Minimal offshore power proa

Discussion in 'Boat Design' started by BrendanfromNZ, Aug 11, 2020.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    Didn't he say he didn't want a sail boat ?
     
  2. philSweet
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    philSweet Senior Member

    Cut off the damaged ama and you have a proa. Trade the rig for a little diesel and voila. But it was a joke. Still, the owner could probably provide real info on open water speed and fuel consumption (albeit an outboard, which is a terrible idea on a boat that size.) Rig probably cost 20k, so about 120k for the hull - no engines. You have to admit, it is a similar SOR executed in aluminum - and it did cross an ocean - once.
     
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  3. BrendanfromNZ
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    BrendanfromNZ Junior Member

    That is a lot of boat for tiny accommodation. Looks fast though, could put big flat upper deck above the beams, turn into a giant party boat
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    A bit of a "fire sale" that one, the cracked beams and lost rudder must have put the frighteners into "old mate" !
     
  5. Russell Brown
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    Russell Brown Senior Member

    The single outrigger is the best ride and the best fuel economy for a single engine multihull motorboat. Not a proa. 73060015 (2).jpeg 73060011.jpeg
     
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  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Excuse my ignorance, but what is the essential difference between the two ?
     
  7. Russell Brown
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    Russell Brown Senior Member

    A proa is a sailing craft (the third multihull type) and it is as is more different from anything else than any vehicle can be from another. As you probably know, a proa is asymmetrical from side to side, but symmetrical from end to end and it tacks by changing ends and only accepts the wind from one side of the boat. In traditional proas and many modern proas the outrigger is always on the windward side of the boat. A motorboat that travels in one direction is not a proa. If someone wants to call it that, that's okay, but it's far from accurate.
     
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Fair enough, I appreciate your explanation, I understand the reversibility factor with the proa, so really a motor proa is a misnomer. Unless your motor can turn 180 degrees !
     
  9. BrendanfromNZ
    Joined: Apr 2020
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    BrendanfromNZ Junior Member

    Hi Russell.
    That outrigger looks amazing, I have seen footage of your sailing proas, blasting along.

    Could you give us some details on this design?

    And how you find the handling with a single engine?

    Seems to me, for a minimal cruiser, a single outrigger has some advantages over a Cat,
    • lower centre of gravity
    • Lighter
    • Much less windage
    • Single drive
    Thoughts?
    Brendan
     
  10. BrendanfromNZ
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    BrendanfromNZ Junior Member

    With a efficient displacement catamaran, you either use the narrow hulls for accommodations,
    or you use the wing deck. Im 6'5" so it going to be boxy.

    With a single outrigger your going to have up to 2.5m internal beam (at sheer height) which is far more spacious than a cat.
    And full headroom without it looking like a brick.

    Another plus is the ama beams could support a lightweight deck for more external living area, or netting at the least.
    Good spot for the inflatable.
     
  11. BrendanfromNZ
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    BrendanfromNZ Junior Member

    For offshore passage - I imagine an Ama with plenty of reserve bouyancy, with a simple ballast system,
    if it's starting to get ugly, 250kg of saltwater will hold that Ama in the water. Almost like a cat.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    So you treat the ama as buoyancy, when it is down-sea of the main hull, and ballast when up-sea ? That sounds tricky, and also alters the athwartship trim of the whole shebang ?
     
  13. Russell Brown
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    Russell Brown Senior Member

    Brendan, I think you are right on all points. The concept has advantages for sure. I've just finished helping Paul Bieker design a 25' version of the boat in the photos. It's an all plywood NC cut kit boat with quite a bit more volume and accommodation than the first one. There is one being built now and I'm hoping to build one to write a building manual.
    The boat pictured is the family car and workboat for a family living in a very remote location and it's got a bajillion miles on it. It goes about 18 knots with 20 hp and hasn't had stability issues, but a ballast system would be appropriate. Can carry one hell of a load too. DSCN0056 (1).jpeg IMG_20160721_190120965.jpeg
     
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  14. BrendanfromNZ
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    BrendanfromNZ Junior Member

    Easy as to to weld a 200L sealed section into the Ama (talking aluminum here) below the waterline. 2" fill point from transom with a ball valve. High point vent. Rest of the Ama foam filled.
    Any speed over 7 knots, will free drain the ballast tank, unless you close the valve to hold it in.
    Slow down or stop, tank fills give epic stability at rest.
     

  15. BrendanfromNZ
    Joined: Apr 2020
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    BrendanfromNZ Junior Member

    Russell, that thing is amazing, an ocean going version of that is it.
    What is it like in rough water ?
    One thing I like about the outrigger is it leaves one side free for fishing, whereas a Tri doesnt
     
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