catamarn with stern drive engine

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

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't see 12 tonnes as correct, the sponsons are say, 9 metres long, even if they were a metre wide the immersion would be ridiculous. If he can't produce a full drawing of it, it is just speculation though.
     
  2. powerabout
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    powerabout Senior Member

    I'm with you there
     
  3. masalai
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    masalai masalai

    Lets just say Cats do not plane (ride up over a "hump" in accelerating, and thus reduce surface contact and improve speed) - - for this exercise - WTF... no chance once a plough to remain a plough and even Moses could only part the waters temporarily, WITH GODS HELP... - - - - There may be some exceptions as I am confident my Sharkcat and then 288 Powercat both "rose" to the occasion, the latter eased back for comfort and reluctance to test rectal muscles and the risk of "piles" in a sometimes very savage pounding encountered in the ride...

    and I also agree that the quoted 12T in bathtub around 30 ft is nothing but crazy - lots of lead ballast? . . . . . . Have it permanently tied to a marina berth and used for socialising on 'days off' and replace the engines with something like 20hp saildrives with fixed 3 blade propellers for basic mobility to facilitate annual haul-out and maintenance...
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Rounded sponsons only exacerbate what is probably already a dire situation, at the speeds intended no worthwhile lift will be generated, and what is, will be centred forward of the COG, further increasing squat. Thing would possibly be rectified by a Marine Dentist, wonderful how they can build up unsightly teeth into perfectly shaped choppers. "Cap" those sponsons with a fat, hard chine overlay ! Probably still end in tears, but who wants to die wondering ? And keep all those spectators off the rear platform underway, up to the bow, thank you, no need to worry about looking at those roostertails, they are just a symptom, not the disease itself.
     
  5. Frosty

    Frosty Previous Member

    What a bunch of ---experts

    It did 23kts with outboards on.

    REPEAT--it did 23kts with outboards on.

    ( Never mind tie it to a dock or insure it),------ maybe he should try another forum for some proper help.

    Cummins are heavy lumps, I use Yanmar 250 at I think 280kilo.

    It would appear you have too much weight aft.

    Rule AAA1 cats dont do weight.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    23 knots full throttle from monster 250 hp outboards is a poor result, but nothing will help it if is as heavy as he says.
     
  7. FMS
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    FMS Senior Member

    Has a stern view out of the water been posted?
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    No. Has been requested, or a lines drawing, but hasn't responded.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    It looks as if someone has taken an existing monohull design and superimposed the sponsons on to it, trouble is it became twice the boat weight-wise !
     
  10. Frosty

    Frosty Previous Member



    My 40 foot water line 12 ton cat needs 2x250 mosters to get 23kts also.

    The manufacturer claims only 21 kts but I use surface drives that some experts say need high RPM , are self cleaning but dont work under 50MPH.

    Hence I invented the drivel thread.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    This one is no more than 30 ft long, and presumably the sponsons are not as wide as your 40 footer. If it is indeed 12 t, it is overloaded to hell.
     
  12. FMS
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    FMS Senior Member

    The styling could be fooling your eye. It is closer to 40 ft if you measure using the man on the stern platform for scale.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    post #16 has a profile in the download titled "38 ft", run a ruler over it and you'll see the sponsons are a lot shorter than the total length, roughly 30 feet. Waterline less.
     
  14. Frosty

    Frosty Previous Member

    Shorter boat needs more HP.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    Requires less power if scaled down proportionally. If it really is a 38 foot cruiser that has been piggy-backed on catamaran sponsons, it has become one of those ideas that should have stayed in the thought bubble.
     
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