight control, and not captive to the limitations of "hull speed", or needing big hp to climb over a resistance hump. Think of flight attendants, no fatties allowed.
     
  11. ecojet
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    ecojet Junior Member

    Thanks anyway Shipwright but Mr Efficiency is correct, I am after a slender hull design running twin 25 or 30 hp outboards looking for a 14-16 knot cruise speed.
    Hulls have a Length to waterline beam ratio of just over 12.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    ecojet, my preference for the stern treatment would be canoe sterns truncated just enough to get a flat transom pad for your engine. That way you can have a boat that can slow down without too much submergence of a transom retarding it.
     
  13. shipwright
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    shipwright Junior Member

    Cat

    Hi Troops: you miss the point I was making. no matter what hull shape you use the tunnel design and bridging structure is paramount concern in cat design.
    Shipwright:cool:
     
  14. ecojet
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    ecojet Junior Member

    Ok I get what you're saying, I was going to do a cad design of it but to learn to use the software takes a bit of time, so I am doing the design on paper and will build a scale model of it soon, then I post some pics of it.
    I am going with the 3m beam version which will keep the weight down and simplifies the build.
     

  15. shipwright
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    shipwright Junior Member

    Nustar

    Hi Troops. Have a look at this attachment: LOA 11m this mould was designed in 1986 and is still in production. All the theories are confounded
    with this hull ,lowest power was a pair of 9.9 4 stroke outboards,diesels the smallest was a pair of 30hp Vetus. I suppose what I am getting at is you dream up all the theories but you have to consider bouyancy versus general arrangement versus cost per sq.meter. this design could not be trailed so eliminates from enquiry. one of these units made 3 voyages fro Sydney to Cooktown thousand miles open ocean.
    If I was looking to build a small cat I would be looking for standard sailing boat-cat hull, a pair of Tornado Hulls would be near the mark.
    Shipwright:cool:
     

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