catamarn with stern drive engine

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

  1. Manie B
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    Manie B Senior Member

    Oh - and Chaser get used to a fuel bill that will bring tears to ANYBODIES eyes in six months time
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Without some clear fore and aft views, I don't see how any conclusions could be arrived at about why it is a slug.
     
  3. chaser
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    chaser Junior Member

    12T in full load.
     
    Last edited: May 26, 2012
  4. powerabout
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    powerabout Senior Member

    do you have a photo of it on the land from behind
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Something showing in the crystal ball, is there ? :confused:
     
  6. Frosty

    Frosty Previous Member

    The wake looks like its still trimmed up too much, are you sure they are full down, not just on the button but mechanically down,-- check oil level.

    Are the engines diesel,-- are you expecting same RPM as outboards.

    Picture of back of boat with full trim Down.
     
  7. powerabout
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    powerabout Senior Member

    My guess is on top of the hook the aft is narrow so pulled way down in the water as the bow has lift makign ti worse, if you look at the level of the outboard versus the static water level post 25 its digging a huge trench, hence large pressure wave coming back up to the surface at slow speed, it will move aft as you go faster
    12T for that size is heavy and Cats cant do heavy and perform
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    If he has a side profile to show, he ought to have the fore and aft, unless it is a secret....
     
  9. powerabout
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    powerabout Senior Member

    The side profile has already killed it
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    I'm not sure exactly what that mesh depiction is meant to define.
     
  11. groper
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    groper Senior Member

    Your hulls are too short and too FAT to make good displacement hulls. They are also too close together and you have very large wave interference drag. The Displacement to length ratio is very poor, and basically you could not have designed a worse displacement catamaran even if you tried to...

    So, perhaps a planning catamaran it is supposed to be... In this case,

    Your hulls do not carry enough lifting surface area to provide the lift it needs to get out of that huge hole and start to plane properly.
    Secondly, the hulls are the wrong shape, they should not have the slight run up towards the transom as it causes excessive drag and bow trim on a planning hull.

    Basically, you have a complete lemon.

    Without changing the hull shape, your only option is to reduce the propeller pitch and increase the diameter of the propellers so that the engines can develop maximum thrust. A little bit more thrust and you just might be able to get it up on the plane and the speed will increase, but you will have shockingly expensive fuel bill if you try to run it like this...

    IMHO your best option at this point, all things considered, would be to insure it and then "accidentally" sink it... :D
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Astounds me that this thing is being written off without a proper illustration of the lines. Not to mention incitement to commit insurance fraud......:eek:
     
  13. Frosty

    Frosty Previous Member

    It did 23kts with outboards on, but you would have to read his posts to know that.


    How can it get on the plane when it is a displacement hull.
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    Not worth discussing until the shape and dimensions are clarified.
     

  15. groper
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    groper Senior Member

    youd be surprised how much you can assume just by looking at those pictures and what has been said already...

    Frosty, see my previous post...

    With the previous outboard powered version, perhaps the outboards were propped better and with the extra 30HP per side, better props and less weight, it just managed to climb over the hump - which the stern drive model clearly cant from the pictures shown...
     
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