catamarn with stern drive engine

Discussion in 'Boat Design' started by chaser, May 23, 2012.

  1. chaser
    Joined: Jun 2009
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    chaser Junior Member

    please see the below profile
     
    Last edited: May 26, 2012
  2. chaser
    Joined: Jun 2009
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    chaser Junior Member

    with out trim tab on the transom,due to it is impossible to fit it on the transom,when i am adjusting the angle of stern drive engine,bow could be raised up too much
     
  3. Frosty

    Frosty Previous Member

    Thats a semi displacement hull and not long enough for your expectations.

    Your expected speed is not attainable and you are therefore over powered.

    There is quite a bit of rocker there too making me think that it is a sailing hull.

    Your top speed should be around 12 kts--possible a bit more.

    To get out of it I would reduce prop pitch to attain max HP and try some trim tabs,--might work.
     
  4. masalai
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    masalai masalai

    It is a *******, - - Displacement type ??? monohull with sponsons added (in green) - - what a bloody 'hodge podge' mess, insure it and blow it up....... . . . . . . . . . . . . ............. or something similar...
     
  5. Frosty

    Frosty Previous Member

    I think he was looking for a bit of help.
     
  6. eastcape
    Joined: Jul 2003
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    eastcape Senior Member

    Sponsons

    Chaser,

    Are the green hulls in the PDF an add on to existing hulls? Did you have to change the hulls because the vessel was overweight?

    Or....is that the original hull design?

    Be careful using the boat as it is.. You might do some serious damage to the stern legs. It is pushing far too much water, your digging a big hole.

    In my humble opinion, you might need to re-design the sponsons bottom shape by flattening out the rocker and adding some lifting stakes. You might even look at extending the hulls forward to increase the waterline length just a little and get a better flow of water around the sponsons. They are indeed too small, too stubby, and too heavy for the stern legs.
     
  7. powerabout
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    powerabout Senior Member

    nice looking boat above the waterline
    That hook in the hull aft is going to be pulled level with water so hence suck the back down and bow goes up no mater how you power it.
    maybe sail power might be better
     
  8. masalai
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    masalai masalai

    Hi Frosty,
    Not much can be done with a dead cat, except recognise and acknowledge it for what is is, a dead dog... and the designer needs to be thoroughly castigated for trying to sell such a thing...
     
  9. powerabout
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    powerabout Senior Member

    cut the bottom off and glue another one on?

    Would like to see the beam profile?
     
  10. masalai
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    masalai masalai

    Hi Powerabout,
    - I agree view from the stern and the bow could help and possibly a "wire-frame drawing"... - at present I am just 'shooting in the dark' and taking wild / educated / ignorant / for the sake of pontification, guesses?
     
  11. chaser
    Joined: Jun 2009
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    chaser Junior Member

    the first boat was powered with two outboard engine(250HP),and the speed is 23knot,so i dont know why this boat cant works well,
    I want to add a trim tabs on the transom,but it looks impossible due to the stern drive engine,
    Yes i am looking for bit of help for fixing the problem of stern terrible spoondrift and speed.
     

    Attached Files:

  12. powerabout
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    powerabout Senior Member

    do you have a photo of it out of the water taken from behind it?

    How much does it weigh?
     
  13. powerabout
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    powerabout Senior Member

    the less weight of the outboards just covered up the design fault and 23kts with 500hp on a boat that size is not very good
    Most US built boats have always had different hulls for sterndrives than the same boat with outboards so they can carry the extra weight aft
     
  14. chaser
    Joined: Jun 2009
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    chaser Junior Member

    The green hull is the original hull design,in my opinion the lifting at the stern is to small ,is it possible to estending the hull sponsons as the below showing
     

    Attached Files:


  15. Manie B
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    Manie B Senior Member

    This boat is digging a hole that if it were any deeper the boat is going to fall backwards into it :eek:

    this is a much bigger problem
    and I think Mas is on the money

    Chaser forget about the speed, you can add anything and everything to that boat, the difference will be so little that it wont be worth the effort. Put on smaller props to get the WOT correct RPM as per engine details but the rest is not worth it.

    Enjoy the boat as a 10 knot cruiser
     

    Attached Files:

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